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Effect of Wheat Maturity and Post-Harvest Temperature Treatments on the Quality of Grain and End-Products.

Lukow, O.M., Suchy, J., Adams, K., Brown, P.D., DePauw, R.M., Fox, S.L., Humphreys, D.G., McCaig, T.N., and White, N.D.G. (2011). "Effect of Wheat Maturity and Post-Harvest Temperature Treatments on the Quality of Grain and End-Products.", Journal of Agro Crop Science, 2(2), pp. 15-22.


Harvesting wheat in a physiologically immature stage, combined with frequent frosts in Canada, poses challenges to farmers and grain processors. The aim of this study was to examine the effect of harvesting immature wheat under normal and freezing temperatures on wheat quality. Six cultivars with a wide range of quality were grown in a randomized design. Samples were harvested weekly, starting one week past anthesis (WPA), until physiological maturity. One-half of the harvested wheat was immediately frozen to -18°C and the other half was air-dried at ambient temperature. Wheat harvested at 4 to 6 WPA was chosen for further quality evaluation. Grain quality was assessed for colour, hardness, weight, diameter, protein content and protein composition. Flour quality was evaluated for colour and rheological properties by farinograph. End-product quality was evaluated by small-scale pan bread and small-scale tortilla baking tests. Grain and flour colour depended strongly on the maturity level of wheat at the time of harvest and post-harvest thermal treatment. Generally, immature (4 WPA) grain showed inferior quality (darker colour and harder grain) when compared to mature grain. When immature wheat was combined with a freezing treatment, additional deterioration in grain, flour and end-product quality was observed. Freezing of the grain at the immature stage resulted in darker grain and flour colour, inferior farinograph dough development time and farinograph stability, lower loaf volume and some inferior bread characteristics. Freezing of immature wheat halted development of polymeric protein and is likely the explanation for some of the observed flour and end-product quality defects.

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