Decimal reduction times of acid-adapted and non-adapted Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes in young Cocos nucifera Linn. liquid endosperm

- Acid adaptation of test organisms resulted in varying responses to heat treatment.
- Non-adapted Escherichia coli O157:H7 was most heat resistant in coconut liquid endosperm.
- The established heat process schedule did not significantly affect sensory characteristics of the endosperm.

The study established the decimal reduction times at 55 °C (D55 °C values) of acid-adapted and non-adapted Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes in young coconut liquid endosperm. Acid adaptation of the test pathogens was conducted by cultivating cells in a gradually acidifying nutrient broth supplemented with 1% glucose. Results showed that acid adaptation had varying influence on the subsequent thermal resistances of the pathogens. The non-adapted E. coli O157:H7 exhibited the greatest resistance among the tested pathogens with a D55 °C of 23.20 min. Prior adaptation to acidity decreased the D55 °C to 16.16 min. On the other hand, acid adaptation increased the D55 °C values of S. enterica and L. monocytogenes from 8.76 to 10.55 min, and from 7.47 to 18.09 min, respectively. The D55 °C of the non-adapted E. coli O157:H7 was used to establish a pasteurization process schedule with an order of lethality equal to 5-logarithmic (99.999%) reduction. Sensory evaluation revealed that the overall acceptability, color, aroma, coconut flavor, and freshness characteristics of non-pasteurized and pasteurized liquid endosperms were not significantly different (p > 0.05). Moreover, the sensory quality attributes of coconut beverages (80:20 vol/vol endosperm-to-water ratio, soluble solids adjusted to 10 °Brix with sucrose) prepared from both non-pasteurized and pasteurized liquid endosperm samples did not significantly vary. The results obtained from the study may be used in the establishment and validation of thermal process schedules for young coconut liquid endosperm beverages.