Free QCE Food & Nutrition Flashcard Review

Monosaccharides are simple sugars with the general formula (CH₂O)ₙ that cannot be hydrolysed into simpler sugars. Common examples: glucose (aldohexose), fructose (ketohexose), and galactose (aldohexose). All have 3–7 carbon atoms; glucose and fructose both contain 6 carbons but differ in functional groups (aldehyde vs ketone).

A disaccharide is a sugar formed by condensation of two monosaccharides, releasing one water molecule. Sucrose = glucose + fructose (table sugar, fruit, honey). Lactose = glucose + galactose (milk, dairy). Maltose = glucose + glucose (malt, beer, grains). All are linked by glycosidic bonds and can be hydrolysed back to monosaccharides.

Starch (plants): energy storage in grains, legumes, tubers; composed of amylose (linear) and amylopectin (branched). Cellulose (plants): structural cell wall component; indigestible by humans, provides dietary fibre. Glycogen (animals): energy storage in muscle and liver; found in small amounts in meat/liver. Each is a polymer of glucose linked by α- or β-glycosidic bonds.

Soluble fibre: dissolves in water to form a viscous gel; slows nutrient absorption, lowers blood glucose and cholesterol, feeds beneficial gut bacteria. Sources: oats, legumes, apples, barley. Insoluble fibre: does not dissolve in water; promotes intestinal motility and prevents constipation. Sources: wholegrain cereals, bran, nuts, vegetables. Both are non-digestible carbohydrates essential for digestive health.

Adequate fibre intake (25–30 g/day for adults) reduces risk of: colorectal cancer, cardiovascular disease (via lipid lowering), type 2 diabetes (improved glycaemic control), and obesity (increased satiety). Soluble fibre lowers LDL cholesterol; both types support healthy microbiota and reduce inflammation. Helps prevent diverticular disease and maintains normal bowel function.

Gelatinisation is the swelling and hydration of starch granules when heated in water above a critical temperature (60–75°C depending on starch source). Granules absorb water, swell, leach amylose, and eventually burst, thickening the liquid. The starch granule loses its organised crystalline structure. Gelatinisation temperature varies: potato (60–65°C) < wheat (61–75°C) < corn (62–75°C).

Gelation is the formation of a gel—a semi-solid network that traps liquid—from a sol (liquid colloidal solution). Occurs when protein (egg, gelatin) or polysaccharide (agar, pectin) molecules form a three-dimensional matrix. Gelatin gels require cooling below 15°C; agar gels set immediately on cooling. Pectin requires specific pH (3–3.5), sugar (55–65%), and calcium for jam-setting via junction zones.

Retrogradation is the recrystallisation of amylose and amylopectin after gelatinisation, as the starch network reorganises and loses water. Occurs over hours/days at room temperature or in refrigeration. Effects: bread becomes stale (firmer, drier crumb); rice hardens; potatoes become grainy. The starch becomes less digestible. Retrogradation can be slowed by storing bread in sealed containers or freezing.

Caramelisation is the thermal decomposition of sugars when heated above their melting point (160–180°C) in the absence of amino acids or proteins. Produces brown colour (caramel), nutty flavour, and bitter notes at high temperatures. No water or acid is required (unlike Maillard). Occurs in: caramel sauce (heated sugar + cream), toffee, praline, burnt sugar toppings. Colour ranges from light amber to dark brown to black.

The Maillard reaction is a non-enzymatic browning between reducing sugars and amino acids/proteins, producing brown colour and complex savoury flavours. Requires: heat (above 140°C, optimal 160–180°C), reducing sugar (glucose, fructose, maltose—NOT sucrose), and amino acid/protein. Occurs in: bread crust, roasted coffee beans, grilled meat, toasted nuts. Produces hundreds of flavour compounds and some harmful by-products (acrylamide) at very high temperatures.

Saturated fatty acids: no C=C double bonds; solid at room temperature; sources: butter, palm oil, coconut oil, lard, fatty meat. Monounsaturated (1 C=C bond): liquid at room temperature; sources: olive oil, avocado, macadamia nuts. Polyunsaturated (≥2 C=C bonds): liquid; sources: sunflower oil, soybean oil, fatty fish (omega-3: sardine, salmon), flaxseed. Polyunsaturates are generally considered healthier; excess saturates increase CVD risk.

Trans fats are unsaturated fatty acids with C=C double bonds in the trans configuration (opposite sides of double bond). Produced industrially via partial hydrogenation of vegetable oils; occur naturally in low amounts in ruminant meat and dairy. Harmful because: raise LDL cholesterol, lower HDL, increase triglycerides, and heighten CVD and inflammation risk more than saturated fats. Largely removed from Australian food supply; still present in some imported products and baked goods.

Emulsifiers are amphiphilic molecules with both hydrophilic (water-loving) and hydrophobic (fat-loving) regions. Function: stabilise emulsions (mix of oil and water that normally don't mix) by coating oil droplets with their hydrophobic tail inward and hydrophilic head outward, forming a protective barrier. Examples: lecithin (egg yolk, soy), monoglycerides, polysorbates. Used in: mayonnaise, ice-cream, chocolate, salad dressings.

HLB is a numerical scale (0–20) describing an emulsifier's balance between water-loving and fat-loving properties. Low HLB (3–9): favour water-in-oil emulsions (e.g. butter, creams). High HLB (11–20): favour oil-in-water emulsions (e.g. mayonnaise, ice-cream). HLB ~13: balanced for stable emulsions. Different oils and water phases require different HLB values for optimal stability. Manufacturers blend emulsifiers to achieve target HLB for specific products.

Cocoa butter has three main polymorphs: β-prime (unstable, melts ~27°C, grainy texture, 'bloom' on surface), β (stable, melts 34–37°C, glossy and snappy, desired form in chocolate). Form V is desirable in tempering. Polymorphic crystallisation depends on temperature history: fast cooling favours β-prime (undesired bloom); slow cooling or seed crystal method produces stable β form. Tempering controls polymorph formation for smooth, glossy chocolate.

Smoke point is the temperature at which an oil begins to smoke and decompose, releasing free fatty acids and potentially harmful compounds (acrolein). Saturated and monounsaturated fats have higher smoke points; polyunsaturates lower. Examples: extra virgin olive oil (~160°C, salads/low heat); refined vegetable oil (~200°C, frying); ghee (~250°C, high-heat cooking). Exceeding smoke point reduces nutritional value, produces off-flavours, and creates harmful by-products.

Oxidative rancidity occurs when unsaturated fatty acids react with atmospheric oxygen, breaking C=C double bonds and producing free radicals, peroxides, aldehydes, and ketones. Mechanism: initiated by light, heat, or trace metals (iron, copper); propagated by free radicals. Promotes: polyunsaturated oils > monounsaturated > saturated. Conditions: high temperature, light exposure, presence of pro-oxidants. Results in rancid smell and off-flavours. Prevented by: antioxidants (vitamin E, BHA), oxygen-free storage, cool/dark conditions.

Hydrolytic rancidity results from hydrolysis of ester bonds in triglycerides, releasing free fatty acids (FFAs) and glycerol. Occurs when: water is present, temperature is elevated, or lipase enzymes (from microbes or food itself) are active. Commonly affects: butter, lard, coconut oil (short-chain FFAs have pungent odours). Conditions: high humidity, microbial contamination, poor storage. Results in off-flavours (butyric acid smells of vomit). Prevented by: dry storage, refrigeration, microbial control.

FATTOM is an acronym for the conditions that allow pathogenic bacteria to grow: Food (nutrients), Acidity (pH 4.6–7.0 is ideal), Temperature (2–60°C 'danger zone'), Time (>2 hours), Oxygen (aerobic or anaerobic, depends on species), Moisture (water activity >0.85). All six must be present for rapid bacterial growth. Use to assess food safety risks: remove any one condition to inhibit growth. Example: refrigeration removes T; salt/acid removes A; dehydration removes M.

Salmonella (poultry, eggs, unpasteurised milk): diarrhoea, fever, abdominal cramps, onset 6–72 hrs. Listeria monocytogenes (soft cheeses, deli meats, raw vegetables): gastroenteritis, fever; severe in immunocompromised/pregnant women. Campylobacter jejuni (raw/undercooked poultry, untreated water): bloody diarrhoea, fever, pain, onset 2–5 days. Clostridium perfringens (beef, poultry, gravies): cramping, diarrhoea (rarely vomiting), onset 8–22 hrs. Symptoms typically last 1–7 days; hospitalisation rare except in vulnerable groups.