Effects of bilimbi ( Averrhoa bilimbi L.) and tamarind ( Tamarindus indica L.) juice on Listeria monocytogenes Scott A and Salmonella Typhimurium ATCC 14028 and the sensory properties of raw shrimps

The potential of using juice of bilimbi ( Averrhoa bilimbi L.) and tamarind ( Tamarindus indica L.) to reduce Listeria monocytogenes Scott A and Salmonella Typhimurium ATCC 14028 populations on raw shrimps after washing and during storage (4 °C) was investigated. The uninoculated raw shrimps and those inoculated with ∼ 9 log cfu/ml of L. monocytogenes Scott A and S. Typhimurium ATCC 14028 were washed (dipped or rubbed) in distilled water (SDW) (control), bilimbi or tamarind juice at 1:4 (w/v) concentrations for 10 and 5 min. Naturally occurring aerobic bacteria (APC), L. monocytogenes Scott A and S. Typhimurium ATCC 14028 counts, pH values and sensory analysis of washed shrimps were determined immediately after washing (day 0), and on days 3 and 7 of storage. Compared to SDW, bilimbi and tamarind juice significantly ( p < 0.05) reduced APC (0.40–0.70 log cfu/g), L. monocytogenes Scott A (0.84–1.58 log cfu/g) and S. Typhimurium ATCC 14028 (1.03–2.00 log cfu/g) populations immediately after washing (0 day). There was a significant difference ( p < 0.05) in bacterial reduction between the dipping (0.40–0.41 log for APC; 0.84 for L. monocytogenes Scott A and 1.03–1.09 log for S. Typhimurium ATCC 14028) and rubbing (0.68–0.70 log for APC; 1.34–1.58 for L. monocytogenes Scott A and 1.67–2.00 log for S. Typhimurium ATCC 14028) methods. Regardless of washing treatments or methods, populations of S. Typhimurium ATCC 14028 decreased slightly (5.10–6.29 log cfu/g on day 7 of storage) while populations of L. monocytogenes Scott A (8.74–9.20 log cfu/g) and APC (8.68–8.92 log cfu/g) increased significantly during refrigerated storage. The pH of experimental shrimps were significantly ( p < 0.05) decreased by 0.15–0.22 pH units after washing with bilimbi and tamarind juice. The control, bilimbi or tamarind-washed shrimps did not differ in sensory panellist acceptability ( p > 0.05) throughout the storage except for odour ( p < 0.05) attributes at 0 day when acidic or lemony smell was noticed in bilimbi- and tamarind-washed shrimps and not in control shrimps.