Authors : O.A. Oyelese
Abstract: The determination of the hypoxanthine levels chemical studies and bacteria flora/ count of alternate frozen/thawed market simulated croaker (Psendotholithus senegalensis) was carried out weekly for 12weeks under cold storage conditions at -4°C. Twenty two pieces of Croaker (Psendotholithus senegalensis) caught within the Nigerian Coastal waters with an average weight of 270 g were removed fortnightly allowed to thaw and exposed for 12 h before taken them for analysis. While organoleptic assessment and biochemical parameters (Hypoxanthine levels (Hx), Trimethylamine (TMA) Peroxide Value (PV) and Free Fatty Acid (FFA) were carried out fortnightly, however microbial assessment (bacteria count and identification) were assessed every 4weeks (monthly). Also initial and final proximate analysis were carried out. The cold storage medium does not totally halt spoilage, this is because hypoxanthine levels increased with storage length just as the bitter taste becomes more pronounced by the end of the 12weeks, this is further confirmed by the organoleptic results which also showed a progressive increase in their values. The biochemical test revealed that all parameters had a consistence increase in their values as the length of storage period increase, significant increase (p< 0.05) was recorded for (PV, TMA, FFA and Hx) with strong positive correlation (R=0.98, 0.99, 0.96 and 0.96, respectively) with length of storage period. The microbial count and identification results shows that 7 bacteria species have invaded the samples, in which Micrococcus acidophilus is the only bacteria with the lowest count of 1.60×104 cfu g 1 (and also showed it presence in the 12th week) and also out of the 7 bacteria identified 4 were prominent which include Lactococcus acidophilus (occurred from 0-12th week) Clostridium welchii (4-12th week) Bacillus substilis (8-12th week) and Proteus morganii ( 8-12th weeks) had the highest number of occurrence with (5.58, 4.29, 3.37and 3.18×104 cfu g 1). Microbial build up rises with increase in the length of storage period, this is because the Total Viable Count (TVC) increase from 0 week (1.64×104 cfu g 1) to(10.5×104 cfu g 1) in the 12 week. However the limit of acceptability for Croaker (Pseudotolithus species) under cold storage at -4°C is 8 weeks (2months) since values of all measured parameters increased drastically and sharply at the end of the 8th week.
O.A. Oyelese , 2007. Hypoxanthine Levels Chemical Studies and Bacteria Flora/Count of Alternate Frozen/Thawed Market Simulated Croaker (Pseudotholithus senegalensis) . Journal of Fisheries International, 2: 134-139.