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Effect of Mixing Time on Gluten Recovered by Ultracentrifugation Studied by Microscopy and Rheological Measurements

¹Department of Crop Science, The Swedish University of Agricultural Sciences, PO Box 44, SE-230 53 Alnarp, Sweden. ²Corresponding author. Phone: +46 40 415563. Fax: +46 40 415519. E-mail: Ramune.Kuktaite@vv.slu.se ³Department of Food Technology, Lund University, PO Box 124, SE-221 00 Lund, Sweden.

The effect of mixing time on gluten formation was studied for four commercial flour mixtures. The gluten phase was separated from dough using a nondestructive ultracentrifugation method. Small deformation dynamic rheological measurements and light and scanning electron microscopy were used. The recovered gluten was relatively pure with a small amount of starch granules embedded. The protein matrix observed by microscopy became smoother with prolonged mixing. No effect of overmixing was observed on the storage modulus (G′) of gluten for any of the flours. The amount of water in gluten increased from optimum to over-mixing for most of the flours. Increased water content during prolonged mixing was not related to an effect on G′. The Standard flour resulted in the highest water content of gluten, which increased considerably with mixing time. The Strong flour had the lowest G′ of dough, a high G′ of gluten, and no increase in gluten water content from optimum to over-mixing. The Durum flour did not show gluten development and breakdown similar to the other flours. The differences in gluten protein network formation during dough mixing are genetically determined and depend on the flour type.