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									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
 color             to minimize negative
                    changes as much as
 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.
 Insect damage can be minor, but this wounds
  the tissue for additional damage by
 Controls for insects include pesticides, inert
  atmosphere and cold storage.
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
Table 1. Useful Shelf
Life at 70 F

   Food                 Days
   Meat                 1 to2
   Fish                 1 to 2
   Poultry              1 to 2
   Dried, smoked meat   360+
   Fruits               1 to 7
Table 1. Useful Shelf
Life at 70 F
 Food                  Days
 Leafy vegetables      1 to 2
 Root Crops            7 to 20
 Dried seeds           360 +
 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 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.

   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.
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.

 Chemical oxidation reactions can destroy
  vitamins (especially A and C), alter food
  colors, cause off-flavors and promote the
  growth of molds.
 Food preservation involves the use of heat,
  cold, drying (water activity or Aw), acid (pH),
  sugar and salt, smoke, atmosphere,
  chemicals, radiation and mechanical

 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.

 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 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.
 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.

 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.

 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 includes X-rays, microwave,
  ultraviolet light and gamma rays. Radiation
  can destroy microorganisms and inactivate
Food Sanitation
 Definition:
      protection from contamination
 Must include
      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
     Rules:
          Setting
          Following
          Breaking
Hygiene and Personnel Practices
 Sanitation program is an attitude
     Willingness
     Effort
     Ongoing training
Hygiene and Personnel Practices
 Personnel Training:
     Appropriate sanitation principles
     Food handling practices
     Manufacturing controls
     Personal hygiene practices
Sanitation Principles/Food Handling
 Training
     Should instill understanding of processing
     Technology for each product
     Where problems exist
     Desire to satisfy consumers
     Guard consumer’s interests
Manufacturing Controls/Essential
 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
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
           After handling contaminated materials
           Using toilet facilities
      Disinfectant hand dips
Personal Cleanliness/Conduct
 Must be maintained in food handling
     PPE
         Sanitary clothing
         Hair covering
         Footwear
         Properly maintained PPE
         Gloves
         Remove all jewelry
         Tobacco, gum, and food are not permitted
 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.

 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.

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

 4. What is the chemical makeup of enzymes
  and how many enzymes exist?

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