Microorganisms. Bacteria, yeast, moldBacteria cause most food spoilageYeast may spoil fruit juices, etc.Mold a problem on breads, othersFermentation is controlled food spoilage. Temperature and Fermentations. Heat and ColdWarmer temperature increase reaction rates Q-10 principalReaction rates can double with every 10
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1. Foods Deteriorate and Spoil More than just obvious spoilage
Sensory and esthetic changes
Physical, chemical, biological changes
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
Reaction rates can double with every 10°C 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)
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
2. Acetic acid
3. Lactic acid
Involves yeast, bacteria, molds
7. Alcohol Fermentation Conversion of glucose and/or fructose into ethanol and carbon dioxide
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:
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
Requires lots of air (or oxygen)
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.
Streptococcus: lactis, cremoris, thermophilus
Lactobacillus: bulgaricus, acidophilus, plantarum, bifidus, casei
14. Lactic Acid Fermentation Examples:
Cucumbers = pickles
Cabbage = sauerkraut
Coffee cherries = coffee beans
Vanilla beans = vanilla
15. Lactic Acid Fermentation Examples:
Salami, summer sausage
Many other sausages
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
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
Inhibits most organisms
Many lactic acid bacteria are salt tolerant
Salting of cheese will allow lactic acid bacteria to predominate
Pickles, olives, sauerkraut
21. Beverages Fun, thirst quenching, stimulation, nutrition
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
23. 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
24. Soft Drink Ingredients Sugar
HFCS or corn syrups
25. 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
26. Soft Drink Ingredients Colors
Caramel (natural color)
Phosphoric in colas, citric in others (Sprite)
Carbon dioxide contributes acidity (carbonic acid)
27. Titratable Acidity
28. Soft Drink Ingredients Microbial inhibitors
The low pH and type of acid helps a lot.
Sparkle, bubbles, mouth sensations
Provides flavor and acts as a preservative
More soluble at lower temperatures (as with most gasses)
29. 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.
32. Beer Production Brewing
Boil the wort with hops = flavor
Other desirable effects
33. 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
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
36. Coffee Produced primarily in the tropics,
but at high elevations
Pulping = remove bean from "cherry"
Remove outer coating on beans
By fermentation and enzymes
37. Coffee Processing
Dry (sun dry or hot air dry)
Remove outer hull, loosened by fermentation
Grade for size, color, quality
Whole bean (better)
Time/Temperature for Maillard
38. Coffee Processing
Vacuum packaging (flavor very sensitive to oxidation)
Solvents (old method….methylene chloride)
Supercritical carbon dioxide (efficient, but expensive)
Swiss Water process (So simple, why didn’t we think of it before?)
39. “As For Me….Make Mine Tea” Many different kinds
Tannins = color and flavor
Essential oils = flavor, aroma
40. Tea Processing
Wither the leaves = softens, dries them slightly
Rupture (crush) with rollers
Releases lots of enzymes (PPO; apple, banana)
Fermentation = color and flavor develops
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
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
44. Irradiation Legality
Spices, potatoes, onions, some fresh fruits and vegetables, pork, poultry, beef
If irradiated, must have a seal
45. Irradiation Potential uses
Reduce or eliminate microorganisms
Remove spoilage and/or pathogenic organisms
Destroy a few or a lot
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
Intense bursts of energy (Cobalt 60 or Cesium 137)
Excellent penetrating power with photons of energy
UV light - some food applications
48. Irradiation Units of radiation
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
49. Irradiation Dose
Depends on desired effects
1 KGy is a common low dose, but varies
Resistance of organisms and enzymes
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.
50. Foods Permitted to be Irradiated Under FDA's Regulations
52. 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 => 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
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
55. 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
56. 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.
57. 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).
58. Facilities for irradiating food Facilities must comply with plant and worker safety requirements of the Nuclear Regulatory Commission and OSHA.
59. Directed Beams or a “Curtain” of Electrons
60. Uses for the Technology E-beam processing also has many non-food applications.
Chain scission reactions
Medical device sterilization
Computer chip (silicon) sterilization
The technology was first invented in the 1930’s and commercialized in the 1950’s.
Used to seal wire insulation jacketing
Thermoset composite curing
Oh…and for food processing!
61. 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.
62. When an E-beam hits a food… Atoms in a food can be ionized, creating a positively charged ion (or free radical)
Or…the 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.
63. 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:
Presence/absence of oxygen
64. 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.