Food Microbiology covers studies on:
- Food spoilage by different kinds of microorganisms such as bacteria and fungi
- Testing of Food/ food products for microbial contamination
- Methods to be employed for prevention of food spoilage and preservation techniques
- Use of various microorganisms in production of various food products
Microorganism Growth and Food Spoilage
Different food products provide ideal growth conditions for microorganisms. Microbial growth is controlled by intrinsic factors like nutrients, pH, moisture content, physical structure of the food and/ or extrinsic factors like temperature, relative humidity, gases (CO2,O2). Microorganisms thus grow in optimum conditions provided by external and internal factors, resulting in spoilage and degradation of the food product resulting in a sour, foul-smelling or fungus-covered inedible mass. Microbial growth in foods can also cause visible changes like change in colour, deposition of powdery growth, effervescences on food surface, etc. Microbial contamination of food can occur at any point in the food production process: growth, harvesting, transport, storage, or final preparation. Spoilage also can occur if foods are not stored properly. Meat and dairy products are rich in protein and fat serves as an ideal environment for microbial spoilage resulting in proteolysis and putrefaction of the food products. Vegetables and fruits have a much lower protein and fat content and undergo a different kind of spoilage.
Microbiological testing of Food
There are basically two main strategies for testing food products.
- Determination of Microbiological Quality: This is done by determining total viable count of the food sample. This includes – Total bacteria count (TBC), Total yeast and mold count (TYMC). This test provides the details about microbial quality of the food
- Determination of Food Safety: This test includes analysis and testing of food samples for food pathogens belonging to group Enterobacteria, Enterococci, coliforms, E. coli and any other pathogens as Pseudomonas sp. Clostridia, Salmonella, Bacillus spp, Staphylococcus, lactic acid bacteria, Salmonella, Listeria, yeasts and molds etc. .
Control of Microbial Growth and Food Preservation
Contamination of food may occur due to the presence of any microbial population during packaging, after opening the packaged food or serving of the food. To ensure long shelf life of preserved and stored food it is vital to eliminate or reduce the populations of spoilage and disease-causing microorganisms and to maintain the microbiological quality of a food with proper storage and packaging. Microbial growth in food products can be controlled by various methods.
- Removal of microorganisms by physical methods such as filtration, centrifugation
- Thermal treatment as Refrigeration, freezing, partial or complete heat inactivation of microorganisms (pasteurization and canning)
- Reduction or removal of moisture/water content by freeze drying (lyophilization)
- Addition of chemical preservatives
- Use of ionizing (gamma rays) and non ionizing (UV) radiation
- Addition of substances such as bacteriocins based inhibition to foods to control food-borne pathogens
Microorganisms in Food Production
- Microorganisms have been widely used in lactic, propionic, and ethanolic fermentations from time immemorial.
- They are characteristically used in production of about 2,000 distinct varieties of cheese throughout the world.
- They are used in production of different alcoholic beverages using variety of carbohydrate substrates.
- Microorganisms can be used to transform raw foods into pickles, sausages, sauces,etc.
- Microorganisms can themselves be used as a food source. The most common example is fungus (Agaricusbisporus) commonly as mushrooms.
- Probiotics are being used successfully with poultry.
Points to remember
- Most food and food products provide an excellent environment for microbial growth leading to food spoilage and degradation.
- Various intrinsic and extrinsic factors as pH, sugar and salt content of the food, moisture content, temperature etc. are responsible for the growth of microorganisms in a food product.
- Microorganisms can spoil meat, dairy products, fruits, vegetables, and canned goods in several ways.
- Microbial testing of food involves the quality and safety analysis of the food samples.
- Microbial contamination of food can be prevented by various methods as physical removal of microorganisms, thermal treatment, freeze drying, addition of chemicals, radiation etc.
- Microorganisms are used in the production of various fermented products, cheese, sauces, pickles, alcoholic beverages etc.