Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2004
Publication Date: 5/20/2004
Citation: Schwarz, P., Henson, C.A., Horsley, R., Mcnamara, H. 2004. Pre-harvest sprouting in the 2002 midwestern barley crop; occurrence and assessment of methodology. Journal of American Society of Brewing Chemists. 62(4):147-154.
Interpretive Summary: Barley growers in the Midwest suffered significant crop losses due to heavy rainfall during harvest in 2002. Compounding the loss of income due to crop quality being too poor to make malting grade, was that many of these same crops were determined to be too high in quality to warrant insurance payments for crop losses. The contradictory crop assessments resulted, in part, because the different parties (grain elevator personnel, federal grain inspectors, and crop scouts from the malting, brewing and milling industries) involved use different methods in the absence of any direct comparisons between the methods. The work reported here provides comparisons of seven methods used to assess preharvest sprouting. The pearling method, which is most commonly used, was shown to be insensitive to the earliest stages of preharvest germination, which is when the crop is most able to be salvaged. Two methods were shown to be more sensitive than pearling to early stages of preharvest sprouting (SN and FN). We also assessed the length of time crops with preharvest damage could be stored and remain useful for industrial processing and found that the accelerated aging test was the best predictor of viability losses during storage. The impact of this work is that it demonstrates discrepancies between the methods used and proves the need for crop producers, industrial users of the grains and federal grain inspectors to re-evaluate their goals and needs.
Technical Abstract: Rainfall received during harvest resulted in a substantial portion of the 2002 Midwestern barley crop exhibiting preharvest sprouting (pregermination). The fact that the incidence was the most wide spread in more than 25 years, has provided a unique opportunity to evaluate and compare methodology for the assessment of sprouting. Samples (N=151) were collected from farms and elevators in North Dakota and western Minnesota during harvest, as part of a survey of regional crop quality. Pearling showed that 40% of samples exhibited visual signs of sprouting (0.1-17.4%). Sprouting was also assessed by staining with fluorecein dibutyrate, determination of alpha-amylase levels, Falling Number (FN), Stirring Number (SN) as determined with the Rapid Visco Analyser (RVA), and by electrolyte leakage from cells (conductivity).The FN and SN assays were the most sensitive to levels of alpha-amylase in the sprouted grain. There was a moderate association (r=0.66) between SN and % sprout determined by pearling. As there is evidence to suggest that the germinative energy of pregerminated samples deteriorates with storage, 72 hr germination was determined after harvest, following several months of storage at room temperature, and following accelerated aging. Initial germination of the samples was 70-100%. Accelerated aging appeared to be a promising technique for predicting the storability of barley. The best associations between decline in germination with accelerated aging and sprouting were with the FN and SN techniques. However, at best these techniques were able to explain <50% of the variation associated with accelerated aging, and factors other than sprout damage are probably involved in the viability of stored grains.