Introduction

Indian fishery sector provides livelihood security to more than 14 million people. The inland water resources of country consists of 29,000 kilometer of rivers, 0.3 million ha of estuaries, 0.19 million ha of back water, 3.15 million ha of reservoirs which contributes about 1.05 million tons of fish annually (Ayappan et al., 2013). Indian reservoirs are diversified and located under different geo-climatic situations. Rapid urbanization is leading to increasing demand for food products. Quality awareness of consumers from availability of technologies like cold chain, faster transportation and quality standards are making fish industry more dynamic and efficient. In semi urban areas fish is being sold by traditional methods which are being sourced from local resources (Hasan et al., 2012). Fish quality is a complex concept involving whole range of factors like handling, processing and storage. Self life of freshly harvested fish depends up on bacterial flora, storage temperature, handling and physiological condition of fish. The quality of fish can be estimated by sensory test, microbial methods, measuring volatile compounds and lipid oxidation, determination of changes in muscle protein, ATP breakdown products and physical changes in fish (Abbas et al., 2008). The maintenance of cold condition from harvest to retail shop is of paramount importance in relation to quality management (Rehman et al., 2003). Fish sold at open market and exposed to ambient temperature increases likelihood of spoilage (Kapute et al., 2012).Fish spoilage results from enzymatic autolysis, oxidation and microbial growth. Shortly after capture chemical and biological changes take place in dead fish due to enzymatic breakdown of major fish molecule (FAO, 2005). A number of proteolytic enzymes found in muscle and viscera of fish which post mortem degradation during storage and processing. Lipid oxidation is a major cause of spoilage of fish; the poly saturated fatty acids present in fish are highly susceptible for oxidation. Fish is one of the most highly perishable foods. Fish meat goes through certain chemical, physical and microbiological transformations during the period between fishing and consumption due to effects of enzymes, external factors and micro-organisms (Pamuk et al.,2011). Labeo rohita, (Rohu) an Indian major carp is one of the most preferred species in the subcontinent, which contributes about 35% of the total production of L. rohita is the highly valued of all carp species farmed using traditional or modern aquaculture systems in the Indian subcontinent ( Khan et al., 2003). Keeping in view the importance of freshness of fish in market, the present study was undertaken.

Materials and Methods

Fish samples were collected for physico-chemical studies from harvest site, during transportation and at retail market in Hyderabad. The samples were collected in sterile polythene bags as per the method described by ICMSF (1998). The samples were transported in ice to the laboratory. A total of 45 samples from three different stages of supply chains viz. harvest, transportation and retail fish shop were collected. Freshness and quality of all fish samples were done as per European Union Freshness grading (EU scheme, 1996) method. The levels or categories are the following- E (extra), A (good quality), B (satisfactory quality), C (not suitable quality).Fish sample pH was determined as per methods prescribed in FSSAI (2012), Lab Manual-6, New Delhi. Thiobarbituric acid value (TBA) of fish flesh was determined as per the extraction method described by Witte et al., 1970, with partial modification which was followed by Singh et al., 2014. Total viable count (TVC) of fish samples were determined as per method described by AOAC (1997).The means of pH and TBA values were calculated and compared by using student’s t -test. The freshness of fish was estimated by grading system. The data generated in the study was analyzed as per the method Snedecor and Cochran, 1967.

Results and Discussion

The present study was undertaken to evaluate supply chain of freshwater fish (Labeo rohita) cultivated in different harvest sites and sold in retail fish market in Hyderabad.

Freshness of Fish

The freshness of fish was recorded by grading them as E (extra grade), A (good quality) and B (satisfactory quality) of each fish. The results are depicted in Table 1.

Table 1: Results of Freshness of Fish at Various Stages of Supply Chain

*EU Grading Method, E- Extra Grade, A-Good Quality, B-Satisfactory Quality

The fish at harvest were found to be of extra grade in all fish samples. Only 40 percent fish samples were found to be of E grade, 50 percent were A grade and 10 percent samples were B grade during transportation. Further the grade of fish at retail shop was 60% B grade and 40% A grade at retail shops. Declining pattern of freshness of fish from harvest to retail shop might be due to time factor. Earlier Triqui and Bouchriti (2003) also reported E grade of fish upon harvest and deteoriation of freshness subsequently. Storage of fish at 4⁰C resulted into freshness of samples of E grade up to one day of storage, during second and third day freshness was of A grade and on fourth day it was of B grade. In present study it was observed that handlers do not maintain 4⁰C temperature properly at various stages of supply chain, thereby resulting into slight shift in freshness gradation of fish during transportation and at retail shop.

pH of Fish

pH of fish is an important physical parameter to ascertain freshness of fish. In present study mean pH values of fish observed were 6.81 ± 0.05 upon harvest, 6.50 ± 0.04 during transportation and 6.23 ± 0.03 at retail shop and shown in Table 2. It is evident that pH values differ significantly (p<0.01) between groups. Dhanapal et al., 2012 and Obemata and Christopher, (2012) also reported raw fish pH of 6.8 ± 0.41 which was similar to the present study findings and decrease of pH subsequently during storage. A wide range of pH (6.11 to 7.33) of freshwater fish was reported by Kapute et al., 2012 and Rahman et al., 2012. Decrease in pH values affects physical characteristics. The low pH value after few hours of harvest indicate that fish have been somewhat stressed. The typical pH of live fish muscle is 7 and during initial storage period it gives to low 6.2 (Abbas et al., 2008). In present study also the pH of fish at harvest was found to be 6.81 ± 0.05 which is less than 7.0 there by indicating stressed condition at harvest. The pH drop during transportation (6.50 ± 0.04) and thereafter at retail shop (6.23 ± 0.03) might have been due to depletion of glycogen reservoirs during rigor-mortis thereby increase in lactic acid.

TBA Value of Fish

Lipids in edible muscle tissue are involved in oxidation reaction and measured by TBA number, which is a measure of MDA, byproduct of lipid oxidation. The results are shown in Table 2. In present study TBA values of fish at harvest, transportation and retail shop were 0.7 ± 0.06 mg/Kg MDA, 1.5 ± 0.18 mg/Kg MDA and 2.73 ± 0.23 mg/Kg MDA respectively. Comparison of mean TBA value at different stages of supply chain revealed significant (p<0.01) differences between groups. It is evident that TBA value increased from harvest (0.7 ± 0.06 mg/Kg MDA) to retail shop (2.73 ± 0.23 mg/Kg MDA) levels of supply chain, due to increased oxidative changes in fish muscles. Dhanapal et al., 2012 reported TBA value of 0.77 ± 0.01 mg/kg MDA of raw fish collected from reservoir of Muthukur in Andhrapradesh which was similar to the present study findings.

Table 2: Results of Physio-Chemical and Microbial Parameters of Fish at Various Stages of Supply Chain

** (p<0.01); a, b, c- significantly different at (p<0.01)

Total Viable Counts (TVC) at Various Stages of Supply Chain

Total viable count (TVC) is used to assess microbial quality of fish and results are shown in Table 2. The mean values observed were 6.21 ± 0.03 log CFU/gm at harvest, 6.39 ± 0.04 log CFU/gm during transport and 6.63 ± 0.02 log CFU/gm at retail shop. It was observed that the mean TVC values of fish differed significantly (p<0.01) within and among groups. Jannat et al., 2007, reported TVC values of 6×10⁷cfu/gm at harvest in raw Hilsha fish, which was higher than the present study findings. Variation in TVC counts was observed during transport and in retail market which was due to influence of the environment that resulted in increasing bacterial count of fish. Other workers reported TVC counts almost similar to the present findings i.e. (Jayasekaran and Ayyappan, 2003; Mandal et al., 2009; Hassan et al., 2012).

Conclusion

It is concluded that freshwater fish (Labeo rohita) sold in Hyderabad was found to be of good quality in relation to physico-chemical and microbial parameters even though there was decrease in quality from harvest to retail shops. Sanitary measure should be attempted to avoid the contamination from environmental sources at retail shop.

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