Effects of Dual Pullulanase-Debranching and Temperature-Cycling Treatments on Physicochemical Properties and In Vitro Digestibility of Sago Starch and Its Application in Chinese Steamed Buns

Effects of dual pullulanase-debranching (PD) and temperature-cycling (TC) treatments on the physicochemical properties and in vitro digestibility of sago starch as well as its potential application in Chinese steamed buns (Mantou) is investigated. Sago starch is debranched using PD (30 pullulanase unit per g) for 0, 2, 4, 8, 16, and 24 h before subjecting to TC (4/30 degrees C, for 24 h each) for 3 cycles. The modified sago starch (MSS) obtained at the optimum conditions is used to replace wheat flour at 20%, 30%, and 40% for production of Mantou. All the MSS samples exhibit B-type crystalline pattern and have lower relative crystallinity than the native starch. The PD results in an increase in the relative crystallinity of the MSS. The 8 h PD followed by TC storage are the optimum conditions for producing MSS with the highest slowly digestible starch (10.76%) and the lowest rapidly digestible starch (81.61%) contents. The physical, textural, and sensorial properties of Mantou decreases with increasing substitution level of the MSS due to a reduction of gluten network and a detrimental effect of retrograded starch. However, the Mantou containing 20% MSS substitution is found to be acceptable based on the sensory evaluation.