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Food Science


Unit Food Science Problem Area Handling and Storing Plant Products Lesson Testing for Food Additives Student Learning Objectives 1. Describe food preservation and its ... – PowerPoint PPT presentation

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Title: Food Science

  • Food Science

Problem Area
  • Handling and Storing Plant Products

  • Testing for Food Additives

Student Learning Objectives
  • 1. Describe food preservation and its benefits.
  • 2. Describe the methods used in controlling food
  • 3. Explain why food additives are important to
    food preservation.
  • 4. Explain a variety of food additives and their

  • air-blast freezing
  • antioxidants
  • blanching
  • chemical drying
  • commercial sterilization
  • conduction
  • convection
  • drying
  • fermentation
  • flavor enhancer
  • food additives
  • food preservation
  • food spoilage
  • freeze drying
  • freezing
  • irradiation
  • liquid freezing
  • mechanical drying
  • pasteurization
  • pickling

Terms cont.
  • plate freezing
  • radiation
  • refrigeration
  • senescence
  • sequestrants
  • sterilization
  • texture enhancer

What is food preservation? How does food
preservation benefit consumers?
  • All foods eventually undergo spoilage some spoil
    much faster than others. Foods can undergo
    natural deterioration or can become contaminated
    by microorganisms causing spoilage to occur at a
    much faster rate.
  • Senescence is considered to be a terminal,
    irreversible deteriorative change in living
    organisms, leading to cellular and tissue
    breakdown and eventually death. Senescence is the
    period following ripening, during which growth
    ceases and aging processes replace ripening

  • A. Food preservation is the treatment of food to
    keep it from spoiling. It also aids in retaining
    nutrients and improving taste.
  • B. Food spoilage is the condition in which food
    becomes unsafe to eat. Food spoilage can be
    caused by the invasion of bacteria, fungi, mold,
    and other foreign materials.
  • 1. Bacteria are one-celled microscopic plants.
    They are the most difficult of all microbes to
    control in the prevention of food spoilage.
    Microorganisms use the food as a food source.
  • 2. Food may be exposed to other foreign
    materials. These materials are not intended to be
    part of the food. Their introduction leads to
    spoilage. Examples of foreign materials that
    cause food spoilage are rodents, insects, and

  • C. Food preservation helps foods retain their
    nutritional value. As foods deteriorate, they
    lose the nutrients that they naturally contain.
    Fruit juices that are not refrigerated typically
    lose their nutrients. The loss of nutrients is
    known as nutrient depletion.
  • D. Food preservation aids in helping foods retain
    their taste. Palatability means that an item has
    an agreeable taste. Various processes are used to
    improve food palatability. Care must be taken to
    not decrease a foods nutritional value when
    increasing its palatability. For example, sugar
    is added to foods to improve its palatability.
    How-ever, if too much sugar is added, the
    nutritional value of the food is decreased.

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What are the methods used in food science to
control contamination?
  • Environmental controls that are commonly used in
    storage of perishable plant products are
  • A. HeatMost bacteria, molds, and yeasts grow
    best at temperatures of 1638ºC. For sterility, a
    temperature of 121º C must be maintained for at
    least 15 minutes. Heat is the most effective
    means of preserving a food product. It is
    commonly used in canning foods.

  • 1. In food processing, heat energy is transferred
    in one of three ways to aid in preservation
  • a. Conduction is a method of heating in which
    energy moves from one particle to another through
    direct contact. Conduction may be compared to a
    chain reaction. As each particle of food is
    heated, it passes energy on to other particles it
    is touching. Examples of foods that are preserved
    through conduction heating include canned tuna or
  • b. Convection is a method of heating that
    involves the movement of a heated air or liquid
    through the food being heated. This is the same
    type of heat used in a kitchen oven. In
    convection heating, the movement of the heated
    air or fluid around the food causes it to be
    heated. Examples of foods that are preserved
    through convection heating are canned soups.

  • c. Radiation is a form of conduction in which
    heat energy is transferred through the
    electromagnetic spectrum. The electromagnetic
    spectrum is a linear arrangement of all known
    forms of energy. In radiation, energy from the
    infrared and ultraviolet range of the spectrum
    are used to heat the food. An example is the
    infrared radiation lamps used in restaurant
    buffets to keep food warm.

  • 2. Heat preservation is the most complete means
    of food preservation. When food is heated, it is
    altered. The extent to which a food is altered
    depends on the amount and duration of heat it is
    subjected to.
  • a. Sterilization is the complete destruction of
    all microorganisms. Sterilized foods will last a
    very long time. Because they have undergone a
    high level of heat treatment, sterilized foods go
    through significant alterations.
  • b. Commercial sterilization is the complete
    destruction of all microorganisms except some
    spores. Commercially sterilized foods will
    eventually become unsuitable to eat. They will
    not cause sickness. Instead, they become

  • c. Pasteurization is a heat treatment that
    destroys all pathogenic microorganisms, but not
    organisms that cause spoilage. A pathogenic
    organism inflicts illness in humans.
  • d. Blanching is a heat treatment used with
    vegetables where their temperature is raised to
    between 180 and 190 and followed by rapid
    cooling. This process does not destroy
    microorganisms. It does inactivate enzymes that
    might alter the taste or color of the vegetable.

  • B. ColdWhen water in foods is completely frozen,
    there is not multiplication of microorganisms. At
    a temperature of below 10º C, growth is slowed
    and becomes even slower as the cold increases.
    Cooler temperatures slow senescence.
    Refrigeration and freezing are not as effective
    as heating in preserving foods. Heating destroys
    all microorganisms. Cold treatments only slow the
    metabolisms of the microorganisms.
  • 1. Refrigeration is the storage of foods at a
    temperature below room temperature, but above
    freezing. It is used as a transitional
    environment. A transitional environment means
    that the food product will ultimately be heated
    or consumed. It will not stay refrigerated

  • 2. Freezing is the storage of food products at
    temperatures where water contained in the
    products becomes ice. When a food is frozen, it
    is the water in the food that freezes. The three
    main methods of freezing used in commercial food
    preservation are
  • a. Plate freezing uses the surface of metal
    plates to sandwich the food product to be frozen.
    As the food and plates contact each other, fluid
    that circulates in the plate removes heat and
    freezes the product.
  • b. Air-blast freezing uses high speed air and
    cold temperatures to freeze the product. Air is
    the freezing medium in this method.
  • c. Liquid freezing involves spraying fluid
    refrigerants such as liquid nitrogen on
    individual food products as they move down a
    conveyor belt. This method is commonly used on
    meat patties.

  • C. DryingPreservation by drying succeeds because
    decay-causing organisms usually do not grow at
    moisture contents below 10-15. Microorganisms
    need water for growth and survival.
  • 1. Drying involves removing the moisture from a
    food product. When moisture is removed, most of
    the substances that lead to spoilage are also
    removed. Food is dried in one of three ways
  • a. Mechanical drying uses a machine to remove the
    moisture in the food product.
  • b. Freeze drying involves freezing the food
    product then placing it in a chamber where all
    air and moisture are removed.
  • c. Chemical drying uses a chemical substance to
    remove moisture from the food. Salt is the most
    common chemical used in chemical drying.

  • D. AcidBecause of their value as preservatives,
    and in some instances their effect as flavor
    enhancers, certain organic acids, including
    acetic and ascorbic acid, are used to preserve
    plant products. Microorganisms can only survive
    at a specific range of pH values. By increasing
    the acidity of the food, the environment becomes
    unfavorable for microbial growth.
  • E. Oxygen and carbon dioxideRespiration is
    directly affected by oxygen and carbon dioxide
    levels. Since respiration is an oxidation
    process, a reduction in the amount of oxygen
    reduces the respiration rate. High concentrations
    of carbon dioxide may inhibit or prevent
    respiration and may inhibit the ethylene
    production that stimulates ripening.

  • F. HumidityIn general, low humidity favors
    desiccation and wilting. Also, high humidity
    favors the development of decay, especially if
    the temperature is too high.
  • G. Fermentation and picklingThe action of
    certain bacteria and yeasts in decomposing
    carbohydrates is known as fermentation.
  • 1. After decomposition by different organisms,
    the end products include carbon dioxide and water
    (complete oxidation), acids (partial oxidation),
    alcohols (alcoholic fermentation), lactic acid
    (lactic acid fermentation), and others. These act
    as preservatives by retarding enzymatic
    deterioration, and they impart flavors that are
    regarded as desirable.

  • 2. When the fermentation process is combined with
    salting, it is called pickling. Pickling may be
    accomplished without the direct use of
    microorganisms by placing food in organic acids
    (vinegar or citric acid).
  • 3. Citric, lactic, maltic, and tartaric are also
    added to foods. All of these acids occur
    naturally in plant juices.
  • 4. Fermentation can take place under either of
    two conditions aerobic fermentation takes place
    with air present and anaerobic fermentation takes
    place without the presence of air.

  • H. Sugar and saltSugar is metabolized by
    microorganisms, but dissolved molecules of sugar
    reduce the activity of water and inhibit the
    growth of microorganisms just like dissolved
    salt. Salt is an efficient preservative because
    it reduces water activity. When bacteria, yeasts,
    or molds are placed in a heavy salt brine, water
    in the cells moves out (diffuses) through the
    cell membranes and into the concentrated brine
    solution (osmosis). Salt can also raise the
    boiling point or lower the freezing point of

  • I. AirWith this process, a partial or total
    vacuum can be created to prevent aerobic
    microorganisms from growing. The storage and
    handling of fresh fruit and vegetable commodities
    must slow the reactions that tend to break down
    the product. These degradation reactions are
    essentially those resulting from respiration,
    whereby the carbohydrates synthesized during
    photosynthesis are broken down to carbon dioxide
    and water. Procedures that slow or stop the rate
    of respiration frequently also slow or stop the
    rate of deterioration. Respiration of stored
    crops can be reduced by limiting the amount of

  • J. Irradiation is the exposure of food to gamma
    rays generated by a radioactive material.
  • 1. Gamma Rays have no charge. They are used to
    destroy enzymes or microorganisms in the food
  • 2. Food that has been irradiated does not mean
    that it is radioactive.
  • K. Controlling Air Movementmolds, yeasts, and
    bacteria travel through the air. If the movement
    of air is controlled, the chances for
    contamination are minimized. This is one reason
    why large food processing machines are covered
    with lids.
  • L. Segregationevery component in food
    preparation is a source of contamination. When
    foods are processed, each step is separated so
    that the contaminant does not travel from one
    step to the other. Segregation is routine in food
    processing plants. Most people are not as careful
    at home. The same cutting board may be used to
    cut different foods without being washed.

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Why are food additives important to food
  • It is almost impossible to eat food that does not
    contain preservatives of some kind. Unless you
    cook all of your meals from scratch and raise
    your own food, preservatives are being consumed.
  • A. Additives are used to keep food from spoiling.
    Food additives are non-nutritive substances that
    are added to foods in small quantities to improve
    flavor, texture, appearance, or shelf life.
    Substances which are not intentionally added to
    foods are called food contaminants.
  • B. Food additives are chemicals added to a food
    product to increase its length of usefulness. The
    chemicals used are not dangerous. Instead, they
    prolong the useful life of the food by slowing
    the natural deterioration process.

  • C. Food additives can be used for a variety of
  • 1. Improve the quality of the food.
  • 2. Reduce the amount of waste.
  • 3. Maintain or improve the nutritional value of
    the food.
  • 4. Improve the shelf life.
  • 5. Increase consumer acceptance.
  • 6. Increase the availability of foods.
  • 7. Make food preparation easier.
  • D. Food additives are not the sole solution to
    food preservation. Additives are used in
    combination with physical and non-chemical
    methods of preservation.

  • E. Companies are responsible for meeting the
    guidelines set forth by the US Food and Drug
    Administration. Other countries have similar
    agencies and requirements. Food additives must
    meet several strict requirements before they are
    allowed in foodstuffs.
  • 1. It must be safe for humans to consume.
    Extensive testing must be completed and validated
    by the FDA.
  • 2. The additive must work as indicated in the
    specified conditions.
  • 3. The nutritional value of foods may be not
    reduced by the additive.
  • 4. Customers must not be deceived by the additive
    and it must not be used to mask unfavorable
  • 5. A specific method for determining the presence
    and amount of must be available.
  • 6. The additive may not be used instead of good
    manufacturing practices.

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What are some food additives and how do they help
to preserve foods?
  • Food additives fall into a variety of substance
    categories. The following table outlines the
    substance categories
  • A. Food Additives Substance Categories

  • B. The following are examples of food additives
  • 1. Monosodium glutamate (MSG) is derived from
    seaweed. It has very little taste, but can be
    used quite effectively as a flavor enhancer.
    Additives that have either no flavor or little
    flavor, but can improve the flavor of a food are
    called flavor enhancers.
  • 2. Natural or synthetic substances that are used
    to boost a flavor or regain a flavor that was
    lost during processing are called flavoring
    agents. Oils, oleoresins, and extracts are
    examples of flavoring agents.
  • 3. Polyols are an example of a texture enhancer.
    Texture enhancers not only improve the texture of
    a food, but they also improve water retention.
    Glycerine, mannitol, propylene glycol, and
    sorbitol are examples of polyols. These are found
    in diet drinks, gum, candy, and ice cream.

  • 4. Many foods contain a variety of metals which
    are naturally present. Sequestrants are additives
    that combine with these metals helping to
    inactivate the metal. Sequestrants prevent the
    metal ions from oxidizing with fatty acids
    resulting in off-flavors. Malic acid, tartaric
    acid and citric acid are examples of
    sequestrants. They are also antioxidants. They
    can prevent oxidative rancidity from occurring.
  • 5. When salt is placed in water, it dissociates
    into sodium and chlorine ions. It can thus
    increase the boiling point or reduce the freezing
    point of water. Osmosis can occur as equilibrium
    is trying to be reaching. This creates a lower
    amount of water present for microbes to use.

  • 6. Mold growth can be inhibited by sodium or
    calcium propionate. The shelf life of bakery
    products is increased, but the flavor is not
  • 7. Sorbic acid hinders mold and yeast growth in
    cheese and fruit drinks.
  • 8. Sodium benzoate and benzoic acid are used in
    candied products.
  • 9. Processed meat products can contain butylated
    hydroxyl toluene (BHT) or butylated hydroxyl
    anisole (BHA). These antioxidants help to prevent
    oxidation of the animal fat.
  • 10. The application of sulfur dioxide allows the
    fruit or vegetable to dry faster and destroys the
    enzymes which are responsible for browning.

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  • What is food preservation? How does food
    preservation benefit consumers?
  • What are the methods used in food science to
    control contamination?
  • Why are food additives important to food
  • What are some food additives and how do they help
    to preserve foods?