CHEMY205 Test 1

Macronutrients vs micronutrients

Macronutrients (protein, carbs, lipids) are large polymer molecules needed in bulk; micronutrients (vitamins, minerals) needed in small amounts but deficiency causes serious disease

Vitamin A deficiency

Nyctalopia (night blindness)

Vitamin B1 (thiamine) deficiency

Beriberi

Vitamin B3 (niacin) deficiency

Pellagra

Vitamin B12 deficiency

Anaemia (B12 obtained exclusively from microbial pathways, not plants)

Vitamin C deficiency

Scurvy

Vitamin D deficiency

Rickets

Vitamin K deficiency

Impaired blood clotting

Protein primary structure

The amino acid sequence

Protein secondary structure

Regularly repeating local structures stabilised by hydrogen bonds - alpha helix, beta sheet

Protein tertiary structure

Overall 3D shape of a single protein molecule; stabilised by hydrophobic core, salt bridges, hydrogen bonds, disulphide bonds

Protein quaternary structure

Structure formed by several protein subunits functioning as one complex

Denaturation

Loss of tertiary/secondary protein structure via strong acid/base, concentrated salt, organic solvent, or heat

Ceviche/kokoda

Fish "cooked" chemically via denaturation from an acidic marinade (citrus juice) rather than heat

Meat browning mechanism

Myoglobin denatures; histidine residue displaced from iron, oxidising Fe(II) to Fe(III)

Essential amino acids

Cannot be made by the body, must come from diet - e.g. leucine, tryptophan, lysine, valine, histidine

Non-essential amino acids

Made by the body from essential amino acids or protein breakdown - e.g. alanine, glutamic acid, aspartic acid

Conditional amino acids

Usually non-essential except in illness/stress - e.g. arginine, cysteine, glutamine, tyrosine

Taurine

Non-essential amino acid in humans (essential for cats); not used in protein synthesis; from meat/fish

Creatine

NOT an amino acid (made from arginine, methionine, glycine); not used in protein synthesis; common supplement for exercise performance

Melamine scandal (2008)

Melamine added to Chinese infant formula (SanLu, part-owned by Fonterra) to falsely inflate apparent protein content on nitrogen-based tests; ~300,000 affected, 54,000 hospitalised, 6 deaths

Monosaccharides

One sugar unit - e.g. glucose, fructose, galactose, ribose, deoxyribose

Disaccharides

Two sugar units joined by glycosidic bond - sucrose (glucose+fructose), lactose (galactose+glucose)

Structural polysaccharides

Cellulose, chitin - provide structural support

Storage polysaccharides

Starch (plants), glycogen (animals) - energy storage

Starch composition

~20-25% linear/helical amylose, ~75-80% branched amylopectin

Glycogen

The glucose storage compound of animals; a more highly branched version of amylopectin

Soluble vs insoluble fibre

Insoluble fibre (e.g. cellulose) bulks stool and decreases bowel transit time; soluble fibre is fermented by gut bacteria

Resistant starch

Starch not digested by amylase within 120 min; passes to large intestine, acts as a prebiotic, metabolised to short-chain fatty acids (butyrate, propionate, acetate)

Resistant starch RS1

Physically inaccessible due to cell walls - e.g. seeds, grains, legumes

Resistant starch RS2

Inaccessible due to compact packing structure - e.g. green bananas, raw potato

Resistant starch RS3

Physically modified after cooking and cooling (retrogradation) - e.g. cornflakes, cooled potato/rice

Resistant starch RS4

Chemically modified starch via industrial processing (crosslinks) - e.g. processed bread, cake

Resistant starch RS5

Amylose-lipid complexes from industrial processing - e.g. pastries, protein bars

Simple vs complex carbohydrates

Simple carbs (sucrose, glucose) give quick energy with no fibre/nutrients; complex carbs (bread, rice, legumes) supply sustained energy plus fibre and nutrients

Fat vs oil

A lipid is termed a fat if solid at room temperature, an oil if liquid at room temperature - usually triglycerides (glycerol + 3 fatty acids)

Saturated fatty acids

No double bonds in the hydrocarbon chain - e.g. stearic acid; high in animal fats, cream, butter, coconut/palm kernel oil

Monounsaturated fatty acid

One double bond - e.g. oleic acid (18:1 n-9), palmitoleic acid (16:1 n-7)

Polyunsaturated fatty acid

More than one double bond - e.g. linoleic acid (18:2 n-6), alpha-linolenic acid/ALA (18:3 n-3)

Trans fats

Unsaturated fatty acids with double bonds in trans (E) configuration; formed by partial hydrogenation; major example is elaidic acid; raise LDL, lower HDL

Omega-3 fatty acids

Polyunsaturated fatty acids with the first double bond 3 carbons from the methyl end; essential (not made by the body); ALA, EPA, DHA; may protect against coronary disease; sources: fish oil, flaxseed, hemp

Omega-6 fatty acids

Polyunsaturated fatty acids with the first double bond 6 carbons from the methyl end; linoleic acid is essential; sources: corn oil, sunflower oil

Omega-3:6 ratio

Western diets typically 5:1 to 10:1 (too high in omega-6); recommended ratio is under 4:1, optimal likely 1:1

Fatty acid nomenclature "20:5 (n-3)"

20 = number of carbons; 5 = number of double bonds; n-3 = first double bond is 3 carbons from the methyl (omega) end

NOVA Group 1

Unprocessed/minimally processed foods - removal of inedible parts, drying, grinding, freezing, pasteurising, packaging

NOVA Group 2

Processed culinary ingredients derived from Group 1 or nature (oils, butter, sugar, salt) - not designed to be eaten alone

NOVA Group 3

Processed foods - Group 2 ingredients (salt/sugar/oil) added to Group 1 foods; generally 2-3 ingredients, recognisable as modified Group 1 food (canned veg, cheese, bread)

NOVA Group 4

Ultra-processed foods - little/no Group 1 food present, multiple ingredients, additives not used in home cooking, extensive industrial processing (hydrogenation, extrusion, hydrolysation)

NOVA Group 4 health risks

Increased obesity, cardiovascular disease, type 2 diabetes risk, poor gut health, malnutrition, overconsumption

Food additive purpose (general)

Maintain consistent/high quality and prevent spoilage since bought food is stored/transported longer than home-grown food

E number system

Standard codes for additives; E100s mainly colours; E200-282 preservatives/acids; E300-341 antioxidants/acid regulators; E400s emulsifiers/stabilisers/thickeners/anti-caking/bulking agents

Emulsifier function

Stabilises oil/water mixtures so they don't separate - e.g. lecithin in mayonnaise, bread, ice cream

Lecithin

Most widely used emulsifier (E322); generic term for phosphoric acid/choline/fatty acid/glycerol compounds; sources include soybeans, eggs, milk

Nutritive sweeteners

Provide energy/calories - e.g. sucrose, honey, corn syrup, HFCS, aspartame, sugar alcohols

Non-nutritive sweeteners

Provide little/no energy - e.g. saccharin, cyclamate, acesulfame K, stevioside, sucralose

Sucrose

Table sugar; disaccharide of glucose+fructose; produced from sugar cane (~80%) and sugar beet (~20%); nutritive

Honey

~80% monosaccharides (fructose+glucose) by weight; slightly sweeter than sucrose due to fructose content

Corn syrup

Made from corn starch via acid or enzymatic hydrolysis; adds bulk, prevents crystallisation, acts as humectant/thickener

High Fructose Corn Syrup (HFCS)

Corn syrup with extra enzymatic processing converting more glucose to fructose; cheaper than sucrose in the US so widely used

HFCS variants

HFCS 55 (~55% fructose, used in soft drinks, sweetness ~sucrose); HFCS 42 (~42% fructose, less sweet than sucrose); HFCS 90 (~90% fructose, sweeter than sucrose, blended to make HFCS 55)

Aspartame

Dipeptide of aspartic acid + phenylalanine methyl ester; 180x sweeter than sucrose; synthetic; nutritive; heat sensitive; methyl ester masks phenylalanine's bitterness

Sugar alcohols (polyols)

~1/2-1/3 fewer calories than sugar (converted slowly to glucose, don't require insulin); e.g. mannitol, sorbitol, xylitol, lactitol, isomalt; can cause bloating/laxative effect

Saccharin

Discovered accidentally in 1879 (tasted off a chemist's hand); ~300x sweeter than sucrose; bitter metallic aftertaste; non-nutritive

Cyclamate

~30x sweeter than sucrose; discovered accidentally in 1937; heat stable; often blended with saccharin (10:1) for better taste

Acesulfame-K

Discovered accidentally in 1967; heat and acid/base stable; slightly bitter aftertaste so often blended with other sweeteners

Stevioside

Natural glycoside from Stevia rebaudiana leaves; ~250-300x sweeter than glucose; heat and pH stable; non-nutritive

Sucralose

Trichlorinated synthetic derivative of sucrose; ~600x sweeter than sucrose; main sweetener in Splenda; non-nutritive; heat and pH stable

Maltodextrin

Oligomer of glucose from partial starch hydrolysis; nutritive; used as thickener/stabiliser, cheap and water stable

Natural vs synthetic food colourings

Natural colourings (e.g. curcumin, cochineal, lycopene) are generally more expensive and can alter taste; synthetic dyes are cheaper and more stable

Azo dye functional group

R-N=N-R' (the azo group) - does not occur naturally; colour arises from electron delocalisation; ~60-70% of all dyes used in food/textiles

Azo dye + fatty foods

Azo dyes are water soluble, insoluble in oil/fat - must modify the structure or formulate as a "lake" (dye adsorbed onto aluminium substrate) for use in fatty foods

Sudan dyes

A subset of azo dyes, oil soluble; NOT approved for food use (carcinogenic); notorious Sudan I contamination of Worcestershire sauce (UK, 2005)

Coal tar dyes

Dyes originally derived from coal tar distillation products (benzene, toluene, naphthalene); overlap with azo dye chemistry - e.g. Brilliant Blue

Tartrazine

Azo dye (E102, FD&C Yellow No. 5); used in Doritos; 2024 study found it makes mouse skin transparent when applied topically

Allura Red

Azo dye (E129, FD&C Red 40); most commonly used red food dye in the USA

Vanillin vs ethyl vanillin

Vanillin is synthetic but occurs naturally (main component of vanilla extract); ethyl vanillin is synthetic and does NOT occur naturally in food

Artificial flavour ester examples

Methyl butyrate = apple; ethyl butyrate = pineapple; amyl acetate = banana; ethyl formate = rum

MSG (monosodium glutamate)

Salt of glutamic acid; identified 1907 by a Japanese scientist as the 5th taste "umami" via kombu seaweed stock experiments; first marketed in Japan 1909

IMP (inosine monophosphate)

First isolated from dried fish; alone has little taste but shows strong synergy with MSG - a mixture has 20x the taste impact of either alone

Preservative examples

Sorbic acid/salts (E200-203, natural), benzoic acid/salts (E210-213, acidic foods only), sulphur dioxide/sulphites (E220-228, wine/dried fruit), nitrite/nitrate (E249/250, processed meats - risk of carcinogenic nitrosamines with heat), propionic acid (E280/283, bakery)

Preservative vs stabiliser

Preservatives prevent microbial spoilage; stabilisers maintain physical/textural properties - not the same function

Antioxidant food additives

Added to prevent oxidation (rancidity in fats, browning in fruit) - e.g. BHT, BHA, citric acid, tartaric acid

Stabilisers, gelling agents, thickeners

Stabilisers maintain physical/textural properties (e.g. prevent large ice crystals in ice cream); gelling agents impart shape/structure (e.g. jams); thickeners increase viscosity (e.g. low-fat milkshakes)

Gum sources (seeds/exudates)

Guar gum (E412) and locust bean gum (E410) from seed endosperm; gum arabic (E414) and tragacanth (E413) are plant exudates

Pectin

E440; extracted from citrus fruits/apples; makes jam set

Agar

E406; from red algae; mixture of agarose and agaropectin; melts at 85°C, solidifies 32-40°C - ideal for food use

Carrageenan types

Kappa-carrageenan (1 sulfate, rigid gels with potassium); iota-carrageenan (2 sulfates, soft gels with calcium); lambda-carrageenan (3 sulfates, does not gel, used as thickener)

Xanthan gum

Polysaccharide produced by the bacterium Xanthomonas campestris via fermentation; common thickener e.g. in salad dressings

Anti-caking agents

Added to powders to keep them flowing freely - e.g. silicon dioxide (E551), calcium silicate (E552), magnesium carbonate (in table salt)

Benzidine (Adler's test)

Old blood test; blue-green colour change with blood + H2O2; discontinued because benzidine is a carcinogen

Phenolphthalein (Kastle-Meyer test)

Blood presumptive test; colourless to pink via oxidation by haem + H2O2; less sensitive than benzidine but safer (non-carcinogenic)

Luminol

Blood presumptive test; chemiluminescence (glowing blue light) with blood (catalyst) + H2O2; very sensitive (detects to 1 ppm); works on decayed blood; no interference with other tests

OJ Simpson case

Luminol detected blood on Ford Bronco door handle and at the murder scene; DNA matched both victims; Simpson acquitted criminally, found liable civilly

Bain family murders case

Dunedin, 1994; luminol found blood on David Bain's socks (none on Robin Bain's); David convicted, later acquitted after retrial; house burned down two weeks later, destroying footprint evidence

Body in the Canal case (Dublin, 2005)

Unidentified torso found; bone marrow DNA profiling + paternity test identified victim; luminol testing at flat proved large blood volume present before a clean-up; daughters (Scissor Sisters) convicted

Fingerprint formation timing

Fingerprints set down at ~12 weeks gestation, unique even to identical twins/clones, unchanged for life unless physically damaged

Eccrine vs apocrine sweat glands

Eccrine glands (numerous on hands/feet) produce latent invisible prints; apocrine glands are in armpits/groin

Eccrine sweat composition

Mostly water plus inorganic ions (Na+, Cl-, NH4+) and organic constituents (amino acids, urea, lactic acid, sugars)

Sebaceous glands

On forehead/head; produce sebum (oily secretion) that transfers to fingertips via touching face/hair; sebum is water insoluble (fats, fatty acids, wax esters, squalene)

Plastic fingerprint

Produced when finger presses into a soft pliable surface (paint, wax, dust); gives a negative image of the ridge pattern