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

Abstract

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.