초록 열기/닫기 버튼
In this study, we assessed the effect of freezing pretreatment on the quality of osmotically extracted syrup from Citrus junos peels. Sliced peels were frozen for 7 days at –20℃ or –70℃, mixed with sucrose and then stored for 40 days at 15℃. Syrups were prepared from these mixtures after osmotic treatment. Non-frozen fruits were used as control. The initial freezing point of C. junos peels was –4℃. Nominal freezing times were 42 and 13 min for –20℃ and –70℃, respectively. The osmotically extracted syrup from the frozen peels was reddish brown while that of the untreated peels was yellow. The titratable acidity of the pretreated syrups was significantly higher than that of the untreated syrup, but clarity, vitamin C content, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were considerably lower. The pretreated syrups showed no notable difference in color, titratable acidity, clarity, and DPPH activity. Furthermore, contents of soluble solids, phenolic compounds, and flavonoids were unaffected. These results suggest that freezing before osmotic extraction affects the quality, producing syrups with higher acidity, reddish brown color, and lower antioxidant activity.
