Effects of Radio Frequency Tempering on the Texture of Frozen Tilapia Fillets

Radio frequency (RF) tempering has been proposed as a new alternative method for tempering frozen products because of its advantages of rapid and volumetric heating. In this study, the texture of RF-tempered frozen tilapia fillets was determined under different RF conditions, the effects of related factors on the texture were analyzed, and the mechanisms by which RF tempering affected the texture of the tempered fillets were evaluated. The results show that the springiness (from 0.84 mm to 0.79 mm), cohesiveness (from 0.64 mm to 0.57 mm), and resilience (from 0.33 mm to 0.25 mm) decreased as the electrode gap was increased and the power remained at 600 W, while the shear force increased as the power was increased for the 12 cm electrode gap (from 15.18 N to 16.98 N), and the myofibril fragmentation index (MFI) values were markedly higher at 600 W than at 300 W or 900 W (p < 0.05). In addition, the tempering uniformity had a positive effect on hardness and chewiness. The statistical analysis showed that the texture after RF tempering under different RF conditions correlated relatively strongly with the free water content, cooking loss, and migration of bound water to immobilized water. The decrease in free water and bound water migration to immobilized water resulted in a significant increase in cohesiveness and resilience.

Value addition of tilapia (Oreochromis niloticus): Preparation of fillet and shelf-life assessment

Although tilapia is one of the most cultivated fish species in Bangladesh owing to its high growth rate, comparatively easy culture practices, higher survival rate and short culture period but low market preference marked it as a low-priced fish. Various approaches have been adopted to enhance consumer acceptability and ensure better use of tilapia, including the production of value-added products such as tilapia-prepared fillets, which attract increasing interest. Therefore, the current study was designed and carried out in order to prepare tilapia fillets and to estimate their shelf life at frozen (-18±20C) and refrigerated (4±10C) temperatures. Fillets were produced from tilapia collected from local fish markets of Sylhet city, Bangladesh with according to Good Manufacturing Practices (GMP) established by International Standards Organization (ISO) and packed in polyethylene bags. Proximate composition, total volatile base nitrogen (TVBN), peroxide value (PV), pH, total plate count (TPC) and sensory properties of fillets were analyzed to determine shelf-life. A portion of the fresh fillet sample was immediately analyzed and the remaining portions were preserved for up to 12 and 90 days at refrigerated and frozen storage temperatures, respectively. Results revealed that, at a definite interval of time, changes in the chemical, microbial and sensory attributes of tilapia fillets were found to be more pronounced in refrigerated storage conditions than fillets stored in frozen conditions. The shelf life of refrigerated and frozen tilapia fillet samples was 9 and at least 90 days, respectively, per the results of sensory, microbial and chemical evaluation. Res. Agric., Livest. Fish.8(2): 231-240, August 2021

Mapping of physical-chemical, microbiological, and chemical component characteristics of water samples from Nile tilapia slaughterhouses

The aim of this study was to analyze the physicochemical and microbiological characteristics of the water used in fish processing and tilapia fillets in slaughterhouses. The study analyzed the processing water from nine slaughterhouses. The water samples for analysis were collected at three points: process water (PW), it is the water used inside the slaughterhouses in direct contact with the fish; clean water entering the purification tank (EPT) and water leaving the purification tank (LPT). The processing waters of the nine tilapia slaughterhouses were analyzed and characterized according to their microbiological and physical-chemical characteristics. The results of microbiological analyzes meet the values indicated by legislation, in most cases. Regarding microbiological data, we can highlight that there was an increase in the total coliforms of the water entering the purification tank to the water leaving the purification tank in five slaughterhouses. Still, there was an increase in the aerobic mesophilic bacteria content observed in the outgoing water in relation to the inlet water of the purification tank in seven slaughterhouses. In relation to the physical chemical analyzes for the process water samples, the results show that the evaluated indices are in accordance with the values indicated by the legislation. The levels of Cd, Mg, Sc and Cd were below that detectable by the analysis in all slaughterhouses. The levels of Al, Sc, As, Rb, Ba, Pb, Mn, As, Se, Rb, Ag, Sb, Ba and Pb were detected only in one or two slaughterhouses. It is concluded that although some abattoirs have water characteristics outside the limits indicated by the legislation, the observed changes were not significant and small adjustments are necessary for the adequacy.