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
 Food
 Acidity
 Temperature
 Time
 Oxygen
 Moisture
FIGHT BAC!
What Bacteria Need to Grow
 Food
 Acidity
– pH = Amount of acidity
– Low acid food = pH > 4.6
 Temperature
 Time
 Oxygen
 Moisture
Bacteria Inhibited by pH
Most Inhibited
Min
Max
Optimum
Gm +
Gm -
4.5
3.8
>9.0
>7.0
Yeast
1.5-3.5
8
4.5-6.8
Mold
1.5-3.5
11
4.5-6.8
Least Inhibited
Department of Food Science and Technology
What Bacteria Need to Grow
 Food
 Acidity
 Temperature
Aerobic: most spoilage
organisms
 Time
Facultatively anaerobic:
5% Oxygen
pathogens
 Oxygen
Anaerobic: No Oxygen
 Moisture
Clostridium botulinum
What Bacteria Need to Grow
 Food
 Acidity
 Temperature
– Danger zone = 40°F to 140°F
(41°F - 135°F)
 Time
 Oxygen
 Moisture
Department of Food Science and Technology
What Bacteria Need to Grow
Products
Affected
 Food
Microbial Group
 Acidity
Normal bacteria
 Temperature
Normal yeast
Torulopsis species
0.88
Fruit juice
conc.
 Time
Normal molds
Aspergillus flavus
0.80
Jams, jellies
Wallemia sebi
0.75
Honey
Xerophilic molds
Aspergillus echinulatas
0.65
Flour
Osmophilic yeast
Saccharomyces
bisporus
0.60
Dried fruits
 Oxygen
 Moisture
Example
aw
Salmonella species
Clostridium botulinum
0.91
Fresh meat,
milk
Halophilic
bacteria
aw 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
Storage Life
0°F
One year
10°F
Three months
20°F
Three weeks
30°F
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 Aw
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