Food Spoilage Flashcards
Food Spoilage
The undesirable alterations in foods or the food undergoes some physiological, chemical and biological changes, which renders it inedible or hazardous to eat
Undesirable Changes in Food due to Spoilage
-Change in color: Bananas turn black after storing for a long period
-Change in smell: Rancid smell of spoiled oils and fats,
-Change in consistency: Splitting of milk, curdling of milk
-Change in texture: Some vegetables like potatoes have too much softening leading to rotting.
Factors Affecting food Spoilage
-Composition of food
-Structure of the food item
-Types of microorganisms involved
-Conditions of storage of the food
Relatively stable or non-perishable foods
Items that have a long shelf life and do not require refrigeration.
-Grains
-Flour
-Sugar
Protectable or semi-perishable foods
Foods that remain unspoiled for a fairly long period if properly handled and stored.
-Potatoes
-Apples
-Onions
Perishable foods
Foods that spoil readily unless special preservative methods are used.
-Milk
-Eggs
-Meat
-Fish
What factors influence bacterial growth in food?
-Food type, temperature, pH, moisture, oxygen.
-Require more moisture than yeasts or molds.
What pH levels do most bacteria prefer?
Best at neutral pH, some thrive in acidic or alkaline.
Why are bacteria harder to kill than molds and yeasts?
-More resilient structure, can exist in dormant spore form.
-Require specific conditions to be killed.
What role does moisture play in bacterial growth?
Moisture is crucial for bacterial growth, as bacteria require more moisture than yeasts or molds.
What are the bacterial processing temperatures for high and low in acid foods?
-High acid: 100°C.
-Low acid: 116°C in steam pressure.
What is the role of Clostridium botulinum in food spoilage?
-Causes spoilage in canned foods.
-Produces harmful toxins.
Bacteria that cause food spoilage
-Staphylococcus aureus (GP)
-Lactic acid bacteria (GP)
-Salmonella spp (GN)
-Escherichia coli (GN)
How does pH level affect bacteria survival in food processing?
-All bacteria sensitive to acids; can be killed in acidic pH.
-Acidic foods processed at lower temperatures.
What are the main bacteria responsible for soft rot in fruits and vegetables?
-Soft rotting species of Erwinia.
-Produce enzymes that macerate tissue.
What role do aerobic bacteria play in food processing?
-Aerobic bacteria like Acetobacter aceti used in vinegar production.
-Contribute to fermentation, flavor, and preservation.
Which bacteria produce lactic acid through fermentation?
Lactic acid bacteria: Lactobacillus plantarum, Pediococcus cerevisiae.
Ferment carbohydrates to produce lactic acid.
How do bacteria affect the shelf life of fruits and vegetables?
-Bacteria like Erwinia carotovora reduce shelf life by causing soft rot in crops like potatoes carrots and cabbages, producing enzymes that macerate tissue.
What conditions are optimal for yeast growth?
-Require less moisture and an acidic pH for growth.
-Grow best at 25-30°C, in low concentration sugar solutions.
What factors inhibit yeast growth?
-Do not grow well in alkaline media.
-Cannot thrive in media with over 65% sugar or 0.5% acetic acid.
How can yeasts be destroyed?
-Heating at 60°C for a few minutes
-Boiling
What are some uses of yeasts in food production?
-Essential bread, beer, and wine production.
-Used in the production of vinegar and other fermented products.
Which types of yeasts are commonly associated with fruit spoilage?
-Saccharomyces spoils low sugar products.
-Candida spoils foods with high acid foods, salty foods, and butter.
Saccharomyces cerevisiae, which is a species of yeast commonly used in baking, brewing, and fermentation processe
What conditions do molds thrive in?
-Grow best in closed, damp, and dark environments.
-Require warmth, moisture, air, and temperatures of 25-30°C.
