Changes in some quality factors of frozen ginger as affected by the freezing storage conditions

Abstract The effects of types of ginger root, the freezing storage temperature and time on quality factors associated with color, off‐odor and acceptability of frozen ginger were evaluated to establish the freezing storage conditions of ginger roots. Whole and ground ginger was packed in Nylon/polyethylene (PE) bags and stored at −5, −20 and −40 °C. The quality of the ginger was determined at the following times and storage temperatures: the ginger stored at −5 °C, −20 °C, and −40 °C was sampled at 30‐day intervals for 4 months, at 90‐day intervals for 12 months, and at 120‐day intervals for 16 months, respectively. The content of free sugars, free amino acids (FAAs), unsaturated fatty acids (FUFAs) and volatile compounds noticeably decreased during the storage period, while the total color difference (Δ E ) increased, and the temperature effect was significant. The changes in these compounds were generally less in the whole ginger samples. The overall preference of ginger roots stored at −5, −20 and −40 °C was significantly different after 2–3, 9 and 16 months of storage, respectively. The increase of Δ E with decreases of free sugars, FAAs and sensory color indicated the discoloration of frozen ginger was due to the browning reaction. The sensory off‐odor scores were closely associated with the decrease of FUFAs, suggesting that the oxidation of FUFAs caused the development of off‐odor in the frozen ginger. Multiple regression analysis between the overall preference scores and other determined quality factors indicated that FAAs, FUFAs and volatile compounds significantly affected the overall preference scores of ground ginger samples stored at −5 °C or −20 °C. The sensory off‐odor and overall preference scores showed that whole ginger could be stored for 2 or 9 months at −5 or −20 °C, respectively, maintaining a good overall quality. Copyright © 2006 Society of Chemical Industry