Temperature and mash thickness are shown to affect both mash performance and enzyme activity. Alpha amylase was found to be considerably more resistant to heat inactivation than was beta amylase. This difference was reflected by changes in wort fermentability that were manifest at temperatures below those which affected levels of extract. Increasing the mashing temperature from 65°C to 80°C had only a slight effect on extract but reduced wort fermentability from over 70% to less than 30%. At 85°C and over, when temperature had a significant effect on alpha amylase, as well as on beta-amylase, extract was lost and starch was present in the wort. Diluting the mash with liquor had a similar effect to that of increasing temperature on both the amylolytic enzymes and on the mash performance. Thin mashes contained more starch and fewer fermentable sugars than did thick mashes at the same temperature. These changes can be related to the stability of the amylolytic enzymes.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1991.tb01055.x

The effects of mashing temperature and mash thickness on wort carbohydrate composition

The relative roles of the scutellum and the aleurone layer in the production and mediation of both germination-specific α-amylase and cell wall breakdown hydrolases has been examined in vivo following treatment of barley seeds with the plant hormones gibberellic acid and abscisic acid. To facilitate entry of these exogenous hormones, a technique is presented where multiple incisions (>nicks<) are made in the outer layers of the seed prior to germination. Treatment of seeds with gibberellic acid and abscisic acid effected major changes on the pattern of hydrolase transport. The nature of the changes were such that it is concluded that the scutellum alone is capable of producing and mediating up to 50% of germination specific hydrolases in a commercial European malting barley, germinating at the conventional European malting temperature of 15°C.

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On the relative role of the scutellum and aleurone in the production of hydrolases during germination of barley

The germination of grains that had been steeped in solutions/suspensions of antibiotics was improved relative to water-steeped controls. The effect of the antibiotics was most striking for dormant grain that had been steeped for 90 min rather than 60 min. By incubating decorticated grains under different amounts of water it was shown that restriction of air to decorticated dormant grains reduced germination much more than was the case with decorticated, mature grains. Incubating the dishes of grain in oxygen, rather than air, overcame the inhibitory effect of excess water, confirming that it was the restriction of the oxygen supply by the water that checked germination. It was shown that sprays of dilute sulphuric acid favoured grain germination by acting on the outer layers of the grain. When acid-sprayed and untreated samples were decorticated and incubated their germination rates under different test conditions were essentially identical. In contrast gibberellic acid was shown to exert its germination-stimulating effects and sodium hydroxide its inhibitory effects on the internal tissues. By comparing the respiration rates of ground samples of grain (entire and decorticated; untreated and surface-sterilised) it was shown that microbes in the surface layers have substantial oxygen uptake rates. It seems that the competition of these microbes with the grain tissues for oxygen is a major cause of dormancy.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1993.tb01160.x

Microbes and grain germination

Barley samples, which varied in maturity, were either steeped with calcium hypochlorite and then with a mixture of antibiotics, or in water, for twenty or sixty hours. The steeped grains were placed on agar and were scored for germination, growth of rootlets and α-amylase production at intervals up to ninety six hours after draining. The rates and final percentages of germination, rootlet growth per germinated corn and α-amylase per germinated corn were all greater where grain had been steeped with antimicrobial agents compared to water-steeped control samples of grain. It was confirmed that the antimicrobial agents reduced the extent of inhibition of germination which followed extended steeping. Thus controlling microbes increased grain germinability and the vigour of the grains which germinated. However, the vigour of more water sensitive grain was not increased enough to be equal to that of mature grain by reducing microbial activity.



Experiments in which grain was reinfected with a suspension of microbes, following steeping with antibiotics, supported the theory that the observed effects were due to reductions in microbial activity and not any secondary effects of the antimicrobial agents.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1992.tb01122.x

The influence of the grain microflora on the germinative physiology of barley

The modified regions of the starch endosperms of malted grains were fragile and, in thin sections, the cell walls in these regions did not stain readily with Congo Red or Trypan Blue, although scanning electron microscopy demonstrated some cell-wall material remained. Initially the enzymes causing modification came from the scutellum, but later more came from the aleurone layer. Patterns of modification in different grains differed significantly, but usually resembled those recorded previously6 except that often modification had advanced further by the nucellar sheaf cells.



In grains treated with gibberellic acid modification advanced faster, particularly beneath the aleurone layer, after two days germination. In tumbled or commercially abraded grains, malted with gibberellic acid, modification was even more rapid, but in more than 99% of the grains the same patterns of modification occurred. Two-way modification was a rare event.



Rapid, general sub-aleurone modification occurred in grains cut at the apex and dosed with gibberellic acid.



Decorticated grains modified exceptionally quickly and, when treated with gibberellic acid, massive subaleurone modification occurred.



The cell walls of the tissues that resisted modification fluoresced strongly in ultra-violet light, in contrast to those of the starchy endosperm.

Patterns of modification in malting barley

After applications of gibberellic acid tumbled, impacted and abraded grains formed α-amylase faster than untreated controls. Apparently apical abrasion was not essential to achieve this enhanced response. The testae of treated grains appeared to be intact, and excluded externally applied gibberellic acid except at the base of the grains, where it normally gains entry. Essentially normal patterns of modification were observed in all grain samples, however treated. Tumbling and abrasion sometimes stimulate enzyme production in the absence of externally supplied gibberellic acid. It is deduced that these treatments do not alter the pattern of gibberellin penetration into grain.



Physical treatments cause limited embryo-damage and create fissures in and between the grain's surface layers. The treatments appear to exert their beneficial effects on enzyme production by allowing better access of oxygen in the air to the living grain tissues. Normally the oxygen supply limits enzyme formation. Surface populations of microbes sometimes limit oxygen levels in grain and repress enzyme formation.

The mechanisms by which tumbling and abrasion alter enzyme formation in malting grain

Starch-iodine colour (S.I.C.) units of α-amylase activity are re-defined. Two improved, alternative methods of calculating results are given, either (a) by a revised graphical procedure used in conjunction with a standard graph, or (b) by a graphical procedure using points calculated from the experimental results with an empirical equation using a programmed electronic calculator. Semiautomation of the measurement of starch-iodine colours usefully reduces the work load involved in this enzyme assay. Enzyme activities may be expressed in S.I.C. units, or as a rate of increase in reducing power.

M. T. Smith

Papers

The mechanisms by which tumbling and abrasion alter enzyme formation in malting grain

THE DETERMINATION OF BARLEY α‐AMYLASE ACTIVITY