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Which of the following is NOT a source of physical contamination of food?
Which of the following is NOT a source of physical contamination of food?
What is a primary cause of sliminess in spoiled food?
What is a primary cause of sliminess in spoiled food?
Which of these is an effect of biochemical changes in food spoilage?
Which of these is an effect of biochemical changes in food spoilage?
Which odor is typically associated with the breakdown of proteins in spoiled food?
Which odor is typically associated with the breakdown of proteins in spoiled food?
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Which of the following changes is NOT typically associated with the spoilage of food?
Which of the following changes is NOT typically associated with the spoilage of food?
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What is an example of chemical contamination in food production?
What is an example of chemical contamination in food production?
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What typically causes unwholesome effects in spoiled food?
What typically causes unwholesome effects in spoiled food?
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Which of the following is an observable sign of food souring?
Which of the following is an observable sign of food souring?
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Which type of microorganism is capable of growing optimally at temperatures around 20°C and can survive down to -10°C?
Which type of microorganism is capable of growing optimally at temperatures around 20°C and can survive down to -10°C?
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What role do antimicrobial substances play in food?
What role do antimicrobial substances play in food?
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Which of the following factors is NOT considered an extrinsic factor affecting microbial growth?
Which of the following factors is NOT considered an extrinsic factor affecting microbial growth?
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Which group of bacteria is primarily associated with food spoilage due to their inability to grow at temperatures below 5°C?
Which group of bacteria is primarily associated with food spoilage due to their inability to grow at temperatures below 5°C?
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What is a common temperature range for thermophilic bacteria growth?
What is a common temperature range for thermophilic bacteria growth?
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What type of biological structure in meat helps prevent microbial entry?
What type of biological structure in meat helps prevent microbial entry?
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Which of the following factors can influence the temperature effect on microbial growth?
Which of the following factors can influence the temperature effect on microbial growth?
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What are the typical optimum growth temperatures for mesophilic bacteria?
What are the typical optimum growth temperatures for mesophilic bacteria?
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Which food type is categorized as non-perishable?
Which food type is categorized as non-perishable?
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Which of the following best describes the role of enzyme activity in food spoilage?
Which of the following best describes the role of enzyme activity in food spoilage?
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What is the primary factor that affects the susceptibility of food to spoilage?
What is the primary factor that affects the susceptibility of food to spoilage?
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Which condition is NOT a factor that affects the growth of microorganisms in stored food?
Which condition is NOT a factor that affects the growth of microorganisms in stored food?
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What type of microorganisms is primarily responsible for food spoilage?
What type of microorganisms is primarily responsible for food spoilage?
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Which food type is likely to spoil most rapidly without preservatives?
Which food type is likely to spoil most rapidly without preservatives?
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What is the main reason for classifying foods by their ease of spoilage?
What is the main reason for classifying foods by their ease of spoilage?
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Which statement about food spoilage is incorrect?
Which statement about food spoilage is incorrect?
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Which group of microorganisms is most likely to spoil canned foods?
Which group of microorganisms is most likely to spoil canned foods?
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What is the primary characteristic of microaerophilic bacteria compared to aerobic bacteria?
What is the primary characteristic of microaerophilic bacteria compared to aerobic bacteria?
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What condition is most likely to lead to spoilage in dry grains?
What condition is most likely to lead to spoilage in dry grains?
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Which of the following is a common sign of microbial spoilage in food?
Which of the following is a common sign of microbial spoilage in food?
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What is the impact of moisture content above 12 to 13 percent on cereals?
What is the impact of moisture content above 12 to 13 percent on cereals?
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Which microorganism is responsible for the souring of milk?
Which microorganism is responsible for the souring of milk?
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What effect does the presence of molds such as Aspergillus and Penicillium have on food?
What effect does the presence of molds such as Aspergillus and Penicillium have on food?
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What type of growth is likely on the surface of raw meat due to aerobic bacteria?
What type of growth is likely on the surface of raw meat due to aerobic bacteria?
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Which of the following bacteria is NOT associated with spoilage in fish?
Which of the following bacteria is NOT associated with spoilage in fish?
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What is a common sign of spoilage in eggs?
What is a common sign of spoilage in eggs?
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Which condition is known to accelerate meat spoilage due to microbial action?
Which condition is known to accelerate meat spoilage due to microbial action?
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What type of bacteria primarily cause soft rot in vegetables?
What type of bacteria primarily cause soft rot in vegetables?
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Which of these spoilage indicators would be least likely observed in canned foods?
Which of these spoilage indicators would be least likely observed in canned foods?
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What type of spoilage do yeasts and molds primarily cause in vegetables?
What type of spoilage do yeasts and molds primarily cause in vegetables?
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Which condition does NOT contribute to spoilage in meat?
Which condition does NOT contribute to spoilage in meat?
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What is a primary factor that causes spoilage of fruits and vegetables after harvest?
What is a primary factor that causes spoilage of fruits and vegetables after harvest?
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Study Notes
Food Spoilage
- Definition: Damage or injury rendering food unsuitable for human consumption. This can be due to contamination with pathogens or poisonous agents.
- Factors affecting spoilage: The composition of the food, the structure of the food item, types of microorganisms present, and storage conditions.
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Classification of foods by ease of spoilage:
- Relatively stable or non-perishable foods: These include grains, flour, sugar, and pulses.
- Protectable or semi-perishable foods: These include potatoes, apples, and onions.
- Perishable foods: These include milk, eggs, meat, fish, poultry, fruits, and vegetables.
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Causes of food spoilage:
- Growth and activity of microorganisms: Bacteria, yeasts, and molds cause food spoilage through enzyme production.
- Enzyme activity: Enzymes present in plant or animal tissues can cause decomposition after death.
- Chemical reactions: Non-enzyme catalyzed reactions can occur , like fat oxidation.
- Vermin: Weevils, ants, rats, cockroaches, mice, birds, and insect larvae can contaminate food. (i) Aesthetically unappealing, (ii) Potentially transmit pathogens, (iii) Consume food.
- Physical changes: Freezing, burning, drying, and pressure can cause spoilage.
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Effects of food spoilage:
- Changes in nutritional value: Decomposition of proteins, carbohydrates, and vitamins.
- Changes in organoleptic features: Changes in color, flavor, taste, and unpleasant odors.
- Unwholesome effects: Biogenic amines, toxins, microbial metabolites, and pathogenic microbes can result in food poisoning.
Spoilage Signs
- Odor: Breakdown of proteins (putrefaction) can cause a "rotten egg" smell.
- Sliminess: This is due to the accumulation of microbial cells and tissue degradation.
- Discoloration: Visible mold growth on bread, blue and green mold on citrus fruit and cheese.
- Souring: Production of acid, like lactic acid in sour milk.
- Gas formation: Can make meat spongy, and cause packages and cans to swell or bubble.
Food Contamination
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Types of Contamination:
- Physical: Soil from the ground, bolts from a processing plant, hair from a cook.
- Chemical: Chemicals from the farm, cleaning products, fly spray.
- Bacterial: This is the most common type of contamination and can occur throughout the food chain.
Microbial Spoilage: Manifestation
- Visible Growth: Visible mold or bacteria.
- Gas Production: From fermentation or bacterial action.
- Slime: Microbial slime on the food surface.
- Off-Flavors: Alteration of taste and odor due to microbial activity.
Sequence of Events in Food Spoilage
- Source: Microorganisms must be present in the food.
- Favorable Environment: The food must have a conducive environment for microbial growth.
- Storage Conditions: Food must be stored under conditions that allow for microbial growth and enzyme production to cause spoilage.
Spoilage of Specific Foods
- Cereal Spoilage: Moisture levels above 12-13% can lead to spoilage. Low moisture content can cause mold growth, while high moisture can cause yeasts and bacteria to grow. Common spoilage microorganisms include Aspergillus, Penicillium, Mucor, Rhizopus, Fusarium. These molds can produce mycotoxins.
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Milk Spoilage: Milk is an excellent medium for microbial growth.
- Souring: Caused by Streptococcus lactis & Enterococci.
- Gas Production: Caused by Coliform, Clostridium, and Yeasts.
- Proteolysis: Caused by Bacillus & Micrococcus, resulting in a bitter taste.
- Changes in Color & Taste: Further signs of spoilage.
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Meat Spoilage: Raw meat is susceptible to spoilage by its own enzymes and microbial action. Excessive autolysis can cause souring.
- Factors influencing spoilage: Gut load of the animal, animal's physiological condition during slaughter, and rapid cooling.
- Predominant spoilage bacteria: Brochothrix thermosphacta, Carnobacterium spp., Enterobacteriaceae, Lactobacillus spp., Leuconostoc spp., Pseudomonas spp., and Shewanella putrefaciens.
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Fish Spoilage: Spoiled due to autolysis, oxidation, or bacterial activity.
- Aerobic Conditions: Change in color of meat pigments (red to green, brown, or grey).
- Off Odors & Tastes: Microbial activity leads to unpleasant flavors.
- Pathogenic Bacteria: Bacillus, Clostridium, Escherichia, Serratia, and Vibrio can cause spoilage.
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Egg Spoilage: Cracks, leaks, stained or dirty spots on the exterior, and blood clots, bloodiness, translucent spots in the interior are signs of spoilage.
- Spoilage Bacteria: Pseudomonas, coliform bacteria, Proteus spp., Aeromonas, Serratia, Sporotrichum all cause rots in eggs.
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Canned Food Spoilage:
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Chemical Spoilage:
- Hydrogen Swell: Caused by gas production.
- Discoloration: Of the can's interior.
- Cloudiness: In the can's liquor.
- Loss in Nutritive Value: Due to chemical reactions.
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Biological Spoilage:
- Thermophilic and Mesophilic Bacteria: These can cause spoilage in canned foods.
- Yeasts, Molds, and LAB: Common spoilage microorganisms in canned foods.
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Chemical Spoilage:
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Vegetable Spoilage: Vegetables are a good substrate for yeasts, molds, and bacteria. An estimated 20% of harvested vegetables are lost to spoilage.
- Soft Rot: Caused by Erwinia carotovora, and can also be caused by endogenous enzymes.
- Mold Spoilage: Occurs in vegetables where bacterial growth is not favored. Most molds require wounds to invade plant tissues.
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Description
Explore the causes and factors affecting food spoilage. This quiz covers definitions, classifications of foods, and the role of microorganisms and enzymes in spoilage. Understand the difference between perishable and non-perishable foods.
