All weeks Flashcards

Question

fat Modification Processes Interesterification

Answer 1

Rearrangement of fatty acids within TAGs Random or directed (controlled via enzymes or temperature) Adjusts melting profile without trans fats

Answer 2

Physically separates TAGs by melting point Used to produce solid fat fractions for margarine, spreads

Answer 3

Desirable oil for frying: High smoke point (≥ 200 °C) Low in polyunsaturates (to reduce oxidation) Neutral flavour and colour

Answer 4

Hydrolysis: FFAs released Oxidation: peroxides, aldehydes formed → rancidity Polymerisation: leads to sticky, viscous oil

Answer 5

Level of unsaturation: Iodine Value (higher IV = more double bonds) Free fatty acids: NaOH titration Oxidation: Peroxide value Smoke point: Determined by heating until visible smoke

Answer 6

Canola oil: high in MUFAs, moderate PUFA; higher melting point at 0 °C than olive oil Olive oil (RBD - refined, bleached, deodorized): >99% TAGs, with different mixed TAG structures EVOO: mechanically extracted, retains polyphenols MCT oil: mostly medium-chain triglycerides (C6–C12); fast energy source, less storage as adipose Coconut oil: mix of MCTs and LCTs; semi-solid at room temp

Answer 7

Disaccharide (glucose + fructose), primary dietary sugar

Answer 8

Hydrolysis of sucrose → glucose + fructose Occurs via: Heat + acid Enzyme (invertase) Properties: More hygroscopic (absorbs moisture from air) Resists crystallisation → smoother textures in syrups, jams Example: Jam left on a bench gets gloopy due to sugar inversion and water absorption

Answer 9

Nut pastes (e.g., peanut butter): Fat separation = oil at top, dry solids at bottom Fix with emulsifiers (e.g., lecithin) to stabilise fat dispersion Fats with low solid fat index (like peanut oil) tend to separate

Answer 10

°Brix: % sugar by weight in solution (refractometry) Reducing sugar test: Benedict’s or Fehling’s Aw: measured to ensure microbial stability

Answer 11

Brix is a measure of the amount of dissolved solids in a liquid via its specific gravity, and is used especially to measure dissolved sugar. One degree Brix is 1 gram of sucrose in 100 grams of solution.

Answer 12

Maillard Reaction Reducing sugar + amino acid → brown pigments, complex aromas Occurs >140°C Key in baked goods, grilled meat, coffee

Answer 13

Sugar heated >170°C → pyrolysis Produces caramel colour and flavour Involves dehydration, fragmentation, polymerisation

Answer 14

fructose > sucrose > glucose

Answer 15

Harvesting Milling & Extraction Billets crushed → juice extracted Imbibition: water sprayed to recover more sucrose By-product: Bagasse (used as biofuel, mulch) Clarification Lime (Ca(OH)₂) neutralises acidity (pH 5–6) Heat (95°C) inactivates invertase enzyme Precipitation of phosphates & organics → mud (used as fertiliser) Evaporation Juice concentrated using multiple-effect evaporators under vacuum ~65% solids (°Brix) Crystallisation supercrystalisation Centrifugation Spins out molasses from sugar crystals Raw sugar dried using hot air Refining Affination: hot syrup washes off impurities Melting: purified crystals dissolved Carbonation: Ca(OH)₂ + CO₂ → CaCO₃ removes pigments, resins Decolourisation: resin filters or activated carbon Crystallisation: white sugar recovered Final drying, sieving, and packing

Answer 16

Without sugar, baked goods may become drier, more crumbly, and less tender, and their overall flavor can become flat. The browning process can also be affected, potentially leading to a lighter color. Additionally, sugar helps to retain moisture, so reducing it can result in a shorter shelf life for the baked goods. - sugar alcohols are less sweet -bulking agents needed to help structure and hardness (dextrose) - softness (dextrose and starch) - aeration: rating agents

Answer 17

whitish or grayish streaking that can appear on the surface of chocolate

Answer 18

occurs whitish or grayish on chocolate surface, occurs when warm temp causes cocoa butter to soften and seperate. When it rises + resolidifies the sugar bloom forms

Answer 19

presents as dry, hard white film on the surface caused by moisture within coating. The sugar dissolves and evaporates, forming larger crystals and a dusty layer

Answer 20

bran (fibre), germ (nutrients), endosperm (main starch/protein source)

Answer 21

Used for wheat, maize → flour Separates bran, germ, and endosperm Endosperm ground into refined flour By-products: bran (fibre), germ (oil source)

Answer 22

Used for maize, rice → starch and protein isolation Soaking softens kernel, allowing component separation Products: starch, gluten, germ oil, fibre

Answer 23

Particle size: affects hydration, dough rheology Protein content: affects gluten network (bread vs cake) Damaged starch: increases water absorption, affects viscosity

Answer 24

Measures α-amylase activity High enzyme activity = low falling number → degraded starch Sprouted/damaged grains have ↑ α-amylase → poor baking quality

Answer 25

Composed of: Amylose: linear, forms gels Amylopectin: branched, provides thickening Granule size, shape, and crystalline structure vary by botanical source

Answer 26

Occurs during heating in excess water (~60–80°C) Granules swell, absorb water, lose crystallinity Viscosity increases, opacity changes Critical for sauces, baking, noodle production

Answer 27

Re-association of amylose chains upon cooling Leads to staling (bread), syneresis (water loss from gels) Occurs faster in amylose-rich starches

Answer 28

leakage of water from a starch gel

Answer 29

Definition: Unfolding of a protein’s native 3D structure (not breaking peptide bonds). Caused by: heat, acid/base (pH), salt, mechanical shear, freezing

Answer 30

Proteins are large biomolecules composed of amino acids linked by peptide bonds. Their structure determines their function in food — affecting texture, emulsification, gel formation, and more.

Answer 31

Once unfolded, proteins may reassociate via hydrophobic, ionic, or disulfide bonds → gel formation or clumping. Aggregation: Unfolded proteins clump together (Cooked egg whites) Gelation: 3D protein network traps water (Yogurt, custard, tofu)

Answer 32

Network traps water for firm texture TOFU, YOGURT

Answer 33

Proteins act as emulsifiers: unfold at fat–water interface Stabilise oil droplets in water 🧁 Example: Egg yolk lecithin in mayonnaise Milk proteins in ice cream

Answer 34

Whipping/Beating unfolds proteins Forms network around air bubbles → stabilised foam 🥚 Example: Albumin (egg white) → meringue Dairy foams (e.g., whipped cream) 🛑 Overbeating → protein films break = foam collapse

Answer 35

Retains moisture in gels/emulsions

Answer 36

Protein unfolding increases thickness

Answer 37

Caseins form stable micelles at pH ~6.6 κ-casein keeps micelles dispersed Acid or rennet disrupts κ-casein → coagulation/curdling 🧀 Example: Rennet cleaves κ-casein in cheese-making → curd forms 🥛 Isoelectric point of casein = pH 4.6

Answer 38

pH at which protein has no net charge Least soluble → precipitates 🧪 Used to coagulate proteins: Cheese (casein at pI = 4.6)

Answer 39

stiffening of muscles after animal slaughter due to ATP depletion.

Answer 40

TP levels drop after slaughter Myosin and actin filaments lock → permanent cross-bridges form Muscles stiffen → meat becomes tough and inextensible 🧠 ATP is needed to release actin-myosin binding; without it, muscles remain contracted.

Answer 41

f meat is chilled too quickly before rigor completes → extremely tough meat ✅ Avoided by maintaining pre-rigor temperature ≥10–15 °C during early postmortem period

Answer 42

Post-rigor mortis, meat needs time to age and break down protein structures to regain tenderness.

Answer 43

Aging (conditioning): Natural enzymes (e.g., calpains) break down myofibrils (Dry-aged beef) Marination (acid)L Lowers pH, unfolds proteins (Lemon juice or vinegar on steak) Mechanical tenderising: Physically disrupts muscle fibres (Needle/blade tenderisers) Enzymatic tenderisers: Plant enzymes degrade proteins (Papain (papaya), bromelain (pineapple)) Cooking (slow/moist heat): Denatures collagen → gelatin (Braising, stewing)

Answer 44

Actin & Myosin: Contractile proteins (Lock together during rigor) Collagen Connective tissue: Tough if undegraded; gelatinises when cooked Elastin: Elastic connective (tissue (Resistant to breakdown; always tough) Proteolytic enzymes: Calpains, cathepsins (Break down structural proteins postmortem)

Answer 45

Spoilage is any undesirable change in food quality (appearance, smell, texture, taste) that makes it unacceptable or unsafe.

Answer 46

Microbial: bacteria, moulds, yeasts Signs: slime, souring, gas, off-odour, visible growth Chemical: lipid oxidation, enzymatic browning Signs: rancid smells, browning (cut apples) Physical: dehydration, bruising, freezer burn Signs: softening, wilting, texture loss

Answer 47

pH: Low pH (<4.6) inhibits Clostridium botulinum Water activity (aw): aw < 0.85 inhibits most pathogens Temperature: Cold slows microbes and enzymes Oxygen: Absence slows aerobic spoilage Nutrients: More sugar/protein = faster spoilage if not preserved

Answer 48

Extend shelf life Maintain quality and safety Minimise waste

Answer 49

Destroys microbes & enzymes (Pasteurisation, sterilisation)

Answer 50

Slows microbial growth (Refrigeration, frozen meals)

Answer 51

Reduces aw (removes water) (Dried fruits, jerky)

Answer 52

Lowers pH to inhibit pathogens (pickles, kimchi)

Answer 53

Alters gas composition (↓O₂, ↑CO₂) (Packaged salads, meats)

Answer 54

Kill/inhibit microbes (Sorbates, benzoates)

Answer 55

Organic acids + antimicrobials via microbes (Yogurt, sauerkraut)

Answer 56

Uses multiple mild techniques together (Chilled cooked meats, soft cheeses)

Answer 57

Measures free water (not bound to solutes). Microorganisms need available water to grow. aw scale: 0 (bone dry) to 1.0 (pure water)

Answer 58

~0.99 Fresh meat, fruit ~0.85 Cheese, cakes ~0.6–0.7 Dried fruit, crackers

Answer 59

Chemical: Sodium benzoate, potassium sorbate (Yeasts, moulds) BiologicalL Nisin (from Lactococcus lactis) (Gram-positive bacteria) Natural: Essential oils (thyme, clove), organic acids (Bacteria & fungi)

Answer 60

Combines multiple barriers to inhibit spoilage without compromising quality. 🎯 Example: Cooked ham: Mild heat (pasteurisation) Refrigeration Vacuum packing (no O₂) Salt and pH adjustment

Answer 61

Fermentation is a metabolic process in which microorganisms convert sugars into acids, gases, or alcohol, usually under anaerobic conditions (no oxygen). It preserves food, enhances flavour and nutrition, and improves safety.

Answer 62

1. Homofermentative Pathway: EMP (glycolysis) End product: Lactic acid ATP yield: 2 ATP per glucose Microbes: Lactococcus lactis, some Lactobacillus spp. Used in: Yogurt, cheddar cheese, fermented sausages 🧁 Reaction: Glucose → 2 Lactic Acid + 2 ATP 2. Heterofermentative Pathway: Phosphoketolase (pentose phosphate) End products: Lactic acid + CO₂ + ethanol/acetic acid ATP yield: 1 ATP per glucose Microbes: Leuconostoc, some Lactobacillus spp. Used in: Kimchi, sauerkraut, kefir 🥬 Reaction: Glucose → Lactic Acid + CO₂ + Ethanol/Acetic Acid + 1 ATP

Answer 63

Lactic Acid Bacteria (LAB): Acidify, inhibit spoilage/pathogens Yeasts: Produce alcohol, CO₂, esters Acetic Acid Bacteria: Oxidise ethanol to acetic acid Moulds: Break down complex substrates

Answer 64

Acidification (via LAB): converts lactose to lactic acid Coagulation: rennet cleaves κ-casein → curds form Processing: Cheddaring = pressing/draining curds Stretching = mozzarella Ripening = enzymes/microbes develop flavour

Answer 65

Preservation: Produces acids/ethanol/CO₂ that inhibit spoilage microbes Enhanced flavour: Complex aroma compounds: esters, aldehydes, acids Improved nutrition: Better bioavailability of nutrients (e.g., B-vitamins in tempeh) Detoxification: Reduces antinutrients/toxins (e.g., bitter compounds in olives) Digestibility: Breaks down indigestible components (e.g., legumes)

Answer 66

Controlled action of microbes to: Modify pH (acid production) Reduce redox potential Produce antimicrobial metabolites (e.g., bacteriocins like nisin) Outcompete spoilage/pathogenic bacteria

Answer 67

Lactic acid lowers pH → prevents pathogens Salt draws out water and inhibits spoilage organisms Anaerobic environment essential (esp. for kimchi, sauerkraut) Starter cultures ensure consistent and safe results

Answer 68

After fermentation: Vacuum or MAP packaging maintains anaerobic conditions Helps extend shelf life without chemical preservatives

Answer 69

Size reduction = decreasing particle size of solid foods using mechanical forces. Purposes: Improve texture and processability Increase surface area (for drying, cooking, mixing) Standardise particle size for consistent product quality Facilitate separation of components

Answer 70

Compression: Food crushed between two surfaces (Fruit pulping) Impact: Food struck by fast-moving object (Hammer mill, pin mill) Attrition: Abrasion between surfaces (Grinding spices) Shearing: Cutting with sharp blades (Dicers, slicers)

Answer 71

Brittleness: Fractures easily (good for grinding) Ductility: Deforms before breaking (e.g., fats) Toughness: Resists fracture (e.g., meat, fibrous roots) Moisture content: High moisture = harder to reduce in size (may smear) Heat sensitivity: Overheating damages flavour/nutrients (use cooling)

Answer 72

Sieving: separates solids based on mesh size Air classification: separates light from heavy particles Centrifugation: density-based separation (e.g., cream from milk)

Answer 73

Formation of solid crystals from a solute in solution when it's supersaturated. Supersaturation – solvent holds more solute than usual Nucleation – small clusters form (can be seeded) Crystal growth – more solute added to nuclei Recrystallisation – rearrangement into more stable form

Answer 74

Separates volatile liquids by differences in boiling point Application: Alcoholic beverages, essential oils, flavour extracts

Answer 75

Removes water by heating (often under vacuum) Concentrates liquids without burning heat-sensitive nutrients Applications: Tomato paste, condensed milk, juice concentrates

Answer 76

Mixing is a unit operation that aims to evenly distribute two or more ingredients (solid, liquid, or gas) to create a homogeneous system.

Answer 77

Ensure consistent product quality Maximise reaction efficiency (e.g., fermentation, emulsification) Facilitate heat or mass transfer Enable uniform texture, flavour, and colour

Answer 78

1. Solid–Solid Powder blending, flour mixing, seasoning Homogeneity influenced by particle size, shape, and density 2. Solid–Liquid Dissolving sugar in water, mixing starch slurry Requires agitation to ensure full dispersion 3. Liquid–Liquid Mixing juices, oils, and aqueous phases (e.g., vinegar + oil in dressings) 4. Gas–Liquid or Gas–Solid Incorporation of air in foams, whipped cream, or dough

Answer 79

Convection: Bulk movement of material (Ribbon blender) Diffusion: Random particle movement (Powder blending over time) Shear: Layers move past one another (High-shear mixers, emulsifiers)

Answer 80

Even after mixing, components can separate during handling or storage, reducing product uniformity.

Answer 81

Sifting: Small particles fall through gaps Percolation: Vibration causes smaller particles to move down Rolling: Rounder/larger particles roll to edges Elutriation: Airflow lifts lighter particles away Example: In cake mix, chocolate chips may sink or rise if not stabilised.

Answer 82

Reduce particle size variation Use agglomeration to bind particles together Add liquid binders or stabilisers Design equipment to minimise vibration

Answer 83

To slow down microbial growth, enzyme activity, and chemical changes Helps extend shelf life, retain nutritional value, and maintain sensory quality ❗ Low temperatures do NOT kill microbes — they only slow their activity.

Answer 84

↓ temp quickly Post-processing, pre-storage

Answer 85

0 – 5 °C Preserves perishables (dairy, meat)

Answer 86

< 0 °C (usually –18 °C or below) Long-term storage; immobilises water

Answer 87

reaction rate doubles or triples with 10 degree increase reaction rate halves or decreases by 3 with 10 degree decrease

Answer 88

Just above freezing point (~–1.5 °C for muscle foods) Maximises shelf life without freezing (prevents texture damage) Avoids drip loss and freeze–thaw cycles

Answer 89

Freezes water → lowers water activity (aw) Halts microbial growth, but not chemical degradation Freezing changes: Texture (ice crystals can damage structure) Water binding (can shift moisture) Flavour (oxidative changes in fats)

Answer 90

Pre-cooling – food temp reduced Supercooling – drops below freezing point, no ice yet Nucleation – ice crystals start forming Crystallisation – rapid formation of ice Post-crystallisation cooling – temperature stabilises below freezing Storage – held at or below –18 °C

Answer 91

Slow freezing: Large crystals Cell rupture, texture loss Quick freezing: Small crystals Minimal damage, better quality ✅ Quick freezing = smoother texture, less drip loss on thawing

Answer 92

Water freezes, but solutes remain in liquid phase → aw decreases Freezing concentrates solutes in remaining water Result: microbial growth is inhibited

Answer 93

Osmotic damage: Water moves out of cells during freezing → shrinkage Structural damage: Ice punctures membranes → leakage on thawing Drip loss: Liquid lost when thawed = reduced juiciness

Answer 94

Lowest temp at which solutes and water coexist in liquid before freezing Below this point, everything freezes → no microbial activity

Answer 95

Short shelf-life: Mild pasteurisation (e.g., 70 °C for 2 min); stored <10 days Chilled lasagna Extended shelf-life: Stronger heat (e.g., 90 °C for 10 min); stored >10 days Vacuum-sealed ready meals

Answer 96

Thermal processing involves applying controlled heat to foods to: Kill or reduce pathogenic and spoilage microorganisms Inactivate enzymes Improve shelf life and safety Modify texture, flavour, colour

Answer 97

Conduction: Heat transfer through solids; particle-to-particle Metal cans, solid foods Convection: Heat via moving liquid/gas Boiling soup, canned liquids Radiation: Electromagnetic waves (no contact) Infrared ovens, broilers

Answer 98

Blanching: ~100 °C Enzyme inactivation (Peas before freezing) Pasteurisation: <100 °C Kill pathogens (Milk, juice) UHT (Ultra-High Temp) 135–150 °C Extended shelf life (Long-life milk) Hot filling >85 °C Sterilise container + product (Bottled juice, sauces) Sterilisation ≥121 °C Destroy all viable microbes (Canned soup)

Answer 99

LTLT (Low Temp Long Time) 63 °C for 30 min Traditional milk method HTST (High Temp Short Time) 72 °C for 15 sec Standard pasteurised milk UHT 140–150 °C for 1–2 sec Long-life milk, cream

Answer 100

Time (min) at a specific temperature to reduce microbial population by 90% (1 log cycle)

Answer 101

Temp increase needed to reduce D-value by 90%

Answer 102

Time to kill a specific organism at a given temperature

Answer 103

Most heat-resistant pathogen = Clostridium botulinum spores Target for canning and sterilisation pH <4.6 = safe from C. botulinum without full sterilisation

Answer 104

Mild heat treatment using steam or hot water Purpose: Inactivate enzymes (e.g., polyphenol oxidase) Preserve colour and flavour Prepare food for freezing or dehydration 🫛 Example: Blanch green beans before freezing to retain colour

Answer 105

Used for acidic foods (pH <4.6) Fills product into sterile container at high temperature Product sterilises the container Hold time = enough to inactivate spores 🧃 Example: Bottled fruit juice, salsa

Answer 106

Destroys all viable microorganisms including spores Performed in-package (retort) or in-flow (aseptic) 🧪 Used for: low-acid canned foods (beans, meats)

Answer 107

Too little heat = unsafe Too much heat = loss of vitamins, flavour, texture Challenge: find the thermal processing sweet spot 🧪 Sensory changes: Maillard browning Nutrient loss (esp. Vitamin C, B1) Texture softening (veg, pasta)

Answer 108

Retorts: batch or continuous pressure cookers (for cans) Plate heat exchangers: for liquids (milk, sauces) Direct steam injection: for UHT (rapid heating/cooling) Hot fill tanks: for acidic liquid foods

Answer 109

Microbial growth models Heat penetration testing Log reduction calculations (based on D- and Z-values) Food pH, aw, and composition

Answer 110

the removal of water from food to lower water activity (aw) and inhibit microbial growth, enzyme activity, and spoilage. 🎯 Goals: Extend shelf life Reduce weight/volume (for easier transport & storage) Improve convenience (rehydratable foods) Enable further processing (e.g., powders)

Answer 111

Drying: usually partial moisture removal (sun-drying fruits) Dehydration: refers to industrial/commercial removal to low moisture content

Answer 112

>0.90 High (bacteria grow) Fresh meat ~0.85 Some bacteria grow Cheese ~0.70 Moulds/yeasts survive Dried fruit <0.60 Microbes can't grow Crackers, powdered milk 🧠 Drying doesn’t kill all microbes — it inhibits growth by removing water.

Answer 113

Hot air drying: Heated air removes moisture Fruit slices, veg chips Spray drying: Liquid → mist → dry powder in seconds Milk powder, instant coffee Sun drying: Traditional, low cost, weather-dependent Raisins, figs, tomatoes

Answer 114

Freeze drying involves freezing the material, then creating a vacuum to sublimate the ice directly into vapor, resulting in minimal structural damage and excellent preservation of quality. Spray drying, on the other hand, involves atomizing a liquid into fine droplets and drying them with hot air, leading to faster drying and lower cost, but potential for some quality degradation.

Answer 115

Blanching: Inactivate enzymes (e.g. polyphenol oxidase) Green beans, apples Sulfiting: Prevent browning & microbial growth Dried apricots Osmotic dehydration: Partial water removal using syrup/salt Candied pineapple

Answer 116

Nutritional: Loss of vitamin C, thiamine (B1) due to heat or oxidation Dried fruit vs fresh Chemical: Browning (Maillard, enzymatic), lipid oxidation Dried bananas, milk powder Physical: Shrinkage, case hardening, cracking, rehydration issues Poorly dried apple chips Sensory: Flavour intensifies or changes Sun-dried tomatoes

Answer 117

Outer layer dries too quickly, forms barrier → traps moisture inside Prevented by controlling air temperature & humidity

Answer 118

Rehydration in food science is the process of restoring moisture to dried food products, reversing the effects of dehydration. Some dried foods are instant (spray dried milk) Others require soaking or cooking (beans, noodles) 🧠 Rehydration quality depends on: Drying rate Structure collapse Type of pre-treatment

All weeks Flashcards

(143 cards)