I came across a very interesting discussion on the effect of full volume mash on the fermentablity of the wort and resulting maltiness and body of the beer in BIAB brewing on HomeBrewTalk.

My approach is to mash with about 2/3 of the water with 1/3 reserved for sparging. I have considered doing a full volume mash, which is the more traditional BIAB approach, but haven’t tried it yet.

Original poster, Bassman2003, who switched to full volume mashes noticed some beers lacking maltiness or body and asks ‘Do you think BIAB results in more fermentable wort? Do you find the need to mash a little higher? if so, how much higher?’

The first response, from dmtaylor, is interesting – ‘If you find your beers are lacking in body, perhaps your efficiency is too high? Or your water too hard? Your mill gap too tight? Mashing too long? I’ve been mashing for only 40 minutes for the past 10 years with no ill effects because it’s a waste of time to mash longer than that for most styles (except maybe Belgians). If you mashed for much longer, like 75-90 minutes, this would certainly hurt body.’ His theory that mash length and efficiency affects body/maltiness is interesting. I am aware that the temperature is a major factor with a lower mash temperature producing more simple sugars and hence a more fermentable wort, but hadn’t considered mash length as important in this regard. My thinking was that mash length and/or efficiency was just about getting more sugars out of the grain and hadn’t considered whether the additional sugars tended to be biased towards complex unfermenatble sugars or the simpler more fermentable sugars.

Gavin C, chips in, ‘No alterations to recipe/mash profile other than the obvious slightly altered mash pH considerations are needed if doing full volume mashes’. He cites an experiment by Braukaiser on the topic of fermentability and mash thickness – ‘Contrary to common believe no attenuation difference was seen between a thick mash (2.57 l/kg or 1.21 qt/lb) and a thin mash (5 l/kg or 2.37 qt/lb). Home brewing literature suggests that thin mashes lead to more fermentable worts, but technical brewing literature suggests that the mash concentration doesn’t have much effect in well modified malts’.

Another fellow, wilserbrewer, mentions an approach that I think might be very practical and worth a go – ‘Another approach I have used, mainly to save heating time while making large batches, is to mash in with around 60% of the total water, then after 40 minutes or so add the remaining water to the mash at say 160 – 180 degrees, stir well, wait a few minutes, stir well again and remove the bag.’ I like the idea of this approach, it eliminates the sparge but does not alter mash thickness. Also this is very practical for me because I have to lift the pot onto the gas burner after the mash and this approach makes the weight that I have to lift more manageable.

On the subject of mash PH Gavin C notes ‘Thinner mashes are more dilute meaning all other parameters being equal they will have a higher pH than a thicker mash’ and ‘an often overlooked method to increase a mash pH is to mash thinner’.

Brulosophy also has done an experiment on sparge vs no sparge. The results of this were somewhat inconclusive. The sparged beer was noticibly more hazy and 14 out of 26 testers were able to detect a difference. 7 out of the 14 preferred the sparged version. Overall though it seems the differences in the final beer were quite minor.

There are so many variables in brewing but luckily I’m not too much of a perfectionist or it would drive me insane. I tend to go with the practical, easy, approach that gets good results and as a result of this discussion I will be trying out the approach mentioned by wilserbrewer, that is to mash with usual volume but add the extra water towards the end of the mash in lieu of sparging.