Food Science

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Unit

• Food Science

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Problem Area

• Handling and Storing Plant Products

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Lesson

• Testing for Food Additives

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Student Learning Objectives

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

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Terms

• 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

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Terms cont.

• plate freezing
• radiation
• refrigeration
• senescence
• sequestrants
• sterilization
• texture enhancer

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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
  processes.

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• 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
  chemicals.

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• 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.

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• 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
  ham.
• 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.

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• 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.

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• 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
  unpalatable.

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• 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.

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• 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
  forever.

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• 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.

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• 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.

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• 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.

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• 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.

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• 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.

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• 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
  water.

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• 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
  oxygen.

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• 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
  product.
• 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
preservation?

• 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.

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• C. Food additives can be used for a variety of
  reasons.
• 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.

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• 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
  ingredients.
• 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

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• 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.

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• 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.

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• 6. Mold growth can be inhibited by sodium or
  calcium propionate. The shelf life of bakery
  products is increased, but the flavor is not
  affected.
• 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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Review/Summary

• 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
  preservation?
• What are some food additives and how do they help
  to preserve foods?