MCB511 FOOD MICROBIOLOGY POSSIBLE QUESTIONS AND ANSWERS

 Explain with reasons the organisms that are important in food Microbiology

Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food,

including the study of microorganisms causing food spoilage. It is also the study of the

interactions between microorganisms and food products.

There are several groups of microorganisms that are important in food microbiology, including

bacteria, fungi, and viruses. These microorganisms can be either beneficial or harmful,

depending on the context in which they are found.

Bacteria are single-celled microorganisms that can be found in almost every environment on

Earth, including in and on food. Some bacteria are essential for the production of fermented

foods such as cheese, yogurt, and pickles. These bacteria, known as starter cultures, help to

preserve the food by producing lactic acid, which lowers the pH and inhibits the growth of

harmful bacteria. However, some bacteria are responsible for food spoilage and foodborne

illness. These include Salmonella, Escherichia coli, and Listeria monocytogenes.

Fungi, including yeasts and molds, are also important in food microbiology. Some fungi are

used in the production of fermented foods such as bread and beer, while others can cause food

spoilage. Molds are particularly problematic in foods with high moisture content, such as fruits

and vegetables.

Viruses are also important in food microbiology, as they can cause foodborne illness. Viruses

are typically transmitted through contaminated water or food, and they can multiply inside the

human body. Some examples of viruses that can cause foodborne illness include Norovirus and

Hepatitis A.
In conclusion, bacteria, fungi, and viruses are all important in food microbiology. Some of these

microorganisms can be beneficial, such as those used in the production of fermented foods, while

others can be harmful and cause food spoilage or foodborne illness. It is important to properly

handle and prepare food to minimize the risk of foodborne illness.

 Describe how microorganisms manifest their presence in food

Microorganisms are present in almost all foods to some extent, and they can manifest their

presence in various ways. Here are some examples:

Visible growth: Some microorganisms, such as mold, yeast, and bacteria, can grow and form

visible colonies on the surface of foods. For example, bread may develop a fuzzy white or green

layer of mold, or fruit may develop a slimy layer of bacteria.

Odor: Some microorganisms produce gases or other substances that can give food a distinct

odor. For example, spoilage bacteria can produce a strong, unpleasant smell, while yeasts can

produce a fruity or sour smell.

Texture: Microorganisms can change the texture of food by producing enzymes that break

down the food's proteins, carbohydrates, and fats. For example, bread that has been fermented by

yeast will be softer and more resilient due to the action of the yeast's enzymes.

Flavor: Some microorganisms can produce flavors that are either desirable or undesirable in

food. For example, the bacteria Lactobacillus and Streptococcus are used in the production of

fermented dairy products such as yogurt and cheese, and they contribute to the characteristic

tangy flavor of these foods. On the other hand, spoilage bacteria can produce off flavors in food.
 Discuss in details microbial growth in food

Microbial growth in food is the proliferation of microorganisms, such as bacteria, fungi, and

viruses, on or within the food. These microorganisms can be present naturally on the raw

ingredients used to make the food or can be introduced during handling, processing, or storage.

Some microorganisms are beneficial and contribute to the production of various types of food,

such as fermented dairy products, bread, and fermented meats. Others can cause food to spoil or

become unsafe to eat.

 What are the factors that influence Microbial growth in food (Intrinsic and Extrinsic

factors)?

There are several factors that can influence microbial growth in food which includes Intrinsic

and Extrinsic factors that determine whether microbial growth will preserve or spoil foods.

Intrinsic or food related parameters are those parameters of plants and animal tissues which are

inherent part of the tissue. E.g., pH, water activity, oxidation-reduction potential (Eh), nutrient

content, antimicrobial constituents and biological structures.

Extrinsic or environmental parameters are properties of storage environments which affect both

foods as well as microorganisms and include temperature of storage, relative humidity of

storage environment, and concentration of gases in environment.

Intrinsic factors

Nutrient content: Microorganisms also need certain nutrients to grow. These can include

carbohydrates, proteins, and fats, as well as trace minerals and vitamins.

Water activity: Water activity refers to the amount of water that is available for microbial

growth. Microorganisms need a certain amount of moisture to grow, and foods with high water

activity are more prone to microbial growth.

Redox potential (Eh): The redox potential, also known as the reduction-oxidation potential or

the redox potential, is a measure of the tendency of a chemical substance to accept or donate

electrons. In the context of food, the redox potential can refer to the potential of the food itself to

undergo redox reactions, or to the potential of the food to influence the redox state of the body.

pH: pH is a term used to describe the acidity or alkalinity of a solution. At pH 7, there is an

equal amount of acid (hydrogen ion: H+) and alkali (hydroxyl ion: OH-), so the solution is

“neutral”. The pH of has a profound effect on the growth of microorganisms. Most bacteria grow

best at about pH 7 and grow poorly or not at all below pH 4.

Extrinsic factors

Extrinsic factors are more easily controlled than intrinsic factors and are therefore frequently the

basis for food preservation.

Storage Temperature or temperature of storage: Most microorganisms grow best within a

certain temperature range. For example, bacteria tend to grow faster at temperatures between

40°F and 140°F (4°C and 60°C), which is known as the "danger zone" for food. Fungi, such as

mold, tend to grow best at cooler temperatures.

Gaseous atmosphere: Many microorganisms require oxygen to grow, while others grow best in

anaerobic (oxygen-free) conditions. For example, spoilage bacteria that produce gases, such as

Clostridium botulinum, grow best in anaerobic conditions.

Relative Humidity of the storage environment

 Write a concise note on food spoilage and food intoxication

Food spoilage is the process by which food deteriorates and becomes unfit for consumption due

to the growth of microorganisms, such as bacteria, fungi, and yeasts. These microorganisms

produce enzymes that break down the food's proteins, carbohydrates, and fats, leading to changes

in the food's appearance, texture, flavor, and smell. Food spoilage can be caused by a variety of

factors, including temperature, water activity, pH, oxygen levels, and the presence of nutrients.

Food intoxication, also known as food poisoning, occurs when a person consumes food or drink

that contains harmful microorganisms or their toxic byproducts. These microorganisms can

produce toxins that cause illness when ingested, and the symptoms of food poisoning can range

from mild to severe, depending on the type and amount of microorganism consumed. Common

symptoms of food poisoning include nausea, vomiting, diarrhea, abdominal cramps, and fever. In

severe cases, food poisoning can lead to hospitalization or even death.

 Discuss the most effective ways of ensuring and controlling quality in a food industry;

before, during and after the production process

There are several ways to ensure and control quality in the food industry at different stages of the

production process. These include:

Before production:

Developing a food safety plan: This should include identifying potential hazards and risk areas,

and implementing controls to prevent or mitigate them.

Training and educating employees: Ensuring that all employees are trained on proper food

handling, hygiene, and safety practices is crucial to maintaining quality.

Implementing good manufacturing practices (GMPs): GMPs are guidelines that outline the

requirements for producing safe and high-quality food products. These include measures such as

maintaining clean and hygienic facilities, using clean equipment and utensils, and storing

ingredients and finished products properly.

During production:

Monitoring and controlling temperature: Proper temperature control is crucial to prevent the

growth of foodborne bacteria and other contaminants. This includes monitoring the temperature

of ingredients, intermediate products, and finished products throughout the production process.

Testing ingredients and finished products: Sampling and testing ingredients and finished

products at various stages of production can help identify potential quality issues early on and

allow for corrective actions to be taken.

Maintaining documentation: Proper documentation of production processes and testing results

can help ensure quality control and traceability.

After production:
Packaging and labeling: Proper packaging and labeling can help protect the quality of the

product and ensure that it is stored and handled correctly.

Storage and distribution: Proper storage and distribution practices can help maintain the quality

of the product and prevent contamination. This includes maintaining appropriate temperatures

and protecting the product from physical damage.

Recall and corrective action: In the event that a quality issue is identified after production, it is

important to have a plan in place for recalling the product and implementing corrective actions to

prevent similar issues in the future.

 Explain Hazard Analysis of Critical Control Points (HACCP) and the stages involved in

the process

Use Mrs Rashida’s explanation for the definition

There are seven principles of HACCP that guide the development and implementation of a

HACCP plan:

1. Conduct a hazard analysis: Identify all potential hazards that could occur at each stage of the

food production process, including biological, chemical, and physical hazards.

2. Determine the critical control points (CCPs): Identify the points in the process where a

hazard could be controlled or prevented.

3. Establish critical limits: Set limits for each CCP that must be met to ensure the hazard is

controlled or prevented.

4. Establish monitoring procedures: Develop procedures for monitoring the CCPs to ensure that

the critical limits are being met.

5. Establish corrective actions: Develop procedures for taking corrective action if the CCP is

not operating within the critical limits.

6. Establish verification procedures: Develop procedures for verifying that the HACCP system

is working effectively and the CCPs are being monitored and controlled.

7. Establish record-keeping and documentation procedures: Develop procedures for keeping

records of all monitoring, corrective action, and verification activities to provide evidence

that the HACCP system is working effectively.

 Discuss in details foodborne illnesses

Foodborne illness, also known as food poisoning, is a type of illness that is caused by

consuming contaminated food or water. These illnesses can be caused by a variety of

pathogens, including bacteria, viruses, parasites, and toxins.

Symptoms of foodborne illness may include nausea, vomiting, diarrhea, abdominal pain,

fever, and dehydration. The severity of the illness can range from mild to severe, and in some

cases, it can be life-threatening.

There are several ways in which food can become contaminated, including:

Poor hygiene: Contamination can occur if food is handled or prepared by someone who is sick or

has poor hygiene practices.

Improper storage: Food that is not stored at the correct temperature can allow bacteria to grow,

leading to contamination.
Cross-contamination: This occurs when bacteria or other pathogens are transferred from one

food to another, usually through contact with utensils or surfaces that have not been properly

cleaned.

Natural toxins: Some types of food, such as certain types of fish and mushrooms, can contain

naturally occurring toxins that can cause illness if consumed.

Pesticides and chemicals: Contamination can occur if food is grown or processed using

pesticides or other chemicals that are not properly handled or disposed of.

To prevent foodborne illness, it is important to follow good hygiene practices when handling and

preparing food, store food at the correct temperature, and properly clean utensils and surfaces. It

is also a good idea to cook food to the appropriate temperature and avoid consuming potentially

toxic foods. If you suspect that you have a foodborne illness, it is important to seek medical

attention as soon as possible.

 Discuss in details any three bacteria that are incriminated in food poisoning

1. Salmonella: Salmonella is a type of bacteria that can cause food poisoning, also known as

salmonellosis. It is found in raw poultry, meat, eggs, and dairy products, as well as in

contaminated water and soil. Inadequate cooking of these products can result in foodborne

infection. Symptoms of salmonella infection include diarrhea, abdominal cramps, fever, and

vomiting, which typically appear within 12 to 72 hours after ingestion of the bacteria.

Salmonella infection can be severe, especially in young children, the elderly, and people with

weakened immune systems.

2. Escherichia coli (E. coli) 0157:H7: Mrs Rashida’s note

3. Staphylococcus aureus: Staphylococcus aureus is a type of bacteria that is commonly found

on the skin and in the nose, throat, and mouth of humans. It can cause food poisoning when it

is allowed to grow on food that is left at room temperature or is not cooked or reheated

adequately. Symptoms of staphylococcal food poisoning include nausea, vomiting,

abdominal cramps, and diarrhea, which typically appear within 4 to 6 hours after ingestion of

the bacteria. In severe cases, staphylococcal food poisoning can lead to dehydration and

sepsis (a potentially life-threatening infection in the blood).

 Explain the various methods that are employed in food preservation (high temp and

low temp)

Define Mrs Rashida’s food preservation

There are several methods that are commonly used to preserve food, including:

1. Canning: This involves heating the food to a high temperature and sealing it in an airtight

container, such as a can or jar. This kills any microorganisms that may cause spoilage and

prevents new ones from entering the container.

2. Refrigeration: Keeping food at a low temperature slows down the growth of bacteria and

other microorganisms, which can help to extend its shelf life.

3. Freezing: Freezing food at a temperature below 0°F (-18°C) can halt the growth of

microorganisms and enzymes that cause spoilage.

4. Dehydration: Removing moisture from food can significantly extend its shelf life by

reducing the growth of microorganisms that require water to survive.

5. Fermentation: This is a process in which microorganisms convert sugars and other

carbohydrates into acids, gases, or alcohol. Fermentation can be used to preserve food by

creating an environment that is inhospitable to spoilage-causing microorganisms.

6. Pickling: This involves preserving food in an acidic solution, such as vinegar or brine.

The acidity of the solution helps to inhibit the growth of bacteria and other

microorganisms.

7. Smoking: This is a method of preserving food by exposing it to smoke, which can help to

kill bacteria and other microorganisms.

8. Vacuum sealing: This involves removing the air from a container and sealing it to prevent

the entry of microorganisms.

9. Pasteurization: This is a process that involves heating food to a high temperature and then

rapidly cooling it to kill bacteria and other microorganisms. It is often used to preserve

liquids such as milk and juice.

10. Irradiation: This is a process in which food is exposed to ionizing radiation, which can

kill bacteria and other microorganisms. It is often used to preserve fresh produce.