Examination of the Mechanical Properties of Puffed Cereals

Abstract

The objective of this study was to elucidate the mechanical properties of four kinds of puffed cereals and to establish an efficient method to measure them. The characteristics of puffed cereals were compared with those of brown rice, adlay, barley, and amaranth, which were puffed by heat processing at pressures ranging between 0.1 and 1.1 MPa. The rupture properties, chromaticity, and moisture content of puffed cereals were determined, and the microstructure of the grains was also observed. To study the rupture properties, grains were subjected to four different compression speeds.

By analysing the microstructure of grain cross-sections and the mechanical properties of puffed cereals, the suitable processing pressure was found to be 0.9 MPa for brown rice, adlay, and amaranth, and 1.1 MPa for barley. In addition, this study suggested that the factors that prevent the swelling of cereals include its high lipid content and its thick exodermis.

Overall, force-deformation curves for the four kinds of puffed cereals showed that the rupture strain increased, while the apparent elastic modulus decreased with increasing compression speed.

Finally, we showed that a single compression with a plunger of 40 mm diameter, and a compression speed of 0.1 or 1.0 mm/s were suitable for effectively measuring the mechanical properties of puffed cereals.