RESUMEN
This study determined the inactivation kinetic parameters of selected pathogens in heat, ultraviolet-C and combined heat-UV-C treated coconut liquid endosperm. Separate cocktails of Escherichia coli O157:H7, Salmonella enterica serovars, and Listeria monocytogenes strains were inoculated into coconut liquid endosperm (pHâ¯5.15, TSS 4.4oBx, TA 0.062% malic acid, extinction coefficient (ε) at 254â¯nm of 0.0154â¯cm-1) for inactivation studies. Result showed that all organisms generally exhibited a log-linear heat inactivation behavior (R2 0.81-0.99). The E. coli O157:H7 cocktail (D55â¯=â¯19.75â¯min, D57â¯=â¯10.79â¯min, D60â¯=â¯3.38â¯min, and D63â¯=â¯0.46â¯min) was found to be significantly more resistant (Pâ¯>â¯0.05) than the tested cocktail of L. monocytogenes (D55â¯=â¯11.68â¯min, D57â¯=â¯4.53â¯min, D60â¯=â¯1.82â¯min and D63â¯=â¯0.26â¯min) and S. enterica cocktail (D55â¯=â¯3.08â¯min, D57â¯=â¯2.60â¯min, D60â¯=â¯0.89â¯min and D63â¯=â¯0.25â¯min). Despite the differences in DT values, computed z values for L. monocytogenes cocktail (5.12⯱â¯0.43⯰C) and E. coli O157:H7 cocktail (4.95⯱â¯0.12⯰C) were not significantly different (Pâ¯>â¯0.05), but were both significantly (Pâ¯<â¯0.05) lower than that of S. enterica cocktail (7.10⯱â¯0.15⯰C). All test organisms also exhibited a generally log-linear UV-C inactivation behavior (R2 0.90-0.99) with E. coli O157:H7 cocktail (DUV-Câ¯=â¯25.26â¯mJ/cm2) demonstrating greatest resistance to UV-C than S. enterica (DUV-Câ¯=â¯24.65â¯mJ/cm2) and L. monocytogenes (DUV-Câ¯=â¯17.30â¯mJ/cm2) cocktails. The D55 values of each organism cocktail were used to calculate for the 3-log reduction heating process schedules, during which UV-C treatments were simultaneously applied. Lethal rates (F values) calculations in the combined processes revealed that within the 3-log reduction heating processes, co-exposure of UV-C resulted in 5.62 to 6.20 log reductions in the test organism populations. Heating caused 69.3, 97.2, and 67.4% of the reduction in E. coli O157:H7, S. enterica and L. monocytogenes cocktails, respectively. These results can be used as baseline data in the establishment of mild heat treatment in combination with UV-C process schedules for coconut liquid endosperm and other similar products.