Metabolic Responses to Starch in Bread Containing Intact Kernels Versus Milled Flour

In the present study, the potential of including intact kernels from different cereals was evaluated as a means of developing bread with 'lente' characteristics. Postprandial glucose and insulin responses to bread products were studied in healthy subjects. In parallel, the in-vitro enzymic starch availability was investigated. Also studied were the contents of in-vitro indigestible starch. Coarse bread (CB) products composed of 80% pre-boiled kernels from wheat, rye, oats or barley and 20% white wheat flour were baked. In the case of barley, two forms for pre-treatments was used, boiling and scalding. A bread with 80% wholemeal barley flour and 20% white wheat flour (WMB) was also included and a white wheat bread (WWB) was used as reference. The glycaemic and insulinaemic indexes (GI and II, respectively) were calculated from the 95 and 120 min incremental blood glucose and insulin areas. The GIs were significantly lower with CB from wheat, rye and barley than with WWB. In contrast, the GIs with CB from oats and WMB from barley were similar to that with WWB. The GIs and IIs were generally closely correlated. However, the II with CB from oats was significantly lower than with WWB despite similar GI. The GIs, and in particular IIs, were closely correlated with the hydrolysis rate index (HI) obtained in vitro, and this procedure can be recommended as a tool for ranking of starchy food. It is concluded that the botanical structure is an important determinant of the enzymic availability and hence of the metabolic responses. The in-vitro indigestible starch content was highest in CB from barley (1.2% dry weight basis) and lowest in CB from oats (0.5%).