Pasteurization of tender coconut water by pulsed light treatment: Microbial safety, enzymatic inactivation, and impact on physicochemical properties

Abstract

The study investigated the potential of pulsed light (PL) in the pasteurization of tender coconut water (TCW). The initial counts of E. coli, B. cereus and L. monocytogenes in the inoculated TCW were 7.00, 9.14 and 7.8 log10 cfu mL−1, respectively. For a PL fluence of 465 J cm−2, E. coli, B.cereus and L. monocytogenes exhibited a log reduction of 5.12, 2.97 and 3.40, respectively. Bacillus cereus and Listeria monocytogenes exhibited greater resistance than Escherichia coli in the TCW. Peroxidase (POD) was more sensitive to PL treatments than polyphenoloxidase (PPO) in TCW. Weibull model and nth order model exhibited excellent fit for microbial inactivation (R2 > 0.96) and enzyme inactivation (R2 > 0.97) kinetics, respectively. While 5-log10 reduction of B. cereus and L. monocytogenes was achieved at 2.5 kV|2.5 min (1073 J cm−2), PPO was inactivated by greater than 99% at 2.9 kV| 5 min (2988 J cm−2). While the total reducing sugars increased, the changes in color (0.49 < ΔE* < 1.51), pH, total soluble solids, and acidity were insignificant after the PL pasteurization. The PL condition of 2.9 kV|5 min preserved 21 and 24% more phenolics and ascorbic acid in TCW, along with greater sensory scores than the thermal treatment (90 °C|3 min). Industrial significanceThe outcome of this study determined the intensity (fluence of 2988 J/cm2) and penetration depth (4–5 mm) required for the pasteurization of tender coconut water (TCW). On an industrial scale of large processing volumes, continuous pulsed light (PL) pasteurization of TCW can be undertaken in an annular flow reactor or thin film flat bed chamber. The thickness of the film can be mimicked from this study to ensure adequate penetration of PL in the sample to achieve adequate lethality.