I recently read an interesting research article pointed out to me by Bleepbloop, thanks Bleepbloop! The article is from China and published in the Wiley Online Library by The Institute of Brewing and Distilling. The title is a doozy: “Optimization of kilning progress for equilibrating multiple parameters that strictly affect malt flavour and sensory evaluation” The researchers objective was to determine what times and temperatures create the “perfect malt”. Unfortunately, to read the whole thing you have to rent it for $6 but you can get the main idea from the summary.
In their experiments they measured the levels of positive and negative flavour compounds in relation to drying times (referred to as withering time in the article) and curing time and temperature. The compounds they were measuring were lipid oxydation or LOX activity, nonenal potential, TBZ (content of carbonyl compounds) methional, furfural, hexanol and phenylacetaldehyde. All of which I believe contribute to either stale or cardboard flavours. They also measured levels of H-hydroxy-2,5-dimethyl-3(2H) or HDMF which is the main contributor to sweetness and malty aroma. As well malt samples were given a sensory score rated by 7 professional sensory panellists from the Tsingtao Brewery
After plotting their data they’ve concluded that the ideal drying time is 14 hours: 1 hr at 45C, 5 hrs. at 55C, 5 hrs. at 65C, 3 hrs at 76C, 50% re-used air at 76C. Note: given the high temperatures I’m assuming that these would be the kiln temperatures below the bed or the “air-on” temperatures. Curing temperature is 86.35C for 3.19 hours.
Most of the article describes their methodology and what kind of testing was used for each flavour compound and it doesn’t go into that much detail about the effects of each compound. They also specify that these results would be different for different varieties of barley. The variety they were using was Gairdner barley grown in Australia. There is a lot of information in this article I don’t understand but the conclusion is interesting. I wish they had included the malt temperature during the kilning because without it, it’s impossible to replicate exactly. I do wonder how detectable these flavours are and at what point are they noticeable? The curing temperatures tested ranged from 84C to 90C, curing times ranges from 2.5-3.5 hours and drying times measured ranged from 10-14 hours. Not a wide range at all, in fact, they kind of seem on the low end of the scale. Unfortunately, there was no mention of diastatic power in the article as the study just focussed on flavour and there was no mention of moisture contents. I also find it strange that they did not include the kilning schedules for the 10 and 12 hour kilned malts. Are we to assume that the temperature increases coincided with the same moisture contents in each sample? There seems to be some key information missing here that would have made this article more useful.
This research paper makes me wonder if “perfect” is something that is worth achieving or does this goal bring with it the risk of industrial uniformity. It still seems to me that there are enough variables involved that what is considered perfect is still subjective. Of course, it’s interesting to see what is at play when making malt and it’s good to know that the levels of those flavour compounds that cause stale or cardboard flavours are measurable. However, I have never noticed these flavours in my malts so it’s not something I’ve ever worried about. I have tried this schedule with my barley, knowing that I couldn’t actually replicate their conditions without using the same equipment, and I found I needed another hour or two curing time to become more friable, meaning my malt was not dry enough. As it was, the roots were still a little flexible and hard to shake off. It would be interesting to see this same experiment done on a greater scale, that is with wider temperature and kilning time ranges. I’m sure for large scale maltsters this is a useful article but for myself I think I prefer variety, good or bad. The best beer I’ve ever had was the pale ale I made from the diastatic brown malt that was dried over fire, very far from scientifically “perfect” I’m sure but beyond perfect in my mind.