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Water Self-Diffusion Coefficient and Staling of White Bread as Affected by Glycerol

¹Department of Food Science, University of Massachusetts, Amherst, MA 01003. ²Current address: Department of Food Science and Technology, Kyung Hee University, Yongin, Kyunggido, South Korea. ³Corresponding author. Phone: 413-545-1025. Fax: 413-545-1262. E-mail: pavinee_chinachoti@hillspet.com. ⁴Current address: Hills Pet Nutrition, Topeka, KS.

Water self-diffusion coefficient (D) was investigated in bread crumb during storage to determine the effect of moisture loss and glycerol on the staling mechanism. D increased with added glycerol in breads of the same moisture content. D remained unchanged after storage without crust (with no moisture loss from crumb to crust). When stored with crust (with moisture loss), more mobile water was lost (probably from glycerol), resulting in a more rapid initial decrease in D in glycerol-added bread. Competition of water may be a key influencing factor. Glycerol and loss of moisture (according to crumb-crust moisture gradient) triggered a shift in moisture redistribution from starch and gluten to glycerol. This could have contributed to the increased structural rigidity and more rapid firming of the glycerol-added bread. As a result, a greater firming rate was observed in glycerol-added bread even with less amylopectin recrystallization as compared with the control.