Investigating physical factors and bioactive components that affect grain quality

The effect of kernel shape on test weight and dehulling of oats

We recently conducted a study to understand how physical factors affect test weight and the dehulling performance of two oat cultivars commonly grown in western Canada: Summit and CS Camden.

A comparison of Summit and CS Camden oats from 2020 and 2021 showed that they had similar kernel widths but that Summit kernels were shorter in length, giving them a smaller and more rounded shape (Figure 1). Although the smaller size of Summit kernels coincided with lower kernel weights, Summit tended to show a higher test weight than CS Camden when equivalent weights were compared (Figure 2). This suggests that the smaller and rounder kernels of Summit can pack more efficiently than those of CS Camden. The elongated shape of CS Camden kernels results in longer hulls that are more likely to trap air when they overlap, leading to a lower packing efficiency and lower test weight.

Kernel shape was also found to affect the dehulling performance of Summit and CS Camden. The shorter and rounder kernels of Summit oats resulted in a greater percentage of groats after dehulling than CS Camden (Figure 3). Although the longer hulls of CS Camden kernels seemed to protect the groats from breakage during dehulling, they also resulted in fewer hulled kernels (Table 1). The groats of CS Camden were, however, slightly larger than those of Summit and groat density was also higher for CS Camden. We found no significant differences in the content of proteins and oil between the two types of groats, but CS Camden contained more β-glucans and less arabinoxylans than Summit.

Influence of germination time on the structure and mass of β-glucans and arabinoxylan in wort

In another recent study, we investigated the effects of germination time on the concentration, molecular mass and structure of β-glucans and arabinoxylans in wort. These compounds are the main types of non-starch polysaccharides found in the cell walls of barley grains. During malting, the controlled germination process breaks them down. If β-glucans are not sufficiently degraded, however, they can affect the brewing process and quality of beer by increasing viscosity, forming gels, and contributing to haze. The role and exact mechanism of how arabinoxylans contribute to these phenomena are not fully understood. We took samples of several different varieties of Canadian covered and hulless barley and steeped them at 13°C for 48 hours (h) and germinated them at 15°C. Five different germination times were compared: 24h (G1), 48h (G2), 72h (G3), 96h (G4), and 120h (G5).

Conclusions

Our study showed that increasing germination time can effectively reduce the content and molar mass of β-glucans in wort, but the length of germination time needs to be optimized to avoid excessive solubilization of arabinoxylans during malting and mashing.