Fats and oils + Overview of Proteins

Question 1

The two key components of simple fats

Answer 1

glycerol and fatty acids linked to form an ester
glycerol has three hydroxyls that can esterify with fatty acids
fatty acids have a carboxyl group (-COOH)

Question 2

chemical structure of fat

Answer 2

organic compounds made up of with carbon, oxygen and hydrogen
very little oxygen is present; has more hydrogens than carbs why they have 9kcal/g

Question 3

saturated fatty acids vs mono- and polyunsaturated fatty acids

Answer 3

saturated-Fatty acids containing all of the hydrogen atoms they can possibly hold.

Mono- and polyunsaturated fatty acids- Fatty acids with one (mono) or two or more double bonds (polyunsaturated).

Question 4

Palmitic acid most ____fatty acid
oleic acid most_____fatty acid
linoleic acid is an
alpha linoleic acid is an
Conjugated linoleic acid is

Answer 4

most abundant saturated fatty acid in foods – 16:0.
 Oleic acid most abundant monounsaturated fatty acid in foods
 Linoleic acid is an omega 6 fatty acid
 Alpha-linolenic acid is an omega 3 fatty acid
 Precursor for eicosapentanoic acid (EPA) – 20:5(n-3) and docosahexanoic acid (DHA)
– 22:6(n-3).
 Conjugated linoleic acid (CLA) is a fatty acid with a cis and trans double
bond on alternate carbons. –

Question 5

How does chain length affect fatty acid melting point?
Which type of fatty acid has higher melting point?
The more _____ the lower the melting point.
what configuration at double bonds has a lower melting point?

Answer 5

Short-chain fatty acids have lower melting points than do long-chain fatty acids.Long-chain fatty acids are more likely to be solid at mixing temperatures than short-chain fatty acids.

saturated fatty acids
double bonds to the higher the degree of unsaturation
cis form

Question 6

Difference between mono-, di-, and triacyl- glycerides

Answer 6

depends on the amount of fatty acids esterified to a glycerol molecule

Question 7

Solid fats at refrigerator and room temperatures appearing to be a solid mass are actually

Answer 7

a mixture of crystals of fat in oil

Question 8

Describe the types of fat crystals and their properties

Answer 8

alpha, beta prime, intermediate, and beta
Alpha crystals are very fine and extremely unstable, melt quickly and recrystallize into beta prime
Beta prime form extremely smooth fat like margarine and vegetable shortening. more stable than alpha. Most desirable form for baking with solid fats. Aid in fine texture
Intermediate cystals make fat look grainy, not reccomeded for use. These form when beta prime melt gradually then recrystallize.
Coarsest form is beta which is also extremely stable. Form when fat melts completely then recrystallizes without being disturbed

Question 9

What is important to control crystal size in solid fats

Answer 9

The β′ crystals are the desired crystals. During commercial production of shortenings, agitation during cooling is the key to achieving the necessary control of crystal formation.
Storage at cool temperatures is also important so quality is not altered

Question 10

What is rancidity

Answer 10

chemical deterioration of fat quality by either oxidative or hydrolytic chemical reactions

Question 11

Oxidative rancidity

Answer 11

involves the uptake of oxygen at a double bond in an unsaturated fatty acid in a fat facilitated by presence of certain metals and by light and/or warm temperatures.

begins when a free radical (unstable w/ unpaired electrons) forms then combines with two oxygen atoms to form a peroxide(O2-O2) then one hydrogen is removed from another unsaturated fatty acid to form hydroperoxide. New free radicals are formed when hydrogen is removed from second fatty acid then a second peroxide and another hydroperoxide this is AUTOCATALYTIC

-INDUCTION/INITIATION PERIOD: early phase when oxygen uptake begins and fatty
acid radical is produce.
-PROPAGATION PERIOD: chain reactions,
acceleration of oxidation phase
ANTIOXIDANTs can provide hydrogen to
block formation of free radicals in
fatty acids or by scavenging metal or
oxygen.

Question 12

Hydrolytic rancidity

Answer 12

Free fatty acids are split from the glycerol in fat molecules, LIPOLYSIS
The uptake of a molecule of water usually is promoted either by the action of LIPASE OR BY HEAT.
A TRIGLYCERIDE MOLECULE undergoes lipolysis to yield three free fatty acid—
and one glycerol molecule.

The free fatty acids may seriously alter aroma & flavor of a fat or oil in which lipolysis has occurred.

Question 13

Reversion

Answer 13

oxidation of some of the linoleic and linolenic acids in oils
results in development of off odors and off flavors
Flavors that develop as a result of reversion are often described as “fishy” or “beany.”
most prominent in soybean oil, but rapeseed oil and various fish oils also are very susceptible to reversion

Question 14

Why do fats and oils begin to degrade at extremely high temperatures?
Temperature for such reaction is usually______
the smoke point of fat is _____
Explain the reaction that occurs for fat to smoke.
How does continuous use of fat affect smoke point?

Answer 14

eventually there is so much
energy, the molecules will begin to degrade and smoke will appear

The temperature for such reactions
is usually 190°C (374°F) or higher. lypolysis occurs at this temp. All fatty acids are removed from glycerol

The smoke point of a fat is not
a specific temperature.
Continuous heating removes two water molecules from glycerol forming acrolein (aldehyde)
acrolein is vaporized causing fat to smoke
As a fat is used at high temperature over time, its smoke point will drop

Question 15

Explain the process of polymerization

Answer 15

The free fatty acids formed as a result of lipolysis follow quite a different course from that of the changes in glycerol. Instead, these free fatty acids undergo additional chemical modification as they continue to be held at frying temperature
Fatty acids containing AT LEAST ONE DOUBLE BOND are particularly susceptible to polymerization(formation of a variety of polymers)
DIMERS AND TIMERS evolve from the free fatty acids
Increased viscosity and darkening of color of fat during extended use is indicates loss of quality.

Question 16

What is acrylamide

Answer 16

a monomer formed in foods containing starch, some sugar, and asparagine when they are cooked at high temperatures.

Potatoes, coffee, cakes and biscuits, bread and toast, chips and French fries not only contain starch, natural sugars, and some proteins (specifically, the amino acid aspar- agine), but they usually are fried or baked at high temperatures [at least 163oC (325oF) and often much hotter], which create some acrylamide. The more browning of a food the more acrylamide

Question 17

Sources of oils and fats

Answer 17

Oils in food preparation may be produced from various plant
sources:
 Cotton, corn, safflower, soy, sesame, and grape seeds.
 Walnuts, hazelnuts, peanuts.
 Olives and avocados.

Animal sources of fats are obtained from
dairy cattle(butter and cream), cattle (tallow) & swine (lard).

Question 17

Steps in manufacturing food fats

Answer 17

Extraction , refining, fractionation, crystallization

Question 18

Explain the extraction process

Answer 18

First step in the manufacturing food fats
is to remove lipids from their natural food
sources.
-The process used for lard from swine and tallow from cattle is RENDERING.
-WET RENDERING, the more common technique for preparing edible fats, uses steam under pressure to heat the tissues and fat to at least 90oC (195oF). The hot, fluid fats are separated from the water. Antioxidants frequently are added to retard the development of rancidity.
- DRY RENDERING is done by simply heating the tissues and collecting the melted fat as it drains and is finally squeezed from the residue.
-Oils are removed from plants by APPLYING PRESSURE with or without adding heat.
A mechanical or screw-type press
can be used to express oils from
appropriate seeds or plant tissue.
-The procedure is termed COLD PRESSING
-In HOT PRESSING, steam is used to warm the tissues to about 70°C (158°F), and then they are pressed to remove the oil
-Another extraction technique involves the application of CARBON DIOXIDE at pressures as high as 8,000 psi at warm temperatures [at least 31°C (88°F)].

Question 19

Explain refining processes

Answer 19

Undesirable constituents may occur in fats after extraction, particularly if rendering was done. Gums, lipoproteins, lecithin, ketones, and aldehydes are just some of the compounds that may appear in fats at this stage of manufacturing.
DEGUMMING AND NEUTRALIZING procedures can remove gums and free fatty acids.
BLEACHING removes undesirable coloring and flavoring contaminants.
DEODORIZING by steam distillation is important in producing high-quality coconut & palm kernel oils. Olive oil is not deodorized.
WINTERIZING removes fractions with melting points high enough to solidify at refrigerator temperatures.
-A very important difference is the significantly lower smoke
point of unrefined oils.

Question 20

Explain Fractionation

Answer 20

Palm oil can be separated into fractions with different physical properties and varying ratios of fatty acids by fractionation.
Fats can be separated by careful temperature control and
removal of the fat crystals that formThe oils left behind have lower melting points. The crystalline fat can be blended with the amount of oil needed to create fats with the desired physical properties. This oil also has the advantage of being free of or low in trans fats because the oil was not hydrogenated.

Question 21

Explain crystallization of fat

Answer 21

careful control of temperature during cooling, combined with an appropriate amount of agitation, helps achieve a smooth fat, with β′ crystals being the predominant crystal size.

To make special fats for confectionery use, fats are tempered to yield a
mixture of crystal shapes. POLYMORPHS.
TEMPERING IS a process in which temperature is carefully controlled by removing the heat as it is released when liquid fats crystallize (the heat of crystallization). the fat is held at a specified temperature for the time required for the crystals to form and to stabilize in the favored crystal form.

Tempered fats can be STORED WITH some variations in temperature, and
still retain textural qualities.
 Sometimes varying more than 25°C (78°F).

Question 22

How are fats modified?
catalysts, reactions, benefits, disadvantages

Answer 22

Hydrogenation- alters the melting point of fatty acids by increasing their saturation with hydrogen
a CATALYST USUALLY nickel is present with HYDROGEN and oil in a heat controlled environment . Hydrogen atoms react
with UNSATURATED fatty acids at the points
of unsaturation
by hydrogenation, vegetable oils can be modified from LIQUIDS TO SOLIDS
 Used for margarines, shortenings, and peanut butter
One undesirable result of the hydrogenation process is that some unsaturated fatty acids undergo ISOMERIZATION, resulting in the formation of some double bonds in the trans configuration, rather than the cis form commonly found in nature. this increases LDL and risk of heart disease

Inter- and inta-esterification
Metal salts and/or lipases can be used to remove fatty acids from glycerol. The catalyst is usually sodium methoxide
This technique results in the formation of fats with altered characteristics, such as a HIGHER MELTING POINT OR a difference in crystallization tendencies. However, no trans fatty acids are created.
Fatty acids removed from glycerol have the potential to recombine—in
different positions. This process is called intraesterification. Also alters textural characteristics of by modifying the ease of
crystallization and crystal aggregation.

Question 23

technique for enhancing the levels of certain fatty acids.

Answer 23

-Selective plant breeding
-genetic engineering, which involves modification of genetic information in cells.

Question 24

Criteria for labeling margarine reduced-fat, light/lower fat, and fat free

Answer 24

Reduced-fat or reduced-calorie diet margarine  No more than 60% oil; 25% calorie reduction Light/lower fat margarine  No more than 40% oil; 50% or more calorie reduction Fat free margarine  Less than 0.5 g per serving

Question 25

_______have emerged as effective compounds in alternative spreads.

Answer 25

Stanol and sterol esters

Question 26

Shortenings and lard are solids with high ______. Fat molecules of lard have spatial configurations that associate readily into __________. Giving a somewhat _____ texture The focus of shortening manufacturing has been _________to reduce ____ Flakes of_____are added to some shortenings to help ensure that it will have fine, β′ crystals.

Answer 26

plasticity.(Ability to be spread or whipped to a heavy fat foam) crystalline aggregates; grainy hydrogenation of vegetable oils; trans fat and achieve desired consistency tallow

Question 27

what is shortening power

Answer 27

The ability of a lipid to accomplish tenderizing action

Question 28

Because of their content of _______, oils have _____shortening power. Plastic fats have much ____ shortening ability than those that are hard and difficult to spread. Hard fats are high in _________, have _____ melting points and ______shortening power.  Restricts their movement; limits ability to coat gluten.

Answer 28

unsaturated fatty acids; great more saturated fatty acids; high; moderate

Question 29

What are the functional roles of fat

Answer 29

color, flavor, texture, tenderness, emulsification, cooking medium

Question 30

Shortened cakes are made with a _____ fat incorporated as a heavy foam.The result of creaming the fat & sugar together.  A stable emulsion helps promote the _____cell size desired in shortened cakes. Broken emulsions should be avoided in cake batters.  Lard tends to _____ as it is creamed into a batter, due to its _______ This quality is better suited to pastries than cakes.

Answer 30

solid fine clump; unique crystallinity.

Question 31

When fat melts & flows during baking, steam in the holes it leaves pushes upward against the cell.  Gluten in the pastry is _______ during baking, and the cell is locked into the extended position. ____properties of oil interfere with formation of the cell pockets needed for flakiness.  Quick breads and most yeast breads contain ____, or ____, to obtain maximum tenderizing.  Biscuits utilize______that can be cut into pieces in a fashion similar to the preparation of pastry.

Answer 31

denatured Flow oil or melted fat a hard fat

Question 32

Shortenings are made with _____ and ___ so fat and milk in cake batters are emulsified. Resulting in a fine-textured cake.Orientation of monoglyceride and lecithin molecules at the interface between oil droplets & water provide a protective layer that stabilizes the emulsion by interfering with the union of oil droplets.

Answer 32

mono- and diglycerides

Question 33

Fats & oils are used for a cooking medium because they can be heated above the boiling point of water.  Shortenings are not well suited to frying. Due to added _____ and _____  Oils are lipid usually selected for frying foods, Except olive oil—due to its low smoke point. Loss of water from the food into the hot oil helps avoid burning on the surface of the food.  The water carries ______ energy from the surface A frying temperature of at least____ and _____ is important. Minimizes fat absorption during frying.  The key to frying is to heat the fat to the correct temperature before adding food. Cooking only a small amount of food at a time.

Answer 33

mono- and diglycerides. thermal 175°C (347°F) and preferably 190–195°C (374–383°F)

Question 34

What are proteins

Answer 34

large molecules composed of 100 or more amino acid residues linked together by peptide bonds amino acids contain an amino group and a carboxyl group a peptide linkage is a covalent bond between the nitrogen of one amino acid and the carbon the carboxyl group of another. molecule of water is eliminated in this reaction

Question 35

different structures of protein

Answer 35

primary- chain of amino acids linked by peptide bonds when primary structure is coiled an alpha helix forms by hydrogen bonds- secondary structure the secondary structure is convoluted and folded into various shapes -tertiary structure two or more peptide chains held tightly in quaternary structure- hemoglobin

Question 36

food proteins with highly hydrophobic nature forcing the molecule into a _____ turn which changes direction every ____ amino acid residue

Answer 36

beta turn fourth amino acid residue

Question 37

what are hydrophobic interactions what amino acids are hydrophobic

Answer 37

important for the shape of proteins methionine, tyrosine, tryptophan, leucine, isoleucine, valine, alanine causes protein molecule to be drawn together facilitating formation of hydrogen bonds

Question 38

What are the general categories of proteins in food

Answer 38

globular, fibrous, conjugated globular proteins- all enzymes, some hormones, and oxygen transporting proteins conjugated proteins are proteins joined with another substance- lipoproteins and glycoproteins fibrous proteins are insoluble collagen and elastin Mucoproteins- contain a carbohydrate moiety combined with protein aka glycoproteins Lipoprotein - composed of protein and lipid Metalloproteins- myoglobin and hemoglobin are itron-containing Phosphoproteins- include the casein in milk

Question 39

Some individual amino acid residues in a protein have the potential to be charged electrically in opposite ways, depending on the pH of the medium in which the protein is found.When the number of positive and negative charges on a protein is equal, the protein is at its __________.In a solution that is more acidic than the isoelectric point, the – COO- accepts an H+, and the overall charge is _______  In a solution that is more basic than the isoelectric point, the – NH3+ group will loose H+, and the overall charge will be ________.

Answer 39

isoelectric point positive. negative.

Question 40

A protein’s minimum solubility occurs at the __________. At pH values below the isoelectric point (______ acidic) protein molecules are drawn to the cathode.  The _______ electrode. At pH values above the isoelectric point (_____acidic) proteins migrate toward the anode.  The ______electrode.

Answer 40

isoelectric point more negative less positive

Question 40

Cheese is made by bringing milk closer to the isoelectric point of _____ to______ some of the protein and form a ____

Answer 40

casein coagulate curd.

Question 41

Stressed proteins may be modified, for decreased solubility, or loss of ability to catalyze reactions. Particularly by ______, _____, and ______ These physical changes are caused by alteration of the _____ of the protein molecule-- denaturation In denaturation, proteins begin to resemble more closely their _______ structure

Answer 41

heat, agitation, and ultraviolet light. shape secondary helical

Question 42

Where the concentration of protein is sufficiently high, the fluid mixture may coagulate into a solid. Heat causes denaturation and coagulation to transform liquid egg into a solid, as seen with a hard-cooked egg. Denaturation and coagulation are ____ changes in the protein molecule. When enzymes are used in food preparation, both _____ and _____of the food must be considered.

Answer 42

physical rather than chemical pH & temperature

Question 43

Functional roles of proteins

Answer 43

foams, thickening, structural

Question 44

Foam role _____ and _____have the ability to form stable foams  Providing a light, airy product with a large volume. The proper amount _____ and _______  create a stable egg white foam.  The foam is stabilized even more by baking this soufflé.

Answer 44

gelatin and egg proteins of beating and some cream of tartar

Question 45

thickening role Egg proteins are effective as thickening agents when ______ and ______by heat. _____ and ______ are examples.  Milk proteins undergo _______ and ______ to precipitate and form the _____for cheese.

Answer 45

denatured and coagulated Hollandaise & cooked salad dressing denaturation and coagulation curd

Question 46

structural role Gluten provides the protein network responsible for ______ characteristics of baked products.  Including both ______ and ____  Edible films can be made from ______, ______, and ______

Answer 46

textural cell structure and volume. milk, wheat and corn proteins.