Shelf Life of Tilepia (Tilapia nilotica) and Bhetki (Lates calcarifer) Stored in Ice and At Ambient Temperature

Abstract

Investigations on the quality changes of Tilapia nilotica and Lates calcarifer were carried out. The parameters assessed were organoleptic, biochemical (TVB-N, TMA-N, TMAO-N and pH), and microbiological (TVC) characteristics. The nature of spoilage was studied during iced storage for 25 days and at ambient temperature for 24 hours. Insulated ice boxes and bamboo baskets covered with banana leaves were used for storage. The rate of spoilage was found to be slower in Lates calcarifer than in Tilapia nilotica during storage in ice and at ambient temperature. In the ice storage study, the rejection time of Tilapia nilotica was between 10 and 13 days, as judged by taste panellists. During this period, the values of TVB-N, TMA-N, TMAO-N, pH and TVC ranged between 20.64 ± 0.10 and 28.03 ± 1.42 mg-N/100 g, 2.52 ± 0.22 and 3.01 ± 0.13 mg-N/100 g, 1.98 ± 0.06 and 2.23 ± 0.10 mg-N/100 g, 6.97 ± 0.10 and 7.05 ± 0.11, and log₁₀ 6.90 ± 0.05 to log₁₀ 7.72 ± 0.05 CFU/g, respectively. The shelf life of Lates calcarifer was found to be between 18 and 19 days, as judged organoleptically. During this period, the values of TVB-N, TMA-N, TMAO-N, pH and TVC varied between 32.90 ± 1.88 and 76.51 ± 3.07 mg-N/100 g, 9.56 ± 1.42 and 26.05 ± 2.60 mg-N/100 g, 24.45 ± 2.42 and 26.45 ± 0.53 mg-N/100 g, 7.03 ± 0.14 and 7.21 ± 0.16, and log₁₀ 6.77 ± 0.04 to log₁₀ 7.91 ± 0.05 CFU/g, respectively. At ambient temperature, the keeping times of Tilapia nilotica and Lates calcarifer were 10–17 and 17–20 hours, respectively. At the 17th hour in Tilapia nilotica, the muscle pH, TVB-N, TMA-N and TVC values were 6.86 ± 0.08, 48.80 ± 0.24 mg-N/100 g, 2.27 ± 0.07 mg-N/100 g and log₁₀ 6.94 ± 0.05 CFU/g, respectively. TMAO-N at this time could not be detected. However, TVB-N, TMA-N, TMAO-N, pH and TVC were 109.54 ± 2.96 mg-N/100 g, 40.75 ± 2.50 mg-N/100 g, 17.98 ± 0.62 mg-N/100 g, 7.23 ± 0.05 and log₁₀ 7.87 ± 0.56 CFU/g, respectively, at the 20th hour in Lates calcarifer (bhetki). A comparative study of the quality changes of Tilapia nilotica and Lates calcarifer during iced storage and storage at ambient temperature showed that the patterns of spoilage rates and quality changes differed between the two species. Lates calcarifer had better keeping quality than Tilapia nilotica under both storage conditions. The proximate composition of the two species was found to vary among different anatomical portions, sizes and sexes. The protein content was higher in all anatomical portions of Lates calcarifer compared with Tilapia nilotica. Lipid and ash contents were found to have almost similar values in both species, whereas moisture content was higher in Tilapia nilotica than in Lates calcarifer. Large-sized fish had higher protein and lipid contents in Lates calcarifer than in Tilapia nilotica. Ash percentage did not vary considerably between sizes or species, while moisture content was higher in all size groups of Tilapia nilotica. Similarly, protein content was higher in male Lates calcarifer, and a similar trend was observed for lipid content. Ash content did not vary between species or sexes, whereas moisture content was higher in both sexes of Tilapia nilotica and Lates calcarifer.