Frost/heatstress damage (FRHTS)
Frost/heatstress is defined in the wheat section of the Official Grain Grading Guide as wheat kernels with blistered brans as a result of exposure to freezing temperatures or prolonged hot weather conditions.
Procedure for assessment
Frost/heatstress (FRHTS) is reported in our grading system without differentiating the factor, since frost and heatstress are visually indistinguishable and have the same detrimental effects on quality.
Frost/heatstress damaged kernels in a sample are considered a subjective grading factor. The overall soundness of the sample is taken into consideration and compared to the standard or guide sample.
The damage is as a result of exposure to freezing temperatures or prolonged hot weather conditions. The degree of blistering is dependent upon the maturity of the grain, the temperature to which the grain is exposed and the duration of the exposure.
In wheat, as the degree of frost/heatstress damage increases,
- Wheat milling becomes more difficult
- Flour yield decreases
- Flour ash content increases
- Flour colour becomes darker, which may not be commercially acceptable
- Bread volume, appearance, crumb structure and crumb colour deteriorate
For more information on frost damage access the Grain Research Laboratory paper on Factors affecting processing performance.