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Effects of gutting on biogenic amine (putrescine, cadaverine, histamine, agmatine, tyramine, spermidine, and spermine) formation, biochemical (pH, TVBN, K value), microbial (APC, H 2 S producing, Coliform bacteria), and sensory quality of farmed monosex tilapia (Oreochromis niloticus) was studied during ice stored at 4 ± 2ºC. Spermine and spermidine levels were high with cadaverine reached 4.66 ppm in gutted sample. The other amines were detected at relatively low level. K value of both samples crossed 60% on 15th and 18th day, respectively. The total phenolic content exceeded 7 log cfu/g after sensory rejection. The shelf life of whole and gutted samples was estimated to be 24 and 21 days, respectively. ARTICLE HISTORY

Summary Abstract Shellfish allergy due to major allergen tropomyosin can lead to anaphylaxis in highly sensitive individuals. Tropomyosin purified from flower tail shrimp, Metapenaeus dobsoni was subjected to in vitro characterisation. Also effect of trypsin and chymotrypsin hydrolysis on shrimp allergenicity was evaluated. The purified tropomyosin was profiled by SDS PAGE and de nova sequenced using MALDI TOF. Peptide sequence showed a significant protein score in the range of 72–137 with 95% confidence level. In silico mapping of IgE‐binding regions showed conservation of IgE‐binding regions along with cross reactivity with other species. The most abundant amino acid present was glutamic acid followed by lysine. IgE‐binding ability got significantly (P < 0.05) reduced by hydrolysis in comparison to raw. The lower peptide fragments resulted from chymotrypsin hydrolysis by SDS PAGE were very feeble than by trypsin and no immunological activity was observed. Chymotrypsin hydrolysis is observed to be effective in retarding immunological activity of tropomyosin both at 37 °C and 50 °C compared with trypsin hydrolysis at 37 °C by immunoblotting analysis. This can be further utilised in the processing of crustacean extracts intended for seasoning purpose. Further research on in vivo assays for reduced immunoreactivity of tropomyosin after hydrolysis of shrimp can be carried out. Practical applications In vitro characterisation of tropomyosin helps in understanding the cross reactivity with other shrimp species. Chymotrypsin hydrolysed shrimp can be utilised in the processing of crustacean extracts intended for seasoning purpose.

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A study of the use of salicylaldehyde thiosemicarbazone (STSC) in the gravimetric determination of nickel is reported. STSC reacts with Ni(II) in aqueous medium in the pH range 6.5–8.2 to form reddish brown water insoluble complex. The complex can be conveniently filtered at the pump using a G4 sintered glass crucible and dried at 100–120 °C and weighed as Ni(C8H8N3OS)2. Interference of foreign ions were examined. The influence of concentration, temperature, and pH on the precipitation were studied. The reagent tested in this work was compared with classical 1,2-dioximes used in the gravimetric determination of nickel. This method was applied to determine nickel in stainless steel.