Food Commodities

Question 1

What is a food commodity?

Answer 1

A product that can be bought and sold and is derived from an agricultural animal or crop and intended for human consumption in its raw or processed state.

Question 2

What constitutes the food commodity ‘cereals’?

Answer 2

• Wheat. Flour: Wholemeal 100%, Brown 85%, white 72%. Strong flour has high protein/gluten content (>12%). Soft flours (8-10%) Durum wheat - high protein. Couscous.
• Maize (corn) - cornmeal used in tortillas, etc. Low in Niacin unless treated with alkali.
• Rice: Brown (outer husk removed), White (bran and germ removed as well). Low in Thiamin.
• Oats: oatmeal, rolled for porridge, flour
• Barley: pearl barley, malted barley can be fermented to make beer.
• Rye: contains little gluten so produces dense breads, crispbreads
• Millet: important dought resistant staple food in India and Africa
• Sorghum: popular for livestock

Question 3

What nutrients do cereals contribute to the diet?

Answer 3

• Starch (60-90%)
• Protein (6-15%): Two main proteins in wheat are gliadin and glutenin which hydrate to form gluten - can cause inflammatory response in people with Coeliac disease. Most are not complete proteins and lack amino acids such as lysine but some such as buckwheat and quinoa are complete.
• Fats (1-7%): wheat 1.5%, maize 7%. Mainly polyunsaturated fatty acids (omega-6)
• Fibre
• Minerals: poor bioavailability. Iron, magnesium, sodium, zinc, selenium, calcium if fortified. 50% associated with bran.
• Vitamins: vitamin E and some B vitamins
• All wheat flours (except wholegrain) must have some vitamins and minerals reinstated to a certain level including B1, B3, iron and calcium
• Bioactive compounds: flavonoids, Carotenoids and tocopherols (anti-oxidants)

Diets rich in wholegrain cereals are associated with a lower risk of cardiovascular disease and some cancers.

Question 4

How do the processes that food commodities undergo change their nutritional composition?

Answer 4

• Milling wheat to flour: over 50% many B vitamins lost: lose 77% Thiamin, 67% riboflavin, 72% Niacin, 68% folic acid.
• processing rice: lose 15% protein, 65% fat and fibre, 80% thiamin, 40% riboflavin, 20% folic acid.
• Water-soluble vitamins are more unstable than fat-soluble
• Nitrogen fertilisers reduce Vitamin C content
• Blanching - before canning or freezing may be heated quickly with steam or water. Lose many water-soluble vitamins
• Canning - food heated to high temperatures inside can to kill dangerous microorganisms. Water-soluble vitamins sensitive to high temperatures.
• This is why fortification may be necessary

Question 5

What constitutes ‘fruit and vegetables’ and what do they generally provide?

Answer 5

• All types of fresh, frozen, canned and dried fruits and vegetables count.
• 80g per portion
• 150ml fruit juice
• Provide carbohydrates, dietary fibre, vitamin C, folate, beta-carotene, potassium.

Question 6

What nutrients do the protein foods provide?

Answer 6

• Essential amino acids (and non-essential)
• Iron
• Zinc
• Magnesium
• B vitamins, especially B12 in animal sources

Question 7

What constitutes the food group ‘Milk and Dairy foods’ and what nutrients do they contain.

Answer 7

• Milk, cheese, yoghurt, diary alternatives (unsweetened, calcium-fortified)
• Does NOT include butter, eggs, cream.
• Calcium, Protein, Vitamin B-12, vitamins A and D.

Question 8

What is the function of the ingredients in bread?

Answer 8

• Strong wheat flour is high protein/gluten (>12%)
• Wheat proteins include gliadin and glutenin which hydrate to form gluten
• Gluten is a strong elastic substance which forms a network throughout the dough which can trap carbon dioxide produced by the added yeast and allow the dough to rise without collapsing in on itself
• Fat can inhibit gluten development but help palatability and keepability
• Salt and ascorbic acid help gluten development