Transcript Avoiding Food Deterioration - Louisiana Association of FFA

Food Deterioration
and its Causes
Main Idea
What is food deterioration,
and how can food science
minimize its effects?
Food deterioration includes:
 changes in
 texture
organoleptic quality
 flavor
(how something is
perceived by a
sensory organ)
To some degree, all foods
 nutritional value
undergo deterioration after
 food safety
harvest.
 aesthetic appeal The role of food science is
to minimize negative
 color
changes as much as
possible.
CATEGORIES OF
DETERIORATION
 occurs when a food is consumed that
contains a chemical toxic to humans.
Staphylococcus aureus and Clostridium
botulinum produce toxins. Molds in foods
produce mycotoxins like aflatoxin that are not
destroyed by heat.
Insects:
 Insect damage can be minor, but this wounds
the tissue for additional damage by
microorganisms.
 Controls for insects include pesticides, inert
atmosphere and cold storage.
The three general categories of food
deterioration are:
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Physical
Chemical
Biological
Factors that cause food deterioration include:
light, cold, heat, oxygen, moisture, dryness,
other types of radiation, enzymes,
microorganisms, time, industrial contaminants
and macroorganisms (insects, mice, and so
on).
Table 1. Useful Shelf
Life at 70 F
Food
 Meat
 Fish
 Poultry
 Dried, smoked meat
 Fruits
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Days
1 to2
1 to 2
1 to 2
360+
1 to 7
Table 1. Useful Shelf
Life at 70 F
 Food
 Leafy vegetables
 Root Crops
 Dried seeds
Days
1 to 2
7 to 20
360 +
SHELF LIFE AND DATING OF
FOODS
 There is a time limit for the usefulness of all
foods. This time limit depends on the type of
food, the storage conditions and other
factors. If food is held at about 70 F (21 C) its
useful life varies as shown in Table 1.
SHELF LIFE AND DATING OF
FOODS
 Shelf life is the time required for a food product to
reach an unacceptable quality. This length of
time depends on the food item (Table 1), the
processing method, packaging and storage
conditions. Food manufacturers put code dates
on their products. "Pack date" is the date of
manufacture. The date of display is called the
"display date," and the "sell by date" is the last
day to sell. Some foods have a "best used by
date," or the last date of maximum quality. The
"expiration date" indicates when the food is no
longer acceptable.
WHAT CAUSES FOOD
DETERIORATION?
 Specific causes of food deterioration are listed below.
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Deterioration can be caused by one or more of the following:
Microorganisms such as bacteria, yeast and molds;
Activity of food enzymes;
Infestations by insects, parasites and rodents;
Inappropriate temperatures during processing and storage;
Gain or loss of moisture;
Reaction with oxygen;
Light;
Physical stress or abuse; and
Time.
Bacteria, yeast, mold
 Thousands of species of microorganisms exist, and a
few hundred are associated with foods. Not all are bad;
in fact, some are desirable in food preservation.
Microorganisms are found in the soil, water and air; on
animal skins, plant surfaces and digestive tracts; but
they are usually not present in healthy tissue.
 Bacteria are single-celled organisms occurring in three
shapes: round (cocci), rod (bacilli) and spiral (spirilla
and vibrios). Some produce spores which are resistant
to heat, chemicals and other adverse conditions.
Bacteria, yeast, mold:
 Yeasts are the largest of the microorganisms but are
still single cells, and some produce spores.
 Molds are larger than bacteria. They are often
filamentous and they all produce spores.
 In foods, these microorganisms attack basically all the
food components -- including sugars, starches,
cellulose, fats and proteins. Depending on the food and
the microorganism, the action on food could be to
produce acids, making the food sour, or to produce
alcohol. Some microorganisms produce gas, making
the food foamy, while others produce unwanted
pigments or toxins.
Bacteria, yeast, mold:
 Environmental conditions that affect microbial growth
include temperature and oxygen. Microbes that prefer
cold temperatures are said to be pyschrophilic.
Mesophilic microorganisms prefer normal temperatures,
while thermophilic microorganisms prefer hot
temperatures. Bacteria or molds that require
atmospheric oxygen are said to be aerobic, while those
yeasts and bacteria that do not require atmospheric
oxygen are called anaerobic. Facultative
microorganisms are adaptive, and can survive in either
aerobic or anaerobic conditions. Obligative
microorganisms are capable of survival in only one or
the other situation.
Foodborne disease:
 Humans may be infected by eating a food
containing a microorganism. Infections can
be caused by Clostridium perfringen,
Salmonella sp., Escherichia coli (E. coli 0157)
and several others. Food intoxication
Food enzymes:
 All foods from living tissues have enzymes.
Most of these enzymes will survive harvest or
slaughter. At the time of harvest or slaughter,
enzymes that control digestion and
respiration proceed uncontrolled and cause
tissue damage. Some of the post-harvest
enzymatic reactions are actually desirable, as
in the ripening of tomatoes and the aging or
tenderizing of beef. Enzyme action can be
controlled by heat, chemicals and radiation.
Heat and cold:
 Normal harvest temperatures range from 50
to 100 F. The higher the temperature, the
faster biochemical reactions occur. In fact, the
rate of chemical reactions doubles with each
10 degree rise in temperature. On the other
hand, sub-freezing temperatures damage
tissues. Cold temperatures may also cause
discoloration, change the texture, break an
emulsion and denature protein. Chilling can
injure the tissue of fruits as well.
Oxygen:
 Chemical oxidation reactions can destroy
vitamins (especially A and C), alter food
colors, cause off-flavors and promote the
growth of molds.
PRINCIPLES OF FOOD
PRESERVATION
 Food preservation involves the use of heat,
cold, drying (water activity or Aw), acid (pH),
sugar and salt, smoke, atmosphere,
chemicals, radiation and mechanical
methods.
Heat:
 Most bacteria are killed at 180 to 200 F, but
spores are not. To ensure sterility, you must
have wet heat at 250 F for 15 minutes. High
acid foods require the same temperature of
heat for less time.
Cold:
 Most microbial growth slows at temperatures
under 50 F. Some bacteria, called
psychrophiles, actually thrive at relatively low
temperatures and will continue slow growth.
Foods frozen at less than 14 F usually do not
have any free water, so these foods also
benefit from low water activity to help protect
against microbial growth. Freezing may kill
some but not all of the microorganisms.
Drying:
 Drying reduces the water activity (Aw) in a
food. Since microorganisms contain about 80
percent moisture, drying or dehydrating the
food also dehydrates the microorganism.
Changing the amount of water in a food also
alters the rate of enzyme activity and other
chemical reactions.
Acid:
 As the food becomes more acid (lower pH)
the heat required for sterilization is reduced.
For example, the pH of corn is about 6.5. At
226 F, 15 minutes are required to destroy C.
botulinum spores. The pH of pears is about
3.8 and only 5 minutes are necessary to
destroy C. botulinum at 226 F. Acid may
occur naturally in foods, be produced by
fermentation or be added artificially.
Sugar, salt and smoke:
 Sugar, salt and smoke are chemical means of
controlling food deterioration. The addition of
sugar or salt to a food item increases the affinity
of the food for water. This removes the water
from the microorganism through osmosis.
 Smoke contains formaldehyde and other
preservatives. The heat involved with adding the
smoke helps reduce the microbial populations
and it dries the food somewhat.
Atmosphere:
 Changing the storage atmosphere reduces
food deterioration. The growth of aerobes is
slowed by removing the oxygen, while
providing oxygen limits the growth of
anaerobes. Adding carbon dioxide or nitrogen
also slows deterioration.
Chemicals:
 Chemical additives such as sodium benzoate,
sorbic acid, sodium or calcium propionate
and sulphur dioxide retard the growth of
microorganisms, modify enzyme activity,
inhibit chemical reactions or modify the
structure of foods
Radiation:
 Radiation includes X-rays, microwave,
ultraviolet light and gamma rays. Radiation
can destroy microorganisms and inactivate
enzymes.
Food Sanitation
 Definition:

protection from contamination
 Must include
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all functions
operations
Food products
 Ongoing / Dynamic (ever changing)
 “Sanitation is a Way of Life”
Temperature Control
 Food Temperatures:
 Danger
zone (40ºF to 140ºF)
 Thermometers
 Monitor temperatures
 Thawing
Hygiene and Personnel Practices
 People are the # 1 consideration
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Rules:
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Setting
Following
Breaking
Hygiene and Personnel Practices
 Sanitation program is an attitude
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Willingness
Effort
Ongoing training
Hygiene and Personnel Practices
 Personnel Training:
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Appropriate sanitation principles
Food handling practices
Manufacturing controls
Personal hygiene practices
Sanitation Principles/Food Handling
 Training
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Should instill understanding of processing
steps
Technology for each product
Where problems exist
Desire to satisfy consumers
Guard consumer’s interests
Manufacturing Controls/Essential
Operations
 Personnel
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Must be trained in critical elements
Importance of these operations
Monitoring these operations
Action to be taken
 Certification Programs
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Ex. Heat processing equipment
Develop specific training programs
Hygienic Practices
 Communicable diseases/ Injuries
 Hand Washing
 Personal Cleanliness/ Conduct
Communicable Diseases
 Restricted access for
 People known to carry or suffer from transmitted
diseases through food
 Restricted from any food-handling areas
 Persons afflicted with
 Infected wounds
 Skin infections
 Sores
 Open cuts
 Completely covered
 Secure
 waterproof
Hand Washing
 Facilities
 Hot water hand washing station
 Convenient to food handling area
 Personnel
 Wash hands with soap
 Warm running, potable water
 Must be washed
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After handling contaminated materials
Using toilet facilities
Disinfectant hand dips
Personal Cleanliness/Conduct
 Must be maintained in food handling
operations
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PPE
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Sanitary clothing
Hair covering
Footwear
Properly maintained PPE
Gloves
Remove all jewelry
Tobacco, gum, and food are not permitted
EXERCISES
 1. Read the labels on food in your home, in a
grocery store or on items you buy during the
day. Make a list of the date codes on five
different foods. List the "sell by date," the
"best used by date," and the "expiration date"
for as many of the foods as you can. Discuss
these in class.
EXERCISES:
 2. Leave a food such as meat, bread, fruit
and so on at room temperature and describe
the changes in food quality. Discuss these
with the class and try to categorize the
changes and their causes.
EXERCISES:
 3. Why is the occurrence of E. coli 0157 in
food such a worry?
EXERCISES:
 4. What is the chemical makeup of enzymes
and how many enzymes exist?