Effect of sporulation medium on wet-heat resistance and structure of Alicyclobacillus acidoterrestris DSM 3922-type strain spores and modeling of the inactivation kinetics in apple juice

Abstract

Alicyclobacillus acidoterrestris is a spoilage bacterium in fruit juices leading to high economic losses. The present study evaluated the effect of sporulation medium on the thermal inactivation kinetics of A. acidoterrestris DSM 3922 spores in apple juice (pH 3.82 ± 0.01; 11.3 ± 0.1°Brix). Bacillus acidocaldarius agar (BAA), Bacillus acidoterrestris agar (BATA), malt extract agar (MEA), potato dextrose agar (PDA) and B. acidoterrestris broth (BATB) were used for sporulation. Inactivation kinetic parameters at 85, 87.5 and 90°C were obtained using the log-linear model. The decimal reduction times at 85°C (D 85°C ) were 41.7, 57.6, 76.8, 76.8 and 67.2 min; D 87.5°C -values were 22.4, 26.7, 32.9, 31.5, and 32.9 min; and D 90°C -values were 11.6, 9.9, 14.7, 11.9 and 14.1 min for spores produced on PDA, MEA, BATA, BAA and BATB, respectively. The estimated z-values were 9.05, 6.60, 6.96, 6.15, and 7.46, respectively. The present study suggests that the sporulation medium affects the wet-heat resistance of A. acidoterrestris DSM 3922 spores. Also, the dipicolinic acid content (DPA) was found highest in heat resistant spores formed on mineral containing media. After wet-heat treatment, loss of internal volume due to the release of DPA from spore core was observed by scanning electron microscopy. Since, there is no standardized media for the sporulation of A. acidoterrestris, the results obtained from this study might be useful to determine and compare the thermal resistance characteristics of A. acidoterrestris spores in fruit juices.

Effects of pomegranate and pomegranate–apple blend juices on the growth characteristics of Alicyclobacillus acidoterrestris DSM 3922 type strain vegetative cells and spores

“…In our previous work (Molva and Baysal, 2014), we found that the wet-heat resistance of A. acidoterrestris DSM 3922 spores varied depending on the sporulation medium used. Such variations need to be considered when evaluating the survival and inactivation of Alicyclobacillus spp.…”

“…Briefly, the membranes (0.45 μm pore size, Sartorius) that had been used to filter the reconstituted juice samples (50 mL) were transferred aseptically onto BATA. Then, the membranes on the plates were incubated at 43°C for up to seven days (Molva and Baysal, 2014).…”

“…Since there is no standardized medium for the production of A. acidoterrestris spores (Molva and Baysal, 2014), different media such as PDA, BATA, BAA, and MEA were used for sporulation. Before inoculation into juice samples, each spore suspension (10 6 CFU/mL) was heat shocked at 80°C/10 min and cooled on ice.…”

The effect of sporulation medium on Alicyclobacillus acidoterrestris guaiacol production in apple juice

“…acidoterrestris DSM 3922 was kindly provided by Karl Poralla 2)] were used. Spore suspensions were prepared based on the protocol as previously described (Molva & Baysal, 2014).…”

“…Diluted juice samples were tested for the presence of Alicyclobacillus spp. by membrane filtration method (Molva & Baysal, 2014).…”