Structure and Dynamics of Wheat Starch in Breads Fortified with Polyphenols and Pectin: an ESEM and Solid-State CP/MAS 13C NMR Spectroscopic Study

Two sets of breads formulated with a 20% difference in water quantity in the absence (control bread), or presence (fortified bread) of high methoxyl pectin (HM) and an apple, kiwifruit, or blackcurrant polyphenol (PP) extract (APE, KPE or BPE) were examined by Environmental Scanning Electron Microscopy (ESEM) and Cross Polarization/Magic Angle Spinning 13C NMR Spectroscopy. ESEM revealed that all the bread doughs had similar microstructures, comprising starch granules and yeast cells embedded in a continuous gluten matrix. However, the microstructure of the finished breads differed. NMR studies revealed differences in amylopectin-related crystalline domains and the amylose-related amorphous domains among the breads. All the breads showed V-type or amorphous starch structures by NMR, and the control bread may also contain some A-type starch. Breads formulated with 20% extra water showed a greater degree of starch gelatinization, a smoother crumb microstructure, and a lower amorphous starch content. It is feasible to incorporate PPs and pectin in breads at reasonably high concentrations.