Efficacy of lactic acid bacteria in the reduction of trimethylamine-nitrogen and related spoilage derivatives of fresh Indian mackerel fish chunks
Different strains of lactic acid bacteria (LAB) such as Pediococcus acidilactici, Pediococcus pentosaceous, Streptococcus thermophilus, Lactococcus lactis, Lactobacillus plantarum, Lactobacillus acidophilus and Lactobacillus helveticus were procured from the NCL (National Chemical Laboratory), Pune, India. These LAB cells were individually coated on the dressed fresh mackerel fish chunks and incubated at 37°C for two days. Different quality indices such as trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), peroxide value (PV) and free fatty acids (FFA) were estimated for 2 days period. P. acidilactici cell coat reduced 40 mg% of TMA-N, 47.66 mg% of FFA, 97 mg% of PV and 97 mg% of PV when compared with control. The TMA-N content was reduced to 20 mg% by S. thermophilus cell coat on the treated fish when compared with control, while no reduction was observed on TVB-N. Out of the seven LAB tested for TMA-N reduction, Lb. helveticus and Lc. lactis reduced 150 mg% identically. All the LAB grew in increasing and decreasing trends using available carbohydrate present in the fish. For, FFA reduction, Lb. plantarum showed the highest (188%) as compared to P. pentosaceous and P. acidilactici followed by S. thermophilus. P. pentasaceous and P. acidilactici showed the highest PV reduction as 98 and 83 milli equivalent fat/kg of fats, when compared with Lb. plantarum in the control. Out of seven LAB tested for quality indices reduction, Lb. helveticus, Lc. lactis and P. acidilactici were the best LAB to control TMA-N and TVB-N, respectively. Lb. acidophilus, showed the best in the reduction of FFA. Therefore, this study confirms that LAB can be used to preserve freshfish through controlling spoilage bacteria and amines for a short period of time. Inplace of chemical preservatives, LAB may be use to extend the shelf life of fish.
Keywords: Lactic acid bacteria, reduction of spoilage indices, trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), peroxide value (PV), free fatty acids (FFA), mackerel chunks