Cameroon GCE A-Level Food Science & Nutrition cheat sheet

Water activity (aw) equals equilibrium relative humidity/100; most bacteria need aw above 0.90, most moulds above 0.70, so aw is a better spoilage predictor than moisture content alone.

Macronutrient energy: carbohydrate 4 kcal/g (17 kJ/g), protein 4 kcal/g (17 kJ/g), fat 9 kcal/g (37 kJ/g), alcohol 7 kcal/g (29 kJ/g), dietary fibre about 2 kcal/g.

Maillard browning needs a reducing sugar plus an amino group; it accelerates above aw 0.6-0.7 and at alkaline pH, and is suppressed by sulfur dioxide or low pH.

Caramelisation requires heat and sugar only (no amine); it proceeds via enolisation and produces bitter, dark polymers at high temperature.

Starch gelatinisation begins near 60-70 degrees C in excess water; on cooling, amylose retrogrades first, causing staling and syneresis in gels.

Protein denaturation unfolds tertiary structure without breaking peptide bonds; it is driven by heat, extremes of pH, urea or shear and changes solubility and water binding.

Peroxide value measures hydroperoxides (early oxidation), while anisidine value measures aldehydes (secondary oxidation); TBA value targets malondialdehyde.

Vitamin C (ascorbic acid) is water-soluble, heat- and oxygen-labile, and leaches into cooking water; losses are minimised by short cooking, low water volume and acid pH.

Saturated fatty acids have no double bonds and higher melting points; each cis double bond lowers melting point and increases susceptibility to oxidation.

Intrinsic factors controlling microbial growth: pH, aw, redox potential, nutrient content, antimicrobial compounds and biological structure; extrinsic factors: temperature, relative humidity, atmosphere.

Classification by temperature: psychrotrophs grow at 0-7 degrees C, mesophiles at 20-45 degrees C, thermophiles at 45-65 degrees C; Clostridium botulinum is proteolytic and mesophilic.

Spore formers survive boiling: Bacillus and Clostridium endospores require 121 degrees C (autoclave, 15 psi) for commercial sterility in low-acid canned foods.

FATTOM summarises growth requirements: Food, Acidity, Temperature, Time, Oxygen, Moisture.

HACCP has seven principles: hazard analysis, CCP determination, critical limits, monitoring, corrective actions, verification, record keeping.

Two-tier food safety: hazard-based limits (e.g. zero tolerance pathogens) versus risk-based microbiological criteria (e.g. 10^2 CFU/g Listeria at end of shelf life).

Foodborne intoxication examples: Staphylococcus aureus enterotoxin (heat-stable), Clostridium botulinum neurotoxin, Bacillus cereus emetic toxin; infection examples: Salmonella, Listeria, Campylobacter.

Aflatoxin is produced by Aspergillus flavus and A. parasiticus in groundnuts and maize; ochratoxin A occurs in cereals and coffee; both are mycotoxins requiring control of moisture and storage.

Blanching inactivates enzymes (peroxidase, polyphenol oxidase) before freezing or drying; it also reduces microbial load and fixes colour but leaches water-soluble vitamins.

Freezing does not sterilise; it stops growth but psychrotrophs and spores survive, and slow freezing forms large ice crystals that damage cell walls and cause drip loss.

Drying removes water to lower aw; the drying curve has a constant-rate period (surface evaporation) and a falling-rate period (internal diffusion controls).

Canning uses a scheduled process based on the slowest-heating point (cold spot); low-acid foods (pH above 4.6) need pressure retorting to destroy C. botulinum spores.

Pasteurisation (typically 63 degrees C/30 min or 72 degrees C/15 s for milk) destroys vegetative pathogens but not spores, so the product needs refrigeration.

UHT treatment (135-150 degrees C for 2-5 s) plus aseptic packaging gives commercial sterility and ambient shelf life, with some vitamin and flavour loss.

Ohmic and microwave heating are volumetric, avoiding conduction-limited slow heating; high-pressure processing inactivates vegetative cells at ambient temperature but not spores.

Modified atmosphere packaging lowers O2 and raises CO2 to slow respiration and microbial growth; vacuum packaging suppresses aerobes but favours anaerobes such as C. botulinum.

Cold chain storage: chilled 0-5 degrees C, frozen -18 degrees C or below; temperature abuse shortens shelf life and can allow pathogen growth.

Energy expenditure components: basal metabolic rate (about 60-70% of total), thermic effect of food (about 10%), physical activity (variable).

Protein quality measures: biological value, net protein utilisation, protein efficiency ratio, and PDCAAS or DIAAS; complementary proteins combine limiting amino acids.

Essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.

Glycolysis yields 2 ATP and 2 pyruvate per glucose; complete oxidation gives about 30-32 ATP including the TCA cycle and oxidative phosphorylation.

Fatty acid beta-oxidation cleaves two carbons per cycle as acetyl-CoA; excess acetyl-CoA in fasting forms ketone bodies.

Micronutrient functions: iron in haemoglobin, iodine in thyroid hormones, calcium in bone and signalling, vitamin A in vision, folate in one-carbon transfer.

Water-soluble vitamins (B group, C) are not stored appreciably and excess is excreted; fat-soluble vitamins (A, D, E, K) are stored in liver and adipose tissue.

Dietary reference values: EAR is the intake meeting the needs of half the group, RDA is EAR plus two SD, and UL is the highest intake unlikely to cause harm.

ABCD of nutritional assessment: Anthropometry, Biochemical tests, Clinical examination, Dietary assessment.

BMI equals weight (kg) divided by height squared (m^2); WHO categories: underweight below 18.5, normal 18.5-24.9, overweight 25-29.9, obese 30 and above.

Waist circumference and waist-to-hip ratio assess central adiposity; elevated risk is commonly set at above 94 cm (men) and 80 cm (women) for waist circumference.

Dietary assessment methods: 24-hour recall, food frequency questionnaire, weighed food record, diet history; each has different recall and recording bias.

Double burden of malnutrition describes coexistence of undernutrition and overnutrition in the same population, household or individual.

Stunting is low height-for-age (chronic undernutrition), wasting is low weight-for-height (acute), and underweight is low weight-for-age.

Iron deficiency anaemia shows low haemoglobin and low ferritin; folate deficiency shows macrocytic anaemia with raised homocysteine.

Dietary guidelines emphasise variety, adequate fruit and vegetables (often at least 400 g/day), limited free sugars and salt, and safe water.

Stage-gate process: idea generation, screening, concept development and testing, business analysis, product development, test marketing, commercialisation.

Concept testing and sensory panel work occur before scale-up; pilot plant trials identify process tolerances before full production.

Product specification covers ingredients, formulation, process parameters, packaging, shelf life, labelling and safety limits.

Shelf-life testing uses accelerated studies (elevated temperature) with Arrhenius extrapolation, plus real-time storage for confirmation.

Hurdle technology combines several preservative factors (aw, pH, temperature, preservatives, packaging) at lower individual intensity to improve safety and quality.

Reverse engineering and reformulation for cost or health (salt, sugar, fat reduction) must be checked for sensory, textural and shelf-life effects.

Sensory testing designs: discrimination tests (triangle, duo-trio), descriptive analysis (QDA), and affective tests (hedonic scales, preference).

Costing includes raw materials, processing, packaging, distribution and wastage; contribution margin equals selling price minus variable cost.

Quality assurance is process-focused and preventive; quality control is product-focused inspection and testing.

Sensory panel types: trained descriptive panels give objective profiles; consumer panels give preference and acceptance data; discrimination panels detect differences.

Triangle test is a forced-choice 3-sample test (two identical, one different) used to detect a difference; duo-trio uses a reference sample.

Hedonic scale (typically 9-point) measures liking; a score of 5 is neutral, 7 and above indicates liking.

Sampling plans: AQL (acceptable quality level) and LTPD (lot tolerance percent defective) define producer and consumer risk in acceptance sampling.

Calibration and traceability are core to measurement quality; instruments must be calibrated against standards, and records must be traceable.

Sensory booth design controls lighting, temperature, odour and noise; samples are coded randomly to avoid bias.

Statistical process control uses control charts with upper and lower control limits (often mean plus/minus three standard deviations) to detect drift.

Elasticity of demand: price elasticity equals percentage change in quantity demanded divided by percentage change in price; food staples are typically inelastic.

Supply and demand: equilibrium price clears the market; a price floor (minimum price) creates surplus, a price ceiling creates shortage.

Marketing mix: product, price, place, promotion (the 4 Ps); for services, people, process and physical evidence are added.

Value chain analysis covers input supply, production, processing, distribution, retail and consumption, with value added at each stage.

Break-even quantity equals fixed costs divided by (unit price minus unit variable cost).

Market segmentation bases: demographic, geographic, psychographic and behavioural; targeting selects segments to serve.

Entrepreneurship in food requires opportunity identification, feasibility study, business plan, financing, registration and food safety compliance.

Costs of production: fixed costs do not vary with output; variable costs vary; average cost falls then rises with scale economies.

Food security has four pillars: availability, access, utilisation and stability; food insecurity can be chronic or transitory.

Food loss occurs between harvest and retail; food waste occurs at retail and consumption; both reduce effective supply.

Sustainable diets are protective of health and the environment, culturally acceptable, accessible and economically fair.

Life-cycle assessment quantifies environmental impacts (carbon, water, land) across a product's life, supporting eco-labelling claims.

Consumer issues: food labelling, nutrition claims, allergen declaration, date marking (use-by versus best-before) and food fraud.

Use-by dates relate to safety and should not be exceeded; best-before dates relate to quality and remain safe after.

Climate-smart agriculture integrates productivity, adaptation and mitigation; agroecology applies ecological principles to farming.

Consumer behaviour is shaped by price, taste, convenience, health perception, trust in institutions and socio-cultural norms.

Food security has four pillars: availability, access, utilisation and stability; food insecurity can be chronic or transitory.

Food loss occurs between harvest and retail; food waste occurs at retail and consumption; both reduce effective supply.

Sustainable diets are protective of health and the environment, culturally acceptable, accessible and economically fair.

Life-cycle assessment quantifies environmental impacts (carbon, water, land) across a product's life, supporting eco-labelling claims.

Consumer issues: food labelling, nutrition claims, allergen declaration, date marking (use-by versus best-before) and food fraud.

Use-by dates relate to safety and should not be exceeded; best-before dates relate to quality and remain safe after.

Climate-smart agriculture integrates productivity, adaptation and mitigation; agroecology applies ecological principles to farming.

Consumer behaviour is shaped by price, taste, convenience, health perception, trust in institutions and socio-cultural norms.

Food security has four pillars: availability, access, utilisation and stability; food insecurity can be chronic or transitory.

Food loss occurs between harvest and retail; food waste occurs at retail and consumption; both reduce effective supply.

Sustainable diets are protective of health and the environment, culturally acceptable, accessible and economically fair.

Life-cycle assessment quantifies environmental impacts (carbon, water, land) across a product's life, supporting eco-labelling claims.

Consumer issues: food labelling, nutrition claims, allergen declaration, date marking (use-by versus best-before) and food fraud.

Use-by dates relate to safety and should not be exceeded; best-before dates relate to quality and remain safe after.

Climate-smart agriculture integrates productivity, adaptation and mitigation; agroecology applies ecological principles to farming.

Consumer behaviour is shaped by price, taste, convenience, health perception, trust in institutions and socio-cultural norms.