Effects of Stir-Frying and Heat–Moisture Treatment on the Physicochemical Quality of Glutinous Rice Flour for Making Taopian, a Traditional Chinese Pastry

Abstract

Taopian is a traditional Chinese pastry made from cooked glutinous rice flour. The effects of heat–moisture treatment (110 °C, 4 h; moisture contents 12–36%, w/w) on the preparation of cooked glutinous rice flour and taopian made from it were compared with the traditional method of stir-frying (180 °C, 30 s). The color of heat–moisture-treated (HMT) flours was darker. HMT flours exhibited a larger mean particle size (89.5–124 μm) and a greater relative crystallinity of starch (23.08–42.92%) and mass fractal dimension (1.77–2.28). The flours exhibited water activity in the range of 0.589–0.631. Although the oil-binding capacity of HMT flours was largely comparable to that of stir-fried flours, HMT flours exhibited a lower water absorption index. Accordingly, the taopian produced with HMT flours exhibited a lower brightness, accompanied by a stronger reddening and yellowing. In addition, more firmly bound water was observed in the taopian produced with HMT flour. The taopian made with HMT flour with a moisture content of 24% exhibited moderate hardness, adhesiveness and cohesiveness and received the highest score for overall acceptability (6.80). These results may be helpful to improve the quality of taopian by applying heat–moisture treatment in the preparation of cooked glutinous rice flour.