Methods of sensory evaluation of quality and application of statistical methods in sensory evaluation problems with special reference to fishery products

The quality of raw and processed fishery products depend on several factors like physiological conditions at the time of capture, morphological differences, rigor mortis, species, rate of icing and subsequent storage conditions. Sensory evaluation is still the most reliable method for evaluation of the freshness of raw processed fishery products. Sophisticated methods like Intelectron fish tester, cell fragility technique and chemical and bacteriological methods like estimation of trimethylamine, hypoxanthine, carbonyl compounds, volatile acid and total bacterial count have no doubt been developed for accessing the spoilage in fish products.

The bacteriology of oil sardine (Sardinella longiceps) and mackerel (Rastrelliger kanagurta) caught from tropical waters off Cochin. 1 - Quantitative aspects

The total aerobic viable plate counts (TPCs) of skin, gills and intestine of newly caught oil sardine (Sardinella longiceps) and Indian mackerel ( Rastrelliger kanagurta) at four different temperatures, namely 36 ± 1°C, 28 ± 2°C (RT), 8 ± 1°C and 1 ±1°C, are reported. The total plate count at RT of the skin of oil sardine and Indian mackerel were in the range of l0 super(3) to 10 super(7) and 10 super(4) to 10 super(6) per cm², that of gills in the range of 10 super(5) to 10 super(9) and 10 super(4) to 10 super(8) per g and that intestine in the range of 10 super(5) to 10 sueper(9) and 10 super(5) to 10 super(8) per g respectively. The TPCs were markedly affected by the incubation temperature. Incubation at 28 ± 2°C gave the highest count; at 36 ± 1°C and 8 ± 1°C, the counts decreased by nearly 1-2 log cycles from that at RT. Incubation at 1 ± 1°C registered the lowest count. The peak values for bacterial counts of these fishes occurred at different periods of the year.

Studies on the ice storage characteristics of blood clam Anadara granosa meat

Ice-storage study of blood clam (Anadara granosa) meat in direct contact and out of contact (in 200 gauge polyethylene bag) with ice was taken up to assess the amenability of the meat to icing. Changes in moisture, total protein, non-protein nitrogen, α amino nitrogen, total volatile base nitrogen, glycogen, free fatty acid, peroxide value, total bacterial count and coliform count were followed every day. The raw and cooked meat were also subjected to organoleptic evaluation. The study showed that the clam meat can be ice-stored in very good condition out of contact with ice in polyethylene packets for 4 days and in direct contact with ice for 2 days.

Assessment of quality of fish landed at the Cochin fisheries harbour

Assessment of quality of fish and shrimps landed at the fish harbour, Cochin, was made over the period January, 1980 to December, 1982. A total of 201 samples were analysed. Nearly 75% of the samples scored between 6-10 in a 10 point hedonic scale and the percentage unacceptability based on sensory assessment was 5. 5%. In 10.1% of the samples, total volatile nitrogen was >30 mg% and in 8.3% of the samples trimethylamine- nitrogen was >10 mg%. Both, the gr Torrymeter and Intellectron Fish Tester VI readings marked significant correlation with sensory scores and chemical indices; but failed to bear any significant correlation with bacterial counts. Of the 5-1 total samples 66.7% had total plate count (TPC) ≥10 super(5) g super(-1) and 8.5% were considered unacceptable based on TPC >5x10 super(5) g super(-1); 63.2% of the samples were free from Escherichia coli; 26.4% had >20 E. coli g super(-1) and 20.4% of the samples contained faecal streptococci >10 super(3) g super(-1). Seven percent of the samples showed coagulase positive staphylococci >100 g super(-1). Salmonella could not be detected in any of the samples examined. Crushed ice samples and the platform of the harbour had high bacterial loads.

Correlation of cell numbers with catalase activities of pure strains of bacteria

An attempt was made to correlate the catalase production with the actual number of aerobic bacterial cells generating the enzyme: bacteria were obtained from the surface of marine fish. A linear correlation was found between the log of catalase activity and log of bacterial count in single culture.

A quantitative study of Vibrio parahaemolyticus (Sakazaki et al) in Etroplus suratensis (Bloch) and Metapenaeus dobsoni (Miers) from Cochin backwater

Seasonal variation of Vibrio parahaemolyticus in fish (Etroplus sauratensis) and prawn (Metapenaeus dobsoni) was monitored from March 1982 to February 1983. Analyses of total viable count, vibrio-like organisms, V. parahaemolyticus like organisms and V. parahaemolyticus showed that they occur more in prawn than in fish. In a more polluted environment, the counts of V. parahaemolyticus associated with fish were found to be higher than in prawn.

Development and storage characteristics of dehydrated salt mince from low priced fish

The study showed that less initial moisture with high salt content will be the best condition for enhanced storage life of dehydrated salt mince. Between sample I (10% salt per meat weight) and sample II (15% salt per meat weight) the latter was comparatively better in colour, odour and longer shelf-life. At room temperature the dehydrated salt mince has not showed any increase in total bacterial count. It is also found that the storage life of the salt mince can be enhanced to a significant extent by lowering the moisture content to below 10% and increasing the salt content to above 30%. Peroxide value, free fatty acid value, total volatile nitrogen and trimethylamine registered gradual increase during storage at room temperature for all the three samples. Among the three samples, the sample treated with 0.1% citric acid and 0.125% butylated hydroxy anisole was comparatively better in appearance and showed less rancidity as indicated by TBA values, up to a period of 15 weeks and thereafter all the three samples were almost similar in storage characteristics. Hence, the treatment with citric acid and B.H.A. has apparently not much significance in improving shelf-life and quality of salted dehydrated fish mince.

On the ice-storage characteristics of Catla catla and Labeo fimbriatus

The ice-storage characteristics of Catla catla and Labeo fimbriatus are reported. Muscle pH, moisture, total volatile nitrogen, alpha amino nitrogen and peroxide value and also the changes in total bacterial count are studied. C. catla and L. fimbriatus both could be stored in ice for 18 days.

Reduction in Chaetoceros populations by furanace

One of the most promising prophylactic agents being tested to control Penaeus monodon larval diseases is furanace (6-hydroxymethyl-2 2(5-nitro-2-furyl) vinyl pyridine). To evaluate further its suitability as a chemotherapeutic agent, its effects on the population growth of Chaetoceros calcitrans, the diatom used as feed for the zoeal stages, was examined. Chaetoceros populations of uniform density (initial density in all runs: 130-141x10 SUP-3 cells /ml) were placed in nine white, circular (382 sq cm), plastic basins. The physio-chemical characteristics of the culture water were as follows: salinity, 28 . 5-30 . 0 ppt; pH, 8 . 62-8 . 72; temperature, 23-25 . 5 degree C; dissolved oxygen, 7 . 1-9 . 3 ppm; nitrate, 0 . 03-0 . 07 ppm; and ammonia, 0 . 005-0 . 03 ppm. Preweighed furanace granules were dissolved in the culture water, with resulting concentrations of 1 and 2 mg/l (3 replicates each). A set of replicates without furanace served as the control. Population counts of the diatom were taken after 2, 4, 6, 8, and 10 hr exposures. After 4 hr, the population decreased in all three levels. The population in 2 mg/l furanace showed the lowest count and that in control the highest. The population means are not statistically different from one another. The results of the study show that the furanace causes reductions in Chaetoceros population at all durations of exposure.

Biology and farming of the green mussel Mytilus smaragdinus

Biological investigations were carried out in Sapian Bay, Capiz from November 1975 to December 1976 with samplings conducted fortnightly. Histological studies on the gonad reveal a high percentage of ripe and spent females during the month of April and May, and ripe to near ripe during November to December. However, larval counts were highest on February 25, 1976 with 253 mytilid larvae per haul compared to 0-79 per haul during all other months. The high larval count was followed by the highest spat settlement during the next sampling period two weeks later, with the spat collector set in the water during the February 25 sampling. The four materials tested, blue polypropylene fiber rope, black polypropylene fiber, and coir rope, all had their highest spat counts during this period with an average of 471 spats per standard 10 cm rope piece. The range during the other time periods is 2-283 spats. Of the 4 materials tested, the black fibrillated polypropylene film had the highest larval counts in 15 out of a total of 25 sampling periods. The blue rope was the poorest spat collector. Coconut husk was tested later on and it proved to have a very high catchability, with spats completely enveloping the husk surface. Growth monitored from one cohort in Sapian Bay averaged 10 mm per month. 50-60 mm is considered marketable size. Trial growth experiments with transplanted mussels were also conducted at Igang Bay in Guimaras Island, Makato River in Aklan, and a milkfish pond in Leganes, Iloilo. Survival in Igang was less than 50% after the second week, and the condition of the surviving mussels can be described only as 'watery' with the mantle completely transparent. Mortality was minimal in Makato but the growth rate was only 30% that of Sapian Bay. The pond experiments were terminated due to severe crab predation.

Studies on iced storage of common murrel (Channa striatus)

The iced storage characteristics of common murrel (Channa striatus) have been studied. The non-protein nitrogen and alpha amino nitrogen in the muscle of the fish decreased during iced storage and the total volatile base nitrogen at the end of iced storage was not high even though the fish became unacceptable during the period. There was steep decrease in total bacterial count during initial storages of storage and then increased steadily on further storage. The fish remained in acceptable condition for 8 to 9 days in ice.

Effect of liquid nitrogen freezing and subsequent storage on survival of Staphylococcus aureus and Streptococcus pyogenes in treated prawn meat

Prawn meat treated with Streptococcus pyogenes B-49-2 culture and Staphylococcus aureus ATCC-12598 culture were frozen in conventional plate freezer at -40°C and by spray type liquid nitrogen freezer. The frozen products were stored at -18°C. Streptococcus pyogenes B-49-2 showed low sensitivity to cold injury during freezing and frozen storage. Staphylococcus aureus ATCC-12598 survived during the entire storage period of 240 days. Total bacterial count of untreated prawn meat was found to be always lesser in liquid nitrogen frozen products than that in plate frozen products.

Studies on iced storage of cultured rohu (Labeo rohita)

The biochemical, bacteriological and organoleptic changes in cultured rohu (Labeo rohita) during iced storage have been studied. Non-protein nitrogen decreased and water soluble nitrogen remained almost same during storage in ice. Initially, when the fish was in pre-rigor and rigor conditions, the extractability of protein was low (45 to 50%) which increased after the resolution of the rigor and the decrease in extractability towards the end of storage was insignificant. The total volatile base nitrogen remained steady up to 7 days in ice and showed slight decrease on further storage. During iced storage the bacterial count increased from 10^3/g to 10^5/g by the 11th day of storage. Nearly 80-90% of the total bacterial population in fresh fish was constituted by mesophiles which decreased gradually (decreased to 1% by 13th day of iced storage). Organoleptically the fish was acceptable up to 15 days in ice.

Incidence and low temperature survival of coagulase positive staphylococci in fishery products

Coagulase-positive staphylococci was found to be absent in all the frozen samples of lobsters, cuttle fish, cat fish, seer fish and red snapper examined. Coagulase-positive staphylococci were present in 38% of the cooked frozen shrimps and only 16% of the samples had staphylococci count more than 100/g. In the case of headless, peeled and deveined, peeled undeveined shrimps, the incidence of the organism was 6, 12 and 16% respectively. The study indicated that the incidence of coagulase-positive staphylococci is not a serious problem in frozen fishery products processed in this country. There was remarkable difference in the rate of destruction of coagulase-positive staphylococci in raw and cooked shrimps during freezing and frozen storage.

The Genomes of Oryza sativa: A history of duplications

We report improved whole-genome shotgun sequences for the genomes of indica and japonica rice, both with multimegabase contiguity, or almost 1,000-fold improvement over the drafts of 2002. Tested against a nonredundant collection of 19,079 full-length cDNAs, 97.7% of the genes are aligned, without fragmentation, to the mapped superscaffolds of one or the other genome. We introduce a gene identification procedure for plants that does not rely on similarity to known genes to remove erroneous predictions resulting from transposable elements. Using the available EST data to adjust for residual errors in the predictions, the estimated gene count is at least 38,000 - 40,000. Only 2% - 3% of the genes are unique to any one subspecies, comparable to the amount of sequence that might still be missing. Despite this lack of variation in gene content, there is enormous variation in the intergenic regions. At least a quarter of the two sequences could not be aligned, and where they could be aligned, single nucleotide polymorphism ( SNP) rates varied from as little as 3.0 SNP/kb in the coding regions to 27.6 SNP/kb in the transposable elements. A more inclusive new approach for analyzing duplication history is introduced here. It reveals an ancient whole-genome duplication, a recent segmental duplication on Chromosomes 11 and 12, and massive ongoing individual gene duplications. We find 18 distinct pairs of duplicated segments that cover 65.7% of the genome; 17 of these pairs date back to a common time before the divergence of the grasses. More important, ongoing individual gene duplications provide a never-ending source of raw material for gene genesis and are major contributors to the differences between members of the grass family.