Investigation of the use of ph sensitive smart label developed using purple onion (Allium cepa L.) peel in determining the quality of rainbow trout (Oncorhynchus mykiss) stored under cold storage conditions

In this study, a pH-sensitive smart label was designed by immobilising anthocyanins obtained from purple onion peel on cellulose paper (Whatman no: 1 filter paper), a natural polymer, by absorption method. The labels were integrated into packages containing different parts of rainbow trout (Oncorhynchus mykiss Walbaum, 1792) fillet (K group: tail, O group: middle, B group: head) and stored under refrigerator conditions (4 ºC) by atmosphere packaging for 20 days. With the smart labels, it was aimed to be able to monitor the deterioration indicators and quality changes occurring in the fish groups during storage in real time in a fast and effective way. The quality changes that occurred in all fish groups during storage were evaluated by physical (in-pack gas measurement, color, aw, water loss of fish meat), chemical (pH, TVB-N) and microbiological (TMAB, TPAB, TYM, TC, lactic acid bacteria and Pseudomonas spp.) analyses, while the changes in the smart labels used in fish packages (ΔE, WI, RI and YI) were also determined. The data obtained from these analyses were evaluated together with sensory test scores (fresh and cooked). Significant increases were observed in TVB-N, pH value and TPAB, TMAB and Pseudomonas spp. counts of samples packed with atmospheric air during storage (p<0.05) and significant changes in indicator colors were detected accordingly. Significant decreases were observed in the odor and flavor scores of the fish samples and in the redness (a*) and WI values of the smart labels on the packages during storage (p<0.05). It was determined that the increases in the amount of CO2 in the packages of K, O and B groups were statistically significant (p<0.05). It was also found that there was a strong correlation between the color changes detected in the smart labels during storage and TVB-N, pH, TPAB results and odor scores (p<0.01). As a result of the analysis, it was determined that K group samples started to deteriorate on the 10th day, O group samples on the 11th day and B group samples on the 9th day, and the smart labels produced showed color changes according to the deterioration moments.