PROCESSING IN HIGH-ACID VS. LOW-ACID

FOODBy: Sheila Mulhern

DEFINING THE ACIDIC GROUPS

Low-acid Food Acidified 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

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.

Acid Food

FDA – look at pH and water activity levels

A food that has a natural pH of 4.6 or below.

LOW ACID Meats, Seafood,

Milk, Poultry, Soups, Mixed canned vegetables

Vegetables, Asparagus, Beets, Pumpkin, Green beans, Corn, Lima beans

ACIDIFIED Cucumbers,

cabbage, artichokes, cauliflower, peppers, tropical fruits

ACIDIC Most natural

fruits Apples,

strawberries, oranges, kiwi, berries

Low-acid Food Acidified Food

Thermal processing Determine the amount of heat

along with time period which is necessary to destroy microorganisms in the food product

Aseptic processing (how the product flows)

Pressure canning or bottling (how fast the product heats)

Ensures elimination or control over pathogens in food products

Acid Food

No preservatives required

Uses boiling water canning

Boiling cycles, short or long depending on acidic elements

FOOD PROCESSING METHODS

CANNING REGULATIONS 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

DANGEROUS PATHOGENS 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

PRESSURE CANNING 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

PRESSURE CANNING STEPS 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

ASEPTIC PROCESSING AND FILLING OF FRUITS

ACIDIFIED FOODS 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.

ACIDIFIED FOODS 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.

REFERENCES 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.hrs-spiratube.com/en/applications/food/aseptic-processing-and-filling.php)

Clemson University Publishing (http://www.clemson.edu/psapublishing/pages/foodsc/ec705.pdf)