Food Spoilage: Types and Causes

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Questions and Answers

What process makes a food product undesirable for consumption?

Food fermentation

Food preservation

Food spoilage (correct)

Food enrichment

Which of the following is NOT a major cause of food spoilage?

Insect damage

Microorganism activity

Refrigeration (correct)

Chemical reactions

What type of spoilage occurs due to the activity of enzymes?

Physical spoilage

Microbial spoilage

Chemical spoilage

Enzymatic spoilage (correct)

Which change is associated with spoiled oils?

Rancid smell Signup and view all the answers

Which of the following factors can contribute to the physical damage of food?

Broken shell of eggs Signup and view all the answers

What type of change might you observe in a banana after long storage?

Change in color Signup and view all the answers

Which type of reaction can cause rancidity in food?

Non-enzymatic reactions Signup and view all the answers

What role do microorganisms play in food spoilage?

They promote spoilage Signup and view all the answers

What is the main consequence of microbial growth in food?

Leads to food spoilage Signup and view all the answers

Which microbes primarily affect carbohydrates in food?

Yeasts and molds Signup and view all the answers

At what pH level are foods primarily susceptible to spoilage by molds and yeasts?

pH below 4.5 Signup and view all the answers

What minimum water activity (aw) is required for most microbes to grow?

0.91 Signup and view all the answers

Which temperature range is most suitable for microbial growth?

20-50°C Signup and view all the answers

What is the role of oxygen in the growth of certain molds?

Oxygen is necessary for mold growth Signup and view all the answers

What is a characteristic of perishable foods?

Readily spoilt Signup and view all the answers

What is one way that natural coverings protect food from microbial growth?

Prevent entry of microbes Signup and view all the answers

What role do phenolases and polyphenol oxidases play in food spoilage?

They oxidize phenols to orthoquinones, leading to melanin formation. Signup and view all the answers

Which conditions are most unfavorable for insect breeding?

Low temperatures below 10°C. Signup and view all the answers

Which chemical reaction is primarily responsible for the formation of black brown pigments in food?

Non-enzymatic browning. Signup and view all the answers

What factor is NOT typically associated with lipid oxidation in food spoilage?

High humidity. Signup and view all the answers

How does freezing contribute to food spoilage?

Through physico-chemical reactions. Signup and view all the answers

What is a common manifestation of microbial activity in spoiled food?

Chemical products of microbial metabolism. Signup and view all the answers

Which statement about chlorophyll degradation in fruits and vegetables is true?

It causes a dull olive-brown color. Signup and view all the answers

What type of spoilage process is associated with the interaction of anthocyanins with metals?

Chemical spoilage. Signup and view all the answers

Study Notes

Food Spoilage: Types and Aetiology

Food spoilage is a process that makes a product undesirable or unsuitable for consumption.
It's a complex ecological phenomenon resulting from microbial activity determined by prevailing conditions.
This involves biochemical reactions within food constituents.

Types of Undesirable Changes in Food

Change in colour: Example, bananas turning brown over time.
Change in smell: Often rancid smells in spoiled oils.
Change in consistency: Milk splitting is an example.
Change in texture: Spoilage often leads to rotting, like rotting carrots.
Mechanical damage: Damage from impacts like eggs with a broken shell.

Major Causes of Food Spoilage

Biological spoilage: Growth of microorganisms (bacteria, yeasts, molds), and activity of food enzymes. Damage from pests, insects, and rodents also contribute.
Physical spoilage: Reactions with oxygen, light, or chemical reactions within the food itself.
Chemical spoilage: Temperature abuse or physical damage can lead to spoilage.
Specific Spoilage Factors:
- Microbial growth and activity (bacteria, yeast, molds)
- Food enzyme activity
- Loss/gain of moisture
- Reactions with oxygen and light (rancidity, color changes)
- Damage from pests, insects, and rodents
- Non-enzymatic reactions (oxidation, mechanical damage)
- Inappropriate storage temperature (hot or cold)

Spoilage due to Enzymatic Activity

Enzymes in foods contribute to deterioration.
Endogenous enzymes:
- Post-harvest senescence and spoilage of fruits and vegetables
- Oxidation of phenols to orthoquinones by phenolases and polyphenol oxidases (PPO) which lead to browning
- Sugar-starch conversion in plant tissues by amylases

Spoilage due to Insects, Pests, and Rodents

Insects and pests attack fruits, vegetables, grains, and processed products.
Warmer and humid environments promote insect and pest growth.
Presence of pests causes loss of nutritional quality, creates off-flavors, and accelerates decay.
Rats and mice carry disease-producing microorganisms which contaminate food.

Spoilage due to Chemical Reactions

Chemical reactions occur in the presence of atmospheric oxygen and sunlight
Lipid oxidation and non-enzymatic browning affect food quality, colour, and flavour.
Lipid oxidation is influenced by light, oxygen, high temperature, iron, and copper.
Maillard reaction (reducing sugars and amino acids reacting to form brown pigments in the presence of heat) and caramelization (sugars reacting in the presence of high heat and low moisture).

Spoilage due to Physical Factors

Temperature, moisture, and pressure can cause spoilage.
Physico-chemical reactions from freezing, burning, drying, and bruising of fruits and vegetables during storage and handling.
Food processing or storage leads to colour deterioration due to chlorophyll degradation (leading to dull olive-brown colour).
Anthocyanins (food pigments) react with metals which can cause unwanted colour changes (e.g., purple discoloration from tin reaction with cherries).

Most Common Manifestations of Spoilage

Visible microbial growth (molds, slime).
Degradation of food structure causing texture loss.
Chemical products of microbial metabolism in the form of odors and off-flavors.
Gas production

Factors Affecting Microbial Growth

Intrinsic factors: Water activity, pH, redox state, nutrient content, antimicrobial presence, and biological structures.
Extrinsic factors: Storage temperature, storage relative humidity, atmospheric gases, and microbial activities.
Other factors: Photo reactivity, presence of oxygen, invader pests, mishandling.

Nutrients and Other Constituents in Food

Proteins are degraded by proteolytic enzymes, leading to putrefaction.
Carbohydrates are affected primarily by yeasts and molds, with subsequent production of various acids and alcohol.
Microbes degrade fats to produce fatty acids and glycerol.

Acidity & Water Content

Foods with pH below 4.5 are generally acidic and susceptible to molds and yeasts, while non-acidic foods are more vulnerable to bacteria.
Microbes require at least 13% free water. Available water (water activity, a_w) is crucial.
Salt/sugar preservation inhibits most microbial growth.

Physical and Environmental Factors

Temperature (20-50°C) is ideal for microbial growth, with pathogens growing between 6 and 35°C.
Some fungi can survive and grow at lower temperatures (e.g., Botrytis cinerea).
Anaerobic microorganisms spoil airtight canned foods. Oxygen is necessary for mold growth.

Presence of Inhibitory Substances

Food contains natural or added inhibitory substances that prevent microorganisms growth.

Biological Structure Inhibits Spoilage

Healthy tissues in plants and animals are usually sterile or have minimal microbial content.
Natural coverings (seed testa, nut shells, fruit coverings) protect against microbial entry.

Types of Foods Based on Spoilage Rate

Perishable: Spoil quickly and need specific storage. Examples include milk, fruits, vegetables, fish.
Semi-perishable: Can be stored for longer periods with proper care, like potatoes.
Non-perishable: Remain good for a long time without specific handling (unless mishandled), examples include sugar, flour.

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Description

Explore the intricate world of food spoilage, including its types and major causes. Understand how microbial activity and environmental factors contribute to undesirable changes in food products. This quiz provides insights into how spoilage affects color, texture, and overall quality of food.