Transcript Food Recalls and Recall Plans
The Science Behind Food Preservation:
Dr. Renee Boyer
Extension Specialist May 21, 2009
Department of Food Science and Technology
Why Preserve Foods ?
Prevent Spoilage of Foods & Extend Shelf Life Types of Spoilage: – Microbiological Molds, yeast, bacteria – Chemical Enzymatic changes – Physical Bruising, water loss
Department of Food Science and Technology
Microbiological Food Spoilage:
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
Department of Food Science and Technology
What Bacteria Need to Grow
F
ood
A
cidity
T
emperature
T
ime
O
xygen
M
oisture
FIGHT BAC !
What Bacteria Need to Grow
F
ood
A
cidity – pH = Amount of acidity – Low acid food = pH > 4.6
T
emperature
T
ime
O
xygen
M
oisture
Bacteria Inhibited by pH
Most Inhibited Min Max Optimum Gm + Gm Yeast 4.5
3.8
1.5-3.5
>9.0
8 >7.0
4.5-6.8
Least Inhibited Mold 1.5-3.5
11 4.5-6.8
Department of Food Science and Technology
What Bacteria Need to Grow
F
ood
A
cidity
T
emperature
T
ime Oxygen
M
oisture Aerobic: most spoilage organisms Facultatively anaerobic: 5% Oxygen pathogens Anaerobic: No Oxygen Clostridium botulinum
What Bacteria Need to Grow
F
ood
A
cidity
T
emperature – Danger zone = 40°F to 140°F (41°F - 135°F)
T
ime
O
xygen
M
oisture
Department of Food Science and Technology
What Bacteria Need to Grow
F
ood
A
cidity
T
emperature
T
ime
O
xygen
M
oisture
Microbial Group Normal bacteria Normal yeast Normal molds Halophilic bacteria Xerophilic molds Osmophilic yeast Example
Salmonella species Clostridium botulinum Torulopsis species Aspergillus flavus Wallemia sebi Aspergillus echinulatas Saccharomyces bisporus
a w Products Affected 0.91
Fresh meat, milk 0.88
Fruit juice conc.
0.80
Jams, jellies 0.75
Honey 0.65
Flour 0.60
Dried fruits a w target = 0.85
Department of Food Science and Technology
Food Preservation Goal:
Control microbial growth / destroy microorganisms by: High temperature (Heat) Low temperature (Cold) No oxygen Low pH Low Aw (water activity)
Department of Food Science and Technology
Methods of Home Food Preservation:
Heat Processing/Canning – Boiling Water Bath – Pressure Canning Freezing Drying
Department of Food Science and Technology
Department of Food Science and Technology
Canning = Preservation by Heat
Destroys microorganisms Inactivates enzymes Seals container during the process to prevent recontamination
Department of Food Science and Technology
Question #1:
Of the growth factors that we discussed, which is the most important to know before proceeding to canning?
Department of Food Science and Technology
Question #2:
What is the target organism associated with this?
Department of Food Science and Technology
Acidity: the most important factor!
Clostridium botulinum
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 Vegetative cells produce toxin
Department of Food Science and Technology
Botulism:
Ingestion of toxin in foods Neurotoxin Causes paralysis and death if medical attention isn’t found quickly Very rare in U.S. now Primarily associated w/ improperly home canned
Department of Food Science and Technology
Question #3:
Name one high acid and one low acid food
Department of Food Science and Technology
High Acid Foods (pH < 4.5)
Apples Oranges Peaches Strawberries Pears Sauerkraut, pickles Blueberries Rhubarb Lemons Grapefruit Pineapple Apricots Cherries Figs Plums Raspberries
Department of Food Science and Technology
Low Acid Foods (pH > 4.5)
Meat, fish Carrots Green beans Potatoes Peas Cabbage Corn Squash Pumpkin Okra Turnips Snap Beans Sweet potatoes Onions Oysters Ripe olives
Department of Food Science and Technology
Tomatoes:
Usually considered an acid food Some now known to have a pH slightly above 4.6
Boiling water bath …MUST be acidified
Department of Food Science and Technology
Canning Foods
Low acid foods: – pH >4.6 – Processing Pressure canner!
High acid foods: – pH <4.6 – Boiling water bath Acidified foods: – pH is decreased to <4.6 by adding acid – Pickling, salsas, tomatoes!
– Boiling water bath
Department of Food Science and Technology
Department of Food Science and Technology
Destruction of Spores in Low Acid foods:
Spores are very difficult to destroy at boiling temperatures Boiling water bath: 212°F – 7 – 11 hours depending on the food Pressure canning: 240 – 250°F (10-15 psi) – 20 – 100 minutes depending on the food
Department of Food Science and Technology
Department of Food Science and Technology
Time/Temperature Dependency
Food Acid, salt, sugar, starch, fat Size of Pieces Consistency Convection heating in liquids Conduction heating in solids
Department of Food Science and Technology
Time/Temperature Dependency
Combination of both Fullness of pack Container size and material Initial temperature of food Microorganisms presen WHEN CANNING ALWAYS USE A RECIPE FROM A REPUTABLE SOURCE!!!
Department of Food Science and Technology
What are reputable sources?
National Center for Home Food Preservation – http://www.uga.edu/nchfp/ USDA Complete Guide to Home Canning – http://www.uga.edu/nchfp/publications/publications_ usda.html
Ball Blue Book
Department of Food Science and Technology
Methods of canning NOT recommended:
Open-kettle canning Processing in conventional ovens, microwaves, dishwashers – Do no prevent all spoilage risks Steam canners – Do not heat as effectively Canning at pressures greater than 15 Use of glass caps or one piece zinc/porcelain-lined caps – Failure to seal properly
Department of Food Science and Technology
Boiling water bath canning:
Large covered cooking pot with a rack Must be deep enough to cover 1 inch above jars Processes foods at boiling temp. (212°F) Acid / acidified foods Heat destroys m/o that spoil acid foods
Department of Food Science and Technology
Department of Food Science and Technology
Pressure Canning:
Heavy pot, lid can be sealed: fitted w/ vent and pressure dial or weighted gauge Processes foods at 240°F (10-11 pds pressure) ONLY safe way to process low acid foods
Department of Food Science and Technology
Department of Food Science and Technology
Question #4:
True or False: Altitude affects the canning process
Department of Food Science and Technology
The Effects of Altitude:
Water boils at lower temperatures as altitude increases.
Lower temps are less effective, so: – Boiling water bath: processing time increased – Pressure canning: pressure increased Altitudes in WV vary greatly: Morgantown: 960 ft Beckley: 2421 ft
Department of Food Science and Technology
Department of Food Science and Technology
Weighted –vs- Dial gauge: Weighted gauges:
0-1000ft: 10 lbs pressure Over 1000ft: must be operated at 15 lbs pressure
Dial Gauges:
0-2000ft: 11 lbs pressure Over 2000ft: corrections must be made Ex: – 2001ft-4000: 12 lbs – 4001 – 6000: 13 lbs
Department of Food Science and Technology
Ensuring Quality:
Use only high quality foods, free of bruises and blemishes Can/preserve w/in 6-12 hours of harvest 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 of Food Science and Technology
Importance of headspace:
Jams/jellies: ¼ inch Fruits / tomatoes: (boiling water bath): ½ inch Low acid: 1-1 ¼ inch Needed for expansion of the food – Higher the temperature, the greater the expansion Forming vacuum in cooling jars
Department of Food Science and Technology
Appropriate Jars/Lids Department of Food Science and Technology
Important notes: Fruit
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 browning while preparing jars
Department of Food Science and Technology
Important notes: Pickling
Pickled foods are acidified, therefore they can be heat processed in a boiling water bath – Prevents spoilage organisms and inactive enzymes Fermentation – Dill pickles/saurkraut – 3 weeks – Refrigerated dill pickles – 1 weeks – Quick process – not fermented
Department of Food Science and Technology
Important notes: Pickling
Level of acidity should not be altered – Recipe MUST be followed Use canning/pickling salt – Other salt has non-caking material added which can make brine cloudy
Department of Food Science and Technology
Important notes: Jams and Jellies
Ingredients – Fruit, pectin, acid, and sugar 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 of Food Science and Technology
Important notes: Jams and Jellies
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 – Must be made w/ low-methoxy pectin (requires addition of calcium to gel) – Typically need to be processed longer
Department of Food Science and Technology
Jams/Jellies and Mold
Low water activity + acidity typically prevents most spoilage 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 of Food Science and Technology
Freezing:
Easiest, most convenient quickest methods Freezing is the safest method, but may not produce the best quality Does not sterilize foods Retards the growth of m/o and slows down chemical changes that affect the quality of the foods
Department of Food Science and Technology
Control of Enzymatic Spoilage:
Enzymes are slowed down considerably, but not eliminated during freezing. For best quality: Vegetables: Blanched – Quick treatment in boiling water (2-3 min) inactivates enzymes prior to freezing Fruits: Ascorbic acid is added – Vit. C, lemon juice, citric acid added to prevent browning before freezing
Department of Food Science and Technology
Changes during freezing:
Water in food freezes and expands Ice crystals formed cause cell water to rupture rendering the product softer when defrosted.
Quicker freezing decrease amount of cell wall rupture Rapid freezing: many small ice crystals form Slow freezing: few large ice crystals Most commercial products are frozen VERY rapidly in blast freezers
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 Example:
Storage Temperature
0°F 10°F 20°F 30°F
Storage Life
One year Three months Three weeks Five days
Department of Food Science and Technology
Foods that don’t freeze well:
Foods that have high water content or are typically consumed raw: – Tomatoes – Lettuces – Celery – Potatoes – Sour cream – Fried foods – Milk sauces
Department of Food Science and Technology
How drying preserves food:
Drying preserves food by removing the moisture (80-95%) to prevent microbial growth Slows down enzymes Removing the moisture = lower A w Drying process is slowed down if humidity is high Best done at temp: 140°F
Department of Food Science and Technology
Drying:
Outdoors – Only for fruits (high acid, sugar content) – Must be treated for insects after drying is complete Indoors – Dehydrator: BEST METHOD!
– Oven: use oven thermometer to monitor temperature Leave door cracked 2 – 6 inches for air circulation
Department of Food Science and Technology
Question #5:
What sort of treatments do you think fruits and vegetables might need before drying?
Department of Food Science and Technology
Treatments for foods to be dried:
Fruits: Dips – Sulfite, Ascorbic acid, fruit juice, honey Vegetables: Blanched 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 of Food Science and Technology
New Technologies that may/may not help consumers:
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
Department of Food Science and Technology