Supermalt as a yeast starter?

[SpamNMash]

Just read something about using "Malta" (http://en.wikipedia.org/wiki/Malta_(soft_drink)) instead of DME for a yeast starter. This an American thing, but I remembered we have Supermalt over here - you often see it in corner shops and the imported foods section of supermarkets. Seems to be brewed but not fermented, so pretty much a bottle of sweetened, carbonated wort I suppose.

Anyone tried it? I don't usually keep DME on hand, so maybe I'll give it a go next time I need a starter - after all it's only ~50p and available in any random corner shop! (in London anyway)

 

[RobWalker]

Malta is made of water, malt, molasses, sugar and yeast.

Sounds good to me, providing the malt content is quite high.

We do also get supermalt, you can buy it from the more jamaican/indian mini/supermarkets. I think most supermarkets will carry it too, a lot of them have an import section now.

 

[graysalchemy]

You shouldn't grow yeast cultures with simple sugars ie the sugar and molasses IMHO, it leads the yeast to switching metabolism whilst it is growing and when it is put into a malt wort it wort convert it as efficiently.

 

[rpt]

You shouldn't grow yeast cultures with simple sugars ie the sugar and molasses IMHO, it leads the yeast to switching metabolism whilst it is growing and when it is put into a malt wort it wort convert it as efficiently.

That will depend on the proportions. Malt extract contains up to around 15% of simple sugars (glucose, fructose and sucrose) so a bit extra of these shouldn't matter. However, as we don't know the proportions I wouldn't risk it.

 

[graysalchemy]

I wouldn't use DME or LME either only wort from grains :thumb: no simple sugars. :grin: :grin:

 

[jimp2003]

I wouldn't use DME or LME either only wort from grains :thumb: no simple sugars. :grin: :grin:

Why wouldn't you use DME or LME? Are there measurable benefits for using wort made from grain yourself?

 

[rpt]

I wouldn't use DME or LME either only wort from grains :thumb: no simple sugars. :grin: :grin:

Wort from grains also contains simple sugars.

 

[saccharomyces]

Wort from grains also contains simple sugars.

Bingo! The only sugar that yeast can use directly is glucose.

Truth be told, dried brewers yeast is propagated in a bioreactor using a low gravity wort that is composed primarily of water and molasses. The gravity is kept very low in order to avoid the Crabtree effect.

Contrary to what many home brewing books claim, brewer's yeast does not respire in normal gravity beer wort. Dissolved oxygen plays no role in the decision to switch from respiration to fermentation in the presence of glucose concentrations greater than 0.3%. The choice of fermentative growth over respirative growth is known as the Crabtree effect. Brewer's yeast consume oxygen while undergoing fermentative growth (which is an anaerobic process) because their metabolic pathways are leaky. The oxygen that goes through the respirative metabolic pathway is used to synthesize ergosterol, which, in turn, improves yeast health.

In an industrial bioreactor, low gravity wort is continuously fed to a stirred well-aerated culture. As the glucose in solution remains below the Crabtree threshold, the yeast culture remains in respiration mode. During respiration the carbon source (a.k.a. sugar) is metabolized to water and carbon dioxide gas (yeast metabolizes the carbon source to ethanol and carbon dioxide gas during fermentation). Respirative growth is significantly more efficient than fermentative growth, which is why it is the preferred way to propagate yeast.

With that said, if propagating brewer's yeast outside of normal brewery wort conditions led to poor wort fermentation, then dried brewer's yeast would never work. Bioreactor grown dried yeast is the poster child for how far from the target environment brewer's yeast can be grown. Dried brewer's yeast cells have never experienced fermentative growth, the toxicity of alcohol, or the osmotic pressure that normal, let alone high-gravity worts place upon yeast cells. Yet, most fermentations reach normal terminal gravity.

In closing, anyone who doubts what I have claimed, should perform a Google search using the terms "Lallemand" and "bioreactor" or "Lesaffre" and "bioreactor" (Lesaffre is the parent company of Fermentis).

 

[RobWalker]

DME and LME are practically wort too - I can't see it making a measurable difference, especially on a home brewing level :hmm: