Removal of fungus and prevention of fungal reinfestation in stored dry salted fish

A simple and effective method is described for converting dry fish products infested with fungus and red halophilic bacteria to acceptable ones. Washing, drying and then smearing with a mixture of 3% sodium propionate in dry, refined salt in a ratio of 1 part mixture: 10 parts dry fish resulted in the fish having a shelf life of 5 months.

Antioxidant effect of betel leaf extract on dry-cured fish

The effect of betel leaf (Piper betle Linn.) extract on control of autoxidation of fat in dry fish has been studied. Oil sardine has been selected for experiments since it contains very high amount of fat. The treatments were given with 5% (w/v) betel leaf extract in water at different stages of salt curing. FFA, PV and TVN values of the samples were determined periodically to assess the keeping quality and autoxidation. The sample, prepared by dipping the fish in the extract immediately after salting and then drying as usual, was found to have better keeping qualities.

Some fungal infestations of dried fishes in Cochin markets

Dried fish constitutes a regular item of trade in India, particularly in the interior parts far away from the sea and rivers. The poor section of the society is the main consumer. The quality of dried fish never receives much attention at any stage of processing (drying) and storage. A good amount of these fish is discarded during drying due to fungal growth to avoid the danger of mycotoxin production. A survey of the dried fish from the Cochin markets had revealed that they do carry fungal infestations and their chances of mycotoxin production cannot be ruled out as the strains of Aspergillus flavus, Aspergillus ochraceus and Fusarium spp. have been isolated.

On the eye diameter-total length relationship of the Indian mackerel Rastrelliger kanagurta (Cuvier)

Results of studies of chemical, bacteriological and organoleptic quality of cured fish collected from four major curing centres along the Tamil Nadu coast are reported. Only 32.43% of the samples had moisture level below 35%, 0.9% had salt 25% and above. None of the samples showed acid insoluble ash below 1.5%. The main defects were unhygienic processing, inadequate salting, use of poor quality salt and incomplete drying. Recommendations for improvement of quality are given.

Quality of cured fish from Tamil Nadu coast

Results of studies of chemical, bacteriological and organoleptic quality of cured fish collected from four major curing centres along the Tamil Nadu coast are reported. Only 32.43% of the samples had moisture level below 35%, 0.9% had salt 25% and above. None of the samples showed acid insoluble ash below 1.5%. The main defects were unhygienic processing, inadequate salting, use of poor quality salt and incomplete drying. Recommendations for improvement of quality are given.

Utilisation of squid waste as meal

The squid waste which includes head, tentacles, viscera, fin, skin and pen amounts to 52% of the whole weight and is discarded at present. A method has been worked out for the conversion of squ.id waste into meal. The waste is boiled in salt solution (2%)/salt (2%) and alumn (0.5%) solution/and water for two minutes, drained and dried. All the dried samples including the control (dried without blanching) were analysed for physical and biochemical changes. Blanching reduced the yield but the product could be dried in a shorter period. The volatile bases were reduced significantly and the colour was improved. Blanching made pulverisation of the dried product easy. Pulverisation before drying yielded a granular product.

Studies on dried/smoked barracuda

Physical, chemical and organoleptic characteristics of dried and smoked barracuda (Sphyraena spp.) during storage at ambient temperature are reported. Initial increase in total volatile basic nitrogen (TVBN) content after drying as well as smoking did not have any significant effect on the organoleptic qualities of the products. Smoking was found effective in delaying the onset of fungal attack and also in improving the organoleptic qualities.

Improvement in quality and shelf-life of whole dried prawns

A simple and effective method is suggested to improve the quality and shelf-life of commercial whole dried thelly prawns (Metapenaeus dobsoni). Treatment of whole prawns in 10% brine containing 0.1% citric acid for 20 min followed by drying in sun yield a product having good physical, chemical and organoleptic characteristics. Retardation of fungal incidence, reduction in total volatile nitrogen (TVBN) and improvement in flavour are some of the advantages of the treatment. The treated product has a shelf-life around 30 weeks compared to 20 weeks for untreated control and 7 weeks for commercial sample.

Preserved algae as food for Penaeus monodon larvae

Uni-algal cultures of C. calcitrans, S. costatum, T. chui and Isochrysis sp. obtained from the laboratory were harvested. The harvest, preserved by either freezing or sun-drying, was fed to the larvae of P. monodon . Among the test algal species, Chaetoceros and Tetraselmis were used in larval feeding trials with frozen food while Chaetoceros, Tetraselmis and Isochrysis species were utilized in feeding experiments with sun-dried algae. Their relative effects on larval survival and development were assessed. Results showed that, except the alum-flocculated cells, both frozen Chaetoceros and Tetraselmis can support survival at the zoea stage. Best survival of 68% was atained with dried Chaetoceros followed by Tetraselmis at 44%. Dried Isochrysis did not perform as well, a significantly low survival of only 25% was obtained.

Studies on the chemical and nutritional quality of protein powders isolated from shrimp waste

Protein powders were prepared from processing waste of prawns either by mechanically squeezing the shell and freeze drying the resultant aqueous extract or by treating the shell with 0.5% sodium hydroxide, filtering it and freeze drying the filtrate. Comparative studies on the proximate composition, amino acid profile, consumer acceptability and nutritional quality of the protein powders showed that the product prepared by freeze drying of the press liquor obtained by passing the waste through a hand operated expeller is better in all aspects studied than the product prepared by mild alkali extraction.

Quality of cured fish on the west coast: comparative study with the IS specifications

Moisture and salt content in cured fish products from various centres on the west coast of India are compared. The moisture contents varied in samples from different centres, whereas the salt content remained more or less uniform. The deviations from the Indian standard specification were highly significant in both cases. The high mean moisture values and low salt values with respect to accepted standards are indicative of the improper drying and poor salting.

Comparative feature on design, construction and installation of three different model of low cost solar tunnel dryers

The study was conducted in collaboration with the ECFC project of the FAO (BGD/97/017) in Cox's Bazar to develop a low cost solar tunnel dryer for the production of high quality marine dried fish. The study areas were Kutubdiapara, Maheshkhali and Shahparirdip under Cox's Bazar district. Three different models of low cost solar dryer were constructed with locally available materials such as bamboo, wood, bamboo mat, hemp, canvas, wire, nails, rope, tin, polythene and net. Size of the dryers were: 20x4x3 ft ; 30x3x3 ft and 65x3x3 ft with the costs of Tk. 3060, 3530, 9600 for dryer 1, 2 and 3, respectively having different models. The drying capacities were 50, 150, 500 kg for dryer 1, 2 and 3 respectively. The average temperature range inside the dryers were 29-43°C, 34-51°C and 37-57°C for dryer 1, 2 and 3 respectively as recorded at 8:30h to 16:30h. The relative humidity were in the ranges of 22-42%, 27-39% and 24-41 % in dryer 1, 2 and 3 respectively. The fish samples used were Bombay duck, Silver Jew fish and Ribbon fish. The total drying time was in the range of 30-42, 28-38 and 24-34 hours to reach the moisture content of 12.3-14.5, 11.8-14.3, and 11.6-14.1% in dryer 1, 2 and 3 respectively. Among these three fish samples the drying was faster in Silver Jew fish followed by Bombay duck and Ribbon fish in all the three dryer.

Production of quality dried small indigenous fish species products using low cost solar tunnel drier

A low cost solar drier was constructed using locally available materials. The size of the drier was 20x3.6x3 having drying capacity of 80 kg of SIS (w/w). Optimization of moisture content was observed for mola, dhela, chapila, chanda and puti at temperature ranges between 40-45°C and 50-55°C in solar tunnel drier. There was little or no change in moisture content at temperature below 40°C during the first 3 hours. Then the moisture content declined gradually with the increase of drying period. On the other hand, at temperature between 50-55°C, moisture content started to decline after 2 hours of drying. The moisture content of the sample reached at about 16% after 26 hours of sun drying at 40-45°C and 20 hours at 50-55°C. The optimum temperature for producing high quality dried products was 45-50°C in solar tunnel drier. The temperature and relative humidity outside and inside the dryers (with fish) at various locations were recorded from 8.00am to 4.00pm. The normal atmospheric ambient temperature was recorded in the range of 25-37°C from at 8:00am to 4:00pm. During the same period the atmospheric relative humidity recorded was in the range of 30-58%. On the other hand, the maximum temperature inside the dryers was recorded in the range of 28-65°C. The lowest temperature recorded was 28°C in the morning and at 13.00pm the highest temperature 65°C was recorded. The maximum relative humidity 58% found in the afternoon and minimum of 28% at noon. There was inverse relationship between temperature intensity of sunshine and humidity which decreased as sunshine increased. In total, it took around 26 hours of drying to reduce the moisture level to about 16%.

Feasibility study of biofuel production from freshwater fern, Azolla sp in Anzali Wetland

Production of bioethanol through acidic and enzymatic hydrolysis of aquatic Azolla sp., as a new source of bio-mass, has been performed, as a means to control increasing growth and reducing undesirable effects of this plant in Anzali lagoon. After sampling, drying and crushing, Azolla was hydrolyzed, using diluted acid and enzyme. Diluted acid hydrolysis was done using both autoclave and a high-pressure system (Batch Synth® Microwave synthesizer). The effects of temperature and time (in autoclave) and concentration of acid (in both) were compared. Cellubrix®, a ommercial cellulase source, was used for enzymatic hydrolysis process. The amounts of reducing sugars, glucose and furfural, released from hydrolyzate, were measured. To produce alcohol, Sacchromyces cerevisiae (to ferment sixcarbon sugars), Zygowilliopsis californica and Pichia stipitis (to ferment five-carbon and sixcarbon sugars) were used. Maximum amounts of glucose (4.83% w/w) and reducing sugars (14.15% w/w) were obtained using acid hydrolysis in autoclave. In the microwave oven, maximum glucose (5.04% w/w) and reducing sugars (13.27 w/w) were obtained at 180 and 200 °C, respectively. Under these conditions, maximum produced furfural was 1.54 g/L. The difference between amounts of furfural obtained from acid hydrolysis of Azolla in microwave oven compared to autoclave was statistically significant. Amounts of alcohol produced and its yields were 3.99 g/L and 33.13% for S. cerevisiae in 48 hours, 3.73 g/L and 30.45% for Pichia stipites in 48 hours, and 3.73 g/L and 30.45% for Z. californica in 24 hours after inoculation, respectively, with significant differences. Statistical comparison of results showed significant differences (P<0.05) in glucose production, at different conditions. Amounts of reducing sugars and glucose increased after optimization of levels of acid, time, and temperature. The overall optimum released sugar and glucose were obtained with 1.67% (w/v) acid using autoclave. Higher temperatures in microwave oven caused a significant increase (P<0.05) in furfural. Furfural severely inhibits fermentation. Hence, regarding the issues of energy consumption and time, amounts of inhibiting substances and sugar production, autoclave is found to be superior to the high temperature and pressure, generated in microwave oven, for hydrolyzing Azolla. Furthermore, given the amounts of Azolla in Anzali lagoon, it may be recommendable to use this plant as a biomass resource.

An assessment of handling and processing methods used for the shrimp fishery by-catch in Kalpitiya, Sri Lanka

The by-catch from the shrimp trawl fishery in Kalpitiya is mainly used for the production of dried fish, which provides an additional source of income for fishermen in the area. It has been observed that current handling practices along the value addition chain are responsible for the poor quality and low price of the end product. This study was aimed at identifying the shortcomings in such handling practices by fishermen and dried fish producers and assessing the quality of shrimp fishery by-catch along the processing chain in order to recommend more efficient utilization methods that will improve the quality of the end product. Fresh fish, dried fish and harbour water samples were tested for total coli forms, faecal coliforms, E. coli and Salmonella in order to assess their microbial quality: In addition, standard plate counts (SPC) of fish samples were also carried out. A survey was carried out from July-October 2006 at Kalpitiya, using a pre-tested questionnaire to collect information from individuals who have been engaged in dried fish processing. Average values obtained for freshly landed and dried fish respectively, were, SPC 9.88x10 super(5) CFU/g and 30.43x10 super(5) CFU/g, total coliforms 23.05 and 24.23 MPN/g and fecal coliforms 8.28 and 9.00 MPN/g. These values exceed the recommendations in the SL standards. A quarter of the landed fresh fish and 38% of dried fish from the producers were positive for E. coli and thus failed to show required end product quality. SPC of harbour water was 14.35x10 super(6) CFU/ml and all samples were found to be contaminated with E. coli. None of the fishermen and dried fish producers were satisfied with the quality of the end product. The reasons for poor quality as indicated by them were: limited availability of ice (75%), lack of infrastructure facilities (65%), uncertainty of markets (52%), lack of emphasis on quality (47%) and poor access to available technologies (41%). Respondents to the questionnaire also identified: unavailability of potable water, insulated boxes, good landing jetty, racks for drying fish, poor cold storage facilities and limitations in dried fish storage facilities, as further factors leading to the loss of quality in their products. Results demonstrate that improvements to the infrastructure facilities and conducting of proper awareness programmes on handling practices could lead for improvements in the quality of value added products prepared from the shrimp fishery by-catch at Kalpitiya.