Color plays a major role in the overall acceptability of food products. It is considered one of man's basic experiences that a particular foodstuff has to be of a distinct color in order to be edible. The color of a seafood is the first characteristic noted by the consumer and is directly related to the subsequent acceptance or rejection of it. Carotenoids contribute to the yellow, orange, and red colors of the skin, shell, or exoskeleton of aquatic animals. Indeed, they are the most widespread pigments found in nature, as they occur in bacteria, yeasts, mold, all green plants, and many animals, and therefore various functions have been attributed to them. From anthropocentric consideration, the most significant aspect of carotenoids is the color they impart to our food and environment. In animals, the carotenoids are also associated with reproductive organs and hence the hatching success and survival of alevins.

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Recently, studies about smoked food tend to identify harmful compounds that potentially appear within the smoking process. The process, conducted in a smokehouse, closely corresponds with the design and method. This paper presents a smokehouse designed by integrating a biomass furnace, a heat exchanger, a cyclone separator, and a smoking chamber. The design target was to obtain a smoking system that produces clean smoked fish. The design and construction phase and the performance tests phase are discussed in this paper. The energy source used was coconut shells, fed into the furnace at predetermined amounts, to achieve the desired temperature. The performance tests were done using skipjack fish, whose weight ranged from 0.7–1.0 kg/head. The results showed that the smoking system was able to complete the smoking process of the fish in 13 h with 20.1% moisture reduction. The temperature of the smoking chamber varied from 70 °C to 108 °C and the internal fish temperature during the cooking phase ranged from 71 °C to 80 °C. The temperature performance was supported by a heat exchanger with an effectiveness of 0.63 and a cyclone separator, which channeled the smoke–heat flow, separated fly ash with particle sizes between 0.2–600 µm and tar. Based on the test results, the indirect smoking system developed and tested in this study is shown to be able to perform the smoking fish process satisfactorily and produce clean smoked fish.

Albumin of snakehead fish has been widely used in the health and nutritional applications for the past 10 - 15 years. An intensive exploitation to produce fish albumin has placed the natural stock of snakehead fish under a great pressure. Furthermore, its aquaculture production has not been significantly developed to balance the industrial demands. Therefore, the present work aimed to look for the potential sources of fish albumin of freshwater origin as an alternative to that of snakehead fish. The present work analysed seven freshwater fish species namely catfish (Clarias gariepinus), common carp (Cyprinus carpio), eel (Monopterus albus), Nile tilapia (Oreochromis niloticus), pangas catfish (Pangasius pangasius), snakehead fish (Channa striata), and three-spotted gourami (Trichogaster trichopterus). Albumin extraction was done by mixing 50 g of pre-homogenised fish meat with 200 mL of distilled water, homogenised in a laboratory homogeniser for 1 min, and heated in a water bath at 50°C for 60 min. The mixture was filtered using a Whatman No. 40 filter paper under reduced pressure. The filtrate volume was recorded and stored at -20°C until further analysis. The parameters analysed were total protein, total soluble protein, and albumin level. Results indicated that the total protein content of meat was 17.93 - 21.87% (w/w), the lowest being in catfish and the highest in snakehead fish; total soluble protein was 2.43 - 5.43 g/100 g (w/w), the lowest being in eel and the highest in snakehead fish; and albumin content was 0.83 - 3.35 g/100 g (w/w), the lowest being in Nile tilapia and the highest in common carp. The higher albumin content in the common carp (3.35 g/100 g) and pangas catfish (3.22 g/100 g) as compared to that of snakehead fish (2.97 g/100 g) indicated that common carp and pangas catfish are highly potential to be used as alternative fish albumin source.