MICROBIOLOGY

1. Food Contamination & Food
Spoilage
Name- Samadrita Banik
ST. GEORGE COLLEGE
2nd Semester
M.Sc Microbiology

2. INTRODUCTION
Food contamination is when food is contaminated with
microorganisms or substances and eating it could result in
food borne disease.
 Food spoilage is any undesired change in the natural colour,
taste or texture of food items that makes it unfit for
consumption because it has lost its quality and nutritional
value.

3. Types of food contamination
There are three different types of food contamination-
 Chemical.
Physical.
Biological.

4. • Chemical contamination refers to food that has
been contaminated by some type of chemical substance.
Because chemicals can be very useful when cleaning in the
kitchen, they can easily contaminate food. Chemicals must
be properly labelled and stored separately for food stuff to
minimise the risk of contamination.There are also
chemicals that occur naturally in foods, like toxins in some
fish, and in some cases, minimal chemical contamination
might not actually lead to illness. However, the food
handler must always be aware of the presence of chemicals
in food and take all reasonable precautions to make sure
that chemical contamination doesn’t happen.

5. • Biological contamination refers to food that’s
contaminated by substances produced by living
creatures – such as humans, rodents, pests or
microorganisms. This includes bacterial
contamination, viral contamination or parasite
contamination that’s transferred through saliva, pest
droppings, blood or faecal matter. Bacterial
contamination is thought to be the most common
cause of food poisoning worldwide, and the best way
to protect against it occurring is by maintaining the
best food safety practices.

6. • Physical contamination refers to food that has been
contaminated by a foreign object at some stage of the
production process. These objects have the ability to
injure someone and can also potentially carry harmful
biological contaminants, which then cause illness. An
additional consequence of physical contamination is
the upset caused to the person who finds the object.
Things like band-aids, fingernails and pieces of
cooking equipment are the last thing you would like
to find in your meal.

7. Types of food spoilage
There are 4 types of food spoilage:
Microbial Spoilage
Physical Spoilage
Chemical Spoilage
Enzymic Spoilage

8.  Microbial Spoilage: It is caused by microorganisms like fungi (moulds,
yeasts) and bacteria. They spoil food by growing in it and producing
substances that change the colour, texture and odour of the food. Eventually
the food will be unfit for human consumption.
 Physical Spoilage: It is due to physical damage to food during harvesting,
processing or distribution. The damage increases the chance of chemical or
microbial spoilage and contamination because the protective outer layer of the
food is bruised or broken and microorganisms can enter the foodstuff more
easily. For example you may have noticed that when an apple skin is
damaged, the apple rots more quickly.

9.  Chemical Spoilage : Chemical reactions in food are responsible for changes in the colour and flavour
of foods during processing and storage. Foods are of best quality when they are fresh, but after fruits
and vegetables are harvested, or animals are slaughtered, chemical changes begin automatically within
the foods and lead to deterioration in quality. Fats break down and become rancid (smell bad), and
naturally-occurring enzymes promote major chemical changes in foods as they age.
 Enzymic Spoilage (autolysis) : Every living organism uses specialised proteins called enzymes to
drive the chemical reactions in its cells. After death, enzymes play a role in the decomposition of once-
living tissue, in a process called autolysis or enzymic spoilage. For example, some enzymes in a
tomato help it to ripen, but other enzymes cause it to decay . Once enzymic spoilage is under way, it
produces damage to the tomato skin, so moulds can begin to can attack it as well, speeding the process
of decay.

10. Prevention of food contamination
Pathogens can be spread from food or unwashed hands to prep areas, equipment, utensils or other food.
Fortunately, there are steps you can take to prevent this. Here are five important tips for preventing cross-
contamination in your operation.
 Implement a personal hygiene program. To lessen the possibility of food handlers contaminating food, institute
a good personal hygiene program that includes policies addressing critical hand practices like proper
handwashing, hand care and glove use. Also address staff cleanliness and work attire, focusing on topics such as
bathing, clean clothing, the proper use of hair restraints and prohibited jewelry. Finally, policies should be put in
place to make sure food handlers come to work healthy.
 Remind employees to wash their hands. This is especially important after using the restroom and after handling
raw meat, seafood and poultry. Once employees have washed their hands, ensure they use a single-use paper
towel or hand dryer, rather than any part of their uniform, to dry.

11.  Use separate equipment. Each type of food should be prepped and handled with a
separate piece of equipment. Some operations use colored cutting boards and utensil
handles to help keep equipment separate. If this system is not possible at restaurants,
prep food at different times.
 Clean and sanitize all work surfaces. All work surfaces, equipment and utensils should
be cleaned and sanitized after each task. Simply rinsing equipment is not enough to
eliminate pathogens that can contaminate food.
 Purchase prepared food. we can prevent cross-contamination by purchasing food that
doesn’t require much prepping. This minimizes handling and can reduce the transfer of
pathogens from one surface or food .

12. Prevention of food spoilage
Food preservation is the process of treating and handling food to stop or slow down food spoilage, loss of
quality, edibility, or nutritional value and thus allow for longer food storage. Preservation usually involves
preventing the growth of bacteria, fungi. Maintaining or creating nutritional value, texture and flavor is an
important aspect of food preservation.
• Drying is one of the most ancient food preservation techniques, which reduces water activity sufficiently to
prevent bacterial growth.
• Refrigeration preserves food by slowing down the growth and reproduction of microorganisms and the action of
enzymes which cause food to rot.
• Freezing is also one of the most commonly used processes for preserving a very wide range of food including
prepared foodstuffs which would not have required freezing in their unprepared state.
• Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The vacuum
environment strips bacteria of oxygen needed for survival, thereby slowing spoiling.
• Salting or curing draws moisture from the meat through a process of osmosis. Meat is cured with salt or sugar, or
a combination of the two. Nitrates and nitrites are also often used to cure meat and contribute to the characteristic
pink color, as well as inhibition of Clostridium botulinum.

13. • Smoking is used to lengthen the shelf life of perishable food items. This effect is achieved by
exposing the food to smoke from burning plant materials such as wood. Most commonly subjected to
this method of food preservation are meats and fish that have undergone curing. It is one of the oldest
food preservation methods, which probably arose after the development of cooking with fire.
• Preservative food additives can be antimicrobial. These inhibit the growth of bacteria or fungi,
including mold, or antioxidant, such as oxygen absorbers, which inhibit the oxidation of food
constituents. Common antimicrobial preservatives include calcium propionate, sodium nitrate,
sodium nitrite, sulfites and disodium EDTA. Antioxidants include BHA and BHT.
• Pickling is a method of preserving food in an edible anti-microbial liquid. Pickling can be broadly
categorized into two categories: chemical pickling and fermentation pickling.
• Canning involves cooking food, sealing it in sterile cans or jars, and boiling the containers to kill or
weaken any remaining bacteria as a form of sterilization. Foods have varying degrees of natural
protection against spoilage and may require that the final step occur in a pressure cooker.

14. Conclusion
 The interaction of versatile nutrients and enzymes present in food leads to several degradative
chemical changes that deteriorate the quality and shelf life of food.
 The deteriorative changes are enhanced by contamination that occurs at various stages of
processing, handling and storage.
 The undesirable changes include lipid oxidation, enzymatic or non-enzymatic browning,
putrefaction and toxicity due to hazardous substances.
 Contamination occurs from various physical, chemical and biological sources and is affected by
external factors such as temperature, poor hygiene and sanitation.
 The intrinsic factors such as pH, redox potential, water content and the presence of antimicrobial
substances in food also affect the degree of contamination and thereby the spoilage.
 Therefore, it is necessary to implement and maintain proper food hygiene during processing and
storage.