Effects of pulsed electric fields and thermal process treatments on quality and shelf life of orange juices

In this study, incremental PEF and heat pasteurization treatments were applied to orange juice samples obtained from Kozan Yerli variety and stored at +4 oC for 180 days. Effects of various processing treatments and their respective intensities on pectin methyl esterase inactivation, color, browning index, hydroxymethylfurfural (HMF), antioxidant activity, ascorbic acid, total phenolic and carotenoid compounds, phenolic and carotenoid complexes, mineral compounds and sensory characteristics of orange juice samples were measured. In addition, analyses were repeated over the storage period to study concentration changes in some compounds to determine the kinetics. Our results indicated that PME inactivation level was 93.82 % following PEF application with E8 (25.26 kV/cm, 1206.2 µs) energy level. PME activity of PEF applied samples decreased or not changed during storage while PME activity of heat pasteurized samples increased during storage. Ascorbic acid, total phenolic, carotenoid and browning index results of the PEF applied samples were better both at the beginning of the storage and at the end of the storage period. HMF was not detected in orange juice samples processed with PEF while it was detected in heat pasteurized samples. HMF increased during the storage period in heat pasteurized samples. Seven carotenoid compounds were determined in orange juice and the most abundant one was ß-cryptoxanthin and the concentrations of the carotenoid compounds decreased during storage. Twelve phenolic compounds were determined in orange juice and the most abundant one was chlorogenic acid while nineteen flavonoids were determined and the most abundant one was hesperedine. Phenolic compounds did not show any changes during storage. According to sensory analyses PEF applied orange juice samples were the most preferred samples at the beginning and at the end of the storage period.