Effect of bread structure on insulin index

Breads with different microstructure (starch granule structure and continuous matrix) and mechanical properties were baked with wholemeal oat, rye and wheat flour, rye endosperm flour, and wheat flour with added fermented wheat bran. 15-20 women with normal glucose tolerance were given samples of the test breads (50 g available carbohydrate) in random order. A fasting and 8 postprandial blood samples were collected at 15-30 min intervals for 3 hr. The reference sample was a normal wheat bread. Insulinaemic index (II) was defined as the postprandial incremental blood insulin area of the test product expressed as percentage of the corresponding value of the reference. The II of the different breads varied in the range 71.5-123.9 and the hardness of the breads in the range of 264-386 g. Correlation between hardness and II was -0.99, suggesting the important role of bread mechanical properties in II. Bread baked of endosperm rye flour gave lowest II (71.5) and was hardest (386 g). Its continuous phase was composed of starch granules. The texture and volume of whole-meal breads was improved by gluten addition. These breads were softer, more porous and had higher II. Of these breads, rye whole-meal bread gave lowest (97.8) and wheat wholemeal bread (123.9) highest II.