Effects of adding farm-raised beluga sturgeon by-products on some physicochemical properties, sensory and shelf life of instant soup

Instant soup is a type of convenience food which is commercially produced for ease of consumption, portable and has a long shelf life. According to quick preparation and inexpensive, it becomes quite popular for people too short on time in the modern world. Instant dried soup powder is meat or vegetable-based product and generally constituted mixture of dehydrated cereals, vegetables and spices. However, interesting in consuming convenience foods has been received criticism due to lack of nutritive value and other health concerns. On the other hand, seafood industry generates great amount of edible wastes or by-products which can be highly perishable and needed to process in various value added products. Beluga or great sturgeon (Huso huso) is an endemic fish species of the Caspian Sea and extremely cultured for meat and caviar purposes in many countries in particular Iran. According to big size of farmed sturgeon, the fish fillet is commonly raw material for consumers, but unfortunately the wastes from the fillet producing and trimming are usually discarded or used for relatively low commercial value products (e.g. fishmeal and oil production). Treated fish waste described as an edible offal or edible by-product which can also be used for various value added products instead of being discarded and causes potential adverse environmental impacts. Fisheries products are highly perishable, while dried fish soup powder can be stored for a long time due to lower water activity. On the other hand, protein deficiency in some countries or low per capita consumption of seafood can be compensated by the production of a variety of fish products. The production of ready-to-eat soups from fish due to their high nutritional value can be considered as a healthy food among other instant foods. This study aimed to use farm-raised beluga sturgeon by-products in instant soup powder, as well as its shelf-life at ambient temperature for 120 days. At first, the fresh beluga fish wastes were processed and dried till lower 10% moisture. Then, the beluga fish powder at 0% (control; vegetable soup), 20%, 35%, 50%, and 65% was used in instant soup formulas to specify the best formula. Then, some physical properties (i.e. color, water activity, and water holding capacity) and chemical properties (i.e. proximate composition, pH, TVN, PV, TBARS, FFA, and fatty acids profile) were compared among the best formula fish soup and control. The highest overall acceptance score (4.70) was obtained in 50% beluga fish formula and selected as a best formula. After 4 months of storage, free fatty acid (8.87%), peroxide value (7.30 meq. O2/kg), thiobarbituric acid-reactive substances (0.1 mg of malondialdehyde in kg), and total volatile basic nitrogen (2.87 mg/100 g) was within the permitted ranges. Also, pH of vegetable soup (7.57) was lower than fish soup (7.82). Water activity was lower than 0.5 in both types of soup samples during storage. The amount of E in fish soup was changed from 1.21 at the begging of the experiment to 2.83 after 120 days. The results showed that fish soup is a good source of high unsaturated fatty acids, and their amounts were decreased during the storage time, especially eicosapentaenoic acid and dicosas hexanoic acid were decreased to 2.01% and 4.14%, respectively. The results of this study showed that the use of 50% of dried beluga sturgeon fish meat in the instant soup formulation received the highest sensory evaluation points compared to other formulas and was selected as the best formula. Study of changes in chemical indices showed that all the measured factors were in the allowed range after 4 months of storage under ambition condition. Also, water activity was lower than the critical level for the growth and activity of spoilage microorganisms. Increasing in the storage time led to a decrease in water holding capacity and whiteness of the fish soup. In addition, unsaturated fatty acids including oleic acid, linoleic acid, and linolenic acid were more susceptible to oxidation during storage, and decreased over the shelf-life. Therefore, fish soup with high protein content (55% in dry weight) and high unsaturated fatty acids has a high nutritional value and can provide an enriched instant soup with a high nutritional value and appropriate shelf life up to four months.