Moisture sorption isotherms and effects of temperature and relative humidity on degradation of polyphenols in instant assam green tea powder = ไอโซเทอร์มการดูดซับน้ำ และผลของอุณหภูมิและความชื้นสัมพัทธ์ที่มีต่อการเสื่อมสลายของสารโพลีฟีนอลในชาเขียวอัสสัมผง
- ผู้เขียน
ณัฐวุฒิ ตอนลาว
- เอกสารที่มา
วิทยานิพนธ์. (2008) 88 หน้า
หัวข้อ:
บทคัดย่อ
Moisture adsorption isotherms of instant Assam green tea powder were determined at 25, 35 and 45 °C. A water activity analyzer, Novasina® model LabMaster-aw, was used to determine the isotherms over the relative humidity range of 30-70%. The sorption isotherms of instant tea weretypical type III sigmoid curves, according the BET classification. Experimental data were fitted to various mathematical modess and it was found that Peleg model is most suitable to describe the equilibrium miisture content-equilibrium relative humidity (EMC-ERH) relatiionships of instant Assam green tea powder over the entire range of temperature. The net isosteric heat of sorption was determined by the Clausius-Clapeyron equation and was found to be between 45.2 and 45.6 kJ/mol at moisture levels varying between 0.05-0.25 g/g dry matter. MOreover, the effects of temperature and relative humidity during storage on degradation of total polyphenols int the tea product was stuied. The stability of polyphenols in instant Assam green tea powder was evaluated durin 20 days of storage at 40, 50 and 60 °C with varied relativehumidity levels of 0, 20 and 30 percent. The results showed that polyphenols in instant Assam green tea powder were stable during 20 days storage at all conditions. It was observed that the total phenolic content (TPC) of each treatment was not significantly affected (p≥0.05) by the storage time