Protective Effects of Green tea, Clove and Thyme against Mullet (Mugil cephalus) Lipid Hydrolysis and Oxidation: Role of Natural Antioxidants

30-04-2018 07:57
Fish is one of the healthiest sections of food. Therefore, the enhancement of the shelf life of fish during freezing storage is important for their quality and toxicity. For these reasons, water extracts with concentration of 10% of three plants; namely green tea, clove and thyme were tested for their abilities to enhance period of shelf life of mullet (Mugil cephalus) during a storage period of six months. To fulfill of this requirement, both biochemical and microbiological examinations were done. From the biochemical point of view; peroxide value (PV), thiobarbituric acid (TBA) values and free fatty acid (FFA) were estimated. Microbiologically, total viable bacterial count (TVBC) and the count of Staphylococcus spp., lactose fermenting and non-lactose fermenting bacteria, Aeromonas spp., Pseudomonas spp. and Vibrio spp. were done. The three plants extracts showed an obvious antioxidant effects via reduction in PV and TBA. Also, this preservation system led to lowering FFA. At the same time TVBC in mullet tissue, gill and intestine showed a variable behavior during preservation. These include absence of bacterial growth after freezing for 1 and 4 months when the fish was treated with clove and green tea, respectively. The three plant extracts showed slight effect on the number of Staphylococcus spp., lactose fermenting and non-lactose fermenting bacteria and Aeromonas spp. Surprisingly, no Pseudomonas spp. or Vibrio spp. were detected during this study. Moreover, the in vitro study using 20 % green tea extract showed the highest effect against Staphylococcus sp. while clove extract (10%) and thyme extract (20%) showed higher effects against Aeromonas sp. than that of green tea. In conclusion: Green tea, clove and thyme extracts can be used to protect against bacterial growth which may participate in tissue lipids deterioration during fish preservation. The possible antioxidants effects of these extracts are also included.