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Influence of vacuum mixing on textural properties and protein structure of noodle dough.
R. LIU (1), Y. q. Zhang (1), L. Wu (1), B. Zhang (1), Y. m. Wei (1). (1) Chinese Academy of Agricultural Sciences/ Key Laboratory of Agro-Products Processing, Ministry of Agriculture, Beijing, , China

The effects of vacuum mixing for noodle dough on textural properties and protein structure were investigated using three wheat cultivars. Dough produced from three flours with vacuum mixing, when sheeted all gave higher levels of adhesiveness, elasticity and chewiness than from non-vacuum mixing. The optimum vacuum applied during mixing was judged to be 0.06MPa for the samples of Ningchun4 and Jimai22, and 0.08MPa for sample of Zhengmai366 which had higher protein content and stronger dough properties. Compared to non-vacuum mixed samples, the sheeted dough at 0.06MPa showed a more continuous and compact internal structure with fewer hollows as well as a more even protein distribution in the surface, as shown in SEM and FTIR micro-imaging. However, extremely high degree of vacuum was detrimental to the developed dough network for Jimai22 and Ningchun4. The degree of polymerization of protein was higher in vacuum mixed dough, as evident by SE-HPLC, GMP and free -SH contents. The more large protein aggregates was observed at 0.06MPa in Jimai22 dough, while 0.08MPa for Zhengmai366. Better dough texture might correspond to the increased protein aggregates. SDS-PAGE showed that vacuum mixing did not affect the protein subunits. Vacuum mixing at 0.06MPa imparted an increase in β-turn of Jimai22 dough at the cost of a reduction in β-sheets, while induced an increase in α-helix at the cost of a decrease in β-turn for Ningchun4 and Zhengmai366. Wheat flours with different protein characteristics behaved differently. High vacuum degree (0.08MPa) may result in the rupture of some large glutenin polymers in dough of weak-gluten flour, while increased the degree of polymerization of protein and induced more ordered secondary structure in dough of high- and strong- gluten flour. The development of the gluten network for weak gluten flour was more sensitive to the degree of vacuum.

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