Food Protection Trends - May 2010 - 268

ARTICLES

Food Protection Trends, Vol. 30, No. 5, Pages 268–272

Use of Linear Models for Thermal Processing of Acidified Foods
FREDERICk BREIDT,1 k. P. SANDEEP2 and FlETChER M. ARRITT*2
USDA/ARS, 322 Schaub Hall, North Carolina State University, Raleigh, NC 27603–7624, USA; Dept. of Food, Bioprocessing, and Nutrition Sciences, 129 Schaub Hall, North Carolina State University, Raleigh, NC 27695–7624, USA
1 2

ABSTRACT

Acidified vegetable products with a ph above 3.3 must be heat processed to assure the destruction of Escherichia coli O157:h7, Salmonella enterica, Listeria monocytogenes, and other pathogenic bacteria that might be present in the product. Recently, the Food and Drug Administration has required that linear models for heat process data be used with electronic process filing forms. Existing recommendations for heat processing acidified vegetables are based on non-linear (Weibull and exponential decay) models.We report here the parameters for a linear model that meets or exceeds the established heat processing conditions needed to assure safety.

INTRODUCTION
Acid and acidified foods are partially defined in the Code of Federal Regulations as foods having a final equilibrium pH at or below 4.6 (21 CFR part 114), with a water activity of 0.85 or greater. Fermented and refrigerated products are excluded from this regulation. The pH 4.6 value was based on data show-

ing that spores of Clostridium botulinum will not germinate and produce neurotoxin at or below pH 4.6 (6). Acid foods include, among other things, fermented vegetables such as cucumber pickles or sauerkraut, which naturally have a pH below 4.6. Acidified foods achieve pH 4.6 or lower by the addition of an acidulent (typically acetic acid) or acid food

ingredients. Acidified foods include most fresh pack cucumber pickle and pepper products. Fermented cucumber pickles are primarily sold to customers who purchase hamburger dill pickle slices on a wholesale basis. Fermented pickles are excluded from regulation in 21 CFR part 114 because a variety of antimicrobial metabolites (such as organic aids, peroxides, antimicrobial peptides) that eliminate vegetative pathogens are produced during fermentation (5). The retail market, however, is dominated by acidified shelf stable pickled vegetables (fresh pack products), including cucumber pickles, peppers and other vegetables. Acetic acid is commonly used as the primary acidulent in these products. The pH of acidified cucumber pickles is typically between 3.4 and 4.1. At this pH, the survival of acid resistant bacterial pathogens (Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes) that may be present on fresh vegetables is a concern. While these pathogens do not grow in acidified vegetables, they may survive long enough to cause disease (2).

A peer-reviewed article
* Author for correspondence: Phone: 919.513.0176; Fax: 919.515.7124 E-mail: fletcher_arritt@ncsu.edu

268 FOOD PROTECTION TRENDS | MAY 2010

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Food Protection Trends - May 2010

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