Nutrition and Food Technology

This chapter asks what the Pinggan Sihat Malaysia campaign by the Ministry of Health Malaysia presents, why the nitrogen cycle matters to plants, and what acts govern the preparation and sale of food in Malaysia p. 46. A smart consumer always checks the safety status of food products and health supplements p. 47.

2.1 Balanced Diet and Calorific Value

A lack or an excess of any class of food can cause malnutrition p. 48. The Ministry of Health Malaysia’s Pinggan Sihat Malaysia fills half the plate with fruits and vegetables, a quarter with rice or other carbohydrate, and a quarter with fish or other protein p. 49. Its main messages are to eat 3 main healthy meals a day, 1–2 healthy snacks if needed, more cereal foods, less fried food or food with coconut milk, and more home-cooked food p. 49.

Calorific value of food is the amount of energy released from the complete oxidation or combustion of 1 g of that food p. 50. One calorie is 4.2 joules, one kilocalorie is 4200 joules or 4.2 kilojoules, and the S.I. unit for calorific value is joule per kilogram p. 50. A bomb calorimeter measures calorific value: carbohydrate and protein give 16.7 kJ g⁻¹ while fat gives 37.6 kJ g⁻¹ p. 50. Palm oil has a calorific value of 38.00 kJ g⁻¹, rice 15.04 kJ g⁻¹ and cabbage only 0.34 kJ g⁻¹ p. 51. In Experiment 2.1, 1 g each of groundnuts, bread and anchovies heats 10 g of water to estimate their calorific values p. 51.

Unhealthy eating habits can cause malnutrition, obesity, anorexia nervosa, arteriosclerosis, diabetes mellitus, high blood pressure, thrombosis, stroke and heart disease p. 53. Obesity comes from consuming food with high calorific value excessively, and high blood pressure from food with high salt content, over long periods of time p. 54. Many restaurants in Malaysia, especially fast food restaurants, operate 24 hours a day p. 55. Excessive sugar in fast food and junk food can cause obesity and tooth decay, and caffeine in carbonated drinks can cause insomnia, anxiety and addiction p. 55.

2.2 Nutrient Requirements in Plants

Plants need nutrients for growth, development and reproduction, classified into macronutrients and micronutrients p. 57. Macronutrients such as nitrogen, phosphorus, potassium, magnesium, calcium, sulphur, oxygen, carbon and hydrogen are needed in large quantities, and micronutrients such as boron, molybdenum, iron, manganese, copper and zinc in small quantities p. 57. Nitrogen synthesises protein, chlorophyll, enzyme and nucleic acid, phosphorus promotes cell division for flowers and fruits, and magnesium is an important component in chlorophyll p. 58. Boron synthesises chlorophyll and cell wall, and zinc helps form chlorophyll and leaves p. 58.

A plant lacking nitrogen has a weak stem and pale green or yellow bottom leaves (chlorosis), but its roots grow normally p. 59. A plant lacking phosphorus has purplish top leaves and bluish green bottom leaves, and its flowers and fruits stop p. 59. A plant lacking potassium has brown spots on its top leaves and dies before reaching maturity p. 59. In Experiment 2.2, maize seedlings grow in complete culture solution and in culture solutions without nitrogen, phosphorus or potassium for two weeks p. 60.

2.3 Nitrogen Cycle

The nitrogen cycle is a natural cycle that recycles nitrogen between plants and animals, and the atmosphere, soil and water p. 62. About 78% of air is nitrogen, but plants can only absorb nitrogen as nitrate ions from the soil through their roots p. 62. During lightning or volcanic eruptions, nitrogen is oxidised to nitrogen dioxide, which dissolves in rainwater to form nitric acid that reacts with minerals to form nitrate ions p. 63. Nitrogen-fixing bacteria in soil, water or legume root nodules convert nitrogen in the air into nitrate ions p. 63. In nitrification, decomposing bacteria convert protein into ammonium compounds and nitrifying bacteria convert these into nitrite ions and then nitrate ions p. 63.

Plants absorb nitrate ions to form plant protein, which passes to animals that eat them p. 64. Denitrifying bacteria convert nitrate ions into nitrogen that returns to the air, and nitrate leaching washes nitrate ions into rivers or underground water p. 64. The nitrogen cycle keeps nitrogen at 78% of the atmosphere, and crop rotation and fertilisers restore nitrate ions to infertile soil p. 64. Nitrification also reduces environmental pollution and is used in green technology to produce compost p. 65.

2.4 Food Production Technology

Food production technology is applied to solve the problem of global food shortage by increasing food quality and quantity, using quality breeds and using modern technology p. 66. Quality breeds are obtained through cloning, cross-breeding, genetic engineering and mutagenesis, for example the Tenera oil palm, the Mafriwal hybrid dairy cow and the Akar Putra chicken p. 67. Quality breeds have high yields, grow and mature rapidly, and resist diseases, pests and extreme weather p. 67. Grinding and liquid filling machines speed up processing, and cloning retains good characteristics in crop and livestock breeds p. 68. Biotechnology such as embryo transfer, cloning and genetic engineering increases food quality and quantity, and drones that spray pesticides save time and labour cost p. 69.

Agencies such as MARDI and the Malaysian Palm Oil Board (MPOB) give farmers education and guidance p. 70. Idle land, abandoned mining pools and marshland can be developed for agriculture and aquaculture, and aeroponic and hydroponic farming need no soil p. 71. FELDA restores idle land into fertile land, and efficient land management uses crop rotation, mixed planting and terrace farming p. 72. Insecticides pollute the environment, increase pest resistance and kill earthworms and useful microorganisms in the soil p. 73. Biological control uses prey-predator interactions, such as barn owls hunting rats, or parasitism, such as wasps laying eggs in butterfly eggs p. 74.

2.5 Food Processing Technology

Processed food lasts longer, is more delicious and attractive, and can be digested easily p. 75. Fermentation breaks down complex substances through bacteria or yeast, as when yeast ferments glucose into ethanol and carbon dioxide to make bread p. 76. Pasteurisation heats fresh milk to 63 °C for 30 minutes or 72 °C for 15 seconds and then cools it immediately p. 77. Canning heats food in sterilised cans to above 115 °C under high pressure, and freezing below −18 °C stops enzyme action and inhibits microorganisms p. 78. Irradiation kills Salmonella sp., Campylobacter sp. and weevils, and vacuum packaging removes air to prevent microorganisms and food oxidation p. 79.

Chemical substances in food processing include preservatives such as sodium nitrite and benzoic acid, colourings such as tartrazine, bleach such as benzoyl peroxide, flavourings and stabilisers such as gelatine p. 80. Sweeteners such as aspartame, antioxidants such as ascorbic acid and emulsifiers such as lecithin are also used, and excess chemical substances can cause cancer and damage the liver and kidney p. 81.

2.6 Health Foods and Health Supplements

Health foods are natural food substances in a normal diet that maintain health and do not contain chemical substances, while health supplements come as capsules, pills, liquids or powders in pre-determined doses p. 83. Taking insufficient or excessive health supplements frequently occurs and may affect the user negatively p. 83. The Drug Control Authority (DCA) registers and monitors health supplements and traditional medicine, which carry labels and QR codes when approved p. 84. The Food Act 1983 protects the public from dangers of health and fraud related to the preparation, sale and use of food p. 84. The Food Regulations 1985 help the public obtain safe, clean food and set the information on food labels p. 85. The Halal Malaysia logo certifies that the food sold is halal p. 86.