Impact of Apple Cold Storage on the Physicochemical and Bioactive Quality of Juice

This study compared the quality and bioactive composition of cloudy apple juices produced from four traditional and four conventional apple cultivars immediately after harvest and following cold storage of the fruit at 4 °C for three and six months. Apples were harvested at the ripening stage at the same criteria, stored as whole fruit, and processed into cloudy juice after harvest, three, and six months of storage. Physicochemical parameters and sugar composition were determined, while phenolic compounds were quantified by HPLC-PDA. Antioxidant activity, total phenolic, and flavonoid content were measured spectrophotometrically. All analyses were performed in technical triplicate. The results revealed notable differences between traditional and conventional cultivars. Juices produced from traditional apple cultivars exhibited significantly higher total polyphenol and flavonoid contents than those from conventional cultivars. Significant variations in catechin, myricetin, quercetin, and epigallocatechin levels were also observed among cultivars. The traditional apple cultivar ‘Mašanka’ showed higher concentrations of quercetin (0.09 ± 0.01 µg/mL), chlorogenic acid (486.58 ± 5.48 µg/mL), catechin (8.76 ± 0.54 µg/mL), epicatechin (20.22 ± 0.20 µg/mL), and phloridzin (13.48 ± 0.19 µg/mL) compared to the other cultivars. In contrast, conventional cultivars showed higher concentrations of myricetin and procyanidin B1. Moreover, the content of TA, sucrose, and glucose decreased, whereas pH, fructose, TSS (except for ‘Fuji’ and ‘Granny Smith’) increased. The TFC decreased in traditional apple cultivars, while it increased in conventional cultivars; however, the TFC in conventional cultivars remained lower than in traditional ones. Overall, these findings demonstrate that the cold storage of apples significantly affects juice composition and highlight the advantages of traditional apple cultivars for producing juices with enhanced phenolic content and antioxidant activity.