Role of transglutaminase-mediated cross-linking of protein in the temperature-dependent setting of Alaska pollack surimi

During the low temperature setting of fish paste, myosin heavy chain (MHC) is polymerized to cross-linked myosin heavy chain (CMHC), which is considered to occur by the action of endogenous transglutaminase (TGase). In this study the contribution of TGase on the setting of Alaska pollack surimi at different temperatures was studied. Alaska pollack surimi was ground with 3% NaCl, 30% h2o and with or without ethylene glycol bis (β-aminoethylether) N, N, N¹,N¹- tetra acetic acid (EGTA), an inhibitor of TGase. Among the pastes without EGTA, highest TGase activity was observed at 25°C but breaking force of the gel set at 25°C was lower than that set at 30°, 35°, and 40°C. Addition of EGTA (5m mol/kg) to the paste suppressed TGase activity at all setting temperatures from 20° to 40°C. Gelation of the pastes and cross-linking of MHC on addition of EGTA were suppressed completely at 20° and 25°C, partially at 30° and 35°C, and not at all at 40°C. The findings suggested that during the setting of Alaska pollack surimi TGase mediated cross-linking of MHC was strong at around 25°C but the thermal aggregation of MHC by non-covalent bonds was strong at above 35°C. Setting of surimi at 40°C and cross-linking of its MHC did not involve TGase

The 66 k-Da protein identified as a light meromyosin is involved in the setting of surimi

The 66 kilo-Dalton (k-Da) protein split off from the cross linked myosin heavy chain (CMHC) formed due to the setting of Alaska pollack surimi, frozen-storage of Pacific cod flesh, and vinegar-curing of Pacific mackerel mince was identified as a light meromyosin (LMM). Puncture and stress-relaxation tests showed that the actomyosin subunits (AMS) of Alaska pollack surimi, upon setting at 30°C, transformed into gel, although the elasticity of this gel was very low when compared to the gels from surimi or actomyosin (AM). Electrophoretic studies showed that the band due to LMM in the gel from AMS gradually disappeared with the progress of setting but higher molecular weight polymer did not form. The intensity of the bands due to other myosin sub-fragments decreased a little. The findings suggest that at setting temperature, LMM of MHC molecule leads to an unfolding resulting in an intramolecular aggregation through non-covalent interactions, and thus plays a significant role in the crosslinking of MHC

Quantitative Risk Assessment for Formalin Treatment in Fish Preservation: Food Safety Concern in Local Market of Bangladesh

AbstractIn Bangladesh, fishes are adulterated by hazardous chemicals at different steps from farm to consumers. Formalin (FA) is reported to be frequently added as preservative either by dipping or spraying to the fresh fishes by the fish traders while transporting to domestic marketing chain to prevent spoilage and extend shelf life. Thus, the objective of the present study was toconduct quantitative risk assessment (QRA) for formalin treated fish in Bangladesh. The probabilistic QRA of formalin treated fish was performed based on available secondary data. Available data on concentration of formalin in fish, daily fish consumption by the consumer and their body weight were used to estimate the risk of residual formalin to the consumers. Based on the data, three different scenarios (average consumption, two and four times of average consumption considered as scenarios 1, 2 and 3, respectively) were used for exposure analysis using @Risk program version 6.0.FA concentration in consumedfresh and cooked (boiling) fish was 5.34x10-02 and 2.340x10-02 (mg/kg bw/day), respectively and national average fish consumption was 200g/day. QRA reveals that FA intake under scenario1 and 2 was lower than acceptable daily intake (ADI 0.2mg/kg bw/day set by the United States Environmental Protection Agency) thus lower risk observed for both fresh and cooked fish. However, scenario 3 revealed that 0.01% population was at risk (FA intake 0.21mg/kg bw/day higher than ADI) upon the fresh fish consumption, where cooked fish (FA 9.38x10-02 mg/kg bw/day) consumer remains safe at the same scenario. The result confirmed that cooking has significant effect to reduction of formalin. Therefore, probabilistic quantitative risk assessment of formalin treated fish could provide important risk information to the risk manager (government), whether the population is at risk or not? The result could be applied to establish effective risk management strategy in Bangladesh

Development of protein enriched shrimp croquette from shrimp industry wastes

Protein fortified and tasty shrimp croquette was developed from different component parts of shrimp wastes by using a combination of vegetables (potato, Colocasia, green banana, green papaya and spinach), spices (green chili, onion, garlic, turmeric, red pepper and ginger) and other ingredients (salt, wheat flour, egg, sugar and milk powder). The ingredients were mixed with variable quantities of shrimp shell powder (3, 5 and 10%), shaped and covered with egg and bread crumb. Proximate composition of shrimp shell powder (SSP) and shrimp croquette was determined as crude protein, crude lipid, ash and moisture. It was observed that the SSP contained 47.48±0.74% crude protein indicating its potentiality as a good protein source for the food industry. The lipid content of SSP was 10.50±0.71% and 19.61±0.64%. When SSP was used in the croquette, protein content increased with the higher levels of SSP. The final protein content found were 7.22±0.66, 9.39±0.37 and 11.73±0.61% in the croquettes added with 3, 5 and 10% SSP, respectively. The suggested recipes containing 5% SSP were preferred by the panelists on the basis of their overall quality. Sensory, chemical and microbiological quality changes of shrimp croquette were determined to evaluate the shelf life and storage stability under different storage conditions. At room temperature shelf life of shrimp croquette was very short, in fact not more than 24 hours. On the other hand, at refrigeration temperature it remained in good condition up to 10 days. At frozen storage it remained in good condition for 1 month. The research reveals that good quality protein fortified shrimp croquette could be manufactured from shrimp shell wastes

Determination of formaldehyde in wet marketed fish by HPLC analysis: A negligible concern for fish and food safety in Bangladesh

Formaldehyde (FA) content in nine commonly available marine and freshwater finfish and one shrimp species marketed in Dhaka was assessed by high performance liquid chromatography (HPLC) method. Limit of detection and limit of quantification values of 6.90 and 22.90 µg kgâ1 were calculated respectively. The study revealed different levels of formaldehyde in analyzed samples. The Kawran bazaar, the Raiyer bazaar and the Mohakhali bazaar of Dhaka city fish were analyzed; the level of the content of formaldehyde was higher in Raiyer bazaar fish samples and lower in Kawran bazaar fish samples. The range of formaldehyde value in freshwater and marine finfish samples and shrimp samples ranged 5.1 ± 0.71â12.26 ± 1.67 mg kgâ1, 10.8 ± 1.72â39.68 ± 7.87 mg kgâ1 and 13.57 ± 1.93 mg kgâ1 respectively. The FA content was in the range of 5.1 ± 0.71â39.68 ± 7.87 mg kgâ1 eventually found in all marketed fish. Keywords: Marketed fish, Penaeus monodon, Food safety, Formaldehyde, HPL