Investigating of production conditions of pastilles by using gelatin extracted from kilika fish and investigating its physicochemical, rheological and sensory properties in comparison with commercial gelatin (cow)

Abstract

Materials and Methods: To compare physicochemical (pH, humidity, brix and water activity), texture properties (adhesiveness, cohesiveness, springiness, gumminess, chewiness, hardness and deformation of hardness), color indices (L*, a* and b*) and sensory (taste, odor, color, texture and overall acceptance) properties of pastille obtained from fish gelatin. The experiments were performed in a completely randomized design. In this study, 5 treatments with three repetitions were examined. In order to compare the means, Duncan's one-way analysis of variance was used at the 95% confidence level using Minitab software version 16. Results and Discussion: According to the results of gel formation temperature, gel melting temperature and gel melting time of fish gelatin were lower than commercial gelatin but gel formation time in fish gelatin was higher than commercial gelatin. Also, the extraction efficiency of gelatin from Kilka fish was 9.204%. Effect of different percentages of extracted fish gelatin on pH, moisture, brix, water activity, color indices (L*, a* and b*), texture properties (adhesiveness, cohesiveness, springiness and gumminess) and sensory evaluation (taste, odor, color, texture and overall acceptance) was significant (p>0.05). The results showed that by increasing the replacement of different percentages of fish gelatin, pH, Brix, L*, all textural histological and sensory evaluation factors decreased and moisture content, water activity and colors a* and b* increased. Differences in pH of gelatins may be due to the type and strength of acid used during the extraction process. Also, due to the replacement of fish with skin and bones in acid and due to having more minerals in the bones than fish meat, more acidic treatment is needed. Therefore, the difference in pH of fish gelatin and cow gelatin can be different depending on the extraction conditions and the type of fish. Hydrochlorothiazine gelatin is a protein that, at temperatures above 35 to 45 degrees Celsius, has a complex structure that dissolves in water and increases brix. The results showed that the amount of water activity of samples containing fish gelatin was higher than commercial gelatin, which could be due to the higher moisture content of gelatin extracted in fish and the extraction conditions and its use in the production of pastilles. The presence of Kilka fish gelatin in the pastel formulation caused the samples to get darken or turn red due to the increase in a * and b * indicators. The reason for the discoloration of the specimens can be due to the presence of carotenoids in the tissues of fish (tonagazantine (yellow), lutein (yellowish-green), beta-carotene (orange), duragazantine (yellow), zaxanthin (orange-yellow), Contagantine (red-orange), astaxanthin (red), and taragzantine (yellow)). The reason for the instability and poor rheological properties of fish gelatin compared to commercial gelatin is mainly related to the low number of proline-rich regions and low amounts of immunoassides (hydroxyproline and proline) in the collagen and gelatin molecules of fish compared to warm-blooded animals. The content of proline and hydroxyproline amino acids in fish gelatin is lower than in animal gelatin, such as pork, which exhibits better viscoelasticity. Therefore, they show weaker viscoelastic properties than commercial gelatin. In addition, fish gelatin contains less alanine, and this amino acid is commonly found in areas rich in proline and hydroxyproline. Most of these amino acids in commercial gelatin are one of the main reasons for their higher viscosity. The release of flavor is significantly related to the texture of the gel, and gelatin gels, due to the harder texture, release less flavor, which in turn reduces the overall acceptance score in samples containing high amounts of gelatin. Watman's filter paper, vacuum pump, ion exchange resin are commonly used to remove odors and derivatives, and vacuum evaporators are used to eliminate the unpleasant odor of fish in order to eliminate odors, dyes, unfavorable fish flavors, and unstressed collagen. However, the smell and taste of the remaining fish of the above methods reduce the sensory evaluation scores in treatments containing fish gelatin, and the main reason for the decrease in sensory evaluation scores in fish gelatins is the persistence of fish odor and taste in gelatin. T2 treatment (containing 50% fish gelatin + 50% commercial gelatin) was selected as superior treatment because of its proximity to control, physicochemical, rheological and sensory evaluation. In general, the results showed that using different percentages of gelatin extracted from Kilka fish had no adverse effect on the physicochemical and rheological properties of pastille and only sensory evaluation reduced due to the taste and odor of Kilka fish. The taste of pastilles produced covered the poor sensory evaluation properties of fish pastels produced from gelatin and used in industrial gelatin production.

Keywords

• pastille
• gelatin
• kilka fish
• commercial gelatin