Heat Resistance of Alicyclobacillus acidoterrestris Spores as Affected by Various pH Values and Organic Acids

Abstract

Alicyclobacillus acidoterrestris, a thermoacidophilic sporeformer, has caused spoilage of fruit juices which had been treated with thermal processes intended to commercially sterilize the juice. The objective of this research was to document the effect of pH, acid, and temperature on the heat resistance of spores of three fruit-juice isolates of A. acidoterrestris. The thermal resistance of spores of A. acidoterrestris strains VF, WAC, and IP were studied in a model fruit-juice system composed of 12% glucose and 30 mM of either citric, malic, or tartaric acid, adjusted to selected pH values ranging from 2.8 to 4.0. Decimal reduction times (D values) and inactivation rates were determined. Spores of strains VF and WAC were similarly resistant to heat under acidic conditions, while strain IP spores were less resistant. In the range of pH 2.8 to 4.0, a statistically effect of hydrogen ion concentration on heat resistance was observed at lower temperatures, but not at the higher temperatures, but not at the higher temperatures. For examples, at 91 degrees C and pH 3.1 and 3.7, D values were 31.3 and 54.3 min, respectively, while at 97 degrees C D values at pH 3.1 and 3.7 were 7.9 and 8.8 min, respectively. The type of acid did not significantly affect the heat resistance. The zd values ranged from 5.9 to 10 degrees C, depending on the acid, pH, and the strain. The models generated from this research can be used to determine adequate thermal processes, accounting for the acid type, pH, and temperature, to destroy A. acidoterrestris spores in beverages, since this organism is able to survive the typical hot-fill and hold process (2 min at 88 to 96 degrees C) currently used to process fruit juice.

Inactivation Kinetics of Alicyclobacillus acidoterrestris Spores in Orange Juice by Ohmic Heating: Effects of Voltage Gradient and Temperature on Inactivation

“…Heat resistance studies have indicated that Alicyclobacillus spores can survive the usual hot-fill processes that are used with commercial juices (4,5,14,(24)(25)(26)(27). Data also indicate that increasing the uBrix makes the spores more resistant to heat.…”

“…Data also indicate that increasing the uBrix makes the spores more resistant to heat. Although the reason Alicyclobacillus spores survive pasteurization and hot-fill and hold processes is still unclear, environmental factors such as pH, soluble solid content, and temperature influence the heat resistance of the spores (10,25,27). D-values for spores of different strains of A. acidoterrestris at 80, 85, 90, and 95uC in conventionally heated fruit juices were 41.1 to 54.3, 50 to 65.6, 7.4 to 23, and 2.3 to 5.3 min, respectively, with zvalues of 7.7 to 12.9uC (3-5, 14, 25-27).…”

Evaluation of different culture media and enrichment in orange juice upon the growth of Alicyclobacillus spp.

“…are commonly present on the soil and may be detected by fine-tuned isolation and culture methodologies that are specific to their nutritional and mineral requirements (Motohiro;Hiroko, 1994). As the thermal resistance of spores may be affected by media composition, ions, pH and organic acids, detection may be conducted in several different ways (Pontius et al, 1998).…”

Growth of Alicyclobacillus acidoterrestris in the Hypoxic Environment of Bottled Fruit Juice

“…Without a perfectly closed system or the ability to control the concentration of oxygen in the bottle, it is impossible to evaluate the effect of oxygen concentration on cell division in culture experiments, and there are no known reports of such Alicyclobacillus spp. are spore-forming and heattolerant acidophilic bacilli that survive a typical sterilization process of 85 for more than 30 min in bottled acidic beverages, such as fruit juices and sport drinks, and cause deterioration Pettipher et al,1997;Pontius et al,1998 . Among the species in this genus, A. acidoterrestris is regarded as one of the most harmful bacteria in acidic beverages, and it produces guaiacol, which has a creosote-like odor.…”