Food and nutrition.pdf

Chapter 29Food SpoilageMost natural foods have a limited life. Perishable foods such as fish,meat, milk, bread, tomatoes and potatoes have a short life span. Otherfoods keep for a considerably longer time but decompose eventually. Oncefood has been harvested, gathered or slaughtered it begins to deteriorateuntil eventually it becomes unfit for consumption. This deterioration isknown as decay and leads to food spoilage.Causes of the Spoilage of FoodMicrobial SpoilageThere are three types of microorganisms that cause food spoilage -yeasts, moulds and bacteria.• Yeasts growth causes fermentation which is the result of yeastmetabolism. There are two types of yeasts true yeast and falseyeast. True yeast metabolizes sugar producing alcohol and carbondioxide gas. This is known as fermentation. False yeast grows asa dry film on a food surface, such as on pickle brine. False yeastoccurs in foods that have a high sugar or high acid environment.• Moulds grow in filaments forming a tough mass which is visibleas 'mould growth'. Moulds form spores which, when dry, floatthrough the air to find suitable conditions where they can startthe growth cycle again.• Mould can cause illness, especially if the person is allergic tomolds. Usually though, the main symptoms from eating mouldyfood will be nausea or vomiting from the bad taste and smell ofthe mouldy food.