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Questions and Answers
What is the primary aim of pasteurization?
What is the primary aim of pasteurization?
Which method of pasteurization employs the highest temperature and shortest time?
Which method of pasteurization employs the highest temperature and shortest time?
What is the purpose of sterilization in food preservation?
What is the purpose of sterilization in food preservation?
How does the D-value relate to temperature in microbial destruction?
How does the D-value relate to temperature in microbial destruction?
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Which method is NOT typically associated with sterilization?
Which method is NOT typically associated with sterilization?
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Which method involves rubbing meat or fish with salt for preservation?
Which method involves rubbing meat or fish with salt for preservation?
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What is the primary temperature range used during the chilling process to preserve food?
What is the primary temperature range used during the chilling process to preserve food?
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Which of the following is classified as a class one preservative?
Which of the following is classified as a class one preservative?
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What is the main principle behind food preservation through drying?
What is the main principle behind food preservation through drying?
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What type of radiation is used in the irradiation method for food preservation?
What type of radiation is used in the irradiation method for food preservation?
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Which gas is commonly used to destroy both vegetative cells and spores in food preservation?
Which gas is commonly used to destroy both vegetative cells and spores in food preservation?
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During which process is milk primarily heat-treated to eliminate spoilage microorganisms?
During which process is milk primarily heat-treated to eliminate spoilage microorganisms?
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What effect do low temperatures have on the growth and activity of microorganisms?
What effect do low temperatures have on the growth and activity of microorganisms?
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What defines perishable foods?
What defines perishable foods?
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Which of the following is NOT a method for achieving the inhibition principle in food preservation?
Which of the following is NOT a method for achieving the inhibition principle in food preservation?
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How can the pH of food be lowered to prevent spoilage?
How can the pH of food be lowered to prevent spoilage?
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What category of food includes items like eggs and pasteurized milk?
What category of food includes items like eggs and pasteurized milk?
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Which of the following methods is used to reduce water activity in food preservation?
Which of the following methods is used to reduce water activity in food preservation?
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What is the purpose of the killing principle in food preservation?
What is the purpose of the killing principle in food preservation?
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Which of the following statements about non-perishable foods is true?
Which of the following statements about non-perishable foods is true?
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What is fermentation primarily used for in food preservation?
What is fermentation primarily used for in food preservation?
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Study Notes
Food Preservation
- Process using physical and/or chemical agents to prevent microbial spoilage, allowing food storage for later use.
- Aim: to prolong storage life.
- Food Classification:
- Perishable: Deteriorate quickly after harvest (e.g., tomatoes, mangoes, papaya, peaches, plums, meat, fish, poultry). High moisture content, susceptible to spoilage.
- Semi-perishable: Less moisture content (e.g., beetroot, carrots, peas, green beans, pumpkins, apples, eggs, pasteurized milk, highly smoked fish, pickled vegetables).
- Non-perishable: Very low moisture content (e.g., mature food grains, cereals, pulses, nuts). Not easily susceptible to spoilage by microorganisms and enzymes.
Food Preservation Principles
- Inhibition Principle (1): Inhibits growth and multiplication of microorganisms. Achieved by these methods:
- Reducing water activity (e.g., drying, salting)
- Reducing pH (e.g., fermentation)
- Using preservatives (e.g., sodium benzoate)
- Using low temperatures (e.g., chilling, freezing)
- Smoking (drying and preservative effect)
- Preservation by inhibition doesn't always destroy organisms.
- Killing Principle (2): Destroys microorganisms. Methods include:
- Heat treatment (pasteurization, sterilization)
- Irradiation (gamma rays, cobalt 60)
- Use of gases (ethylene oxide, ozone)
Food Preservation by Lowering pH
- Lowering pH prevents growth of spoilage and pathogenic bacteria.
- Achieved by adding acids or fermentation.
- Fermentation breaks down carbohydrates under anaerobic conditions into alcohol, lactic acid, and carbon dioxide.
Food Preservation by Lowering Water Activity
- Achieved by adding high salt content (e.g., sodium chloride, sometimes nitrates and nitrites)
- Achieved by adding high sugar content.
- Salting procedures can be: dry cure, pickling, injection cure, or direct salt addition.
Food Preservation by Low Temperatures
- Chilling (0-15°C), common range 4-5°C, slows down or stops microbial growth.
- Freezing (-1°C to -35°C)
Preservatives
- Defined as substances that inhibit, retard, or arrest microbial growth, their enzymes, or their genetic mechanisms.
- Chemical preservatives are added after food processing.
- Divided into two classes: Class 1 (common salt, sugar, dextrose, glucose syrup, vinegar/acetic acid) and Class 2 (benzoic acid, sodium benzoate, methyl and propyl p, nitrites, chlorine, carbon dioxide)
Preservation by Drying
- One of the oldest food preservation methods.
- Essential for preserving cereal grains.
- Sun-drying is the most common method.
- Milk and meats can also be preserved through drying.
Killing Principle (continued)
- Methods include heat treatment (pastuerization and sterilization), radiation (gamma rays etc), and use of gases (ethylene oxide and ozone).
Pasteurization
- Heat treatment of milk (or other liquids) aimed at destroying harmful pathogens without significantly affecting the food's nutritional value.
- Three main methods:
- Low Temperature Long Time (LTLT) - 63°C for 30 minutes
- High Temperature Short Time (HTST) - 72°C for 15 seconds
- Flash Method: 80°C for 1-2 seconds
Sterilization
- Destroys all microorganisms, including spores.
- Achieved using physical or chemical means.
- Can involve heating food at high temperature (100-140°C) or irradiation.
Important Terminology in Heat Preservation
- D-Value: Time required at a given temperature to destroy 90% of the spores or vegetative cells of a specific organism. The higher the temperature, the faster the destruction.
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Description
Explore the various methods and principles of food preservation to extend shelf life and maintain quality. This quiz covers classifications of food, including perishable, semi-perishable, and non-perishable items, as well as techniques like drying, salting, and fermentation.
