Drying Kinetics and Quality Characteristics of Indian Mackerel (Rastrelliger kanagurta) in Solar–Electrical Hybrid Dryer

Quality evaluation of improved and traditionally dried Bombay duck (Harpodon nehereus) through biochemical, microbiological, and organoleptic analysis

The study was conducted to compare the quality and shelf life of traditionally dried (collected from the local markets) Bombay duck (Harpodon nehereus) with improved dried products (produced using a newly developed fish dryer) to assess its suitability. The quality of these products was evaluated through organoleptic, water reconstitution, nutritional, chemical, and microbiological characteristics. The organoleptic quality of improved dried fish was excellent while those produced traditionally were with grayish and dark brown color, rancid odor, and soft and fragile texture with insect infestation. The water reconstitution properties of the improved dried sample were 75.71% and 89.39% at room temperature and 80 °C, respectively, which were comparatively higher than the traditional dried products. The protein, ash, and contents were significantly higher in improved dried fish products while the lipid and total volatile base nitrogen (TVB-N) content were much lower than those of market-dried samples. The total viable counts (TVC) of bacteria were significantly higher in the traditional products which indicated poor quality. To find out the best storage method, dried fish was kept at three different conditions: in the open air at room temperature, in a sealed pack at room temperature, and a sealed pack at refrigeration temperature (4 °C). The shelf life of the products in different storage conditions was evaluated by estimating their moisture, protein, lipid, ash, TVB-N, and TVC values. The products kept at 4 °C temperature was found almost unaltered in terms of their nutritional properties after 4-months storage period. Results indicated that the newly developed fish dryer produced high-quality dried fish products with longer shelf life can be expected if the dried fish is stored at 4 °C refrigeration temperature. Our findings will be a valuable tool for the fish processors to ease the fish drying process and its storage that will enable them to commercially supply good quality dried Harpodon nehereus in the market chain at a low-cost.

Effects of thermal and salt water soaking pre-treatment on the physicochemical and nutritional properties of sundried tilapia fish (Oreocromis niloticus) products

The effects of saltwater soaking (10-30 %, w/v) and thermal (60°C-90 °C) pre-treatment on the physicochemical and nutritional quality of sundried tilapia fish (Oreocromis niloticus) products were assessed. The wet reduction was 14.47 % in the sample treated with a 30 % salt solution at 90 °C, whereas the wet reduction of 21.23 % was observed in the sample without treatment (control). Protein, lipid, and ash content were increased significantly (P < 0.05) with higher pre-treatment salt concentration and temperature, while the moisture content showed the opposite trend. The content of essential and non-essential amino acids in the treated samples ranged from 7149.97 mg/100 g to 8063.42 mg/100 g and 10530.66 mg/100 g to 11365.59 mg/100 g, respectively, whereas the values were 7018.55 mg/100 g and 10400.84 mg/100 g, respectively in the control. The fatty acids composition, particularly ω-3 polyunsaturated fatty acids, was higher in pretreated samples (6.14-7.08 %) compared to the control. Mineral content was found to improve with saltwater and thermal pre-treatment, and the levels of heavy metals, including Ni and Cu, were significantly lower in the sundried tilapia fish. The sample pretreated with 10 % salt solution and 75 °C showed the highest rehydration capacity of 66.63 %. These findings suggest that saltwater and thermal pre-treatment can effectively enhance the physicochemical and nutritional properties of sundried tilapia fish products.

Development of Fermented Sweet Potato Flour (Ipomoea batatas L.) Supplemented with Mackerel (Scomber scombrus) Meal-Based Biscuits

The fermentation of sweet potato (Ipomoea batatas L.) with a strain of Lactobacillus plantarum leads to an increase in its exopolysaccharides (EPS) content which is useful for enhancing the functional properties of flour. The objective of this study was to develop healthy and nutritious meal-based biscuits from fermented sweet potato (FSP) flour supplemented with mackerel flour. Eleven formulations containing wheat flour, FSP flour, nonfermented sweet potato (NFSP) flour, and mackerel flour at different proportions defined following a mixture design were used to prepare biscuits. Physicochemical, microbiological, and sensory analyses of the different biscuits were performed. Biscuits prepared with FSP at 100% scored the lowest lipid ( $10.83\pm 0.97\text{g}/100\text{g}\text{DM}$ ) and the highest sugar ( $67.43\pm 0.64\text{g}/100\text{g}\text{DM}$ ) contents. The incorporation of mackerel flour in the formulation led to a significant ( $p<0.05$ ) increase in the protein and mineral contents of biscuits thus conferring an immune-boosting property to these latters. All the biscuits were of good microbiological quality independent of the formulation. The highest DPPH free radicals scavenging activity (IC50 of 1.90 and 3.41 μg/mL for ethanolic and methanolic extracts, respectively) were observed with biscuits prepared with FSP flour at 100%. The sensorial characteristics of biscuits prepared with equal proportions of wheat and FSP flours were highly appreciated by the panelists with scores close to the ones prepared with wheat flour at 100%. The results of this study demonstrate the potential of FSP flour as a substitute for wheat flour in biscuits preparation. It also suggests biscuits prepared with FSP flour supplemented with mackerel flour as a functional and immune-boosting food.

Sensory evaluation of fresh/frozen mackerel products: A review

Mackerel has received considerable attention in the global food market as one of the most important pelagic commercial fish species. The quality of mackerel is influenced by species, season, fishing area, nutritional status, catching method, handling, and storage. Due to the mackerel's perishability, its quality is mainly measured by sensory procedures. Although considerable effort has been made to explore quick and reliable quality analysis, developing a practical and scientific sensory evaluation of mackerel has been an active ongoing study area to meet the quality evaluation demand of the industry. Different sensory evaluation methods have been used to assess the mackerel fish quality, including Palatability and Spoilage test, Torry scheme, EU scheme, Quality Index Method, Catch damage index and Processed fish damage index, Affective test, Discriminative test, and Descriptive test. Each method has its strength and weakness. Despite mackerel sensory evaluation protocols having undergone partial harmonization, specific sample process needs to be carefully followed to minimize the change during sample preparation. This review summarizes the sensory evaluation methods in mackerel research, the factors affecting sensory evaluation, and then updates the latest advances in mackerel sensory evaluation and offers guidance for presenting its application in the mackerel chain. Also, each technique's advantages and limitations are discussed. In our opinion, the future trends for sensory evaluation of mackerel should be consumer-centric.

Solar drying of residue from Brazil nut processing

Abstract Brazil nuts are often used for direct consumption or in the preparation process of water-soluble extract. After obtaining the water-soluble extract, a large amount of Brazil nut residues with good sensory characteristics are generated. Thus, this study aimed to dry Brazil nut processing residues in layers with different thicknesses in a direct solar dryer as well as by direct exposure to the sun, in order to fit different mathematical models to the experimental data of drying kinetics, and calculate the drying rates and effective diffusivity. The drying procedures began at 9 a.m. on a concrete base, for samples dried by direct exposure to the sun, and in a solar dryer constructed with expanded polystyrene foam zinc plated and a glass cover. The mass loss of the samples was monitored by weighing at regular times until the hygroscopic equilibrium was obtained. The direct solar dryer had temperatures about 80% higher than those recorded in the open environmental air temperature. Drying rates were higher in dehydrations performed in the solar dryer compared to the drying by exposure to the sun. The Midilli model was selected as the most adequate for predicting the drying of the samples under all experimental conditions, showing coefficients of determination above 0.99. The effective diffusion coefficients of moisture were higher in samples dehydrated in the solar dryer when compared to those dried by exposure to the sun. Regarding the research conducted under the experimental conditions of this study, the performance of the solar dryer to dry Brazil nut processing residues was satisfactory.