Transcript Processing in High-Acid vs. Low-Acid Food

By: Sheila Mulhern
FDA – look at pH and water activity levels
Low-acid Food

Any food (other
than alcoholic
beverages) with a
finished
equilibrium pH
greater than 4.6
and a water
activity greater
than 0.85,
excluding
tomatoes and
tomato products
having a finished
equilibrium pH
less than 4.7
Acid Food
Acidified Food

A low-acid food
to which acid(s)
or acid food(s)
are added and
which has a
finished
equilibrium pH
of 4.6 or below
and a water
activity (aw)
greater than
0.85.

A food that has a
natural pH of 4.6
or below.
Meats, Seafood, Milk,
Poultry, Soups, Mixed
canned vegetables
 Vegetables,
Asparagus, Beets,
Pumpkin, Green
beans, Corn, Lima
beans

 Cucumbers,
cabbage,
artichokes,
cauliflower,
peppers, tropical
fruits
 Most
natural fruits
 Apples,
strawberries,
oranges, kiwi,
berries
Low-acid Food
 Thermal




Acid Food
Acidified Food
processing
No
preservatives
Determine the amount of heat
along with time period which is
required
necessary to destroy
microorganisms in the food product  Uses boiling
water canning
Aseptic processing (how the
product flows)
 Boiling cycles,
Pressure canning or bottling (how
short or long
fast the product heats)
depending on
Ensures elimination or control over
acidic
pathogens in food products
elements

FSIS Canning Regulations – requires
commercial sterility
 Condition achieved by application of heat,
sufficient alone or in combination with other
ingredients or treatments, to render the
product free of microorganism capable of
growing in the product at non-refrigerated
condition (over 50°F) where the product is
intended to be held during distribution &
storage


Consider growth
values of
microorganisms and
nature of the food
being heated

Thermal Death Time
tests (TDT)

Determine the amount
of heat required to
destroy
microorganisms in a
product

Use D & Z values –
thermal
characteristics of
microorganisms used
in thermal death time
tests





As pressure increases,
temperature increases
Creates an air tight seal
Low acid foods require
higher temperatures (240
F) when processing to kill
harmful bacteria
Dial gauge – indicates
pressure inside canner
Weighted gauge –
regulates pressure in
canner

Add hot water in canner and
place jars in canning rack

Exhaust all air from the
cooker with the vent port
open

Pressure the canner by
placing weight on the vent
port

Begin timing when pressure
gauge reads correct pressure

Regulate heat

Remove from heat, cool

Vent port

Place jars on cooling rack


Blanch the food ingredients in an acidified aqueous
solution. To acidify large food particulates, the particulates
could be blanched in a hot acid bath. The ability to obtain a
properly acidified product is dependent upon blanch time
and temperature, as well as the type of and concentration of
acid.
Immerse the blanched foods in an acid solution. That is,
blanch the product in the normal steam or water blancher.
Then, dip it into an acid solution, remove it from the acid
solution and place it into containers. Proper acidification
depends upon how well the product is blanched, the
concentration of the acid and the contact time.


Direct batch acidification. This is normally the best way to
acidify fluid material. Ingredients are mixed in a kettle, and
acid is added directly to the batch. (An elevated
temperature may improve the rate of acid penetration into
solid particles.) The pH of the batch is checked before the
material is sent from the batch kettle to the filler.
Add acid foods to low-acid foods in controlled portions.
Essentially, this is how a formulated product such as pasta
sauce is made. Components in the sauce, such as meat or
onions, are low-acid foods, while the tomato sauce is an acid
food. The acid food is mixed with the low-acid food to get an
acidified food product. The formulation, including the
proportion of tomato sauce to low-acid components, is
critical to obtain uniform and accurate control of pH of the
finished product.

FDA Acidified and Low-Acid Canned Foods
(http://www.clemson.edu/psapublishing/pages/foodsc/ec705.pdf)

FSIS (http://www.fsis.usda.gov)

HRS Spiratube (http://www.hrsspiratube.com/en/applications/food/aseptic-processing-andfilling.php)

Clemson University Publishing
(http://www.clemson.edu/psapublishing/pages/foodsc/ec705.pdf)