Abstract
In Japan, dried ginger is called shokyo, and ginger dried after soaked in hot water or steamed is called kankyo. The quality of processed ginger might be affected by the processing methods. Previously, we reported that the heating method used to process fresh ginger affected the color of the resultant product and how its color was correlated with its 6-shogaol to 6-gingerol ratio ([S/G]); i.e., the a* value (indicating redness) of steamed ginger positively correlated with its [S/G], the a* value of ginger soaked in hot water remained constant regardless of its [S/G], and the a* value of ginger heated at 180°C displayed a logarithmic correlation with [S/G]. In this paper, we used the above results to evaluate the quality of shokyo and kankyo products on the market.
As a result, we found that the a* values of most shokyo products logarithmically correlated with their [S/G]. However, shokyo products with whitish surfaces displayed a* values of less than + 2, and their a* values and [S/G] showed no correlations.
Meanwhile, kankyo products were divided into 3 groups by the relationships between the a* values and [S/G]; i.e., samples whose a* values correlated with their [S/G], those with a* values around + 9, and those with a* values less than + 8. These kankyo samples might be produced by steaming, soaking in hot water, and soaking in warm water, respectively. Therefore, we confirmed that the combination of color values and [S/G] could be used to infer processing methods of ginger products.
