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Food Deterioration and its Causes

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... shapes: round (cocci), rod (bacilli) and spiral ... Hot water hand washing station. Convenient to food handling area. Personnel. Wash hands with soap ... – PowerPoint PPT presentation

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Title: Food Deterioration and its Causes


1
Food Deterioration and its Causes
2
Main Idea
  • What is food deterioration, and how can food
    science minimize its effects?

3
Food deterioration includes
  • changes in organoleptic quality (how something is
    perceived by a sensory organ)
  • nutritional value
  • food safety
  • aesthetic appeal
  • color
  • texture
  • flavor
  • To some degree, all foods undergo deterioration
    after harvest.
  • The role of food science is to minimize negative
    changes as much as possible.

4
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.

5
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.

6
The three general categories of food
deterioration are
  • 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).

7
Table 1. Useful ShelfLife at 70 F
  • Food Days
  • Meat 1 to2
  • Fish 1 to 2
  • Poultry 1 to 2
  • Dried, smoked meat 360
  • Fruits 1 to 7

8
Table 1. Useful ShelfLife at 70 F
  • Food Days
  • Leafy vegetables 1 to 2
  • Root Crops 7 to 20
  • Dried seeds 360

9
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.

10
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.

11
WHAT CAUSES FOOD DETERIORATION?
  • Specific causes of food deterioration are listed
    below. 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.

12
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.

13
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.

14
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.

15
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

16
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.

17
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.

18
Oxygen
  • Chemical oxidation reactions can destroy vitamins
    (especially A and C), alter food colors, cause
    off-flavors and promote the growth of molds.

19
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.

20
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.

21
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.

22
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.

23
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.

24
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.

25
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.

26
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

27
Radiation
  • Radiation includes X-rays, microwave, ultraviolet
    light and gamma rays. Radiation can destroy
    microorganisms and inactivate enzymes.

28
Food Sanitation
  • Definition
  • protection from contamination
  • Must include
  • all functions
  • operations
  • Food products
  • Ongoing / Dynamic (ever changing)
  • Sanitation is a Way of Life

29
Temperature Control
  • Food Temperatures
  • Danger zone (40ºF to 140ºF)
  • Thermometers
  • Monitor temperatures
  • Thawing

30
Hygiene and Personnel Practices
  • People are the 1 consideration
  • Rules
  • Setting
  • Following
  • Breaking

31
Hygiene and Personnel Practices
  • Sanitation program is an attitude
  • Willingness
  • Effort
  • Ongoing training

32
Hygiene and Personnel Practices
  • Personnel Training
  • Appropriate sanitation principles
  • Food handling practices
  • Manufacturing controls
  • Personal hygiene practices

33
Sanitation Principles/Food Handling
  • Training
  • Should instill understanding of processing steps
  • Technology for each product
  • Where problems exist
  • Desire to satisfy consumers
  • Guard consumers interests

34
Manufacturing Controls/Essential Operations
  • Personnel
  • Must be trained in critical elements
  • Importance of these operations
  • Monitoring these operations
  • Action to be taken
  • Certification Programs
  • Ex. Heat processing equipment
  • Develop specific training programs

35
Hygienic Practices
  • Communicable diseases/ Injuries
  • Hand Washing
  • Personal Cleanliness/ Conduct

36
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

37
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
  • After handling contaminated materials
  • Using toilet facilities
  • Disinfectant hand dips

38
Personal Cleanliness/Conduct
  • Must be maintained in food handling operations
  • PPE
  • Sanitary clothing
  • Hair covering
  • Footwear
  • Properly maintained PPE
  • Gloves
  • Remove all jewelry
  • Tobacco, gum, and food are not permitted

39
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.

40
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.

41
EXERCISES
  • 3. Why is the occurrence of E. coli 0157 in food
    such a worry?

42
EXERCISES
  • 4. What is the chemical makeup of enzymes and how
    many enzymes exist?
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