need definitions for each Principles of food microbiology The role of microbes i
ID: 271553 • Letter: N
Question
need definitions for each
Principles of food microbiology The role of microbes in food spoilage, definition of food spoilage/unsafety of spoiled food Intrinsic factors (water activity, pH, nutrients, biological barriers, antimicrobial substances naturally present) and extrinsic factors (storage temperature, presence/absence of oxygen), that affect growth of microbes in foods (bacteria and fungi that cause food spoilage)?Food poisoning (Intoxication and infection) – Intoxication (S. aureus and C. botulinum), infections through foods can be caused by Salmonella, Campylobacter, certain strains of E. coli, Shigella, Vibrio cholerae and Giardia intestinalis (can contaminate both food/water) Strategies used to preserve foods: refrigeration/freezing, drying, addition of sugar/salts, lyophilization, lowering the pH by fermentation of foods or by addition of organic acids, addition of nitrates/nitrites (to prevent germination of endospores of Clostridia), sulfur dioxide, irradiation
Explanation / Answer
1.Principles of Food Microbiology- It is defined as the study of the microbes or micro-organisms that causes contamination of food which makes it unfit for human consumption. Food microbiology is the branch of science that mainly focuses on the general biology of the microbes that are found in food, such as, their growth parameters, pathogenecity and their identification. This study highlights the areas of interest such as food spoilage and food preservation.
2. Role of Microbes in Food Spoilage- Food spoilage is defined as the detereoration is the quality of food from its normal state. Such changes are characterized by change is smell, putrid taste or sometimes changes may occur in the texture. Microbes such as fungi and bacteria are involved in majrity of food spoilages. The sources of these micro-organisms are air, water, soil, sewage,etc. there are certain microbes which are present on the surgace of the food and when the optimum conditions are found, they start their multiplication. Optimum conditions includes proper moisture, adequate aeration and optimum temperature; that favors their growth. On attacking the food, microbes secretes their metabolic byproducsts or some toxins that can cause the food to spoil.
3. Food Spoilage- Food spoilage is defined as the detereoration is the quality of food from its normal state. It may be caused by microbial action, or when environmental conditions changes, etc.
4. Instinsic Factors- Water is present in the form of moisture that aids in the microbial multiplication. Water helps in diluting the electrolytes or nutrients which are taken up by the microbes required for their growth. pH gives the idea of the acidity or basicity of the medium. Microbial growth normally occurs at neutral pH but it may vary from species to species and their natural habitat. There exist some naturally occuring anti-microbial substances that can inhibit the microbes to perform their action. Such substances are present in leaves, bark of plant, flower, stem or fruit.
5. Extrinsic Factors- Improper storage of food can cause decrease in the shelf life of the food which makes the food an easy target for the microbial attack. It is therefore suggested to keep the food in refrigerators or in the freezers as they will protect the food by increasing their shelf life. Oxygen causes food spoliage as it lead to oxidation of food. The process by which food quality decreases due to oxidation is termed as rancidity..
6.Refrigeration/Freezing- Refrigeration merely increases the shelf life of food which will increase the time period for the food consumption. It happens because at low temperature, most micro-organisms cannot survive. Whereas, freezing is advantageous over regrigeretion because it deactivates the enzymes at very low temperature present in food and microbes fails to grow at such lower temperature. Freezing also increases the shelf life of food similar to regrigerators.
7. Drying- In this process, food is dried so that excess moisture can be removed from the food so that absence of moisure does not favour the microbial growth. Drying of fruits is the classical example in order to preserve food. It has one more advantage, that, drying causes the increase in the availibility of nurtients per unit area.
8. Addition of Sugar/Salts- In this process of food preservation, saturated amounts of sugar or salt is added to the food material. It is based on the principles that, excess concentration of salt/sugar will cause osmosis of the microbial cell that will lead to imbalance in their osmolarity and cause their cell lysis and therefore prevent their growth by their killing. For example: preparation of jams by adding sugars and pickles by adding salt.
9. Lyophilization- In this techniques of food preservation, water or moisture is removed from the food aterial either by heating or drying and the food is converted into the dried powder form which is free from any contaminaton from the microbial source.
10. Irradiation- It is a mechanism whereby a food is preserved by irradiating it. High energy radiations are given to the food that will kill the food pathogen nd causes its sterilizaton.
11. Addition of Nitrates/Nitrites-In this method, food is treated with the nitrates or nitrites or their derivatives. It is based on the principle that these compounds will destroy the microbial electron transport chain that will affect their metabolism and ultimatel causes the death of them.
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