The factors that affect microbial growth in foods 1- Physico-chemical properties of the food itself (intrinsic factors). 2- Conditions of the storage environment (extrinsic factors). 3- Properties and interactions of the microorganisms present (implicit factors).

Warmth, moisture, pH levels and oxygen levels are the four big physical and chemical factors affecting microbial growth.

The rate of growth or death of a particular microbial species is influenced by a variety of physical factors in its environment including temperature, osmotic pressure, pH, and oxygen concentration.

When microorganisms grow in food, they cause varying degrees of change in the food’s characteristics as a result of metabolic activity. Some of these changes, like those taking place during fermentation, are desirable, while others, like those resulting in food spoilage and food poisoning, are undesirable.

Most foods contain sufficient nutrients to support microbial growth. Several factors encourage, prevent, or limit the growth of microorganisms in foods, the most important are aw, pH, and temperature. aw: (Water Activity or Water Availability).

Remember the two-hour rule, and put foods away within two hours of eating. If the temperature outside (or inside) is really warm, put foods away within one hour of eating. Oxygen is needed for bacteria to grow, but some, like the botulinum toxin grow best in climates without oxygen.

Moderate changes in pH modify the ionization of amino-acid functional groups and disrupt hydrogen bonding, which, in turn, promotes changes in the folding of the molecule, promoting denaturation and destroying activity. The optimum growth pH is the most favorable pH for the growth of an organism.

Microbiological Quality and Safety Microbial growth can make meat less pleasant to eat (spoilage) and can make the consumer ill if the numbers of pathogenic microorganisms are too high or if too many toxins are produced. Bacteria and molds have a temperature range in which they prefer to grow.

Control of growth usually involves the use of physical or chemical agents which either kill or prevent the growth of microorganisms. Agents which kill cells are called cidal agents; agents which inhibit the growth of cells (without killing them) are referred to as static agents.

Among the oldest methods of preservation are drying, refrigeration, and fermentation. Modern methods include canning, pasteurization, freezing, irradiation, and the addition of chemicals.

Answer: FOOD PRESERVATION usually involves preventing the growth of bacteria and other microorganisms in food.

The main cause of food spoilage is invasion by microorganisms such as fungi and bacteria.

• 1 Microbial spoilage. Microbial spoilage is caused by microorganisms like fungi (moulds, yeasts) and bacteria.
• 2 Physical spoilage.
• 3 Chemical spoilage.
• 4 Appearance of spoiled food.

Various factors cause food spoilage, making items unsuitable for consumption. Light, oxygen, heat, humidity, temperature and spoilage bacteria can all affect both safety and quality of perishable foods. When subject to these factors, foods will gradually deteriorate.

Signs. Signs of food spoilage may include an appearance different from the food in its fresh form, such as a change in color, a change in texture, an unpleasant odour, or an undesirable taste. The item may become softer than normal. If mold occurs, it is often visible externally on the item.

21 Telltale Signs Your Food Has Gone Bad And Should Be Avoided At All Costs

• Your eggs float in water.
• Veggies are yellow-ish.
• Your canned goods have lots of dents.
• Your potatoes have green skin.
• Rice has been in the fridge for more than six days.
• It has mold on it.
• It smells pretty bad.
• There’s a slimy film on top.

Common test formats for microbial food testing are ELISA assays, real-time PCR tests, nutrient plates and agar plates. For detection of pathogenic bacteria, immunological based methods (ELISA) are available.

Food spoilage can be detected by foul odour, surface discolouration and sour taste.

Preservatives are natural or man-made chemicals that are added to foods to stop them from spoiling. We preserve fresh foods every day, by storing foods in the fridge or freezer. Smoking fish or meat over burning wood or coal are also methods of preservation.

Ans: Pasteurization is a method to preserve milk, in which the milk is heated to about 700C for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur. It is called pasteurization.