Dietary inclusion of Tenebrio molitor larvae meal: Effects on growth performance and final quality treats of blackspot sea bream (Pagellus bogaraveo)

Fish are a nutrient rich food but highly perishable due to its high water activity, protein content, neutral pH and presence of autolytic enzymes. This explains why fresh fish quality deteriorates rapidly if not properly stored after catch such as use of low temperature. The implication is that delayed processing of fresh fish negatively influences consumer taste of fish. Further, fresh fish that are not processed on time lose nutrients due to spoilage. In Malawi, most fresh fish are sold in the open due to lack of storage facilities such as refrigerators – a condition that accelerates spoilage of fish. This study was carried out to assess the effect of delayed processing on nutrient composition, pH level and organoleptic quality of pond raised tilapia - Oreochromis shiranus which is the commonest grown tilapia in Malawi. Thirty freshly pond harvested O. shiranus fish (average weight 100g) were cleaned then deep fried in edible cooking vegetable oil at time intervals of 0, 6 and 12 hours from catch and stored at ambient temperature. A pre-trained sensory evaluation panel consisting six members described changes in the sensory quality of the fresh and fried fish at every sampling time interval. Crude protein, crude fat, ash, moisture content and pH were also determined at each sampling time. Determined crude protein and crude fat decreased while ash content increased with storage time though these were not significantly different from baseline (P>0.05). Moisture content decreased from 0 (fresh) to 6 hours then increased again up to 12 hours of storage. Ash and moisture content correlated positively (0.93 and 0.79% respectively), whilst crude protein, crude fat and pH were negatively correlated (-0.91, -0.05 and -0.97, respectively) to sensory quality demerit scores. pH decreased from 5.94 at 0 hours to 5.92 after 6 hours then increased sharply to 5.98 after 12 hours of ambient fish storage. Consumers started to significantly (P<0.05) dislike the fish after 7 hours and eventually rejected the samples after 12 hours of ambient storage time. The study recommends that for optimum consumer satisfaction and nutritional benefit, fresh O. shiranus should be processed at most 7 hours after harvesting. Key words : Nutrients, taste, Tilapia, ambient storage

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Effect of delayed processing on nutrient composition, pH and organoleptic quality of pond raised tilapia (Oreochromis shiranus) stored at ambient temperature

The processing and preservation processes are necessary to guarantee the microbiological, technological, organoleptic and nutritional qualities of fish. This article describes the technological (fish flesh composition, fish flesh evolution after capture, evisceration, filleting, water content, water holding capacity and pH), organoleptic (fish freshness state, color and aspect, flavor, texture), hygienic and nutritional qualities of fish and their variation factors. The processing and preservation processes of fish (refrigeration, freezing, smoking, salting and drying) were described and finally, these processes impact on fish sensory, microbiological, technological and nutritional qualities is reported. The knowledge of processing and preservation processes as well as the control of variation factors will improve the hygienic, technological, organoleptic and nutritional qualities of fish useful for human consumption. Resume Les procedes de transformation et de conservation sont necessaires pour garantir les qualites microbiologiques, technologiques, organoleptiques et nutritionnelles des poissons. Cet article decrit les qualites technologiques (composition de la chair des poissons, evolution de la chair de poisson apres la capture, evisceration, filetage, teneur en eau et la capacite de retention d’eau et le pH), organoleptiques (etat de fraicheur des poissons, couleur et aspect, flaveur, texture), hygieniques et nutritionnelles des poissons et leurs facteurs de variation. Les procedes de conservation et de transformation des poissons (refrigeration, congelation, fumage, cuisson, salage et sechage) ont ete ensuite decrits et enfin, l’impact de ces procedes sur les qualites sensorielles, microbiologiques, technologiques et nutritionnelles des poissons est expose. La connaissance des procedes de transformation et de conservation et la maitrise des facteurs de variation au profit de ces procedes serviront a ameliorer les qualites hygieniques, technologiques, organoleptiques et nutritionnelles des poissons utiles pour la consommation humaine.

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Qualité de la Chair des Poissons : Facteurs de Variations et Impacts des Procédés de Transformation et de Conservation

Lake Malawi Tilapia (chambo) fish species is widely consumed and forms the most important commercial fishery in Lake Malawi. However, as a highly perishable commodity, knowledge regarding how long fresh fish would remain in acceptable and safe condition in storage is indispensable for consumers and processors. Presently, no such information exists for the Lake Malawi Tilapia in Malawi. A study was therefore conducted to estimate shelflife of whole fresh Lake Malawi Tilapia stored in ice (0
	oC) for 21 days. Sensory, microbiological and pH analyses were conducted to describe changes in quality and freshness of the fish with storage time in ice. Shelflife of the fish was estimated between 16 and 18 days. A strong linear correlation (R2=0.95) was observed between sensory demerit scores and storage time in ice. Total bacteria viable counts and pH at the time of sensory rejection of the fish were 1.6×107 cfu/g/cm2 and
	5.84 respectively. Pseudomonas and Micrococcus bacteria were found in relatively high numbers throughout the storage period. The study demonstrated that like other tropical fish, Lake Malawi Tilapia has a relatively longer shelflife. The long storage life in ice of Lake Malawi Tilapia is advantageous to most small scale fresh fish sellers and processors especially from rural areas in Malawi who solely depend on ice as a sole and affordable way of preserving fresh fish.

Shelflife of whole fresh Lake Malawi tilapia (Oreochromis species

The organoleptic evaluation and proximate analysis of Clarias gariepinus and Cyprinus carpio were determined in fresh fish and when refrigerated at two different temperatures (-21 °C and 4 °C) for a period of six weeks. A panel of twelve trained judges evaluated the color (live), texture, softness and flavor of fish meat after two minutes' steam cooking. Average score revealed a general decline in organoleptic properties such as color, texture, freshness, and taste of C. gariepinus and C. carpio stored at two temperatures compared to the fresh fish. Proximate analysis revealed a more decrease in crude protein and lipid contents and increase in ash content in C. gariepinus and C. carpio at the two storage temperatures compared to the fresh fish muscle. Moisture content decreased in the fish muscle samples of both the fish species stored at -21 °C but increased in the 4 °C stored samples. pH of fish was found to increase in the two stored temperatures. There were significant differences (P<0.05) in the organoleptic and proximate composition of the ice stored and fresh C. gariepinus and C. carpio, the same temperature and between the two different temperatures. The quality of fish muscle stored at 4 °C deteriorated faster than that of the -21 °C. Thus, storage temperature and duration have adverse effects on the nutritional quality of fish meat.

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Study on assessment of proximate composition and meat quality of fresh and stored Clarias gariepinus and Cyprinus carpio

Microbiological analysis of Tilapia guineensis was assessed at two ice stored temperatures, -18 and 4°C, for 4 weeks. Bacteria and fungi counts decreased from 7.9 × 103 to 5.4 × 101 cfu/g for bacteria and 6.2 × 103 to 3.2 × 102 cfu/g for fungi in the samples stored at -18°C, while for the samples stored at 4°C, an increase was shown in counts from 7.9 × 103 to 7.6 × 107 cfu/g for bacteria and 6.2 × 103 to 6.8 × 104 cfu/g for fungi. Pseudomonas, Staphylococcus, Bacillus,Proteus, Micrococcus and Aeromonas sp. were the bacteria species isolated before cold storage, while only Pseudomonas, Staphylococcus, Bacillus andProteus sp. were isolated from samples stored at -18°C. The same organisms isolated before cold storage were also isolated for samples stored at 4°C. Fungal species isolated before cold storage include: Cladiosporium, Aspergillus andFusarium sp. All these fungi species were also isolated from samples stored at -18°C. Cladiosporium, Pichia, Aspergillus and Fusarium sp. were isolated from samples stored at 4°C. The level of bacteria and fungal growth in fish stored at 4°C temperature exceeded the acceptable microbiological limits (102/g for moulds and 103/g for bacteria). However, the pH of fish was found to increase in the two stored temperatures. It was within the alkaline range in the -18°C stored samples, but within the acidic range in the 4°C stored samples. There were significant differences (P<0.05) in the microbiological composition of the ice stored Tilapia guineensis within the same temperature and between the two temperatures. The quality of the 4°C stored sample deteriorated faster than that of the -18°C. Thus, storage temperature and duration have effects on the quality of stored fish.

	 

	Key words: Tilapia guineensis, fish, sample, bacteria.

Frank ndash

Papers

Microbiological assessment of stored Tilapia guineensis