Processing Acid and Acidified Foods - Aggie Horticulture

ACIDIFIED FOODSProcessing Acid and Acidified FoodsFBNS 10-0101ACIDITY AND pHFood scientists measure the acidity of a food based on itspH value. The pH scale ranges from 0 to 14 with pH 7being neutral. The lower the pH value, the higher the levelof acidity. In order to preserve foods with acid, theregulations require the equilibrium pH of the finishedproduct to be 4.6 or below. At these levels, toxins formedby the deadly organism causing botulism are inhibited.Because all products and processes exhibit normalvariation, the pH must be measured using a pH meter. Forproducts with a pH below 4.0, pH test strips may be usedfor monitoring purposes. Records of pH monitoring must bemaintained for all products classified as acid or acidified.CLASSIFICATIONWe refer to foods with a pH greater than 4.6 as low-acidfoods. For foods with a pH below 4.6 that are preservedwith acid, there are two classifications. The distinctionbetween these two categories is important.Acid Foods: Foods, such as tomatoes, which have a naturalpH of 4.6 or below are considered to be acid foods. Somefoods which contain small amounts of low-acid foods in apredominantly acid food, such as herbal vinegars, are alsoin this category. If the finished equilibrium pH does notvary significantly from the pH of the predominant acidfoods, the food is considered to be an acid food.Acidified foods are low-acid foods to which acids or acidfoods have been added to produce a pH of 4.6 or below. TheFood and Drug Administration (FDA) has additionalrequirements for the processing of acidified foods. These canbe found in the Code of Federal Regulations (21CFR114). Inthe absence of information to the contrary, foods preservedwith acid are considered to be acidified foods.The manufacturer of acidified foods must register theirestablishment and file a scheduled process established bya competent process authority. In addition, the operationmust be under the supervision of an individual who hassuccessfully completed an FDA approved course onprocessing acidified foods. The regulation addresses otherimportant aspects of manufacturing such as monitoring andrecord keeping. These regulations do not apply to naturallyfermented foods or jams, jellies and carbonated beverages.Visit online: Instructions for Establishment Registration andProcessing Filing for Acidified Foods.CONTROLLING SPOILAGELow pH cannot take the place of proper sanitation and carein manufacturing. Good Manufacturing Practices (GMPs)were designed and instituted by the federal government toassure that foods are manufactured and handled in a safeand sanitary manner to prevent adulteration. The conditionsset forth in the regulation (21CFR110) must be met tooperate your business.Typically acid and acidified foods are heat treated in one oftwo ways:1. Hot fill and hold - The product is filled at atemperature of 180°F or above and the heated closureis applied by a steam capper or alternately, the closedcontainer is inverted. The increased temperature abovethe minimum process temperature is necessary to heatthe container and closure to destroy themicroorganisms on inside surfaces.2. Water bath or steam process - The preheatedproduct is filled into the container and the closure isapplied. The container is subjected to hot water andsteam until the coldest spot in the container reaches theminimum process temperature. The minimum processtemperature typically used is 165°F for 15 seconds orthe equivalent.Post processing contamination and preservativesThe thermal process destroys vegetative cells in the productand the hermetic seal protects the product fromrecontamination while it is intact. Once the seal integrity iscompromised by leakage, lack of vacuum, or simply by theconsumer opening the container, microorganisms mayreenter the product and cause contamination. For thisreason, preservatives should be used in acid and acidifiedfoods, especially when the consumer is likely to open andre-close the container. Sodium benzoate and potassiumsorbate are often chosen for this purpose. They are typicallyused together at a rate of 0.1% each by weight, to take

FBNS Fact Sheet 2advantage of their combined effects. They are especiallyeffective against yeasts and molds.PLASTIC CONTAINERS AND PRODUCTS WHICHCAN NOT BE HEATEDMost plastic containers will not withstand the hightemperatures of “hot fill and hold” or “water bath”processes. However, under certain conditions, alternativeprocessing can be used for acid or acidified foods. If theproduct is classified as an acidified food, a processauthority would need to approve any alternative processingmethods.1. First - Destroy the vegetative cells in the producta). At low pH, pathogens may not grow, but they canstill survive and cause foodborne illness. One methodof destroying these cells would be to heat the productto180°F or above, then be cooled sufficiently prior tofilling plastic containers.b). If the product does not allow for a heat treatment,an alternative process would be to adjust the pH tobelow 3.3, prior to filling. When a product with a pHthis low is stored for 24 hours at 75°F, research showsthat the vegetative cells of common foodbornepathogens are destroyed.An adequate sanitation program should be in place anddocumented to ensure that containers and the processingenvironment will not contribute to the contamination of theproduct.2. Second - Prevent the growth of other organisms,specifically yeasts and moldsa). Use preservatives such as sodium benzoate andpotassium sorbate to prevent the growth of yeast,molds and other organisms. Certain microorganismsthat re-contaminate the product from the environmentmay grow in the product and cause spoilage. Oneconcern is that molds might actually grow andconsume acids, thereby increasing the pHCHALLENGE STUDIESThere is a possibility that some products contain inhibitoryproperties that will prevent the growth of microorganismsof public health significance without using the standardtreatments mentioned above.The “Hurdle Concept”The “hurdle concept” refers to the combined effect ofvarious factors such as salt, water activity, pH andtemperature on the inhibition of bacterial growth. Thistechnique is often used by larger food companies who areable to exert high levels of technical control over theprocess and the product. Challenge studies would be neededto validate the use of this method. These studies areexpensive and time-consuming. They require very carefuldesign to validate safety. Anyone who wishes to pursue thehurdle concept and challenge studies is directed to privateoutside laboratories.LABELING THE FOODRegulations dealing with the food label are extensive andcomplicated. Before purchasing any labels, it would be wiseto consult with regulatory authorities. The North CarolinaDepartment of Agriculture and Consumer Services,NCDA&CS (919-733-7366) will review your label forcompliance at no charge. The FDA also has an excellentresource: Food Labeling GuideOTHER RESOURCESThe Code of Federal Regulations (CFR), referenced above,is the published rules of the federal government. It isdivided into 50 chapters. Chapter 21 deals with food anddrugs. The searchable documents can be accessed online at:Code of Federal RegulationsAcid and acidified foods are regulated by the NCDA&CS,phone 919-733-7366. Contact them for the appropriateregulatory guidance concerning facility inspection, GMPs(Good Manufacturing Practices) and labeling.In addition to the establishment registration for thosefacilities processing acidified foods, all facilities thatmanufacture, process, pack, or hold food for human oranimal consumption in the United States must register withthe FDA under the Bioterrorism Act. There is no fee andregistration can be completed on-line at:Food Facility RegistrationDr. John Rushing and JoAnna FoegedingNorth Carolina State University College of Agriculture and Life SciencesDepartment of Food, Bioprocessing and Nutrition SciencesCampus Box 7624 Raleigh, NC 27695-7624919.515.2956 fax 919.515.7124 www.ncsu.edu/foodscience/extension_program