Effect of superheated steam and hot water spray treatment on polyphenol oxidase activity in sweet potato leaves
2016
Sasaki, K. (Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, Koshi, Kumamoto (Japan)) | Sotome, I. | Okadome, H. | Kai, Y. | Oki, T. | Okuno, S.
In this study, a newly developed heating system, which consisted of superheated steam and hot water spray (Aqua-gas) treatment, was applied to sweet potato leaves. Upon initiation of Aqua-gas treatment, the internal temperature of sweet potato leaves was immediately increased, and reached 95degC in 30 seconds. Notably, polyphenol oxidase (PPO) activity was not deactivated by short-term Aqua-gas treatment, while 5-minute treatment almost completely inactivated PPO activity. Moreover, the amounts of caffeic acid and 7 species of caffeoylquinic acids (CQAs) in sweet potato leaves after Aqua-gas treatment were significantly higher compared to leaves subjected to boiling treatment. Therefore, we propose that Aqua-gas treatment is a useful heating system to maintain the nutritional components such as CQAs.
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