Genetic variation in the extract viscosity of rye (Secale cereale L.) bread made from endosperm and wholemeal flour: impact of high-molecular-weight arabinoxylan, starch and protein

BACKGROUND: To verify the viscous potential of rye bread made from population and hybrid cultivars, the overall extract viscosities (EVs) of endosperm and wholemeal breads (EBs and WMBs respectively) were assessed using extractants of different pH. Also, arabinoxylan-dependent EV (AX-EV) was determined after combined action of starch- and protein-degrading enzymes. RESULTS: The synergistic effect of a combination of a-amylase, amyloglucosidase and protease on EV was almost two times higher than the effects observed after single addition of each of them. However, water-extractable arabinoxylans (WE AXs) were the major contributors to EV. Unexpectedly, a decrease in the mean WE AX contents observed in the following order, WMB (31.7 g kg(-1)) and EB (29.3 g kg(-1)) of hybrid rye and WMB (28.8 g kg(-1)) and EB (23.8 g kg(-1)) of population rye, was accompanied by an increase in their AX-EVs (12, 21, 21 and 29 mPa s respectively). CONCLUSION: In some cases the structure of WE AXs is a more important determinant of AX-EV than their content in rye bread. Nevertheless, both factors influence AX-EV, which may reflect the viscosity of the human small intestine after rye bread consumption, related to some beneficial metabolic effects. Therefore AX-EV can be a preliminary parameter for selection towards high-viscosity bread. (C) 2010 Society of Chemical Industry