Effect of spelt flour addition on expansion ratio and bulk density
of extrudates is shown in Fig. 1. With addition of spelt flour
expansion ratio of extrudates decreased. While influence of 5% and
10% addition wasn’t so marked, 20%-addition of spelt flour significantly
decreased expansion of extrudates. Addition of the common
bean flour to corn starch-based extruded snacks also decreased
expansion of obtained products (Anton et␣al., 2009). Furthermore,
Pastor-Cavada et␣al. (2011) observed that the addition of legumes
produces a decrease of expansion in both rice- and corn-containing
samples. Many other authors observed that with replacement of
corn grits with other ingredients, which have higher content of
fiber and protein, caused the reduction of expansion rate
(Ainsworth et␣al., 2007; Brncic et␣al., 2008; Jozinovic et␣al., 2012;
Sacchetti et␣al., 2004; Veronica et␣al., 2006). Explanation for this
is in interaction of these components with starch, and besides that
fiber can rupture cell walls and prevent air bubbles from expanding
to their maximum potential (Anton et␣al., 2009).