Grapefruit (Citrus paradisi) juice production and determination of quality parameters

In this study, grapefruit juice samples obtained from Marsh Seedless and Star Ruby varieties were pasteurized and stored at -25ºC for 6 months. During the storage, changes were examined in quality values. Effects of the pasteurization treatment on pectin methyl esterase (PME) inactivation, color, viscosity, browning index, hydroxymethylfurfural (HMF), antioxidant activity, ascorbic acid, total phenolic and carotenoid content, phenolic and carotenoid compounds, mineral compounds and sensory characteristics for different varieties of the grapefruit juices were measured. PME activity was not detected during the storage period on the pasteurized samples. In general, Marsh Seedless varieties had higher values for ascorbic acid, total phenolic content and viscosity measurements at the beginning of the storage and at the end of the storage period. While there was no significant effect on the browning index, the pasteurization treatment causes formation of HMF at ppb level. L and b values of both pasteurized samples were higher than the control group, however lower a values were observed. ?E values of Marsh Seedless varieties were 2.13 and 1.54 for 0 and 6 months of the storage, respectively while ?E values of Star Ruby varieties were 2.30 and 2.20, respectively. Three kinds of carotenoids were detected in grapefruit juice, ß-cryptoxanthin in Marsh Seedless, ß-carotene and lycopene in Star Ruby varieties. Eleven phenolic compounds were determined in the grapefruit juice and the most abundant one was chlorogenic acid while seventeen flavonoids were determined and the most abundant one was naringin. Generally, phenolic compounds did not change during the storage. There were no significant changes in sensory characteristics of the pasteurized grapefruit juice samples during storage. However, Star Ruby variety was the most preferred one.