Peel Browning of Mizu-Nasu Eggplant Pickles and Its Prevention Using Improved Technology

Abstract

During the Mizu-nasu eggplant pickling processing, there can be problems with the alum used to fix the eggplant's deep blue color. Primarily, browning can occur that alters the deep blue color of the eggplant. This study investigated the cause of pickle browning, and methods to improve pickle color. Minimal browning occurred on the side of the fruit closest to the stalk, or along the equator of fruit, which are areas where the anthocyanin levels are high. However, browning occurred more frequently at the fruit apex due to low anthocyanin levels after pickling. There was only ３ ５％ penetration of aluminum ion(Al ３＋ )in the fruit peel in areas where browning occurred. Several methods were tested to improve the penetration of the color-fixing agent. Scraping the eggplant surface with rice hull before pickling increased penetration of the color-fixing agent into the fruit peel, thereby, suppressing browning. Thus, peel scraping with rice hull before pickling seems to be suitable for the suppression of browning and improving the color stability of Mizu-nasu eggplant pickles.