Pericarp alpha-amylase activity in wheat has largely been ignored as a potential cause of low Hagberg falling number (HFN) in the UK, because pericarp alpha-amylase enzymes have been thought too temperature-sensitive to affect HFN and are usually degraded by harvest. Nevertheless, there are several circumstances where immature grains may be present in harvested grain. Therefore, we tested the hypotheses that pericarp alpha-amylase enzymes in immature grains could lower HFN, but also that inactivation of the enzymes during drying and storage could ameliorate the effect. The first hypothesis was tested by addition of large amounts of pericarp alpha-amylase activity from freeze-dried, defrosted or fresh green grains to high HFN flours of low alpha-amylase activity, followed by HFN measurement. Enzyme assay and HFN analysis assessed the effect of drying on pericarp alpha-amylase activity after different storage treatments. Addition of pericarp alpha-amylase, from all three sources, to high HFN flours caused an exponential decrease in HFN. A drop in HFN from over 470 s to below 250 s resulted from addition of 5-10% by weight of green grains. Between 35-70% of the a-AMY-2 activity in immature grains was eliminated by air-drying at 20ºC over 8-10 days, although the residual activity could still lower HFN. Thus, pericarp alpha-amylase activity may be a cause of low HFN in some UK wheat crops.

Although wire flame spraying has been used for many years, there has been relatively little attention given to understanding the process dynamics. In this work, imaging of the molten wire tip, particle imaging using the Oseir SprayWatch system and particle capture (wipe tests) have all been employed to quantify plume behavior. Aluminum wire feedstock is melted and then breaks up close to the exit of the spray nozzle in a non-axisymmetric manor. The mean velocity and diameter of the particles detected by the SprayWatch system change little with standoff distance with values of approximately 280 m/s and 70 lm, respectively, for the spray parameters employed. The particle diagnostic system could not detect particles~45 lm in diameter, and it is estimated that these account for no more than 53% of the sprayed material. Overall, wire flame spraying generates a surprisingly stable particle stream.

In 1998 and 1999 the UK winter wheat variety Rialto produced unexpected low Hagberg falling numbers that could not be directly linked to sprouting. It was proposed that these reductions in quality could be due to pre-maturity α-amylase activity (PMAA). The problem was not identified during the selection and commercial development stages. Our study tested the hypothesis that the variety Rialto is PMAA-susceptible. Analysis was done on 13 year-location combinations of field grown Rialto. Together, visual and chemical assessments of sprouting and iso-electric focusing of α-amylase isozymes identified several samples with significant α-amylase activity in the apparent absence of sprouting. In addition, tests with α-amylase sensitive Phadebas gel revealed distinctive PMAA discoloration patterns in 10-44% of the grain from the 13 samples, leading to the conclusion that Rialto is PMAA-susceptible. Diurnal temperature range accumulated for an 11 day period during a warm spell in early simulated grain development displayed a significant but negative correlation with the number of grains showing clear PMAA discoloration patterns on Phadebas gel. The number of clear PMAA grains correlated positively with rainfall accumulated over 11 days. These results suggest that PMAA can increase under conditions similar to those conducive to pre-harvest sprouting. It is however also possible that in some instances both PMAA and incipient sprouting could have produced similar patterns of α-amylase activity. In addition to tests with Rialto, Phadebas gel tests were therefore also done with the known high Hagberg varieties Option and Malacca, sprouted in a controlled environment. Results from the additional gel tests suggest that visual and chemical assessments of sprouting in the grain combined with Phadebas gel analysis could identify PMAA more reliably in grain sub-samples than Phadebas gel analysis alone.

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