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PRINCIPLES UNDERLYING SPOILAGE. FITNESS OR UNFITNESS OF FOOD FOR CONSUMPTION: According to Thom and Hunter (1924),
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PRINCIPLES UNDERLYING SPOILAGE FITNESS OR UNFITNESS OF FOOD FOR CONSUMPTION: According to Thom and Hunter (1924), “A product is fit for food if a discriminating consumer, knowing the story of its production and seeing the material itself, will eat it, and, conversely the same product is spoiled when such an examiner refuses it as food.”
Criteria for assurance of fitness 1. The desired stage of development or maturity. 2. Freedom from pollution at any stage in production or handling. 3. Freedom from objectionable change resulting from microbial attack or action of enzymes of the food.
CAUSES OF SPOILAGE Decay or decomposition of an undesirable nature usually is implied when the term “spoiled” is applied to food, while food unfit to eat for sanitary reasons usually is not called spoiled.
Spoilage may be due to one or more of the following:1.Growth and activity of microorganisms (or higher forms occasionally). Often a succession of organisms is involved. 2.Insects. 3.Action of the enzymes of the plant or animal food.4.Purely chemical reactions, i.e., those not catalyzed by enzymes-of the tissues or of microorganisms.5.Physical changes, such as those caused by freezing, burning, drying, pressure, etc.
CLASSIFICATION OF FOODS BY EASE OF SPOILAGE On the basis of ease of spoilage, foods can be placed in three groups: I. Stable or nonperishable foods: These foods, which do not spoil unless handled carelessly, include such products as sugar, flour, and dry beans. 2 Semiperishable foods: If these foods are properly handled and stored, they will remain unspoiled for a fairly long period, e.g., potatoes, some varieties of apples, waxed rutabagas, and nutmeats. 3 Prishab1e foods: This group includes most important daily foods that spoil readily unless special preservative methods are used. Mea , fish, poultry, most fruits and vegetables, eggs, and milk belong in this class ication.
FACTORS AFFECTING KINDS AND NUMBERS OF MICROORGANISMS IN FOOD The kinds and numbers of microbes present and on the environment about them. Pretreatments of foods.
FACTORS AFFECTING THE GROWTH MICROORGANISMS IN FOOD • Associative Growth : Associations of microorganisms with each other are involved in spoilage or fermentations of most kinds of food. • If conditions are favorable for all, bacteria usually grow faster than yeasts, and yeasts faster than molds.
Two kinds of microorganisms may be synergistic; i.e., when growing together they may be able to bring about changes, such as fermentations, that neither could produce alone.Pseudomonas syncyanea growing alone in milk produces only a light-brownish tinge, and Streptococcus lactis causes no color change in milk; however, when the two organisms grow together, a bright blue color develops, resulting from a pH effect on the brown pigment produced by P. syncyanea.
A most important effect of a microorganism on another is the metabiotic.When one organism makes conditions favorable for growth of the second. Both organisms may be growing at the same time, but more commonly one succeeds the other.
Raw milk at room temperature normally first supports an acid fermentation by Streptococcus lactis and coliform bacteria Bacteria are inhibited by the acid they have produced. Acid-tolerant lactobacilli increase the acidity further They are stopped acidity produced by them.. Then film yeasts and molds grow over the top, finally reducing the acidity so that proteolytic bacteria can become active.
Effect ofEnvironmental Conditions FAT TOM F-Food A-Acidity T-Time T-Temperature O-Oxygen M-Moisture
