What is the purpose of yeast during maceration?

[JT101]

Hi everyone

So I've been making country wines and regular grape wines for a while now, and I'm just starting out in brewing beer.

It was my understanding that during the maceration period of the fruit, that the yeast, already present in grapes, and intentionally added with country wines such as blackberry is left with the soaking fruit in the must for up to 7 days or so in a bucket with a t-towel over it, after which it is transferred to the demijohn. And this is the way I've always made it and never had any issues.

Now this vastly differs from the way you approach beer, and yet to me, I can't see any reason for the difference. With beer, you go straight to the demijohn with the wort and yeast, albeit aerated.

I was always told, that during those 7 days, the yeast replicates due to the access to oxygen in the air, and build stronger cell walls. So ignoring the actual maceration of fruit, building up strength in the yeast colony is a good thing, so why not do the same thing with beer?

If maceration is the key activity here, then there is no reason to pitch the yeast until it goes in the demijohn, or just before, so there is clearly a reason for it.

Thanks

 

[bernardsmith]

The problem with grain is that it is very susceptible to souring - lactic bacteria love the grain and this can and will result in lactic acids being formed. That does not happen with fruit. Moreover, with fruit in order to obtain the flavor and aroma you tend not to "brew" anything. You wouldn't dream of cooking your wine grapes or mango or honey or .. you name it. With grain the only way to get at fermentable simple sugars is to break down the complex carbohydrates and to break them down you need to heat the grains in hot water to make a porridge brewers call a mash. This mash activates enzymes in the grain that will then break down the complex sugars into sugars that the yeast can use. No maceration involved here because the chemistry is very different. You are not extracting the flavor molecules or the aromatics from the grain. You are not going to be using the grain itself once you have extracted all the sugars from it. In fact after the mash - what's that? about an hour of soaking, heating and sparging? you can dump the grains (I often freeze them and add them to my dough when I bake bread.. )
As for creating a healthy colony of yeast, brewers often use yeast starters to improve the health of their yeast. I think they assume that the colony size increases too but I think the jury may still be out on that. But note too that wine makers tend to use half the colony size that brewers use. Our packs of dry yeast contain about 5 g of yeast. Brewers pay for 11 g a pack...

 

[JT101]

Brilliant thanks. So basically you don't allow the yeast to multiply and build up on the wort in an exposed envrionment because:
A) Lactic acid bacteria love wort, and would quickly colonise it far quicker than must
B) A larger amount of yeast or a yeast starter is used and so there is no need to grow the population of yeast
and C) I believe the fermentation would happen so quickly, it would be complete before you even got a chance to put it into the demijohn, but would likely have soured in the process

 

[bernardsmith]

But also there is no need to macerate grains. The act of making a mash and sparging will provide all the flavor and color. This is not the same with wine making. Sure you can express the juice from fruit but for example, simply using grape juice will give you a white wine. Macerating on the skins will produce a rose or red wine. Using the skins of other fruit will provide more tannin and color and body.

 

[JT101]

Ok great. Thanks