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Biology 002 > Food Spoilage > Flashcards

Food Spoilage Flashcards

1
Q

Food Spoilage

A

The undesirable alterations in foods or the food undergoes some physiological, chemical and biological changes, which renders it inedible or hazardous to eat

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2
Q

Undesirable Changes in Food due to Spoilage

A

-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.

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3
Q

Factors Affecting food Spoilage

A

-Composition of food
-Structure of the food item
-Types of microorganisms involved
-Conditions of storage of the food

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4
Q

Relatively stable or non-perishable foods

A

Relatively stable or non-perishable foods.
-Grains
-Flour
-Sugar

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5
Q

Protectable or semi-perishable foods

A

Foods that remain unspoiled for a fairly long period if properly handled and stored.
-Potatoes
-Apples
-Onions

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6
Q

Perishable foods

A

Foods that spoil readily unless special preservative methods are used.
-Milk
-Eggs
-Meat
-Fish

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7
Q

What factors influence bacterial growth in food?

A

-Food type, temperature, pH, moisture, oxygen.
-Require more moisture than yeasts or molds.

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8
Q

What pH levels do most bacteria prefer?

A

Best at neutral pH, some thrive in acidic or alkaline.

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9
Q

Why are bacteria harder to kill than molds and yeasts?

A

-More resilient structure, can exist in dormant spore form.
-Require specific conditions to be killed.

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10
Q

What role does moisture play in bacterial growth?

A

Moisture is crucial for bacterial growth, as bacteria require more moisture than yeasts or molds.

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11
Q

What are the bacterial processing temperatures for high and low in acid foods?

A

-High acid: 100°C.
-Low acid: 116°C in steam pressure.

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12
Q

What is the role of Clostridium botulinum in food spoilage?

A

-Causes spoilage in canned foods.
-Produces harmful toxins.

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13
Q

Bacteria that cause food spoilage

A

-Staphylococcus aureus (GP)
-Lactic acid bacteria (GP)
-Salmonella spp (GN)
-Escherichia coli (GN)

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14
Q

How does pH level affect bacteria survival in food processing?

A

-All bacteria sensitive to acids; can be killed in acidic pH.
-Acidic foods processed at lower temperatures.

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15
Q

What are the main bacteria responsible for soft rot in fruits and vegetables?

A

-Soft rotting species of Erwinia.
-Produce enzymes that macerate tissue.

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16
Q

What role do aerobic bacteria play in food processing?

A

-Aerobic bacteria like Acetobacter aceti used in vinegar production.
-Contribute to fermentation, flavor, and preservation.

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17
Q

Which bacteria produce lactic acid through fermentation?

A

Lactic acid bacteria: Lactobacillus plantarum, Pediococcus cerevisiae.
Ferment carbohydrates to produce lactic acid.

18
Q

How do bacteria affect the shelf life of fruits and vegetables?

A

-Bacteria like Erwinia reduce shelf life by causing soft rot.
-Produce enzymes that macerate tissue.

19
Q

What conditions are optimal for yeast growth?

A

-Require less moisture and an acidic pH for growth.
-Grow best at 25-30°C, in low concentration sugar solutions.

20
Q

What factors inhibit yeast growth?

A

-Do not grow well in alkaline media.
-Cannot thrive in media with over 65% sugar or 0.5% acetic acid.

21
Q

How can yeasts be destroyed?

A

-Heating at 60°C for a few minutes
-Boiling

22
Q

What are some uses of yeasts in food production?

A

-Essential bread, beer, and wine production.
-Used in the production of vinegar and other fermented products.

23
Q

Which types of yeasts are commonly associated with fruit spoilage?

A

-Saccharomyces spoils low sugar products.
-Candida spoils foods with high acid foods, salty foods, and butter.

24
Q

What conditions do molds thrive in?

A

-Grow best in closed, damp, and dark environments.
-Require warmth, moisture, air, and temperatures of 25-30°C.

25
Q

What are some common types of molds?

A

-Common molds include Aspergillus, Penicillium, Rhizopus, and Heliminthosporium.

26
Q

What types of food do molds prefer?

A

-Prefer sugar-containing substances which provide the nutrients they need for growth.

27
Q

What are the pH conditions suitable for mold growth?

A

-Can grow in a pH of 2 to 8.5.
-Majority of molds thrive in acidic pH environments.

28
Q

How does heat affect molds?

A

They are sensitive to heat and can be destroyed at 60°C when heated for 30 minutes.

29
Q

What is the significance of understanding the factors that affect the growth of microorganisms in food?

A

Understanding these factors is essential for grasping the principles of food spoilage and preservation, as they influence the nutritive value and wholesomeness of food.

30
Q

What do microbes produce when they degrade carbohydrates?

A

Microbes produce alcohol, lactic acid, acetic acid, propionic acid, and butyric acid.

31
Q

What happens to proteins during microbial degradation?

A

Proteins are degraded by proteolytic enzymes, leading to putrefaction and unpleasant odors.

32
Q

How do microbes break down fats in food?

A

Microbes break down fats, resulting in the production of fatty acids and glycerol.

33
Q

What is the minimum free water percentage required for microbial growth?

A

Microbes require at least 13 percent free water for growth.

34
Q

What salt concentration inhibits bacterial growth?

A

A salt concentration of 5-15 percent inhibits the growth of bacteria.

35
Q

What is enzymatic spoilage and why is it significant?

A

Enzymatic spoilage is the greatest cause of food deterioration, caused by enzymes that control essential metabolic processes in living organisms. They can lead to undesirable or desirable changes in fruits, vegetables, and other foods.

36
Q

What are some examples of enzymatic spoilage?

A

-Oxidation of phenols in plant tissues leading to enzymic browning,
-Sugar-starch conversion by amylases

37
Q

What happens if enzymatic reactions are uncontrolled?

A
  • Can lead to the development of off-odors and off-colors in foods.
38
Q

Factors that affect enzymatic activity

A

-Temperature
-Water activity
-pH

39
Q

How does temperature effect enzymatic activity?

A

-The optimum temperature for enzymatic activity is 37°C.
They can permanently be inactivated when above
60°C?
-All enzymes are inactivated at 80°C.
-For each 10°C increase the activity of enzymes increases by at least twice within the range of 0-60°C.

40
Q

What are the main chemical reactions that contribute to food spoilage?

A

-Lipid oxidation
-Non-enzymatic browning

41
Q

What are some methods to inhibit enzymatic activity in foods?

A

-Controlling temperature
-Adjusting pH
-Reducing water activity

Biology 002 (18 decks)

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