Investigation of physicochemical changes during maturation of fish marinade prepared at different acid and salt concentrations

Marinades are products with a limited shelf life that are ripened with acid and salt. Acetic acid and salt are used to delay the effects of bacteria and enzymes, and to improve the taste, texture and structural properties of fish meat. The edibility of marinades, which is called ripening, is the result of highly complex physicochemical changes. In this study, it is aimed to examine the physicochemical changes that occur during the ripening of the marinade and to explain the ripening mechanism. Rainbow trout (Oncorhynchus mykiss) was used as material in the study. Filleted fish were left in a marinade solution prepared at 4 different concentrations using table salt and acetic acid. These concentrations were established as follows: A=8% salt, 2% acetic acid; B=8% salt 4% acetic acid; C= 12% salt 2% acetic acid; D= 12% salt, 4% acetic acid. Fish were left into solutions at a ratio of 1 / 1.5 fish / solution and stored at 4°C. During the maturation of the marinade, both fish and solution samples were taken for 48 hours at 6-hour intervals and analyzed. Physicochemical changes during maturation were investigated by comparing with raw fish analyses. Salt determination, acidity determination and pH measurements were performed in both fish and solution, while cooking loss, color measurements, texture measurements free amino acid analysis and sensory analyzes were performed in fish meat. During the maturation of the marinade, acetic acid and salt penetrated the fish tissue, while their concentration in the meat increased, and their concentration in the solution decreased. The acidity level decreased rapidly in the solution of group A in the first 6 hours, and increased rapidly in fish meat. No significant change was observed in the following hours. Acidity level decreased rapidly in the first 12 hours in the solution of group B, and increased in the first 6 hours in fish meat. No significant change was observed in the following hours. While the change in acidity level in the solution of group C was not found statistically significant, it increased in the first 6 hours in fish meat, but no significant change was detected thereafter. In the solution of group D, it decreased after 6 hours and this value did not show a significant change until 30 hours. However, after the 30 hour, it showed a significant decrease. The acidity value in the fish meat of group D increased until the first 6 hours, and then no significant change was observed. Acidity levels in the solution and meat reached equilibrium in 24 hours in groups A and B, and in 30 hours in groups C and D. The salt level in the solution of all groups decreased rapidly in the first 6 hours, continued to decrease in the following hours, and increased significantly during the maturation process in fish meat. The amount of salt in the solution and meat reached equilibrium in 36 hours in groups A and D, and in 42 hours in groups B and C. During the maturation of the marinade, the pH values of the meat decreased, while the pH values of the solution increased. A sharp increase was observed in the pH values of groups A, B, C and D of the solutions in the first 6 hours during maturation. No significant changes were detected in pH values during the remaining maturation periods. While the lowest pH values in meat were determined in groups B and D, the highest pH values were determined in groups A and C. The highest cooking losses were determined in group A, and there was no significant difference between the other groups. There was an increase in the first 12 hours in groups A, B and C, and in the first 6 hours in group D, but no significant change was observed in the remaining hours. A significant increase was observed in the L* values of all groups in the first 6 hours during the maturation of the marinade. There was no significant change in L* values after the 6th hour of maturation. Among the groups, the highest L* values were determined in group B and the lowest values in group C. The a* value in raw fish, decreased significantly after being left in the marinade solution, and this decrease continued during the holding period in the marinade solution. The b* value in raw fish, increased significantly after being left in the marinade solution, and this increase continued during the holding period in the marinade solution. It was determined that the groups with 12% salt concentration had higher hardness values. The highest hardness values were reached after 36 h in A and D groups, and after 42 h B and C groups. The elasticity values decreased after 6 h and did not show a significant change in the following hours. No significant effect was found on the adherence, gumminess and chewiness values of the application groups and the waiting time in the marinade solution. While no significant effect of the application groups was observed on the elasticity of fish meat, it was determined that the waiting time in the solutions had a significant effect. There was no significant difference between the groups in terms of total free amino acid content and during maturation. After 30 hours, fish meat reached the appropriate texture for marinating in all groups. When the sensory color characteristics of fish meat were examined, the white color specific to the marinade was reached after 24 hours, and this white color did not change until 48 hours. According to the results of acidity and salt taste analysis carried out after the 24th hour, the typical acid taste of the marinade was reached in 30 hours, the salt taste in 36 hours in groups B and C, and in 42 hours in groups A and B. With these results, the changes in fish meat during the maturation process in marination have been scientifically proven and will guide the determination of appropriate concentrations for the production of marinades with the best sensory properties.