Final Exam Material Flashcards

Question

When does a coagulum type gel result?

Answer 1

From hydrophobic bonds and possibly disulfide linkages

Answer 2

False. At extreme pH, protein gels are weakest due to charge properties.

Answer 3

Enzyme action causing an increase in hydrophobicity of the micelle

Answer 4

* Alpha-amino acids are the basic structural units of proteins * Consist of an alpha-carbon atom covalently attached to a hydrogen, an amino group, a carboxyl group, and a side chain R group. (Contains C, H, O, & N, [S, P]) * Amino acids differ only in the chemical nature of the side chain of the R group

Answer 5

The alpha carbon is an asymmetric carbon atom in all amino acids (except for glycine), thus amino acids exist in two optically active forms: L- and D- isomers.

Answer 6

* Differences in solubility of properties of amino acids is due to the type of side chain. * Dependent on the dissociation properties of the amino acid, known as dissociation constant (pKa)

Answer 7

Essential amino acids cannot be synthesized *de novo* by the organism, and must be supplied in the diet. **PVT TIM HLL** Phenylalanine Valine Tryptophan Threonine Isoleucine Methionine Histidine Arginine Leucine Lysine

Answer 8

* Quality of proteins depends on the richness of essential amino acids (limiting amino acids) and the digestibility of the protein. * A limiting amino acid is the essential amino acid found in the smallest quantity in the food (e.g., gelatin lacks 4 eAA) * Limiting amino acids affect the net protein utilization or biological value

Answer 9

These three amino acids have nonpolar side chains that are branched and thus restrict the internal flexibility and give rise to surface hydrophobicity.

Answer 10

Polar side chains form hydrogen bonds. Serine and threonine have hydroxyl groups that form hydrogen bonds.

Answer 11

Cysteine has an important role in forming sulfydryl (S-S) bridges between different parts of the peptide chain.

Answer 12

* L-glutamate suppresses certain ‘undesirable’ flavours, such as: * Sharpness of onion flavour * Rawness in many veggies * Earthiness of potatoes * Glutamate activity to modulate taste in foods is noticeable between pH 3.5 to 7.2, being more intense in lower pH.

Answer 13

* D-amino acids generally evoke a sweet taste perception while L-amino acids are tasteless or bitter. * Short side-chain of L-amino acids can also elicit a sweet taste * As the side chain length of L-amino acids increases, the sweetness will change to bitter * If the hydrophobicity increases on the L-amino acid, the sweetness will be lost and replaced either with bitter or no taste. * Preference for D-amino acids tend to increase with molecular weight and hydrophobicity. * The correlation between the hedonic score and D-amino acid molecular weight or bulk of the side chain reflects that the lower threshold score, the less required from the sample to elicit a positive preference.

Answer 14

Maillard reaction, which occurs in both food and biological systems. Amino component → proteins and amino acids Carbonyl component → reducing sugars, ascorbic acid (vitamin C) and carbonyl compounds

Answer 15

* The 3rd pathway of the Maillard reaction; carbonyl-amine reaction * The oxidation of amino acids by an alpha-dicarbonyl or other conjugated dicarbonyl compound that is produced on the breakdown of Amadori compounds * Amino acids are degraded to aldehydes, pyrazines, sugar fragments, ammonia, and carbon dioxide. * Strecker degradation of each amino acid produces a specific volatile compound and provide unique aromas and flavours

Answer 16

Aldehydes, pyrazines, sugar fragments, ammonia, and carbon dioxide.

Answer 17

* The presence of oxygen and the enzyme tyrosinase are essential for the oxidation of tyrosine to dihydroxyphenylalanine (DOPA) * Copper is an essential co-factor for tyrosinase enzymatic activity * Optimal pH ranges from 6.7 - 7.2 * Sequestering copper agents (e.g., organic acids) and decreasing pH result in the inhibition of tyrosinase * The reaction is also reduced by: * Reduction of oxygen concentration (i.e., vacuum packaging) * Use of reducing agents (e.g., ascorbic acid, sulfites)

Answer 18

Tyrosinase (and a copper cofactor catalyst) pH 6.7 - 7.2

Answer 19

Sequestering copper agents (e.g., organic acids) Reducing of oxygen concentration (e.g., vacuum packaging) Use of reducing agents (e.g., ascorbic acid, sulfites)

Answer 20

* Amino acid decarboxylation reactions result in their formation * Tyrosine to tryamine * Histidine to histamine * Phenylalanine to phenylethylamine * Arginine to putrescine * Bioactive amines are the result of the action of the bacterial enzyme: L-amino acid decarboxylase

Answer 21

* Formed by decarboxylation reaction catalyzed by bacterial L-amino acid decarboxylase. * Naturally present in small amounts in bananas, pineapples, and produced by *streptococci* action in cheddar cheese * Poisoning can occur as low as 40mg * Causes hypertension and intense headaches

Answer 22

* Decarboxylation reactions * Formed from the enzymatic action of gram-negative bacteria mainly found in fish * Poisoning symptoms include headache, nausea, hypertension, and vomiting * Histamine production can also be synthesized by the normal flora of the colon. * Intake of foods rich in histadine may favour endogenous production of histamine * Histidine decarboxylase is also present in tissue mast cells and blood cell basophils, thus typical signs of inflammation can be due to the release of this enzyme.

Answer 23

Release of histidine decarboxylase, present in mast cells and blood cell basophils.

Answer 24

Decarboxylation reaction

Answer 25

Decarboxylation reactions

Answer 26

* Protein in different food matrices like beef patties, chicken meat, raw pork, and different types of fish can be oxidized during frozen storage * The usage of sodium nitrite, in cured meat, is another cause of protein oxidation. * Specific amino acids are involved * Lysine (alpha-aminoadipic acid) * Tyrosine (kynurenine) * Tryptophan (kynurenic acid) * Consequences → protein functionality and human health

Answer 27

Proline Tryptophan Tyrosine Cysteine Arginine Histidine

Answer 28

Preservation against *C. botulinum*

Answer 29

Nitrous anhydride, which reacts with amines containing ionizable groups, forming *nitrosamines* (risk of cancer) Nitrosamides are derivatives of substituted amines

Answer 30

Conditions of low pH (stomach environment) and at high temperatures (frying, roasting)

Answer 31

When metabolically activated by the hosts' oxidative enzymes

Answer 32

* Organic compounds formed by 100-500 amino acids linked together * Necessary in the diet, since not all amino acids can be synthesized * Built from a central carbon bonded to four *different* groups * Hydrogen * Amino group * Carboxyl group * Side chain

Answer 33

* **Albumins** → soluble in water * **Globulins** → soluble in neutral salt solutions * **Glutelins** → soluble in dilute acid or alkali * **Prolamins** → soluble in 70% alcohol

Answer 34

Proteins that contain amino acids combined with a non-protein constituent.

Answer 35

A conjugated protein Phosphate groups linked to hydroxyl groups of serine or threonine E.g., casein in milk and phosphoprotein in yolk

Answer 36

Conjugated proteins Combination of lipids and protein with excellent emulsifying properties

Answer 37

Conjugated proteins Combination of nucleic acid with protein Found in cell nuclei

Answer 38

Conjugated proteins With carbohydrate (8-20%) Has strong allergenic properties E.g., ovomucin in egg white

Answer 39

Conjugated proteins Have prosthetic groups E.g., hemoglobin, chlorophyll, myoglobin, flavoproteins

Answer 40

Derived proteins are obtained by chemical or enzymatic methods. They are soluble in water and not coagulated by heat.

Answer 41

Limited hydrolyzed proteins - coagulated proteins E.g., rennet coagulated casein

Answer 42

Peptones and peptides: a combination of two or more amino acids Examples are the breakdown products formed during processing of milk products: the peptides formed during the ripening of cheese

Answer 43

Primary structural properties of proteins → sequence of amino acids Associated with the properties of individual amino acids comprising the protein Amino acids are linked by covalent bonds through amide bonds, also known as peptide bonds.

Answer 44

* Refers to the periodic spatial arrangement of amino acid residues at certain segments of the polypeptide chain * The regularly repeating local structures are stabilized by hydrogen bonding; notable examples are the alpha helix, beta sheet, beta turns, and random coil * Two forms of periodic secondary structures are found in proteins: helical and sheet structures. * Because secondary structures are local, many regions of different secondary structure can be present in the same protein molecule.

Answer 45

* From the helical structures the major form in proteins is the alpha-helix, which is the most stable * Each backbone N-H group is hydrogen bonded to the C=O group of the fourth preceding residue * Can exist in either right or left-handed orientation → the right-handed helix is more stable * The helix makes a complete turn every 3.6 amino acids. * In the alpha-helix, the backbone atoms form a coil while the carbonyl groups form hydrogen bonds with the amide groups

Answer 46

False. The right-handed alpha-helix is more stable.

Answer 47

* The C=O and N-H groups are oriented perpendicular to the direction of the chain * Hydrogen bonding is possible between segments but not within a segment * Comprised of individual beta-strands usually 5-15 a.a. long * Two beta-strands of the same molecule interact by hydrogen bonds, forming a beta-pleated sheet * Beta-strands often have a hydrophilic and hydrophobic side * Beta-sheet is generally more stable than the alpha-helix * Fibrous in nature and insoluble in aqueous solvents * E.g., soy globulin, beta-lactoglobulin

Answer 48

Beta-sheet

Answer 49

False. They are INSOLUBLE in aqueous solvents (they are fibrous in nature).

Answer 50

May be parallel or antiparallel. Anti-parallel beta-sheets are stronger than parallel due to the hydrogen bonds lying on the same plane.

Answer 51

* Refers to the spatial arrangement attained when a linear protein chain with defined (alpha-helix or beta-sheets) or non-defined (random coil) secondary structure segments folds further into a compact 3D form. * Amino acid linkages fold over into compact structures stabilized by hydrogen bonds, disulphide bridges, and van der Waals forces.

Answer 52

The spatial arrangement of a protein when it contains more than one polypeptide Formation of oligomeric structures is the result of specific protein-protein interactions

Answer 53

Hydrogen bonds van der Waals forces Hydrophobic interactions Disulfide linkages Ionic interactions

Answer 54

* **Covalent** → atoms bound by a common electron pair e.g., peptide bonds, disulfide bonds * **Ionic** → attraction between opposite forces e.g., solvent interaction, salt working * **Hydrogen →** hydrogen shared between two electronegative atoms; stabilizing/bridging * **Hydrophobic** → apolarity; strand thickening, strengthening, stabilizing * **Electrostatic** **repulsion** → coulombic repulsion between particles with like-charges e.g., polar groups of side chains * **van der Waals repulsion** → repulsion of apolar groups that are close; steric hindrance between side chain groups

Answer 55

Interaction of a hydrogen atom that is covalently bonded to an electronegative atom (N, O, S) with another electronegative atom.

Answer 56

* Protein stability depends on maintenance of an apolar environment * Hydrophobic interactions are the major forces to drive protein folding and stability * Hydrophobic interaction between nonpolar side chains of amino acid residues is the major reason by which proteins fold into unique tertiary structures.

Answer 57

Hydrophobic interactions

Answer 58

* Disulfide bonds occur between two cysteine (Cys) resides by oxidation of the sulfhydryl groups by molecular oxygen. * Once formed, disulfide bonds help stabilize the folded structure of the protein.

Answer 59

* Acids * Strong salt solutions * Heat * Alkaline conditions * Radiation

Answer 60

False. Protein denaturation is usually reversible (in the absence of aggregation) when the denaturant is removed (except egg white).

Answer 61

* Loss of solubility * Increase intrinsic viscosity * Altered water holding capacity * Increased digestibility * Increase susceptibility to protease attack * Improves foaming and emulsifying properties

Answer 62

* Loss of solubility * Increase intrinsic viscosity * Altered water holding capacity * Increased digestibility * Increase susceptibility to protease attack * Improves foaming and emulsifying properties

Answer 63

* **Primary** structure is not disrupted. * **Secondary** structure → proteins lose all regular repeating patterns like alpha helices and beta pleated sheets and adopt a random coil configuration. * **Tertiary** structure → covalent interactions (like disulfide bonds), non covalent interactions between polar side chains and surrounding solvent, and v.dw. interactions between non polar amino acid side chains are all disrupted * **Quaternary** → protein sub-units are dissociated and/or the spatial arrangement of protein subunits is disrupted

Answer 64

1. Solubility 2. Viscosity 3. Water binding 4. Gelation 5. Cohesion-adhesion 6. Elasticity 7. Emulsification 8. Foaming 9. Fat binding 10. Flavour binding

Answer 65

* Charged groups: ion-dipole interaction * Backbone peptide groups * Amide groups of Asn and Gln * Hydroxyl groups of Ser, Thr, and Tyr residues * Non-polar residues, dipole-induce dipole interaction and hydrophobic interaction

Answer 66

Grams of water per gram of protein when a dry protein is equilibrated with water vapour at 90-95% relative humidity. Also known as hydration capacity.

Answer 67

pH and isoelectric point Presence of salts Temperature

Answer 68

* At the isoelectric point, proteins exhibit the least hydration, but greatest protein-protein interaction * Water binding capacity increases above and below the isoelectric pH * The greatest is usually at pH 9-10 * Exposure of groups

Answer 69

* At low concentrations (\<0.2M), salts increase water binding capacity. Hydrated salt ions bind weakly to charged groups of proteins - “**salting in**” * At high salt concentration, water is bound to salt ions, resulting in dehydration of the protein - “**salting out**”

Answer 70

* As temperature is raised, water binding capacity generally decreases because of decrease in hydrogen bonding and decrease in hydration of ionic groups * If temperature leads to aggregation, water binding capacity decreases due to increase in protein-protein interactions

Answer 71

Refers to the ability of the protein to imbibe water and retain it against gravitational force within a protein matrix. Refers to the (1) sum of bound water, (2) hydrodynamic water, and (3) the physically entrapped water.

Answer 72

False. Its contribution is larger than those of the bound and hydrodynamic water.

Answer 73

Juiciness and tenderness of meat products Desirable textural properties of bakery and other gel-type food products.

Answer 74

A mixture of two immiscible substances, stabilized by emulsifiers.

Answer 75

* Proteins in native form act as emulsifiers by having hydrophobic amino acids hidden, or protected from the water phase, by hydrophilic amino acids. * On denaturation, the protein unfolds and hydrophobic amino acids align with non-polar or oil phase and the hydrophilic amino acids align with polar or aqueous phase.

Answer 76

Because they are edible, surface active, and provide superior resistance to coalescence They provide amphiphilic domains With adsorption, native conformation is changed: side chains of hydrophobic amino acids → to surface of oil droplet; hydrophilic amino acid side chains remain in aqueous solution Result = water-oil interface

Answer 77

They cannot be used for (w/o) emulsions because of insolubility in oil. Reduces interfacial tension.

Answer 78

1. **Solubility of protein** → optimal at 25-80% solubility 2. **pH** → proteins with high solubility at their isoelectric point have maximal emulsifying capacity. 3. **Salt** → may increase protein solubility thereby increasing emulsification 4. **Temperature** → small increase in temperature will influence the rate of diffusion and the rate of adsorption and protein unfolding thus increasing emulsification 5. **Denaturation** → with partial denaturation, proteins start to unfold so that free sulfhydryl groups and disulphide bonds form interactions at the oil/water interface = increase flexibility and surface hydrophobicity = increase emulsification

Answer 79

* A foam consists of an aqueous continuous phase and a gaseous (air) phase * The foaming property of a protein refers to its ability to form a thin tenacious film at gas-liquid interfaces so that large quantities of gas bubbles can be incorporated and stabilized * Protein-stabilized foams are formed by bubbling, whipping, or shaking a protein solution

Answer 80

* Proteins themselves are odorless. * Flavours come mainly from aldehydes, ketones, and alcohols * Noncovalent interactions are normally the mechanism of flavour binding to proteins; covalent bonding may also happen * Only the noncovalently bound fraction can contribute to aroma and taste of the protein food

Answer 81

1. **Protein denaturation** → thermally denatured proteins exhibit increased ability to bind flavours; ability to bind flavours is lower in denatured than in native proteins 2. **Salts** → ‘salting in’ destabilize hydrophobic interactions, thus decreasing flavour binding; ‘salting out’ increases flavour binding 3. **pH** → flavour binding is enhanced at alkaline pH 4. **Disulfide bonds** → breakage of disulfide bonds causes unfolding of proteins thus increasing flavour binding 5. **Proteolysis** → hydrolysis of protein causes disruption and decreases hydrophobic regions and thus decreases flavour binding; proteolysis usually produces peptides of bitter taste

Answer 82

Protein gelation refers to the transformation of a protein from a solid state to a gel-like state. Two types → coagulum and translucent

Answer 83

**Irreversible gel** Original protein have large amounts of non-polar residues that undergo hydrophobic aggregation, or insoluble aggregates that **randomly associate**

Answer 84

* Main linkages are H-bonds and electrostatic forces * Formed by proteins with relatively small amounts of insoluble residues and high amounts of polar amino acid residues * **Reversible** soluble complex after denaturation * **Ordered aggregation**

Answer 85

Hydrogen bonding and hydrophobic and electrostatic interactions

Answer 86

Translucent gels hold more water and are less prone to syneresis than coagulum-type gels, due to hydrogen bonding interactions.

Answer 87

* Gels formed by noncovalent interactions, mainly hydrogen bonds, are thermally reversible * Gels formed by hydrophobic interactions are irreversible (e.g., egg white gel) * Proteins can undergo polymerization via sulfhydryl-disulfide interactions → usually thermally irreversible (e.g., whey gels)

Answer 88

Minimum point concentration, least concentration end point (LCE) is required Soy protein = 8% Egg albumin = 3% Gelatin = 0.6%

Answer 89

Humectants bind to free water causing high protein-protein interaction and low protein-water interaction This results in strong gels formation with greater heat stability.

Answer 90

* At or near pI, proteins usually form a coagulum-type gel. * Acid conditions increase the amount of free water, thus decreasing the negative charge and increasing aggregate formation * Extreme pH → weak gels are formed because of strong electrostatic repulsion * Optimum pH = 7-8 for most proteins

Answer 91

* Limited proteolysis facilitates gel formation * Addition of chymosin (rennin) to casein in milk results in formation of coagulum-type gel

Answer 92

* Enzymatic cross-linking at room temperature can result in gelation * Transglutaminase is used to form highly elastic and irreversible gels, even at low protein concentration

Answer 93

1. Type of interaction 2. Protein concentration 3. Humectants (sugar or salt) 4. pH 5. Proteolysis 6. Cross-linking

Answer 94

Bovine milk contains 30-36 g/L (%) of total protein Milk proteins: casein (80%) and whey (20%)

Answer 95

* Mainly alpha, beta, and kappa caseins * Calcium sensitive alpha and beta (addition of calcium precipitates protein); kappa caseins are calcium insensitive (addition of protein will not affect protein, it remains soluble) * Amphipathic * Self-associate in solution to form micelles

Answer 96

* It cleaves k-casein at Phe105 - Met106 into para-k-casein and a glycopeptide * para-k-casein micelles form small aggregates, which then assemble into a gel

Answer 97

**(1) Hydrophobicity** * αs2- **(2) Calcium binding capacity** * The higher degree of phosphorylation, the higher binding capacity to calcium. * α_s2- \> α_s1- \> β- \> κ-

Answer 98

Micelles are kept together by electrostatic interactions: * Calcium or calcium phosphate bridges with phosphoserine and glutamic residues * Hydrogen bonds and minimal hydrophobic bonding

Answer 99

False. 9 kcal/gm

Answer 100

* Fatty acid composition of the lipid * The number of allyl groups present * The presence of antioxidants.

Answer 101

* Radical-induced chain reaction * Divided into initiation, propagation, and termination phases * Involves abstracting the H-atoms from activated methylene groups on unsaturated fatty acids * Culminating into formation of non-hydroperoxide molecules

Answer 102

The initiation reactions

Answer 103

Photosensitizers Lipoxygenases Transition metal ions

Answer 104

Includes 4 condensed rings with the first 3 being in the chair configuration and the last one being planar. Rings B and C, and C and D are fused by *trans*-configuration, rings A and B are fused in *trans-* or *cis-* configuration. A characteristic of steroids is the presence of alcoholic OH-group in position C3.

Answer 105

* Butylated hydroxytoluene (BHT) * A blank without lipid sample * Construction of a standard curve

Answer 106

True. However, some lipids are surface active since some are amphipathic molecules. (e.g., phospholipids)

Answer 107

Energy storage (9 kcal/g) Structural component of cell membranes Signalling molecules

Answer 108

Influence flavour and texture Many fat soluble vitamins require lipids for bioavailability; low fat diets will reduce the absorption of lipid soluble vitamins (A, D, K, E) Can be used as a cooking medium

Answer 109

**Simple lipids** Free fatty acids Isoprenoid lipids (i.e., steroids, carotenoids, monoterpenes) Tocopherols

Answer 110

**Acyl lipids** Mono-, di-, triacyl- glycerols Phospholipids Glycolipids Diol lipids Waxes Sterol esters

Answer 111

Fatty acids (\> 12-C) Mono-, di-, triacyl- glycerols Sterols, sterol esters Carotenoids Waxes Tocopherols

Answer 112

Glycerophospholipids Glyceroglycolipids Sphingophospholipids Sphingoglycolipids

Answer 113

Acylglycerols [= Esters (glycerol + fatty acids)] The acyl residues influence the hydrophobicity and reactivity of the acyl lipids.

Answer 114

False. They are unique in high content of lauric acid (50%) and medium chain triglycerols (C6-C10)

Answer 115

False. High saturated:unsaturated ratio Narrow melting range.

Answer 116

True. Most abundant, all vegetable origin.

Answer 117

False. They are n-3

Answer 118

C 16 - C 18 Cholesterol present

Answer 119

False. They are less resistant to oxidation and rancidity compared to animal fats. They have multiple unsaturated fatty acids.

Answer 120

Saturates Monounsaturates (omega-9) Polyunsaturates (omega-6, omega-3)

Answer 121

Generally as chain length increases melting point increases as well.

Answer 122

C12:0 Lauric acid Saturated fatty acid

Answer 123

C16:0 Palmitic acid Saturated fatty acid

Answer 124

C14:0 Myristic acid Saturated fatty acid

Answer 125

C18:0 Stearic acid Saturated fatty acid

Answer 126

C18:1 n9 Oleic acid Unsaturated fatty acid

Answer 127

C18:3 n3 linolenic acid Unsaturated fatty acid

Answer 128

C18:2 n6 linoleic acid Unsaturated essential fatty acid

Answer 129

C20:4 n6 Arachidonic acid Long-chain unsaturated fatty acid

Answer 130

C20:5 n3 Eicosapentaenoic acid Long-chain unsaturated fatty acid Found in fish oils

Answer 131

C22:5 n3 Docosapentaenoic acid Long-chain unsaturated fatty acid Found in fish oils

Answer 132

Oleic acid * Desaturation* * Elongation* * Desaturation* Palmitoleic or Eicosatrienoic acid

Answer 133

Linoleic acid (EFA) * Desaturation* * Elongation* * Desaturation* Arachidonic acid

Answer 134

Alpha-linolenic acid (EFA) * Desaturation* * Elongation* * Desaturation* * Elongation* * Desaturation* Docosahexaenoic acid

Answer 135

* Double bonds of unsaturated fatty acids an be either in the *cis-* or *trans-* conformation * A *cis* configuration means that adjacent carbon atoms are on the same side of the double bond * The *cis* isomer causes the chain to bend and restricts the conformational freedom of the fatty acid.

Answer 136

* A *trans* configuration means that the next two carbons are bound to opposite sides of the double bond * *Trans* configuration does not cause the chain to bend much, and their shape is similar to straight saturated fatty acids

Answer 137

The main constituents of vegetable oils and animal fats. A.K.A. triglycerides Fatty acids esterified to glycerol

Answer 138

These molecules are made from glycerol, two fatty acids, and (in place of the 3rd fatty acid) a phosphate group, with another molecule attached to the other end. The hydrocarbon tails of the fatty acids are hydrophobic, but the phosphate group end of the molecule is hydrophilic because of the oxygen constituents with all pairs of unshared electrons (= phospholipids are soluble in both water and oil)

Answer 139

* The property of fats to exist in different crystalline phases/forms while having the same chemical composition. * The crystalline forms have a specific melting point, solubility, density, and heat of fusion. * Upon melting polymorphic forms yield identical liquid phases. * Polymorphism plays a significant role in the sensory attributes of the lipids (e.g., texture, mouthfeel, and gloss)

Answer 140

* Triacylglycerides aggregate together to form highly ordered structures, called *nuclei.* * Nuclei serves as points of crystal growth (e.g., crystallization) * Nuclei are precursors of crystalline structures * Each of the triacylglyceride polymorphs possesses specific crystal characteristics * Melting properties are determined by the arrangement of the acyl residues in the crystal lattice.

Answer 141

There are three primary polymorphic forms: α, β, and β’ α → unstable due to high degree of disorder; random order chain axis; do not align efficiently or pack tightly; usually small and numerous β → packed to a much greater extent compared to alpha with more aligned structures; allows formation of larger crystals; greater stability and can achieve longer lengths; more likely to accumulate in fats β’ → parallel rows with the same orientation opposite to orientation of rows above and below; larger than α; smaller than β Conversion of β to β' is done in the production of margarine for example which allows a softer/spreadable fat.

Answer 142

**Beta** → highest MP **Beta-prime** → intermediate MP **Alpha** → lowest melting point Species of fatty acids present (e.g., chain length, saturated/unsaturated, cis/trans) affects which type of crystal will form

Answer 143

alpha → rapid cooling beta-prime → slow cooling beta → very slow cooling

Answer 144

Beta-prime crystals Allows low-temperature spreadability and storage and high-plasticity

Answer 145

Membrane phospholipids (substrate) Pro-oxidants (hemoglobin & myoglobin) Presence of antioxidants

Answer 146

The oxidative deterioration of lipids with molecular oxygen via a self-catalytic mechanism. Singlet oxygen is the excited state of oxygen which is usually generated by a photosensitizer pigment, and is less stable than triplet oxygen. Singlet oxygen has the same quantum state of food nutrients, therefore it can react more readily (1500x) than triplet oxygen.

Answer 147

Initiation Propagation Termination

Answer 148

* Characterized by the abstraction of a hydrogen atom from a methylene carbon that is located in between two double bonds of the unsaturated fatty acid. * Has a fairly high energy of oxidation, which is why pro-oxidants are required to initiate the reaction * Yields a carbon-centered radical

Answer 149

Concentration of the unsaturated fatty acid is in the rate law Induction period is affected by the type of unsaturated fatty acid (e.g., stearic acid creates an extremely long induction period and the slowest oxidation rate; a single double bond would have an induction rate of 82 hours and the slowest rate of o; two double bonds lowers the induction bond further ~19 hours, with a much higher oxidation rate; three double bonds has an induction period of ~1.5 minutes with the highest oxidation rate)

Answer 150

* Once the carbon radical is formed, it will immediately react with molecular oxygen to form an unstable fatty acid peroxyl radical (ROO\*) * This reaction is relatively fast and is the start of a chain reaction, where the peroxyl radical reacts with another fatty acid (by hydrogen abstraction) to form more peroxyl radicals * Forms hydroperoxides which are recognized to contribute to the off-odours and off-flavours associated with rancidity → very unstable and readily decompose to shorter chains which lead to subsequent reactions (secondary products of lipid oxidation)

Answer 151

Initiation = lipid radicals Propagation = hydroperoxide Secondary products = aldehydes, ketones, alcohols, small acids, alkanes

Answer 152

* The chain reaction continues until termination, which can occur by the donation of a hydrogen atom to the peroxyl radical from chain breaking antioxidants (TH), and by the reaction of the peroxyl radical and an antioxidant radical.

Answer 153

Hydroperoxides undergo beta-scission **Malonaldehyde** → dialdehyde preferentially formed by autooxidation of fatty acids with three or more double bonds; odorless; very reactive; through cross-linking can bind proteins and denature them or nucleic acids and inactivate them Even at trace levels, malonaldehyde is an indicator of lipid oxidation (=TBA test)

Answer 154

Occurs from lipolysis (release of free fatty acids) by action of enzymatic lipases Released PUFA are oxidized by lipooxygenase or cyclooxygenase to form hydroperoxides or endoperoxides Enzymatic cleavage of hydroperoxides yield further breakdown products (secondary; flavours)

Answer 155

Ionizing irradiation of fats; not natural Radiolytic products (dependent on FA composition) Chemical breakdown and generation of free radicals In presence of oxygen, irradiation accelerates autooxidation (free radicals generated will combine with oxygen to form hydroperoxides; their breakdown forms carbonyl compounds and free radicals; destruction of antioxidants)

Answer 156

Lipoxygenases

Answer 157

* A family of iron-containing enzymes that catalyze the dioxygenation of polyunsaturated fatty acids and associated esters or acylglycerols to produce active hydroperoxides. Causes oxidative damage and destruction of vitamin A and carotenes * Activation: iron (ferrous - Fe+2) (oxidized) → iron (ferric - Fe+3) * Has a copper prosthetic group * May be prevented by blanching, pasteurization etc.

Answer 158

1. **Nutritional losses** * Oxidation of EFA (linoleic, linolenic, and arachnidonic acids) * Interaction with essential a.a. causes damage/loss of protein functionality 2. **Colour changes** 1. Bleaching of carotene or carotenoid destruction 2. Destruction of chlorophyll 3. Destruction of skin pigmentation in some fish products 3. **Flavour changes** 1. Production of off-flavours in frozen vegges and stored cereals 2. Off-flavour product is a cardboard-like flavour 3. Rancidity of meats 4. **Texture changes** 1. Loss of SS-SH balance of proteins and hydrophobic bonding of lipids in glutens, which contributes to reduction of flour dough quality

Answer 159

Pigments in the lipid (e.g., chlorophyll, porphirin, myoglobin) convert triplet oxygen to singlet oxygen which will initiate oxidation reaction

Answer 160

The higher the temperature, the faster the reaction. Anisidine value is a measure of hydroperoxides (primary/initial product of lipid oxidation) At 50 degrees C, the end of the line indicates that the hydroperoxides have begun to decompose into secondary lipid oxidation products

Answer 161

* If too low, there is little reducing power to neutralize the hydroperoxides (a_w = 0.1 - 0.2) * Inreased water activity accelerates oxidation reactions by solubilizing the catalyst, or swelling macromolecules to expose catalytic sites. * If too high, a dilution of the catalyst occurs to retard oxidation (a_w = 0.75 - 0.85)

Answer 162

* Prevents lipid oxidation by reacting with free radicals directly which breaks the chain reaction by either: * Decomposing peroxides (propagation phase) * Complexing with metal catalysts (initiation phase)

Answer 163

Tocopherols (Fat soluble) Citric acid Ascorbic acid (water soluble) Lecithin Phenolic compounds Vitamin A (Fat soluble)

Answer 164

Molecules with one or unpaired electrons Unstable, thus reactive Reactive oxygen species

Answer 165

* Control generation of free radicals * Control availability of lipid oxidation catalysts * Inactivate oxidation intermediates and alter lipid oxidation breakdown products * Change in physical factors (e.g., surface area) * Control exposure to light and oxygen thru packaging

Answer 166

* Control generation of free radicals * Control availability of lipid oxidation catalysts * Inactivate oxidation intermediates and alter lipid oxidation breakdown products * Change in physical factors (e.g., surface area) * Control exposure to light and oxygen thru packaging

Answer 167

* Antioxidants bind to free radicals and form a more stable anti-oxidant radical thus blunting the reaction * Free radical scavengers react mainly with the peroxyl radicals (LOO\*) * Carry-through characteristics (BHA & BHT - food additives/synthetic anti-oxidants) * Regulations for use in foods (do not exceed 0.02%) * Necessary because natural antioxidants cannot survive food thermal processing

Answer 168

They have reducing activity, pro-oxidant sequestering activity, transition metal ion sequestering activity.

Answer 169

**Hydroxyl (OH) containing compounds** * Often phenolic compounds (e.g., BHA, BHT, PG, TBHQ, natural plant phytochemicals). * Non-enzymatic antioxidants: * Tocopherol, ascorbic acid, beta-carotene, carnosic acid, ubiquinone

Answer 170

Beta-carotene is the most effective singlet-oxygen quencher. Tocopherols work less effectively. BHA, BHT, TBHQ are also less effective but are allowed by FDA for use in foods.

Answer 171

Beta-carotene is the most effective singlet-oxygen quencher. Tocopherols work less effectively. BHA, BHT, TBHQ are also less effective but are allowed by FDA for use in foods.

Answer 172

* **Reduction potential** (FRS \> PUFA \< free radical) * FRS will donate the hydrogen to the radical more readily than the PUFA, therefore sparing the PUFA from oxidation. * Hydrophilic FRS are more effective in bulk oils than hydrophobic FRS. * Hydrophobic FRS are more effective in oil-in-water emulsions than hydrophilic FRS because solubility influences the phase partitioning of the FRS in the food system.

Answer 173

Solubility influences the phase partitioning of the FRS in the food system.

Answer 174

False. Hydrophobic FRS are MORE effective in bulk oils than hydrophobic FRS.

Answer 175

False. Hydrophobic FRS are LESS effective in bulk oils than hydrophilic FRS.

Answer 176

1. Control of prooxidant materials 2. Control of singlet oxygen 3. Control of hydrolytic activity (e.g., lipoxygenases)

Answer 177

Transition metals are controlled by metal chelators or proteinaceous compounds (e.g., transferrin)

Answer 178

Inactivated by presence of reactants that contain unsaturated groups, or by physical quenching (e.g., carotenoids)

Answer 179

Lipid oxidation catalysts (e.g., lipoxygenases) are active in plants and some animal tissues. Generates hydroperoxides from C18:2, n-6. Lipoxygenases are indirectly inhibited by phenolics which reduce iron in enzyme active site. Denatured by heat (e.g., blanching).

Answer 180

* Light activated sensitizers (e.g., chlorophyll, riboflavin, and heme-containing proteins) raise electrons to an excited state * Thus, promote oxidation by interacting with oxidizable substrate by transferring energy or excited electrons * _Result_ → produces free radicals or superoxide anion * Inactivated by carotenoids which absorb the energy.

Answer 181

1. Fatty acid oxidation causes a breakdown of secondary lipid oxidation products (e.g., aldehydes that evoke rancidity; e.g., head space volatiles) 2. Lipid oxidation products inactivate enzymes and causes oxymyoglobin oxidation leading to colour changes 3. Generation of these compounds will adversely affect the sensory and nutritional quality of foods.

Answer 182

Sterols/steroid alcohols; synthesized endogenously from the precursor squalene. High molecular weight alcohols which are present in the **un-saponifiable** fraction of lipids Subgroup of steroids with a hydroxyl group in the 3-position of the A-ring.

Answer 183

Phytosterols Sitosterol (corn) Stigmasterol (soybean)

Answer 184

Cholesterol

Answer 185

Originally isolated from ergot, but can be obtained from yeast.

Answer 186

Cholesterol

Answer 187

Sitosterol (corn)

Answer 188

Stigmasterol

Answer 189

* An increase in cholesterol deposition within hepatic cells also results in an increase in the serum LDL-cholesterol, an atherogenic lipoprotein. * Control of hypercholesterolemia is important for the prevention of atherosclerosis and coronary heart disease.

Answer 190

* Reducing sources of dietary cholesterol * Increasing amount of fibre in diet; interferes with bioavailability of dietary cholesterol * Consuming oils high in polyunsaturated fatty acids while reducing the intake of saturated fats * Plant products (e.g., flaxseed, peanuts) also contain cholesterol-like compounds, known as phytosterols, which are suggested to help lower serum cholesterol; compete with animal sterols for biosalts which are required to emulsify biosterols for absorption, which reduces the extent of animal cholesterol

Answer 191

* Cholesterol oxidation products have been identified in several processed foods including dried eggs, meat and dairy products, in fried foods, and heated fats.

Answer 192

Initial products are 7α- and 7β-hydroperoxides.

Answer 193

* Initial products are 7α- and 7β-hydroperoxides. * Decomposition of the hydroperoxides produce the isomeric 7α- and 7β-hydroxycholesterols, cholesterol α- and β-epoxides, and 7-ketocholesterol. * Side-chain derivatization result in production of 20- and 25-hydroxycholesterols. * Cholesterol 3,5-diene, cholesta-3,5-dien-7-one and other ketones arise from elimination reactions.

Answer 194

1. Cholesterol is initiated by a free radical or a trace metal ion to produce a allyl radical. 2. Allyl radical reacts with oxygen to form a peroxyradical. 3. The peroxy radical then further converts to a hydroperoxide. 4. The hydroperoxide is transformed into either the more stable products (alcohol radicals) 7-hydroxycholesterol or 7-ketocholesterol OR it can become an even more cytotoxic isomer called 5,6-epoxide radical (of which we are particularly concerned about for cholesterol oxidation)

Answer 195

Fresh egg yolk has no cholesterol oxides. Under storage conditions cholesterol oxides are generated.

Answer 196

Cholesterol disappears over time at these temperatures. The higher the temperature the faster the disappearance. The disappearance of cholesterol is correlated with the appearance of the oxidized products (not shown in graph).

Answer 197

Peroxide value Anisidine value Thiobarbituric acid test

Answer 198

* Peroxides are the **main initial products** of autooxidation. * Peroxides can be measured by their ability to liberate iodine from potassium iodine (iodimetry) or to oxidize ferrous to ferric ions (thiocynanate method). * The amount of iodine liberated from KI by oxidative action of peroxides present in the oil is determined by titration in a biphasic system with Na₂S₂O_3.

Answer 199

* Most frequently employed method; measures **secondary products.** * Substrate is malondialdehyde (MDA), a major breakdown product of lipid peroxides * MDA derives from beta-cleavage of endocyclization of fatty acids hydroperoxide and reacts with thiobarbituric acid (TBA) to give a pink and fluorescent chromogen that is measured by colorimetry or fluorimetry. * This method lacks specificity for MDA since all compounds with reducing activity will react with TBA. * The TBA test is often useful for comparing samples of a single material at different stages of oxidation.

Answer 200

* The temperature at which an oil gives the first trace of smoke when heated at a specific rate. * A high smoke point is desirable for frying fat. * The smoke point will vary depending on the molecular weight of the fat. * A good frying oil will have a smoke point of 420-450 degrees F.

Answer 201

Frying in hot oil under very high temperatures; thermal lipid oxidation is assured. During frying, the sensory and nutritional quality of the frying oil change. The increased temperature increases the solubility of oxygen; thus, making greater access between the oxygen and the lipid component. In addition there are dynamic changes with water with release from the food sample and the dehydration associated with this; hydrolysis increases susceptibility to lipid oxidation

Answer 202

During deep fat frying, oxygen is introduced into the oil as the food enters the hot oil causing oxidation. Oxidation products include hydroperoxides, aldehydes, ketones, acids, hydrocarbons, and polymeric compounds.

Answer 203

Moisture is released from the frying food into the frying oil and the food absorbs the oil. As the food absorbs the frying fat, the food lipids and pigments are solubilized and released into the frying oil.

Answer 204

* Excessive heat and presence of moisture in the frying oil results in hydrolysis of triglycerides yielding free fatty acids, glycerol, mono- and di-glycerides. * The volatile degradation products are released from the oil with the steam as smoke.

Answer 205

* Occurs with prolonged and high temperature frying. * Leads to formation of **Diels-Alder** reactions that include the formation of polymers as the reaction products condense. * Products include dimers and cyclic compounds * Polymerization leads to changes in molecular weight, viscosity, and heat-transfer efficiency of the oil.

Answer 206

* Occurs with prolonged and high temperature frying. * Includes the formation of polymers as the reaction products condense * Products include dimers and cyclic compounds. * Leads to changes in molecular weight, viscosity, and heat-transfer efficiency of the oil.

Answer 207

**1) Temperature and frying time** Optimal is 150 to 180˚C (300 – 350˚F) **2) Fryer type** _Batch_: a space in which a product is lowered into the oil, e.g. french fries. (greater access to air) _Continuous_: a conveyor belt transports the product through the cooking oil bath, e.g. doughnuts (can minimize uptake of oxidation products into food product by reducing contact time) **3) Source of oil** _Chemistry_: with frying, fatty acid content increases, iodine value decreases, and refractive index changes. _Physical_: viscosity changes, development of darker colour, decrease in surface tension, and increase tendency to foam. **4) Source of food** _Properties_: release of lipids into frying oil. Bidirectional transfer of free fatty acids will influence the susceptibility of thermal oxidation of the oil. _Chemical_: presence of the food contributes to Maillard reaction.

Answer 208

Processing is required to remove substances such as fatty acids, phospholipids, carbohydrates, proteins, degraded products, water pigments (carotenoids and chlorophyll), as well as other lipid oxidation products. Removal prevents from undesirable flavour, colour, and keeps quality of lipid source intact.

Answer 209

Settling and degumming Neutralization Bleaching Deodorization

Answer 210

Removal of high-molecular weight hydrocarbons during refining of vegetable oils

Answer 211

**Crude oil** (flax, sunflower, soybean etc.); oil systems with at least 8-10% oil content → **degumming** (involves removing components that would otherwise interfere with further processing such as lecithin or phytosterols) → **neutralization** (removal of free fatty acids associated with soap stock, a product of the previous reactions) → **washing & drying** → **winterisation** (specific lower temperatures to induce crystallization of the lipids in order to remove high molecular weight hydrocarbons like waxes; thus, providing a better textural oil) → **bleaching** (remove pigments that can bring about photooxidation) → **deodorisation** (bleaching step must be deodorised using steam; produces a fatty acid distillates; natural tocopherols are lost and must be added back, that is, fortified in order to provide some stability after the process) → **refined oil**

Answer 212

Involves the addition of hydrogen to double bonds in the fatty acid chains. It is commercially used for the production of margarine, salad oils, shortening and cooking fats.

Answer 213

1. To allow conversion of liquid oils into semisolid or plastic fats more suitable for specific applications 2. To improve the oxidative stability of the oil.

Answer 214

1. Oil, hydrogen gas and nickel catalyst are mixed together in a reactor. 2. The starting oil must be refined, bleached, low in soap, and dry. 3. The hydrogen gas must be dry and free of sulfur, CO₂, or ammonia.

Answer 215

* The oil is first mixed with the catalyst. * Heat to 140-225 degrees C. * Expose to hydrogen gas under pressure of 60psi. * Mixture is agitated to enhance the dissolving of hydrogen to uniform catalyst with the oil and to help dissipate the heat of the reaction. * Selectivity refers to the rate of hydrogenation of the more unsaturated fatty acids as compared with that of less unsaturated acids. (e.g., linolenic acid compared to linoleic)

Answer 216

Trans fat formation Governments have regulations that do not allow foods that are high in trans fatty acids to carry claims for low in saturated fatty acids. Information on trans fatty acids in nutritional information label should be included.

Answer 217

* To create fats with no trans fatty acids but with improved functionality. * The physical characteristics of a fat are affected not only by the nature of the constituents fatty acids (e.g., chain length and unsaturation) but also their distribution in the triglycerol molecules * Interesterification involves rearranging the fatty acids so they become distributed randomly among the triglycerol molecule.

Answer 218

* Accomplished by heating fat at relatively high temperatures (\<200degreesC) for long periods. * Catalysts are used to allow the reaction to be completed in shorter times (e.g., 30 mins) and at lower temperatures (as low as 50degrees C) * The process results in the shuffling of fatty acids within a single molecule and among triacylglyceride molecules until an equilibrium is achieved in which all possible combinations are formed. * After esterification, the catalyst is inactivated by addition of water, or acid, and products are removed.

Answer 219

* Restructuration of desirable lipids that meet essential fatty acid dietary requirements (achieved by temperature control; done automatically based on the fact that different chain lengths and degree of unsaturation changes the recrystallization temperature) * Production of new medium chain triglycerides for specific purposes (e.g., lower caloric density) * Its greatest application is the manufacture of shortenings * Salad oils, high-stability margarine blends, hard butter * Reduction of the content of linolenic acid (C18:3 an EFA) in soybean oil, which is responsible for bitterness in soybean oil

Answer 220

Iodine value/number Ultraviolet (UV) spectrophotometry Chromatographic methods

Answer 221

Peroxide value (PV) Ultraviolet (UV) spectrophotometry Chromatographic methods

Answer 222

Anisidine value Thiobarbituric acid (TBA) test Total and volatile carbonyl compounds Fluorescence Rancimat method Sensory evaluation Chromatographic methods

Answer 223

Active oxygen method

Answer 224

Aka P-Anisidine value (PAV) Measures aldehyde & ketone levels in oil or fat (especially sensitive to unsaturated) Aldehyde/ketone + P-anisidine → schiff bases (yellow; absorb @350nm)

Answer 225

TBA-reactive substances. TBA test lacks specificity for MDA since all compounds with reducing activity will react with TBA. TBARS react with TBA.

Answer 226

False. Citric acid is used as both an acidulant _and_ a metal-chelating agent to prevent oxidation reactions.

Answer 227

We use the HLB (hydrophobi-lipophile balance) expression.

Answer 228

* a numerical expression for relative simultaneous attraction of emulsifier for water or oil * an indication on how an emulsifier will behave but _not_ how effective it is

Answer 229

1. A weak acid and a salt of the acid's conjugate base 2. A weak base and a salt of the base's conjugate acid

Answer 230

False. Citrates are preferred over phosphates for tartness modification since they yield smoother sour flavours.

Answer 231

Sodium salts of gluconic, acetic, and phosphoric acids.

Answer 232

1. Buffering 2. Preservation 3. Flavour enhancement 4. Leavening

Answer 233

Evoke tartness Each acid has varying degrees of acidity.

Answer 234

Logarithm of the concentration of free protons, expressed with a positive sign.

Answer 235

Proton equivalence (# of protons or hydrogen ions that the organic acids would contain if they were undissociated)

Answer 236

protons recovered during a titration with a strong base to a specific endpoint Not synonymous with total acidity Easier to measure than total acidity. Titratable acidity \< Total acidity

Answer 237

False. Titratable acidity \< total acidity

Answer 238

False. Titratable acidity is easier to measure.

Answer 239

We measure titratable acidity to give an idea about the potential of the acidulant to function during changes in buffering capacity of the food system.

Answer 240

* pH measures only those protons that are free in solution and not associated with salts or proteins, so it is a better process control tool (e.g., important for quality parameters such as microbial control, sour taste, and protein functionality (the pH will influence moisture, mineral contents, texture, and flavour) * TA measures both free protons and those associated with organic acids and proteins. * Example → the pH of fresh milk ranges between 6.6-6.8, which gives a true indication of the acid development. The TA will vary with initial milk composition, milk heat treatments, and the procedure used to standardizew milk composition (e.g., if you remove protein, like whey, you change the buffer capacity of milk, thus TA changes)

Answer 241

A low pH results in: * Saturation of cell walls with hydrogen ions, thus limiting cation transfer in microbes. * Penetration of cell wall by hydrogen and changes in intracellular pH and enzyme function

Answer 242

Fumaric acid Succinic acid Malic acid Tartaric acid Citric acid

Answer 243

2 pK values Used to preserve shelf-life of dehydrated food products. Used with benzoic acids.

Answer 244

2 pK values Derived from fumaric acid; used in dough making; has use as an emulsifier as well (monoester with glycerol)

Answer 245

2 pK values Used as a monoester with fatty alcohols in frying fats and oils

Answer 246

2 pK values Has a hard taste; utilized in fruit juices and sour candies.

Answer 247

3 pK values Utilized in fruit juice, ice cream, jelly, vegetable canning and milk. Suppresses enzymatic browning as it is a synergist to antioxidants.

Answer 248

Citric → lemon, lime Malic → apple Oxalic → rhubarb Acetic → vinegar Lactic → sour milk Carbonic → soft drink

Answer 249

Citric → lemon, lime Malic → apple Oxalic → rhubarb Acetic → vinegar Lactic → sour milk Carbonic → soft drink

Answer 250

Dual effect Citric acid: pK₁ = 3.09; pK₂ = 4.74; pK₃ = 5.41 * suppresses enzymatic browning * Synergistic activity with antioxidants.

Answer 251

Citric acid predominates in the most protonated form (citric acid)

Answer 252

The citric acid will lose all its protons and occur predominantly in the citrate^-3 form.

Answer 253

To determine the dominant form of an acid at any pH. pH=pKa+log[A-]/[HA]

Answer 254

Chelating agents/ligands that either precipitate the metal or suppress its reactivity. May be organic (e.g., citric acid, tartaric acid, sorbitol (i.e., long chain alcohols)) or inorganic (e.g., phosphates).

Answer 255

M: metal ion L: ligand ML: metal-ligand complex k = stability of complex

Answer 256

They are effective catalysts of oxidation reactions that lead to rancidity, discolouration, and undesirable textural changes in food.

Answer 257

Iron Copper Aluminum

Answer 258

Iron participates in the Haber-Weiss cycle in which ferrous ion reduces oxygen to superoxide anion (O^-2). The resulting products are H₂O₂ and O₂ (these feed into the Fenton reaction) This is a bidirectional reaction.

Answer 259

The combination of ferrous ion with hydrogen peroxide (H₂O₂). The Fenton reaction produces highly reactive hydroxyl radical which oxidizes most food constituents.

Answer 260

Ethylenediamine tetraacetic acid Very strong capacity to sequester iron. It has 6 possible coordination interactions (3 on each side of the molecule) This may be sufficient to sequester copper, but it's not 100% effective for iron.

Answer 261

False. EDTA has the capacity to interact with 6 coordination sites. Effective at sequestering many ions. It's not 100% effective when it comes to iron. Iron is chelated to EDTA, but iron has 7 coordination sites, so 1 is not occupied by the EDTA. Thus, the 7th site (i.e., aquasite) is open for reactions. So EDTA is not 100% effective although it will significantly suppress the Haber-Weiss cycle and Fenton reaction. The 7th site left open is particularly reactive since it is more soluble.

Answer 262

* Iron chelated to EDTA has seven coordination sites, one of which is occupied by water, and therefore available for reduction-oxidation reactions. * The high solubility of Fe³⁺-EDTA and the free coordination sites promote oxidative damage by increasing both the solubility and oxidation-reduction potential of iron.

Answer 263

False! Ascorbate **enhances** the uptake of ferrous iron in humans and animals, attributable to the chelation and reducing power of ascorbate.

Answer 264

Ascorbate is a strong reducing agent (Fe³⁺ → Fe²⁺), that contributes to the Haber-Weiss cycle and the Fenton reaction in producing hydroxyl radical. Thus, at low concentrations ascorbate can act as a prooxidant. At high concentrations, ascorbate will act as an antioxidant because there is sufficient ascorbate to sequester the hydroxyl radical that is produced from the Fenton reaction.

Answer 265

1. Free radical terminators (chain breakers) → involves propagation (scavenge the hydroxy-radical with tocopherol) 2. Reducing agents → reduce radicals and regenerate the lipid antioxidants which act as hydrocarbons 3. Oxygen scavengers → beta-carotene is very good at scavenging superoxide ion 4. Chelating agents → ties up free metal ions that can initiate lipid oxidation.

Answer 266

* A substance used to preserve food by retarding deterioration, rancidity, or discolouration due to oxidation reactions. * Antioxidants slow down the effects of oxidation and preserve the nutritional and organoleptic qualities of the food product.

Answer 267

Mitigate the free-radical chain reaction (e.g., vitamin E) * Retard the free-radical chain reaction by donating hydrogen from their phenolic hydroxyl group. * These antioxidants are: * More easily oxidized than other substances * Once oxidized they are relatively stable

Answer 268

* Butylated hydroxyanisol (BHA) * Butylated hydroxytoluene (BHT) → BHT and BHA often used together due to synergistic effects * Tertiary butylhydroxyquinone (TBHQ) → most effective synthetic antioxidant often used in preventing oxidation of frying oils * Propyl gallate (effectiveness decreases at higher temperatures) * Vitamin E (tocopherols) * Carotenoids (Beta-carotene)

Answer 269

They function by transferring hydrogen atoms to radicals.

Answer 270

* Ascorbyl palmitate * Sulfites * Ascorbic acid * Glucose oxidase * Erythrobic acid

Answer 271

False. They are not true antioxidants, but they are usually used in combination with true antioxidants.

Answer 272

Citric acid EDTA Phosphates

Answer 273

The unshared pair of electrons in their molecular structure promotes the chelating/sequestering effect with the ions.

Answer 274

* An example of a dispersed system, usually characterized by 2-immiscible liquids. Other forms include foams, aerosols, and suspensions. * Consist of an outer phase (continuous) and an inner (dispersed) phase.

Answer 275

When the outer phase is water (and inner is oil), we refer to it as an oil in water (o/w) type emulsion. e.g., mayonnaise, ice cream (milk)

Answer 276

When the outer phase is oil (and inner is water), we refer to it as a water in oil (w/o) type emulsion. e.g., salad dressing, margarine

Answer 277

Droplet diameter ## Footnote e.g. 1micrometer or greater = milky-turbid…. When the diameter is very, very small, such as close to light wavelength (10-5 cm) it is optically clear & micro/nano emulsion

Answer 278

Results in the breaking of an emulsion.

Answer 279

1. Chemical structure of lipids 2. Oxygen concentration 3. Antioxidants 4. Interfacial characteristics 5. Droplet characteristics 6. Aqueous phase components 7. Ingredient quality

Answer 280

Agents that can decrease the surface tension at the interface of two immiscible phases (e.g., w/o or o/w) Amphiphilic nature of these molecules are responsible for their characteristic surface active properties.

Answer 281

Esters of fatty acids; mono- & di-glycerides.

Answer 282

Ionic (proteins, phospholipids like lecithin)

Answer 283

Ionic (stearyl-2-lactylate) Non-ionic (mono/di-acylglycerols; with esters (citric, lactic, tartaric; sorbitol; saccharose fatty acid esters)

Answer 284

* Indicates the kind of emulsion for which the emulsifier is best suited * Emulsifiers with low HLB values tend to be oil soluble and are used to prepare w/o emulsions. * High HLB values shows a water-soluble emulsifier and then will be effective in preparing o/w emulsions

Answer 285

* Method to select emulsifier * Useful in relating the complex temperature-dependent phase behaviour of emulsifiers * As the temperature increases, non-ionic emulsifiers change from being preferentially water soluble to oil soluble.

Answer 286

W/O * Monoglycerides, diglycerides, and lecithin * Water droplets coated with emulsifiers are important for minimizing the potential of microbial contamination and improving stability during storage. * All emulsifiers improve the consistency and creaming properties of the margarine.

Answer 287

By reducing interfacial tension between the oil and water phases when combined.

Answer 288

False! Most food systems exhibiting creaminess characteristics are o/w emulsions

Answer 289

Uniform Smooth Creamy

Answer 290

Plays a significant role in perception of creaminess

Answer 291

A logarithmic increase in viscosity.

Answer 292

* Emulsifiers extend the shelf life or strengthen the dough by forming water insoluble inclusion complexes with the amylose fraction of starch * Complexes retard starch recrystallization/retrogradation * Emulsifiers interact with the proteins of yeast-raised wheat dough, shows better retention of carbon dioxide produced during leavening; hence giving a product increased volume and finer texture.

Answer 293

* Emulsifiers function as aerating agents, speeding up the whipping rate of batter, providing a finer distribution of air cells and improving the tenderness of the cake by retarding starch gelatinization.

Answer 294

False. O/W emulsions, in contrast to bulk oils, are better protected from oxidation by nonpolar antioxidants than polar ones.

Answer 295

The paradoxical behaviour of antioxidants in different media.

Answer 296

Greater affinity for the oil-water interface

Answer 297

At the oil-water interface forming a protective membrane around the lipid droplet

Answer 298

In less polar media (e.g., bulk oils)

Answer 299

In polar media (e.g., O/W emulsions)

Answer 300

* Oil/air interface → the site where oxidation is initiated and propagated to the inner parts of the oil * Partially fat soluble, polar antioxidants orient themselves at the oil-air interface where surface oxidation occurs. * BUT: bulk oil contains micro-nano-water environments from atmospheric moisture * Hence, evidence supports the hypothesis that the association of colloids are the site of lipid oxidation in bulk oils * Polar antioxidants are preferentially located at the interface of the colloid (e.g., the oil-water interface) * Non-polar antioxidants are dissolved in the lipid phase.

Answer 301

* A heterogenous system (emulsified matrix in foods) * O/W → lipid droplets; continuous aqueous phase and the O/W interface * Pro/Anti-oxidants partition into these 3 phases depend on solubility and surface activity (structure and polarity) * Nonpolar antioxidants have a higher capacity in O/W due to greater affinity for the oil-water interface * Nonpolar antioxidants concentrate in the O/W interface, forming a protective membrane around the lipid droplet, while polar antioxidants are dissolved in the aqueous phase. * Free radicals are scavenged by the lipophilic antioxidants at the interface before they cross the droplet membrane and enter the lipid phase * Lipophilic antioxidants (e.g., BHA, Toc-isomers) are most effective in O/W emulsion

Answer 302

* Influences activity in multiphase media due to: * Prevent or retard initiation (sequester, quench initiators) → polar antioxidants inhibit initiation of oxidation at interface more ffectively than nonpolar antioxidants in the lipid phase * Breaking propagation chain → non polar antioxidants chain-breaking more efficient to inhibit propagation of oxidation in the lipid phase (where nonpolar oxygen molecules are preferentially dissolved)

Answer 303

Effects the polarity-effectiveness relationship and the polar paradox may only be effective over certain concentration ranges. Interfacial phenomenon dominates over the solubility issue.

Answer 304

Mobility of the antioxidant in the multiphase system is an issue. Bulky structures (e.g., long alkyl chains) have low mobility due to steric hindrance. Mobility equates with diffusibility

Answer 305

Oxygen is 3 times more soluble in oils than water. Rate of diffusion of oxygen through the aqueous phase is a rate-limiting step at low oxygen concentration. High oxygen concentration → rate of diffusion through aqueous phase is very fast.

Answer 306

Polarity → nonpolar antioxidants reside in the oil droplet or at the oil-water interface; readily interact with hydroperoxides. Electrical charge → dependent on pH and charge of the surfactant; ionizable groups may alter affinity for interface

Answer 307

Metal chelators are most important (they prevent metal redox cycling, form insoluble metal complexes; occupy metal coordination sites; give steric hindrance between metals and lipids)

Answer 308

* Concentration of oil droplets in emulsion increases → more lipids are oxidized * Size → the rate of oxidation increases as the size of oil droplets decreases * Physical state → rate of lipid oxidation is slow when the fat is crystalline versus fluid.

Answer 309

False. The rate of lipid oxidation increases as the size of the oil droplets decrease.

Answer 310

False. The rate of lipid oxidation is slower when the fat is crystalline versus fluid.

Answer 311

Synthetic → BHA, BHT (highly effective in controlling lipid oxidation) Natural → high price, tastes and colours limited their utilization in the industry

Answer 312

Chelators → chelating irons to retard lipid oxidation, however it can also have counter effect.

Answer 313

True. Use ingredients that have low transition metal concentration, or add substances that chelate and inactivate the transition metals.

Answer 314

Addition of primary / secondary antioxidants.

Answer 315

Addition of primary / secondary antioxidants.

Answer 316

* A food colourant improves food acceptability by increasing attractiveness * Colour has an indirect effect on nutritional perception. * Consumers perceive a richly coloured food to be more nutritious and flavourful.

Answer 317

* Used since 1856 * Few are FDA approved * Associated with negative connotation * E.g., FD&C blue No. 1; FD&C red No. 40, FD&C Yellow No. 5.

Answer 318

* Used since antiquity * Preferred by consumers * Patented * E.g., Annato (orange-red), saffron (orange, yellows), paprika (orange), anthocyanins (blues, purples), carotenoids (reds), curcumin (yellows, oranges)

Answer 319

* Anthocyanins are natural water-soluble pigments responsible for the attractive red, purple, and blue colours of many flowers, fruits and vegetables. * e.g., grapes, berries, red cabbage, apples, and wine. * Sensitive to pH change, being reddest in strongly acidic conditions and become more blue as the pH rises * *Enter → acidulants*

Answer 320

False. Anthocyanins are reddest in strongly acidic conditions and become more blue as pH rises.

Answer 321

* Stability → react with ascorbic acid, metals, sugars, oxygen, light, and enzymes; results in production of polymers and degradation products * Sensitivity to pH → decolorize at values above 4; limits their use as colourants in neutral and basic food systems.

Answer 322

Fumaric \> Tartartic \> Malic \> Acetic \> Citric \> Lactic FTMACL (Featuring macklemore)

Answer 323

The large surface area that facilitates interactions between lipids and water soluble prooxidants.

Final Exam Material Flashcards

(446 cards)