Foods Deteriorate and Spoil

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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
Foods Deteriorate and Spoil

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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 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) 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

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

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

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 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)

27. Titratable Acidity

28. 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)

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 Bitterness Flavor

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 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 didn?t we think of it before?)

39. ?As For Me?.Make Mine Tea? Many different kinds Major compounds Caffeine Tannins = color and flavor Essential oils = flavor, aroma

40. 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

44. Irradiation Legality Spices, potatoes, onions, some fresh fruits and vegetables, pork, poultry, beef Non-food uses 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 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

48. 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

49. 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.

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 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

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. Polymer cross-linking Chain scission reactions Medical device sterilization Cosmetics sterilization Pharmaceutical 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 Heat-shrinkable plastics Thermoset composite curing Semiconductor enhancements 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: Irradiation dose Temperature Food composition 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.


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