Department Department of Food Science and Technology The Science Behind Food Preservation: Dr. Renee Boyer Extension Specialist May 21, 2009

Department Department of Food Science and Technology Why Preserve Foods? Prevent Spoilage of Foods & Extend Shelf Life Prevent Spoilage of Foods & Extend Shelf Life Types of Spoilage: Types of Spoilage: –Microbiological  Molds, yeast, bacteria –Chemical  Enzymatic changes –Physical  Bruising, water loss

Department Department of Food Science and Technology Microbiological Food Spoilage: Microorganisms can get onto a food product from anywhere in the environment… Microorganisms can get onto a food product from anywhere in the environment… –People, animals, dirt, insects, other surfaces Spoilage microorganism: cause food to spoil NOT pathogenic!! Pathogens: make you sick

What Bacteria Need to Grow F ood F ood A cidity A cidity T emperature T emperature T ime T ime O xygen O xygen M oisture M oisture FIGHT BAC !

What Bacteria Need to Grow F ood F ood A cidity A cidity –pH = Amount of acidity –Low acid food = pH > 4.6 T emperature T emperature T ime T ime O xygen O xygen M oisture M oisture

Department Department of Food Science and Technology Bacteria Inhibited by pH MinMaxOptimum Gm + Gm >9.0>7.0 Yeast Mold Most Inhibited Least Inhibited

What Bacteria Need to Grow F ood F ood A cidity A cidity T emperature T emperature T ime T ime Oxygen Oxygen M oisture M oisture Aerobic: most spoilage organisms Facultatively anaerobic: 5% Oxygen pathogens Anaerobic: No Oxygen Clostridium botulinum

Department Department of Food Science and Technology What Bacteria Need to Grow F ood F ood A cidity A cidity T emperature T emperature –Danger zone = 40°F to 140°F (41°F - 135°F) T ime T ime O xygen O xygen M oisture M oisture

Department Department of Food Science and Technology What Bacteria Need to Grow F ood F ood A cidity A cidity T emperature T emperature T ime T ime O xygen O xygen M oisture M oisture Microbial GroupExampleawaw Products Affected Normal bacteria Salmonella species Clostridium botulinum 0.91 Fresh meat, milk Normal yeastTorulopsis species0.88 Fruit juice conc. Normal moldsAspergillus flavus0.80Jams, jellies Halophilic bacteria Wallemia sebi0.75Honey Xerophilic moldsAspergillus echinulatas0.65Flour Osmophilic yeast Saccharomyces bisporus 0.60Dried fruits a w target = 0.85

Department Department of Food Science and Technology Food Preservation Goal: Control microbial growth / destroy microorganisms by: High temperature (Heat) High temperature (Heat) Low temperature (Cold) Low temperature (Cold) No oxygen No oxygen Low pH Low pH Low Aw (water activity) Low Aw (water activity)

Department Department of Food Science and Technology Methods of Home Food Preservation: Heat Processing/Canning Heat Processing/Canning –Boiling Water Bath –Pressure Canning Freezing Freezing Drying Drying

Department Department of Food Science and Technology

Canning = Preservation by Heat Destroys microorganisms Destroys microorganisms Inactivates enzymes Inactivates enzymes Seals container during the process to prevent recontamination Seals container during the process to prevent recontamination

Department Department of Food Science and Technology Of the growth factors that we discussed, which is the most important to know before proceeding to canning? Question #1:

Department Department of Food Science and Technology What is the target organism associated with this? Question #2:

Department Department of Food Science and Technology Acidity: the most important factor! Clostridium botulinum Clostridium botulinum Spore-former: spores ubiquitous in the environment Spore-former: spores ubiquitous in the environment –Can’t make you sick –Infant botulism ONLY: Under anaerobic conditions (commonly created during preservation), spores germinated into vegetative cells ONLY: Under anaerobic conditions (commonly created during preservation), spores germinated into vegetative cells Vegetative cells produce toxin Vegetative cells produce toxin

Department Department of Food Science and Technology Botulism: Ingestion of toxin in foods Ingestion of toxin in foods Neurotoxin Neurotoxin Causes paralysis and death Causes paralysis and death if medical attention isn’t found quickly Very rare in U.S. now Very rare in U.S. now Primarily associated w/ Primarily associated w/ improperly home canned

Department Department of Food Science and Technology Name one high acid and one low acid food Question #3:

Department Department of Food Science and Technology High Acid Foods (pH < 4.5) Apples Apples Oranges Oranges Peaches Peaches Strawberries Strawberries Pears Pears Sauerkraut, pickles Sauerkraut, pickles Blueberries Blueberries Rhubarb Rhubarb Lemons Lemons Grapefruit Grapefruit Pineapple Pineapple Apricots Apricots Cherries Cherries Figs Figs Plums Plums Raspberries Raspberries

Department Department of Food Science and Technology Low Acid Foods (pH > 4.5) Meat, fish Meat, fish Carrots Carrots Green beans Green beans Potatoes Potatoes Peas Peas Cabbage Cabbage Corn Corn Squash Squash Pumpkin Pumpkin Okra Okra Turnips Turnips Snap Beans Snap Beans Sweet potatoes Sweet potatoes Onions Onions Oysters Oysters Ripe olives Ripe olives

Department Department of Food Science and Technology Tomatoes: Usually considered an acid food Usually considered an acid food Some now known to have a pH slightly above 4.6 Some now known to have a pH slightly above 4.6 Boiling water bath …MUST be acidified Boiling water bath …MUST be acidified

Department Department of Food Science and Technology Canning Foods Low acid foods: Low acid foods: –pH >4.6 –Processing Pressure canner! High acid foods: High acid foods: –pH <4.6 –Boiling water bath Acidified foods: Acidified foods: –pH is decreased to <4.6 by adding acid –Pickling, salsas, tomatoes! –Boiling water bath

Department Department of Food Science and Technology

Destruction of Spores in Low Acid foods: Spores are very difficult to destroy at boiling temperatures Spores are very difficult to destroy at boiling temperatures Boiling water bath: 212°F Boiling water bath: 212°F –7 – 11 hours depending on the food Pressure canning: 240 – 250°F (10-15 psi) Pressure canning: 240 – 250°F (10-15 psi) –20 – 100 minutes depending on the food

Department Department of Food Science and Technology

Time/Temperature Dependency Food Food Acid, salt, sugar, starch, fat Acid, salt, sugar, starch, fat Size of Pieces Size of Pieces Consistency Consistency Convection heating in liquids Convection heating in liquids Conduction heating in solids Conduction heating in solids

Department Department of Food Science and Technology Time/Temperature Dependency Combination of both Combination of both Fullness of pack Fullness of pack Container size and material Container size and material Initial temperature of food Initial temperature of food Microorganisms presen Microorganisms presen WHEN CANNING ALWAYS USE A RECIPE FROM A REPUTABLE SOURCE!!! WHEN CANNING ALWAYS USE A RECIPE FROM A REPUTABLE SOURCE!!!

Department Department of Food Science and Technology What are reputable sources? National Center for Home Food Preservation National Center for Home Food Preservation – USDA Complete Guide to Home Canning USDA Complete Guide to Home Canning – usda.html usda.htmlhttp:// usda.html Ball Blue Book Ball Blue Book

Department Department of Food Science and Technology Methods of canning NOT recommended: Open-kettle canning Open-kettle canning Processing in conventional ovens, microwaves, dishwashers Processing in conventional ovens, microwaves, dishwashers –Do no prevent all spoilage risks Steam canners Steam canners –Do not heat as effectively Canning at pressures greater than 15 Canning at pressures greater than 15 Use of glass caps or one piece zinc/porcelain-lined caps Use of glass caps or one piece zinc/porcelain-lined caps –Failure to seal properly

Department Department of Food Science and Technology Boiling water bath canning: Large covered cooking pot with a rack Large covered cooking pot with a rack Must be deep enough to cover 1 inch above jars Must be deep enough to cover 1 inch above jars Processes foods at boiling temp. (212°F) Processes foods at boiling temp. (212°F) Acid / acidified foods Acid / acidified foods Heat destroys m/o Heat destroys m/o that spoil acid foods

Department Department of Food Science and Technology

Pressure Canning: Heavy pot, lid can be sealed: fitted w/ vent and pressure dial or weighted gauge Heavy pot, lid can be sealed: fitted w/ vent and pressure dial or weighted gauge Processes foods at 240°F (10-11 pds pressure) Processes foods at 240°F (10-11 pds pressure) ONLY safe way to process low acid foods ONLY safe way to process low acid foods

Department Department of Food Science and Technology

True or False: Altitude affects the canning process Question #4:

Department Department of Food Science and Technology The Effects of Altitude: Water boils at lower temperatures as altitude increases. Water boils at lower temperatures as altitude increases. Lower temps are less effective, so: Lower temps are less effective, so: –Boiling water bath: processing time increased –Pressure canning: pressure increased Altitudes in WV Altitudes in WV vary greatly: vary greatly: Morgantown: 960 ft Beckley: 2421 ft

Department Department of Food Science and Technology

Weighted –vs- Dial gauge: Weighted gauges: ft: 10 lbs pressure ft: 10 lbs pressure Over 1000ft: must be operated at 15 lbs pressure Over 1000ft: must be operated at 15 lbs pressure Dial Gauges: ft: 11 lbs pressure ft: 11 lbs pressure Over 2000ft: corrections must be made Over 2000ft: corrections must be made Ex: Ex: –2001ft-4000: 12 lbs –4001 – 6000: 13 lbs

Department Department of Food Science and Technology Ensuring Quality: Use only high quality foods, free of bruises and blemishes Use only high quality foods, free of bruises and blemishes Can/preserve w/in 6-12 hours of harvest Can/preserve w/in 6-12 hours of harvest Hot pack (especially acid foods) Hot pack (especially acid foods) –Helps to remove air from the food –Keeps food from floating in jar –Increases the vacuum seal –Helps food maintain color during storage

Department Department of Food Science and Technology Importance of headspace: Jams/jellies: ¼ inch Jams/jellies: ¼ inch Fruits / tomatoes: (boiling water bath): ½ inch Fruits / tomatoes: (boiling water bath): ½ inch Low acid: 1-1 ¼ inch Low acid: 1-1 ¼ inch Needed for expansion Needed for expansion of the food –Higher the temperature, the greater the expansion Forming vacuum in cooling jars Forming vacuum in cooling jars

Department Department of Food Science and Technology Appropriate Jars/Lids

Department Department of Food Science and Technology Important notes: Fruit Some recipes call for ascorbic acid dip Some recipes call for ascorbic acid dip –Apples, pears, nectarines, apricots, peaches etc…. –Pure powdered form –Vitamin C tablets –Commercially prepared mixes This dip prevents the fruit from This dip prevents the fruit from browning while preparing jars

Department Department of Food Science and Technology Important notes: Pickling Pickled foods are acidified, therefore they can be heat processed in a boiling water bath Pickled foods are acidified, therefore they can be heat processed in a boiling water bath –Prevents spoilage organisms and inactive enzymes Fermentation Fermentation –Dill pickles/saurkraut – 3 weeks –Refrigerated dill pickles – 1 weeks –Quick process – not fermented

Department Department of Food Science and Technology Important notes: Pickling Level of acidity should not be altered Level of acidity should not be altered –Recipe MUST be followed Use canning/pickling salt Use canning/pickling salt –Other salt has non-caking material added which can make brine cloudy

Department Department of Food Science and Technology Important notes: Jams and Jellies Ingredients Ingredients –Fruit, pectin, acid, and sugar Pectin Pectin –Form a gel when in the right combination of acid and sugar –All fruits contain some pectin –Fully ripened fruit has less pectin (when not adding pectin, ¼ fruit should be under-ripe)

Department Department of Food Science and Technology Important notes: Jams and Jellies Acidity Acidity –Too much – gel won’t set –Too little – gel with lose liquid –Low acid fruits must have lemon juice added –Commercial pectins contain acid to help w/ gelling Reduced sugar Reduced sugar –Must be made w/ low-methoxy pectin (requires addition of calcium to gel) –Typically need to be processed longer

Department Department of Food Science and Technology Jams/Jellies and Mold Low water activity + acidity typically prevents most spoilage Low water activity + acidity typically prevents most spoilage Except: MOLDS Except: MOLDS –Mycotoxins have been found in jellies/ jams which have surface mold growth –Known to cause cancer –PROCESS in boiling water bath  5 minutes  Do not use paraffin or wax seals

Department Department of Food Science and Technology Freezing: Easiest, most convenient quickest methods Easiest, most convenient quickest methods Freezing is the safest method, but may not produce the best quality Freezing is the safest method, but may not produce the best quality Does not sterilize foods Does not sterilize foods Retards the growth of m/o and slows down chemical changes that affect the quality of the foods Retards the growth of m/o and slows down chemical changes that affect the quality of the foods

Department Department of Food Science and Technology Control of Enzymatic Spoilage: Enzymes are slowed down considerably, but not eliminated during freezing. Enzymes are slowed down considerably, but not eliminated during freezing. For best quality: For best quality: Vegetables: Blanched Vegetables: Blanched –Quick treatment in boiling water (2-3 min) inactivates enzymes prior to freezing Fruits: Ascorbic acid is added Fruits: Ascorbic acid is added –Vit. C, lemon juice, citric acid added to prevent browning before freezing

Department Department of Food Science and Technology Changes during freezing: Water in food freezes and expands Water in food freezes and expands Ice crystals formed cause cell water to rupture rendering the product softer when defrosted. Ice crystals formed cause cell water to rupture rendering the product softer when defrosted. Quicker freezing decrease amount of cell wall rupture Quicker freezing decrease amount of cell wall rupture Rapid freezing: many small ice crystals form Rapid freezing: many small ice crystals form Slow freezing: few large ice crystals Slow freezing: few large ice crystals Most commercial products are frozen VERY rapidly in blast freezers Most commercial products are frozen VERY rapidly in blast freezers

Department Department of Food Science and Technology Importance of temperature: Frozen foods should be stored below 0°F to prevent deterioration of the product and improve quality Frozen foods should be stored below 0°F to prevent deterioration of the product and improve qualityExample: Storage TemperatureStorage Life 0°FOne year 10°FThree months 20°FThree weeks 30°FFive days

Department Department of Food Science and Technology Foods that don’t freeze well: Foods that have high water content or are typically consumed raw: Foods that have high water content or are typically consumed raw: –Tomatoes –Lettuces –Celery –Potatoes –Sour cream –Fried foods –Milk sauces

Department Department of Food Science and Technology How drying preserves food: Drying preserves food by removing the moisture (80-95%) to prevent microbial growth Drying preserves food by removing the moisture (80-95%) to prevent microbial growth Slows down enzymes Slows down enzymes Removing the moisture = lower A w Removing the moisture = lower A w Drying process is slowed down if humidity is high Drying process is slowed down if humidity is high Best done at temp: 140°F Best done at temp: 140°F

Department Department of Food Science and Technology Drying: Outdoors Outdoors –Only for fruits (high acid, sugar content) –Must be treated for insects after drying is complete Indoors Indoors –Dehydrator: BEST METHOD! –Oven: use oven thermometer to monitor temperature  Leave door cracked 2 – 6 inches for air circulation

Department Department of Food Science and Technology What sort of treatments do you think fruits and vegetables might need before drying? Question #5:

Department Department of Food Science and Technology Treatments for foods to be dried: Fruits: Dips Fruits: Dips –Sulfite, Ascorbic acid, fruit juice, honey Vegetables: Blanched Vegetables: Blanched Meat: safety measures Meat: safety measures –Pork or wild game meat should be frozen for 30 days before use to kill trichinella –Heat in marinade before drying –Heated in oven after drying (to reach 160°F)

Department Department of Food Science and Technology New Technologies that may/may not help consumers: Home vacuum packagers: Home vacuum packagers: –Removing oxygen can increase quality of food therefore extending shelf-life BUT: –Less likely for spoilage organisms to grow –MORE likely for pathogens to grow –Can make perishable foods unsafe –Safe for foods that will be frozen –BUT they should be thawed using safe practices