Studies on the antimicrobial activity of Tamarind (Tamarindus indica) and its potential as food bio-preservative

Tamarind (Tamarindus indica) is used in Indian spices as a souring agent to provide the desired acidity in the various food recipes. In this era of increased concern on safety of chemical food additives, natural methods of preservation and natural preservatives are receiving increased attention. The antimicrobial activity of tamarind extract (50% ethanol) was tested against ten bacterial strains (7 Gram-positive and 3 Gram-negative) and seven fungi known to cause food spoilage by agar well diffusion assays. The aqueous-ethanolic extract exhibited a broad spectrum of anti-bacterial activity inhibiting both the groups of bacteria. Tamarind extract was active against all the test Gram-positive bacteria isolates but was highly effective against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis and Listeria monocytogenes with an inhibition zone of 18 mm, 19 mm, 16 mm and 16 mm, respectively. It also inhibited the growth of all Gram-negative bacteria isolates but produced an inhibition zone greater than 15 mm only in the case of Pseudomonas aeruginosa, Pseudomonas sp. and Salmonella sp. However, the extract was found to be ineffective against majority of test fungal species. Only Aspergillus sp. and Penicillium sp. were found to be partially sensitive to the extract. The phytochemical analysis of tamarind extract revealed the presence of tannins, terpenoids and citric acid. This study shows the potential for replacement of synthetic food grade preservatives with the use of natural extracts of tamarind.