Maybe it's just me, but I find the information in this section of Lott's article fascinating. It takes a very close look at the different sugars in wort and finished bottled beer and their relationship with the degree of attenuation. I know, I've very strange taste in reading material.
"I will now ask you to refer to the figures on Table III. First with regard to the malt analyses, the average figures of which are given in the first column.
These worts, obtained with an initial heat of about 151º F., showed, prior to fermentation, an average composition of 1 of non-sugar to 3 of sugar, and after a vigorous fermentation, practically carrying the attenuation to a fourth the original gravity, the ratio of non-sugars to sugars was 1 to 2.6. The average amount of maltose remaining unfermented is practically the same as the average amount of dextrin, i.e., 0.99 to 1.
Comparing these figures with the finished beers, we find but little difference in the ratio of total non-sugars to total sugars, except in the peculiar samples in the last two columns. Omitting these samples, it will be seen that the average attenuation is also the same as in the fermented wort, i.e., one-fourth, except in the case of the old pale ales, which average very nearly one-eighth.
Newly racked mild ales. Newly racked pale ales. Old matured bottled pale ales. Old matured bottled strong ales. Peculiar samples. (Average) 13. (Average) 5. (Average) 6. Typical. (Average) 6. Typical. (Average) 6. Typical. Very old strong ale 24 years old. Pale ale 9 months old. Original gravity 1029 1076.5 1061 1063 1065 1067 1110 1113 1132 1060 Present gravity 1007.5 1021.7 1015.7 1016 1008.1 1008.6 1027 1027 1047 1000 Ratio present to original gravity 3.9 3.5 3.9 4 8 7.8 4 4 2.8 - Fermented matter 58.7 60 61 69 70.5 70.6 61 61.9 47.8 81.6 Free maltose 2.8 2.7 2.6 3.2 0 0 1.6 3.4 9.8 0 Combined maltose 11.2 10.5 9 9.4 6 6.2 10.4 9.2 10.6 2.7 Combined dextrin 4 5.2 6.5 5.4 2 1.8 3.4 2.6 0 0 Free dextrin 10.1 7.2 5.8 6.6 7 7.4 9.3 8.3 14.2 0 Inactive matter 13.2 14.4 15.1 15.8 14.5 14 14.3 14.6 17.6 15.7 100 100 100 100 100 100 100 100 100 100 Ratio Total sugars/Total not sugar 2.66 2.73 2.65 2.6 3.7 3.7 2.7 2.92 2.14 5.37 Percentage of dry solids, possibly fermentable 76.7 78.4 79.1 77.6 78 78 76.4 77.1 68.2 84.3 Percentage of fermentable matter fermented 77 76 77 77 69.7 90 80 80 70 57 Percentage of unfermentod residue, possibly fermentable 44 46 47 45 27.5 27 40 40 39 14 Ratio Total unfermented maltose/Total unfermented dextrin 0.99 1.06 0.95 1.05 0.66 0.67 0.95 1.16 1.44 -
Journal of the Federated Institutes of Brewing, Volume 7, Issue 2, March-April 1901, pages 204 - 205.
I find apparent attenuation more understandable than the ratio of present to original gravity used in the table. That gives us figures like this:
|Original gravity||Present gravity||apparent attenuation|
|Fermented malt wort.||(Average) 13.||1029||1007.5||74.14%|
|Newly racked mild ales.||(Average) 5.||1076.5||1021.7||71.63%|
|Newly racked pale ales.||(Average) 6.||1061||1015.7||74.26%|
|Old matured bottled pale ales.||(Average) 6.||1065||1008.1||87.54%|
|Old matured bottled strong ales.||(Average) 6.||1110||1027||75.45%|
|Peculiar samples.||Very old strong ale 24 years old.||1132||1047||64.39%|
|Pale ale 9 months old.||1060||1000||100.00%|
The fermented wort and newly-racked Pale Ales are about what you would expect, near as dammit 75% attenuation. The Mild Ales are slightly lower at just under 72%. It's no surprise to discover that matured bottled Pale Ales - which would have undergone a long secondary conditioning in the cask and then bottle - have attenuation of over 85%. It is a shock to see that matured Strong Ales managed to reach 75% attenuation. OK, they too had a long secondary conditioning, but with the lower fermentability of Strong Ales worts from the type of malt used and the mashing scheme, I wouldn't have expected quite so high a degree of attenuation. It also doesn't tally with what I've seen in brewing records.
Here are beers of the period from my favourite London breweries:
|Whitbread Beers in 1901 - 1902|
|Year||Beer||Style||OG||FG||ABV||App. Attenuation||lbs hops/ qtr||hops lb/brl|
|1901||FA casks||Pale Ale||1050.4||1013.0||4.95||74.21%||11.71||2.66|
|Whitbread brewing records held at the London Metropolitan Archives, document numbers LMA/4453/D/01/066 and LMA/4453/D/01/067.|
|Barclay Perkins Beers 1899 - 1900|
|Year||Beer||Style||OG||FG||ABV||App. Attenuation||lbs hops/ qtr||hops lb/brl|
|Barclay Perkins brewing record held at the London Metropolitan Archives, document number ACC/2305/1/593.|
One thing to bear in mind is that the FG's of all the above beers were measured at the end of primary fermentation, thus are newly-racked beers. With the exception of Whitbread's KK and KKK Stock Ales and Barclay Perkins X Ale, all have apparent attenuation of around 75%. Even allowing for a long secondary conditioning, I doubt Whitbread's KK and KKK would ever have attained 75% attenuation.
Looking at the unfermented residue, the percentage possibly fermentable is also much the same in the malt wort and new beers, but falls considerably in the old pale ales, and appreciably in the old strong ales.
Comparing the total maltose and dextrin in the unfermented residue, it will be seen that there are about equal amounts in the fermented malt wort and in all the ales, except the old pale ales, the M/D ratio varying from 0.95 to 1.16, whilst in these latter there is nearly double the amount of dextrin, the ratio being 0.66.
The ratio of combined maltose to combined dextrin is lower in most of the ales than in the malt wort, except in the old strong ales. In the strong ale this figure is very different, being greater than in the average malt wort, but it is not quite strictly comparable, because the malt used for the production of the strong ale would no doubt have given very different figures to those in column 1, and I may refer you again to Tables Ia and IIa.
It may at first sight appear somewhat strange to find free maltose in old ales, but it will be noted that this is only the case in the old strong ales, and especially noticeable in the peculiar old sample 24 years old. I think the very high figure for the original gravity, and the corresponding large percentage of alcohol present, will probably explain this fact and at the same time I would draw your attention to the fact that in nearly all beers, no matter how old, it is possible to produce a further fermentation by degrading with C.W.M.E. or diastase, and adding new yeast.
The peculiar composition of the pale ale given in the last column is probably due in the first place to the use of an undercured malt, and in the second place to a low mashing heat. It will be noted that 97 per cent. of the possibly fermentable matter has been fermented in nine months, a most unusual thing."
Journal of the Federated Institutes of Brewing, Volume 7, Issue 2, March-April 1901, page 206.
You would expect the free maltose content of the matured Pale Ales to be lower than the newly-racked ones, as fermentation would have continued after racking. It's difficult to draw any conclusions from the dextrin content of the matured Pale Ales. Had it been significantly lower than in newly-racked beers, I would have suspected the action of a secondary-conditioning yeast such as Brettanomyces. The 9 month-old Pale Ale in the last column, with its FG of 1000 and almost zero remaining sugars, certainly looks like it's had Brettanomyces at work on it.
In the case of the 24 year-old Strong Ale, it looks as if, as Lott suggests, the residual sugars are the result not of everything possible being fermented out, but because the high level of alcohol (I make it 12.5% ABV) stopped the yeast working.
And that's me done with Lott's extremely informative article. What on earth will I do now?