sugar and starch

[GilesN]

yesterday I was talking to a cider maker who said that starch in apple juice will affect the reading of a hydrometer in the same way as sugar. Also that the starch will be converted by yeast into alcohol anyway so it doesn't matter too much. 

For him the issue with starch was principally to do with the impact on milling and  pressing, ie reduced yield.

so questions.

1 will starch press out into the juice to a similar extent as sugar would? (given starch is insoluable in cold water)

2 if it does will it read the same as sugar on the hydrometer?

3 will the starch convert to alcohol?

4 if so will  the yeast need help, are there enough nutrients / enzymes in apple juice etc to help it through the additional step(s)?

thanks

Giles

[Andrew Lea]

The answer to all four questions is no.

1. Starch is in the form of insoluble granules in fruit and rapidly
drops to the bottom of the tank. You can easily see the white layer if
you press under-ripe fruit.

2. No because it isn't soluble.

3. No. Starch cannot convert to alcohol directly.

4. No. This cannot happen. The only way to convert starch to alcohol
'offline' is to deliberately use an amylase enzyme which degrades the
starch to glucose. The glucose is then fermentable to alcohol by yeast.
The amylase has to be purchased and deliberately added. It is not
naturally present in fermenting yeast.

I'm sorry you have been so badly informed.

Andrew



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Wittenham Hill Cider Portal
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[Giles Nicholson]

Thankyou Andrew,

you confirmed what i thought. I just had some doubts about my own thinking as this guy has years more experience then me and the "industrial" cider makers often seem to use unripe fruit which would implicitly be high in starch. I wondered about amylase (whether there is any / enough naturally present).  

Does the starch to glucose conversion during ripening in the apple rely on amylase? or is it a different process ?

Giles

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[Andrew Lea]

Yes the industrial cidermakers do sometimes treat mash from underripe fruit with amylase to achieve maximum sugar levels if they cannot wait for fruit to ripen naturally. 

The natural conversion of starch to sugars in ripening fruits is much more complicated and dynamic than the simple action of amylases although they may in part be involved. There are other enzymes such as starch phosphorylase which are thought to play a key role. In maturing apple fruits, the hydrolysis of starch often leads to an increase in sucrose (not glucose)  which could not occur by simple amylase action. 

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

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[Giles Nicholson]

Thank you Andrew, most helpful to my understanding
Giles

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[Andrew Lea]

Here for instance is a typical data sheet for an amylase recommended for use in cider making, as well as for brewers wort. An important criterion is the ability to work at the low pH of apple mash, compared to wort. 

http://www.murphyandson.co.uk/Datasheets/FUNGAL%20ALPHA%20AMYLASE.pdf

Perhaps your industrial cidermaking friend uses these routinely, hence his remarks?

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

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[Max Nowell]

So the only real problem with starch is that it isn't sugar?  

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[Andrew Lea]

Starch isn't fermentable by yeast. So if you use unripe fruit you aren't exploiting the maximum potential sugar that you could be if the fruit were ripe. 

Unchanged starch also means that the fruit is unripe in other more subtle flavour aspects. In other words it will likely give a less interesting cider. No amount of amylase will alter that. 

For most people on this list, using fully ripe fruit which contains no starch is the best plan. 

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

[Jason MacArthur]

On Sunday, October 16, 2016 at 3:28:07 PM UTC-4, Andrew Lea wrote:

Starch isn't fermentable by yeast. So if you use unripe fruit you aren't exploiting the maximum potential sugar that you could be if the fruit were ripe. 

Unchanged starch also means that the fruit is unripe in other more subtle flavour aspects. In other words it will likely give a less interesting cider. No amount of amylase will alter that. 

How does this process differ on and off the tree?

Jason