Processing in High-Acid vs. Low-Acid Food By: Sheila Mulhern

Defining the Acidic Groups FDA – look at pH and water activity levels Low-acid Food Acidified Food 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 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.

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

Food processing methods Low-acid Food Acidified Food Acid 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 No preservatives required Uses boiling water canning Boiling cycles, short or long depending on acidic elements

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)