Investigating physical factors and bioactive components that affect grain quality

Five containers of processed grains.
Dr. Marta S. Izydorczyk

Dr. Marta S. Izydorczyk
Research scientist/program manager
Milling and Malting / Research on Barley and other Grains
marta.izydorczyk@grainscanada.gc.ca

The Milling and Malting / Research on Barley and other Grains Program conducts research to identify, characterize, and quantify the factors and molecular mechanisms responsible for the quality, functionality and performance of Canadian barley and other grains, such as oats and buckwheat. We develop new technologies for measuring quality and explore innovative ways to use barley and other grains. We monitor the quality of barley destined for export, evaluate new barley lines and assess the quality of malting barley produced in western Canada.

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).

Results of our study
  • As germination time increased, the concentration of β-glucans in wort significantly decreased but the concentration of arabinoxylans increased (Figure 4).
  • The molecular mass of both β-glucans and arabinoxylans decreased significantly with increasing germination time (Figure 5).
  • Conditions favourable to the breakdown of β-glucans (high hydration, longer germination time) resulted in the β-glucans remaining in the wort having long polymeric chains that exhibit a relatively high ratio of cellotriosyl/cellotetraosyl units (DP3/DP4). These molecular properties likely contributed to the tendency of the chains to separate from wort if there is a change in solvent conditions such as temperature, sugar or alcohol concentrations, and shear forces.
  • Arabinoxylans that remained in wort resisted enzymatic hydrolysis due to their highly branched structure and the presence of other substituents along the xylan chains (ferulic acid residues).
  • Targeted hydrolysis of non-starch polysaccharides in wort revealed that the average molar mass of wort arabinoxylans was consistently higher than that of β-glucans (Figure 6).

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.

Table 1  Dehulling results for CS Camden and Summit in 2020 and 2021. The category of total groats includes whole and broken groats.
Total groats (%) Broken groats (%) Hulls (%) Hulled grain (%)
Cultivar Year Mean SDFootnote 1 Mean SD Mean SD Mean SD
CS Camden 2020 73.5 1.5 0.8 0.8 26.4 1.5 4.2 2.9
2021 71.8 1.9 1.9 1.2 27.9 1.9 5.1 3.0
Summit 2020 76.3 3.1 1.8 1.6 23.7 3.1 1.2 1.3
2021 74.8 1.7 2.5 1.2 25.2 1.7 1.1 0.6
Table 1 Notes
Footnote 1

SD = standard deviation

Return to footnote 1 referrer

Figure 1  Average kernel width, length and roundness in millimetres (mm) for CS Camden and Summit grown in 2020 and 2021. Number of samples equals 37 (CS Camden) and 25 (Summit).
Average kernel width, length and roundness in millimetres (mm) for CS Camden and Summit grown in 2020 and 2021. Number of samples equals 37 (CS Camden) and 25 (Summit).
Graph data
Cultivar Kernel width (mm) Kernel length (mm) Kernel roundness
Mean SDFootnote 2 Mean SD Mean SD
CS Camden 2.76 0.12 11.2 0.4 0.453 0.012
Summit 2.76 0.09 10.4 0.3 0.466 0.010
Table 2 Notes
Footnote 2

SD = standard deviation

Return to footnote 2 referrer

Figure 2  Scatter plot showing the relationship between thousand kernel weight in grams (g) and test weight in kilograms per hectolitre (kg/hL) for CS Camden and Summit grown in 2020 and 2021. Number of samples equals 37 (CS Camden) and 25 (Summit).
Scatter plot showing the relationship between thousand kernel weight in grams (g) and test weight in kilograms per hectolitre (kg/hL) for CS Camden and Summit grown in 2020 and 2021. Number of samples equals 37 (CS Camden) and 25 (Summit).
Graph data
CS Camden Summit
Thousand kernel weight (g) Test weight (kg/hL) Thousand kernel weight (g) Test weight (kg/hL)
31.1 51.0 31.5 51.4
34.1 51.2 29.8 51.8
33.9 51.4 30.5 52.0
32.5 51.4 31.2 52.0
34.8 51.8 33.9 53.0
32.8 52.4 31.7 53.0
36.7 53.4 39.2 53.6
33.4 53.6 31.0 54.8
35.9 53.6 35.8 55.0
37.3 54.8 35.9 55.6
38.9 54.8 36.7 56.1
34.9 55.0 34.5 56.3
36.7 56.1 30.5 48.4
40.5 56.3 30.4 51.0
42.3 57.3 29.9 51.0
40.4 58.3 30.5 52.2
30.0 48.0 30.9 53.0
30.5 48.0 33.0 53.0
28.7 48.0 29.7 53.0
33.3 48.2 32.8 53.2
33.5 49.6 36.5 53.4
33.2 49.6 35.8 54.8
30.7 49.8 33.7 55.9
35.6 51.0 32.5 55.9
35.7 51.0 34.8 57.7
33.5 51.0
32.7 51.0
33.2 51.2
34.0 51.4
31.7 51.8
37.8 53.0
36.1 53.0
31.9 53.4
38.2 53.6
33.5 54.0
29.0 54.2
32.7 56.3
Figure 3  Scatter plot showing the relationship between kernel length in millimetres (mm) and percentage of groats obtained after dehulling for CS Camden and Summit grown in 2020 and 2021.
Scatter plot showing the relationship between kernel length in millimetres (mm) and percentage of groats obtained after dehulling for CS Camden and Summit grown in 2020 and 2021.
Graph data
CS Camden Summit
Kernel length (mm) Groats (%) Kernel length (mm) Groats (%)
11.5 71.9 10.3 79.9
10.8 74.2 10.4 78.6
11.8 73.7 10.8 75.0
11.2 73.7 10.2 77.2
10.6 75.1 10.1 78.9
11.0 73.3 10.3 75.1
11.0 73.2 10.4 73.2
11.3 70.7 10.6 78.2
10.5 72.8 10.1 80.6
11.0 70.5 10.2 73.5
11.1 75.3 10.1 75.5
11.0 75.1 10.6 73.7
11.2 74.1 10.4 73.5
10.8 74.5 10.6 74.5
10.9 73.5 9.9 77.6
11.0 75.1 10.6 76.9
11.8 72.6 10.7 75.9
11.3 68.6 10.7 71.0
11.5 72.2 10.6 73.8
11.5 69.6 10.2 74.5
11.9 68.9 10.5 76.6
10.6 74.1 10.1 75.3
11.5 71.7 10.8 75.2
11.5 72.4 10.6 74.3
11.5 74.4
11.6 72.6
11.2 69.1
10.9 69.5
10.9 74.9
10.7 71.5
11.5 71.6
11.0 74.5
11.8 74.0
11.1 72.5
11.3 72.9
12.0 72.3
11.4 72.1
Figure 4  Effect of germination time on the concentration in milligrams per litre (mg/mL) of β-glucans and arabinoxylans (AX) in wort made from AAC Synergy. Time was measured in hours (h) and samples identified as G1 (24h), G2 (48h), G3 (72h), G4 (96h) and G5 (120h).
Graph showing effect of germination time on the concentration in milligrams per litre (mg/mL) of β-glucans and arabinoxylans (AX) in wort made from AAC Synergy. Time was measured in hours (h) and samples identified as G1 (24h), G2 (48h), G3 (72h), G4 (96h) and G5 (120h).
Graph data
Wort sample Beta-glucan (mg/L) Arabinoxylan (mg/L)
G1 1529 770
G2 612 1045
G3 150 1050
G4 79 1060
G5 60 1150
Figure 5  Effect of different germination time on the molar mass of non-starch polysaccharides (β-glucans and arabinoxylans) in wort. Time was measured in hours (h) and samples identified as G1 (24h), G2 (48h), G4 (96h) and G5 (120h).
Molecular weight distribution curves of wort samples G5, G4, G2 and G1.
Figure 6  The average molar mass (Daltons) of β-glucans and arabinoxylans in wort when barley was germinated for different lengths of time. Time was measured in hours (h) and samples identified as G1 (24h), G2 (48h), G4 (96h) and G5 (120h).
Graph showing the average molar mass (Daltons) of β-glucans and arabinoxylans in wort when barley was germinated for different lengths of time. Time was measured in hours (h) and samples identified as G1 (24h), G2 (48h), G4 (96h) and G5 (120h).
Graph data
Molar mass (Daltons)
Wort sample Beta-glucans Arabinoxylans
G1 179,000 162,000
G2 147,000 152,000
G3 41,000 179,000
G4 50,000 189,000
Team members

Research scientist/program manager

  • Dr. Marta S. Izydorczyk

Chemists

  • Tricia McMillan
  • Arzoo Sharma

Technicians

  • Anna Chepurna
  • Debby Kelly
  • Jerry Kletke
  • Cherianne McClure
  • Shin Nam
  • Shawn Parsons
  • Dave Turnock
Recent publications
  • Izydorczyk, M.S., Badea, A. and A.D. Beattie. 2022. Physicochemical properties and malting potential of new Canadian hulless barley genotypes. J Am Soc Brew Chem 81 (2): 299-307.
    https://doi.org/10.1080/03610470.2022.2065453
  • Chen, W., Cheung, H.Y.K., McMillan, M., Turkington, T.K., Izydorczyk, M.S. and T. Gräfenhan. 2022. Dynamics of indigenous epiphytic bacterial and fungal communities of barley grains through the commercial malting process in western Canada. CRFS 5: 1352-1364.
    https://doi.org/10.1016/j.crfs.2022.08.009
  • Izydorczyk, M.S. 2022 Sept. 21-25. Effects of grain hydration and germination time during malting on the molecular structure and mass of β-glucans and arabinoxylans in wort [abstract]. 23rd North American Barley Researchers Workshop, Davis, CA, USA.
  • Izydorczyk, M.S. and T. McMillan. Barley Harvest Annual Report 2022. Barley Production and Quality of Western Canadian Malting Barley.
    https://www.grainscanada.gc.ca/en/grain-research/export-quality/cereals/malting-barley/2022/
  • Izydorczyk, M.S., Kletke, J., Sharma, A., Chepurna, A. and S. Nam. 2022 Nov. 9-11. Effects of grain steaming on the milling performance and physicochemical properties of dietary fibre in hulless food barley [abstract]. Cereals & Grains 2022, Bloomington, MN, USA.
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