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Abstract:

Wheat flour, water, yeast and salt are essential bread ingredients. The main biopolymers of wheat flour are the starch glucose polymers amylose and amylopectin, and the gluten proteins. During storage, bread becomes unacceptable for the consumer. It is generally accepted that crystallization of amylose during cooling and recrystallization or retrogradation of amylopectin during storage contribute to bread crumb texture and how it evolves in time, but it is also clear that these structural changes in the starch fraction alone cannot fully explain the crumb firming mechanism. Gluten is somehow involved in bread firming, and changes in water content and distribution due to moisture loss, moisture migration from crumb to crust and/or moisture redistribution between the different bread constituents are believed to further impact crumb firmness. Since water related phenomena are involved in crumb firming, the use of time domain (TD) proton Nuclear Magnetic Resonance (1H NMR) to assess bread aging holds promise in this respect. In this presentation, a profound view on the bread firming mechanism is proposed based on the use of TD 1H NMR to study water and biopolymer mobility in (stored) bread crumb. The proposed crumb firming mechanism was further verified by using several α-amylases, process and storage conditions.