The aim of this study is to investigate the effects of combined drying conditions on the quality characteristics of lotus root chips. A combined drying was conducted using the superheated steam (SHS) at 220°C for 6 min, then subsequent contact drying at 150°C for specified times (2, 4 or 6 min) and finally hot air at specified temperatures (50, 60 or 70°C) for 1 hr. Changes in appearance of lotus root chips such as surface color, shrinkage and deformed shape were resulted from the extent of time and temperature of post-drying conditions. Moisture content of lotus root chips decreased with increasing the time and temperature of post-drying process. Surface color of lotus root chips was determined mainly by the contact drying step of a combined drying process. Polyphenol content was influenced by the temperature of hot air rather than the duration of contact drying. Meanwhile hardness of lotus root chips decreased significantly with increasing the duration of contact drying. These results suggested that a combined drying process with appropriate processing conditions could be applicable successfully for the manufacturing of un-fried lotus root chips.

Physicochemical properties of buckwheat roasted at specified temperatures (175, 200, 225 and 250°C) and times (5 and 10 min) were investigated. Appearance of roasted buckwheat showed that non-enzymatic browning reaction occurred mainly at the embryo due to the presence of sugars and proteins. Microstructure of roasted buckwheat showed the formation of air cells inside the endosperm indicating the expansion of grain during roasting. Rapid Visco Analyzer profiles revealed that the extent of starch gelatinization was depending preferentially upon the roasting time rather than temperature. Total polyphenol and flavonoid content in roasted buckwheat were not significantly different from those of unroasted grains, although polyphenols and flavonoids in ethanol extracts increased slightly after roasting. Antioxidant activities of buckwheat increased after roasting.