Studies Of Evaluation And Mechanism Of Hydroxypropylmethylcellulose Addition Affecting Performance Of Frozen Dough

Improving performance of frozen dough is meaningful for indusrial-scale production of Chinese steamed bread (CSB). The objective of this study was to evaluate the effect of Hydroxypropylmethylcellulose (HPMC) addition level (0.5%,1%, and 2%) on processing properties of frozen dough and quality of CSB. In addition, the methodology of fractionation and reconstitution experiment provide insight into the function of separated ingredients of dough system at impacting quality of CSB, therefore, the effect of HPMC addition on structure and properties of such three main fractions as wheat gluten, wheat starch, and yeast was investigated.The results revealed HPMC addition improved both mixing and extensional properties of dough, moreover, stabilized viscoelastic properties of dough during frozen storage which was subjected to dynamic frequence sweep. Compared with the control, specified volume and springiness of CSB with 2% HPMC significantly increased, but hardness dropped for the same frozen storage.Wheat gluten is critical for formation of dough network. The results of Differential Scanning Calorimetry and Time-Domain NMR showed HPMC addition could suppress growth of freezable water and transition of water state from the confined to the free, which meanwhile inhibited the recrystallization. Furthermore, compared to the control, HPMC addition kept conformation and microstraucture of wheat gluten stable in accordance with determination of free sulfydryl content and observation of scanning electron microscopy (SEM).Wheat starch is primary dry matter within dough system. X-Ray Diffraction graph suggested relative crystallinity and pasting enthalpy of starch increased, but swelling power decreased, as frozen storage prolonged. However, this trend weakened with HPMC addition, especially with 2%.Yeast palys a particular role in affecting quality of CSB. The results indicated that HPMC addition could protect yeast cells from damage of ice crystals, and remain fermentation vitality of yeast, and meantime, reduce growth rate of glutathione outside of cells.Therefore, it was concluded that HPMC could be applied as an effective cryoprotectant in practice to improve performance of frozen dough and quality of CSB.