1. Nutrient content of food
Nutritional value of foods affected by:
• specie-type of plant or animal.
• Where and how they are grown or rared.
• Effect of harvest and slaughter.
• Time taken to transport.
• Effect of processing food in factory.
• Amount of wastage when preparing food.
• Effect of various processes and cooking practices in kitchen.
Practices which lead to a loss of nutrients:
HEATING
• destroys Vitamin C-thiamin-riboflavin.
• With alkali (bicarbonate of soda to preserve colour in green leafy vegetables)
destroys Vit C and Riboflavin.
• Overheating proteins leads to hardening and reduces digestibility.
• Keeping food hot further destroys Vitamin C, thiamine, riboflavin.
SOAKING
• leads to loss of Vit C, thiamin, riboflavin, nicotinic acid into de liquid.
EXPOSURE TO AIR
• oxidation Vit C.
• gradual deterioration of fat, RANCIDITY.
EXPOSURE TO LIGHT
• destruction of riboflavin and Vit A.
Practices which conserve nutrients
STEAMING
WS-vitamins are retained more as food does not come into direct contact with water.
STEWS AND GRAVY
Preparation of gravy from vegetable cooking water retains some WS-vitamins and are also
retained in liquid used in a stew.
PRESSURE COOKING
Less destruction by heat as cooking time is reduced

2. Practices that enhance nutritional value
COMBINING FOODS
• Two low biological value protein foods (bread with lentil soup)
• Vitamin C and Iron
PREPARING FOODS
• grating cheese (fat content more easily digested).
• homogenizing milk (fat content more easily digested).
Storing vegetables
• Preparation just before cooking prevents oxidation of Vit C.
• If the previous does not happen, they can be stored in clean plastic bags to prevent
oxidation of Vit C.
• Placing green vegetables into boiling water for cooking without pre soaking reduces
loss of WS-Vitamins by leaching.
• Minimum cooking time reduces heat destruction of Vit C, thiamine and riboflavin.