Shelf Life Extension of Tuna Fillets using Natural Preservatives Isolated from Garlic

Abstract

In order to develop a natural preservative for improving the shelf life of fishery products, solventfree extracts were prepared from raw, water bath boiled (WBB) and microwave-boiled (MOB) garlic (Allium sativam). Garlic juices showed antioxidant activity as determined by DPPH radical scavenging method and FRAP antioxidant power assay and antibacterial activity against all the 13 fish spoilage and fish-borne bacteria tested by agar well diffusion method. Raw garlic juice showed significant (p<0.05) radical scavenging effect (96.81±0.11%) followed by WBB juice (58.70±2.51%) and MOB juice (50.33±0.22%) at 20% concentration. The IC50 value of raw, WBB and MOB garlic juices were respectively 7.63, 14.86 and 18.76 μg ml-1. Among the three garlic juices, the raw garlic juice showed the strongest antibacterial activity against both gram-positive and gram-negative bacterial strains. Highest zone of inhibition was against gram-positive bacteria Bacillus licheniformis (55.0±0.57 mm) followed by gram-negative bacteria Yersinia enterocolitica (44.0±0.57 mm) indicating its potential as a natural preservative. The natural preservative isolated from garlic significantly delayed the rate of microbial spoilage and extended the shelf life of tuna fillets by six days during refrigerated storage demonstrating its potential as an excellent natural antioxidant and antibacterial agent which can be used as an effective alternative to synthetic antioxidant and antibacterial agents.