Effect of sprouting conditions on the properties of direct expanded extruded wheat

Abstract

The present study investigates the use of flour from sprouted wheat for the production of extruded, directly expanded products. Until now, studies on the use of sprouted material in extrusion have not been concerned with differences in the sprouted material. This contribution documents the first attempt to study the effect of the variation of the sprouting process on extrudate properties. Extrudates were produced at standard conditions using material produced by the variation of sprouting times (steeped, 1, 3, 5, 7, and 9 days sprouted). It was found that an increasing duration of the sprouting process also increases the starch degradation and hence sugar generation. During this process, vitamin C levels showed an increase of up to 10-fold. The accompanying changes in viscosity propagate systematically into different observations. With increased starch degradation back pressures in the extrusion die were reduced, extrudates show less sectional expansion, but densities were decreased because longitudinal expansion was increased significantly. The extrudates made with sprouted material were preferred during sensory assessment.The degree of sprouting, which was defined earlier proved to be a useful property to characterize the progress of the sprouting process and correlated well with changes observed for the sprouted flour and extrudate properties. Practical applicationThe use of sprouted wheat in the production of direct expanded extrudates is a promising opportunity to change and improve extrudate properties. On the one hand, the nutritional value of the extrudates is improved due to the use of sprouted wheat flour which contains newly synthesized vitamins, more essential amino acids, and a decreased phytic acid content. On the other hand, the texture of the extrudates is improved and less additives are needed in the production. Due to the starch degradation in the sprouting process short-chain sugars were formed, which naturally increase the sweetness of the extrudates.

Effect of sprouting temperature on selected properties of wheat flour and direct expanded extrudates

“…Combining the results presented here with earlier work of ours (Krapf, Arysanto, et al, ) it appears that optimization of sprouting time at a given temperature or optimization of the sprouting temperature at a given time yield similar extrudate properties. The methodical investigation of this and previous studies on the sprouting process have resulted and very valuable insights that can be useful in developing products from sprouted grain.…”

“…Compared to another study of ours (Krapf, Arysanto, et al, ), where the effect of the sprouting time was investigated, the results presented here reveal a similar effect of advantageous sprouting temperatures and long sprouting times.…”

“…These sprouted wheat grains were milled and the resulting flours were used for the production of extrudates. Studying the properties of the extrudates allowed their correlation with the DoS (Krapf, Arysanto, Walther, & Flöter, ).…”

“…Extrudate properties considered in this study are expansion, density, hardness, and the cold‐water solubility index. Additionally, the effect of the sprouting time that was studied previously (Krapf, Arysanto, et al, ) and the temperature effect on extrudate properties were compared to be presented in a more comprehensive way.…”

“…Moreover, the influence of sprouting time on the properties of extrudates produced from flour of sprouted wheat grains was studied by sprouting wheat for different sprouting durations at 20 C. These sprouted wheat grains were milled and the resulting flours were used for the production of extrudates. Studying the properties of the extrudates allowed their correlation with the DoS (Krapf, Arysanto, Walther, & Flöter, 2019).…”