Enrichment of samples is of considerable importance for the recovery of small numbers of alicyclobacillus from concentrated juices, purees, and nectars. Although the general concept of enrichment is consistent from one study to the next, conditions for assaying different samples vary and are not applicable to all situations. Protocols typically involve incubation of a sample that is diluted in either a minimal broth medium that contains minerals with nutrients, or plain water. The level of dilution varies from single-strength to as little as 2° Brix. Sample sizes typically range from 1 to 100 ml of concentrate, puree, or nectar.
After dilution, samples are heat shocked followed by incubation at 40 to 55°C for 3 to 7 days. A yeast/mold inhibitor may be added in cases where a heat shock is not used or is inadequate. At the end of incubation, samples are streaked onto appropriate media and plates are incubated aerobically at 45 to 50°C for several days. Development of colonies suggests the possible presence of alicyclobacillus although confirmation requires further analysis.
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