Intrinsic and extrinsic factors of food spoilage

how intrinsic and extrinsic factors contribute in food spoilage

1. Intrinsic and E xtrinsic Factors of Food Spoilage By: Zarafshan zeb , Food microbiology Department of Human Nutrition And dietetics Add a footer 1

2. Intrinsic factors 2.1. Moisture content 2.2. Antimicrobial components 2.3. B iological structure 2.4. Hydrogen ion concentration (pH) 2.5 . Oxidation-reduction potential 2.6. Nutrient content Add a footer 2

3. MOISTURE CONTENT Microbial cells require water in an available form to grow in food products. In ancient time foods are preserved by controlling their moisture content. Microbiologist usually express the water requirements of microorganisms in terms of the water activity(aw) of the food or environment. Add a footer 3

4. ANTIMICROBIAL COMPONENTS Some foods intrinsically contain inherent naturally-occurring antimicrobial compounds that can provide microbiological stability to them. There are a number of plant-based antimicrobial constituents known. Examples are; cinnamon , oregano, garlic , basil. Add a footer 4

5. BIOLOGICAL STRUCTURES Biological structures are basically natural covering found on plant and animal origin foods, may prevent the entry and growth of microbial cells. Examples include outer covering of fruits and vegetables, shell of nuts. Add a footer 5

6. HYDROGEN ION CONCENTRATION (PH) The intrinsic pH of foods varies with origin and types of food i.e. in their natural state, most foods such as meat, fish and vegetables are slightly acidic while most fruits are moderately acidic. pH value are : Acidic : yeast and molds Alkaline; bacteria Neutral; mostly bacteria can grow on neutral pH. Add a footer 6

7. Nutrient content Microorganisms have need of certain basic nutrients for their growth and maintenance of physiological functions . These nutrients include water, a source of energy, nitrogen, vitamins, and minerals . Microorganisms select their food as substrate on the basis kinds and proportions of nutrients present in foods . Add a footer 7

8. Oxidation-reduction potential Micro organisms display varying degrees of sensitivity to the oxidation reduction potential of their growth of medium. it is influence by its chemical composition, specific processing treatment given and storage condition in relation to air. Processes such as heating can increase or decrease reducing compounds and alter Eh. Add a footer 8

9. Extrinsic factors Factors in the environment and external to the food, which affect both the microorganisms and the food itself during processing and storage . 2.1: Storage temperature 2.2: Relative humidity 2.3: Gases Add a footer 9

10. Storage temperature Foods are exposed to different temperatures from time of production until the time of consumption. Microbial growth is accomplished through enzymatic reactions which is depended on temperature. Microbial Groups: Psychrophiles, Mesophiles and Thermophiles Add a footer 10

11. Relative humidity Relative humidity is a measure of water activity of the gas phase. High RH influence the water content of food and high water content promote microbial growth. When food stored in high relative humidity, dormant spores of bacteria or fungi to germinate. Add a footer 11

12. Gases Presence or absence of gases affects microbial populations. Carbon dioxide regulates cell growth of certain bacteria. Carbon dioxide is used in packaging of some food items in order to control the growth of microbes. Add a footer 12

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