This study was conducted to determine the optimal hydrothermal pretreatment conditions for manufacturing processed ginger products. Ginger slices heated at different temperatures (60-100°C for 1 h) for varying durations (1-5 h at 80°C) were compared in terms of their physiochemical properties, antioxidant activities, and functional compound contents. The pH and soluble solid content decreased with increasing hydrothermal treatment temperature. Browning occurred at temperatures > 80°C. The 2,2-diphenyl-1-picrahydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging were highest after heating at 80°C for 1 h, and the total phenolic compound content showed a similar trend. As the hydrothermal treatment temperature and duration increased, the 6-gingerol content decreased and the 6-shogaol content generally increased. Based on sensory testing of ginger jeonggwa (with sugar syrup) prepared using hot water-treated ginger slices, the optimal hot water treatments were conducted at 70 and 80°C for 1 h, with no significant difference between these temperatures in terms of smell, taste, and texture. Therefore, hydrothermal treatment of ginger at 70-80°C for 1 h was a suitable to improve the functionality and antioxidant ability while maintaining the sensory quality. Therefore, this may be used in the production of processed ginger.

In this study the physicochemical properties and antioxidant capacities of ginger (Zingiber officinale Rosc) Jungkwa with different kinds of sweeteners were determined. Jungkwa made with different sugars (sugar, xylitol, honey or oligosaccharides) were compared in aspect of physiochemical properties, antioxidant activities, total phenolic contents and sensory evaluation. Moisture contents Jungkwa treated different kinds of oligosaccarides showed highest value, in the order of honey, xylitol and sugar. L* value of Jungkwa treated with xylitol was the highest, a* value of Jungkwa treated with honey, sugar Jungkwa were higher then others. Free sugar contents of Jungkwa treated with sugar showed the highest value in sucrose, glucose and galactose. Jungkwa with xylitol showed lowest value in all free sugar contents. Hardness and chewiness of Jungkwa treated with xylitol showed the highest value. The antioxidant activity measured by DPPH and ABTS radical scavenging activity and total penolic content were the highest in Jungkwa treated with honey, followed by Jungkwa treated with xylitol, oligosaccharides and sugar. Appearance and color of oligosaccarides and honey treated Jungkwa were preferred. In ginger taste, sweetness, chewiness were highest in sugar treated Jungkwa (not significant difference in treatments). As a result, honey treated Jungkwa has higher antioxidant activity and quality than other sugar treatments.