Foods Deteriorate and Spoil

1
Foods Deteriorate and Spoil

• More than just obvious spoilage
• Sensory and esthetic changes
• Safety changes
• Nutritional changes
• Physical, chemical, biological changes
• Others
• All foods deteriorate and/or spoil

2
Microorganisms

• Bacteria, yeast, mold
• Bacteria cause most food spoilage
• Yeast may spoil fruit juices, etc.
• Mold a problem on breads, others
• Fermentation is controlled food spoilage

3
Temperature and Fermentations

• Heat and Cold
• Warmer temperature increase reaction rates
• Q-10 principal
• Reaction rates can double with every 10C
  increase in temperature (higher or lower)
• Cold temperatures slow growth
• Bacterial fermentations are not chemical
  reactions, so optimal or sub-optimal conditions
  are critical

4
Controlling Fermentations

• Temperature (high or low)
• Atmospheric conditions (aerobic or anaerobic)
• Acid
• Sugar
• Chemicals
• Presence of other organisms

5
Fermentations

• Very old method of preservation
• Used mainly to create desirable flavors
• Encourage growth of microorganism

6
Fermentations

• Benefit of fermentations
• Preservation effect (acids, alcohol)
• Unique and desirable flavors
• Types of fermentations
• 1. Alcohol
• 2. Acetic acid
• 3. Lactic acid
• Combination
• Involves yeast, bacteria, molds

7
Alcohol Fermentation

• Conversion of glucose and/or fructose into
  ethanol and carbon dioxide
• Yeast
• Anaerobic

8
Alcohol Fermentation

• Examples
• Malt beers
• Fruit wines
• Wines brandy
• Molasses rum
• Grain mash whiskey
• Bread dough bread

9
Alcoholic Fermentation

• Wine is a good example
• High quality wines are produced by a multiple
  step process, and for red wines the process often
  lasts over a year or more.
• The basic winemaking steps are
• Grape processing
• Fermentation
• Clarification
• Stabilization
• Bulk ageing
• Bottling
• Each step has an impact on overall wine quality.

10
Wine

• When yeast comes in contact with grape sugars,
  the yeast organisms feed on it, grow, and
  reproduce.
• Yeast innoculation rates can vary, but 6,000
  yeast cells per ounce of liquid (must) is common.
  
• The enzyme zymase within the yeast converts sugar
  in the grape juice into roughly equal parts of
  ethanol and carbon dioxide.
• C6H12O6 ZYMASE 2 C2H5OH 2 CO2
  HEAT
• This process continues until the sugar is used up
  or until the yeast cells are no longer able to
  tolerate the level of alcohol or CO2.

11
Acetic Acid Fermentation

• Main component of vinegar
• Conversion of ethanol into acetic acid
• Usually start with "hard" cider, wine, grain
  alcohol, etc.

12
Acetic Acid Fermentation

• Vinegar bacteria convert alcohol to acetic acid
• Acetobacter
• Requires lots of air (or oxygen)
• Oxidative fermentation
• Vinegar is usually around 10 acetic acid
• 4 is lowest legal level
• 5.0 to 5.5 is common

13
Lactic Acid Fermentation

• Conversion of carbohydrates to lactic acid
• Bacteria (several strains), natural of inoculated
• For the bacterial cells to utilize lactose, they
  must also possess the enzymes needed to break
  lactose into glucose and galactose.
• Bacterial strains
• Streptococcus lactis, cremoris, thermophilus
• Lactobacillus bulgaricus, acidophilus,
  plantarum, bifidus, casei

14
Lactic Acid Fermentation

• Examples
• Vegetables
• Cucumbers pickles
• Olives
• Cabbage sauerkraut
• Coffee cherries coffee beans
• Vanilla beans vanilla

15
Lactic Acid Fermentation

• Examples
• Meats
• Salami, summer sausage
• Many other sausages
• Dairy products
• Sour cream
• Butter
• Buttermilk
• Yogurt
• Nearly all cheeses

16
Ways to Control Fermentations

• Acid
• Add acid or add organisms that produce acid
• Inhibits many organisms
• Make acid until they kill themselves

17
Ways to Control Fermentations

• Alcohol
• Produced by organisms (yeast)
• Inhibit many or all organisms
• Wine (10-15 alcohol) needs some further
  preservation (dry, sulfite, filtration, sorbate)
• Beer (4-5 alcohol) pasteurization, sterile
  filtration, or refrigeration is needed
• Above 20 not much will grow
• Whisky, brandy, other hard liquors

18
Ways to Control Fermentations

• Starter culture
• Add a specific organism(s) it dominates
• Out competes other bacteria
• Temperature
• Encourage or discourage organisms
• Based on optimal temperature of growth
• Often fermentations are conducted at low
  temperatures inhibits extraneous organisms

19
Ways to Control Fermentations

• Oxygen
• Some fermentations are aerobic, some anaerobic
• Salt
• Inhibits most organisms
• Many lactic acid bacteria are salt tolerant
• Salting of cheese will allow lactic acid bacteria
  to predominate
• Pickles, olives, sauerkraut

20
BEVERAGES
21
Beverages

• Fun, thirst quenching, stimulation, nutrition
• Soft Drinks
• Beer
• Coffee
• Tea

22
Soft Drinks

• Market has taken a hit in recent years.
• But still there is a high per capita consumption,
  and overall markets are still increasing
• Can you name any new soft drinks recently on the
  market
• Historically, consumption is about twice that of
  coffee and milk.5 times that of fruit juices

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Soft Drink Ingredients

• Water
• 90 - 100
• Should be pure
• Iron, other minerals, chlorine/bromine, organic
  matter or solids
• May have to process or treat the water
• Filter, deionize, treat with carbon, etc.
• Quality and composition varies from location to
  location, due to inherent differences in water
  quality

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Soft Drink Ingredients

• Sugar
• 8-14
• HFCS or corn syrups
• Sucrose syrup
• Non-nutritive sweeteners
• Aspartame (Nutrasweet)
• Saccharin
• Acesulfame-K
• Sucralose
• Others coming?

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Soft Drink Ingredients

• Flavors
• Natural or artificial
• Fruit juices usually taste like the labeled juice
• But not always
• Must be stable
• Often many different flavors
• Very secretive

26
Soft Drink Ingredients

• Colors
• Caramel (natural color)
• Artificial
• Acid
• Enhances flavor
• Phosphoric in colas, citric in others (Sprite)
• Carbon dioxide contributes acidity (carbonic
  acid)

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Titratable Acidity
Also known as total acidity or potential acidity.
Colas use phosphoric acid, since it acts as a
good buffering agent and a weak acid (thus,
colas are VERY safe microbiologically).
pH
Typical Acid Dissociation Curve (3 COOH)
10
8
6
4
2
0
1.0
0.5
1.5
OH- added (eq)
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Soft Drink Ingredients

• Microbial inhibitors
• Sodium benzoate
• The low pH and type of acid helps a lot.
• Carbon dioxide
• Sparkle, bubbles, mouth sensations
• Provides flavor and acts as a preservative
• More soluble at lower temperatures (as with most
  gasses)

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Beer

• A lot of tradition
• Consumption rate is two-thirds that of soft drinks

30
Beer Production

• Malting
• Germinate barley slightly, then dry
• Activates enzymes to break down starch
• Alpha and beta amylase
• Other cereals may be added (rice, corn)

31
Beer Production

• Mashing
• Add water, heat gradually, then separate liquid
  from insoluble fibers
• Breaks down of starch and solubilizes protein
• Extracts color and flavor from barley
• Primary purpose to obtain the liquid (called
  wort) for subsequent fermentation.

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Beer Production

• Brewing
• Boil the wort with hops flavor
• Other desirable effects
• Bitterness
• Flavor

Hop Cone
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Beer Production

• Fermentation
• Yeast innoculation (wort is now sterile)
• Takes 9 days at a cool temperature
• Usually 4.5 alcohol in final product
• Filter to remove yeast
• Clarify

34
Beer Production

• Storage or aging
• Weeks to months at cool temperatures
• Adds flavor, body, acts as an additional
  clarifying step
• Chill proofing to prevent haze
• Holding at cold temperature will precipitate
  haze-forming proteins or undigested starch.

35
Beer Production

• Finishing
• Filter
• Further carbonate.
• Final preservation
• Heat pasteurize
• Sterile filter
• Refrigerate

36
Coffee

• Produced primarily in the tropics,
• but at high elevations
• Processing
• Pulping remove bean from "cherry"
• Remove outer coating on beans
• By fermentation and enzymes

37
Coffee

• Processing
• After fermentation
• Dry (sun dry or hot air dry)
• Remove outer hull, loosened by fermentation
• Grade for size, color, quality
• Roasted
• Whole bean (better)
• Time/Temperature for Maillard

38
Coffee

• Processing
• Vacuum packaging (flavor very sensitive to
  oxidation)
• Decaffeinated
• Solvents (old method.methylene chloride)
• Supercritical carbon dioxide (efficient, but
  expensive)
• Swiss Water process (So simple, why didnt we
  think of it before?)

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As For Me.Make Mine Tea

• Many different kinds
• Major compounds
• Caffeine
• Tannins color and flavor
• Essential oils flavor, aroma

Epigallocatechin gallate
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Tea

• Processing
• Black Tea
• Wither the leaves softens, dries them slightly
• Rupture (crush) with rollers
• Releases lots of enzymes (PPO apple, banana)
• Fermentation color and flavor develops
• Dry

41
Tea

• Processing
• Green tea and Oolong tea
• Heat leaves to prevent color development
  (inactivates enzyme)
• Less heat with oolong tea, some color exists
• Rupture with rollers
• Dry
• Tea bags or loose leaves

42
Juices and Fruit Beverages

• Degree of preservation
• Fully Pasteurized destruction of all pathogenic
  organisms
• Lightly Pasteurized reduce spoilage organisms
• Refrigerated

A Juice Lightly pasteurized Keep Cold Not
commercially sterile
A Beverage Fully pasteurized Shelf
stable Commercially sterile
43
Food Irradiation
A review on food irradiation will also be posted
on the website. The review is from the Food
Marketing Institute.
44
Irradiation

• Legality
• Spices, potatoes, onions, some fresh fruits and
  vegetables, pork, poultry, beef
• Non-food uses
• If irradiated, must have a seal

Radura Seal
"treated with radiation" or "treated by
irradiation."
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Irradiation

• Potential uses
• Reduce or eliminate microorganisms
• Remove spoilage and/or pathogenic organisms
• Destroy a few or a lot
• Dose dependent
• Eliminate insects, larvae, eggs
• Currently in use in Hawaii for papaya export

46
Irradiation

• Potential Uses
• Reduce the need for chemicals (methyl bromide)
• Reduce need for refrigeration (extended shelf
  life)
• Delay ripening of some fruits and veggies
• Limits sprouting (ie. potatoes, onion, garlic)

47
Irradiation

• Kinds of energy used for food irradiation
• Gamma rays
• Intense bursts of energy (Cobalt 60 or Cesium
  137)
• Excellent penetrating power with photons of
  energy
• Machine generated
• Electron beam
• X-rays
• UV light - some food applications

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Irradiation

• Units of radiation
• RAD
• Measure of energy absorbed by material
• 1 Kilorad 1000 Rad
• Gray or KiloGray (KGy)
• 100 RAD 1 Gray
• 100 KRAD 1 KGy
• The kilogray (KGy) is the common unit of food
  irradiation measurement.
• Measured by dosimeter

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Irradiation

• Dose
• Depends on desired effects
• 1 KGy is a common low dose, but varies
• Must consider
• Resistance of organisms and enzymes
• Quality changes
• Maximum doses permitted by the FDA for foods
  vary
• Fruits and vegetables 100,000 rads (1
  kiloGray)
• Poultry 450,000 rads (4.5 kiloGray)
• Red meat 700,000 rads (7 kiloGray)
• Spices 3,000,000 rads (30 kiloGray).
• A 1 KGy dose is equivalent to millions of chest
  x-rays.

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Foods Permitted to be Irradiated Under FDA's
Regulations
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Microwave Heating

• Properties of microwaves
• Radiant energy, very LONG wavelengths
• 0.025-0.75 meters long
• Travel in straight lines
• Reflected by metals
• Long wavelengths are absorbed by water and other
  polar food constituents causing vibration gt heat
• Long wavelengths pass through air, most glass,
  paper, plastic

53
Irradiation

• Effects of radiation
• Does not heat food (unlike microwaves)
• High energy generates free radicals
• Highly reactive
• Reacts with microorganism DNA
• Also reacts with food components
• May effect quality

54
Irradiation

• Irradiation Tricks
• Limit free radical formation while destroying
  microorganisms.
• Irradiate frozen foods
• Irradiate in a vacuum or in the presence of an
  inert gas
• Reduce oxygen, to eliminate oxygen free radicals

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Irradiation

• Safety and wholesomeness
• A lot of research over the past 30 years
• General conclusions from research
• Just as nutritious as heat preserved
• No significant production of toxins or
  carcinogens
• Does not make food radioactive

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E-Beam for Food Irradiation

• Primary use is to reduce or eliminate the threat
  of bacterial spoilage or contamination.
• An efficient cold process that uses beams from
  electrons or X-rays to target a bacteria's DNA
• The process is an on or off function.
• No chemical additives are used and no residue
  from the electrons/X-rays persist.
• Generally, no alteration in appearance, taste, or
  chemical makeup of a food is present
• .but a dose-dependent response.

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Food Irradiation

• Food undergoes the irradiation process on a
  conveyor belt or small rail system (no humans
  needed to move product).
• Packages or cartons are sealed and irradiated
  under the inspection of the USDA Food Safety
  Inspection Service (FSIS).

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Facilities for irradiating food

• Facilities must comply with plant and worker
  safety requirements of the Nuclear Regulatory
  Commission and OSHA.

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Directed Beams or a Curtain of Electrons
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Uses for the Technology

• E-beam processing also has many non-food
  applications.
• Polymer cross-linking
• Chain scission reactions
• Medical device sterilization
• Cosmetics sterilization
• Pharmaceutical sterilization
• Computer chip (silicon) sterilization
• The technology was first invented in the 1930s
  and commercialized in the 1950s.
• Used to seal wire insulation jacketing
• Heat-shrinkable plastics
• Thermoset composite curing
• Semiconductor enhancements
• Ohand for food processing!

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E-beam Basics

• An atom is composed of protons and neutrons,
  located in the nucleus
• Negatively charged electrons orbit the nucleus.
• Electrons are light and are only loosely
  attracted to the nucleus, thus separating easily
  from the atom
• The loose electrons are accelerated using
  magnetic and electric fields and focused into a
  beam of energy.
• The beam can be altered with electromagnets to
  produce a "curtain" of accelerated electrons.
• Electrons will loose some of their energy due to
  interaction with air, so efficiency is gained by
  irradiating in a vacuum.

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When an E-beam hits a food

• Atoms in a food can be ionized, creating a
  positively charged ion (or free radical)
• Orthe electron is moved to a higher-energy
  atomic orbital, creating an excited atom.
• These radicals (ions) are precursors to any
  chemical changes that may be measured in
  irradiated foods.
• It is a classical free radical mechanism.
• Breaking the chains of DNA, altering
  macro-molecules (i.e. lipids), vitamins, or
  antioxidants.

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Radiolytic Products

• The breaking of chemical bonds involves the
  formation of stable radiolytic products from the
  reactive free radicals.
• Radiolytic species identified after radiation are
  similar to those formed during common food
  processing techniques.
• In over 30 years of investigations, no unique
  radiolytic products have been found that are
  attributable solely to irradiation.
• The FDA estimates the maximum level of damaging
  radiolytic products at 1 kGy to be less than 3 mg
  per kg of food (3 ppm).
• Retention of chemical properties is a factor of
• Irradiation dose
• Temperature
• Food composition
• Presence/absence of oxygen

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Changes in Irradiated Food

• Food irradiation is conducted at the temperature
  of the food.
• Physically, irradiated and non-irradiated foods
  are indistinguishable at recommended doses.
• Defects have been reported in high-fat foods and
  some fruits.
• Some off-flavors in meat and tissue softening in
  peaches and nectarines have been reported.
• Radiation does not seem to impair the activity of
  certain nutrients, with losses similar to other
  methods of food preservation.
• Vitamin C is often used as an indicator of
  irradiation loss, since it is very sensitive to
  oxidation.
• Loss in Vit. C is mostly due to a conversion to
  dehydroascorbic acid, but the losses are
  nutritionally negligible in our society.
• Tocopherols (Vit. E) are particularly sensitive
  to irradiation in the presence of oxygen.
• Space flights have shown Vit. D status and folate
  was in jeopardy.