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The aim of this study was to produce protein isolates from rainbow trout (Oncorhynchus mykiss) and to investigate its nutritional, structural, functional and sensory properties. Fish protein isolates were produced by pH change method using alkaline and acidic pHs (2.5, 3.5, 11 and 11.5). The extracted proteins were evaluated for nutritional value, and functional properties, sensory properties, color, and structural changes of proteins. The extracted proteins showed relatively high nutritional value in the amount of essential amino acids. The solubility, gelling and foaming capacity of the proteins depended significantly on its extraction pH. So that the percentage of solubility and foaming capacity of proteins extracted under alkaline conditions showed a higher rate than acidic conditions while the least gelation concentration was related to pH 11.5. Examination and comparison of color (L, a, b and whiteness) and sensory properties of isolated proteins showed that proteins at acidic pH had a brighter and whiter color and better sensory properties than those from alkaline pH. The change in pH caused extensive protein degradation as shown by FTIR and SEM. The above results showed that the protein isolated from rainbow trout waste has good functional and nutritional properties in alkaline conditions, while the sensory properties and color of acidic conditions showed better results.

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The purpose of this study is to investigate the ability of smart scaffolds of Kappa-carrageenan (Carr) and the combination of Kappa-carrageenan and quince seed mucilage (Carr:Quc) to support C2C12 viability and growth for cultured meat production. Carr and Carr:Quc with a final concentration of 1.5% (v/w) were developed using a 5% potassium chloride solution. The capability of the scaffolds to respond to the pH change of the environment was evaluated, and the viability of C2C12 at normal pH (7.4) and varying pH levels (7.4-5.5) was assessed. The evaluation of swelling changes with varying pH (pH 1-7) showed that for the Carr scaffold, the highest swelling was observed at pH 5, reaching 145%, which showed a significant difference compared to swelling at other pH levels (p < 0.05). The highest swelling for the Carr:Quc scaffold was also observed at pH 5, reaching 428%, with a significant difference compared to swelling at other pH levels (p < 0.05). Moreover, the change in the swelling behavior of the scaffolds was evaluated by changing the pH from 7.4 to 5.5. Carr did not show any swelling change, while Carr:Quc demonstrated a significant change in swelling after exposure to pH 5.5 for 30, 45, 60, 180, and 360 min. On Carr:Quc, C2C12 showed higher viability in normal conditions compared to varying pH levels from 7.4 to 5.5. Furthermore, after culturing on Carr:Quc, C2C12 maintained their viability throughout the culture period for 15 days at pH 7.4 and showed the potential for spheroid formation. The findings of this study could pave the way for the design of scaffolds made of edible biopolymers to facilitate tissue engineering of cultured meat