Press efficiency

[Simon McKie]

Many postings refer to press efficiency expressing it as a percentage.
Of what is it a percentage ? Is it the amount of juice extracted
expressed as a percentage of the total juice assumed to be in the
juice? How would one know that total? If one presses apples wighing
100kgs with a press of 70% efficiency can one say how much juice will
be produced? With a Vigo basket press I usually obtained a litre of
juice for each 2 kgs of apples. With the Vigo hydropress it is
something like 1.4-1.5 litres. How do these figures correspond to
press efficiency percentages?

[AdamD]

If you assume that 1 litre of juice weighs 1 kg, a press that presses
at 70% efficiency would give 70L for every 100kgs of fruit pressed. So
with your basket press you are getting 50%, whereas with the hydro
press it is approaching 75%.

[Andrew Lea]

I would say when we talk about efficiency on this list we are equating
it with yield. Loose usage, but there you are! Hence your basket press
is giving you 50%, but your hydropress is giving you 75%. The percentage
of juice is calculated on the original weight of fruit (and usually we
assume 1 litre = 1 kg which is not so far out really).

It is as you suggest possible to be more accurate about true efficiency.
One way I have seen it done is to calculate the yield as above and then
to weigh the pomace before and after oven drying. In that way you can
make allowance for the remaining moisture and by knowing the true 'dry
matter' of the apple (about 10% if memory serves me correctly - I
haven't checked) the true efficiency can be measured. If you do those
calculations then by certain types of extraction (e.g. hot water
diffusion or use of cell-wall-degrading enzymes) it is actually possible
to get efficiencies greater than 100% since substances are leached out
of the apple which would normally not be.

Andrew

--
Wittenham Hill Cider Page
http://www.cider.org.uk

[Claude Jolicoeur]

You can make it a bit more accurate by taking the SG of the juice.
So if from 100 kg of apples you get 50 L of juice at SG 1.050, the
yield efficiency really is 52.5%. This actually means the weight of
your 50L of juice is 52.5 kg.
Another way is to measure the weight of the pomace. It this particular
example, the pomace should weight 47.5 kg.
Claude

[Simon McKie]

My thanks to Adam, Andrew and Claude,

The normal method would seem to assume that all apples contain the
same amount of juice for any given weight of apples. If one is
comparing pressings of similar mixes of fruit, however, I presume the
result is a reasonable approximation to efficiency. Andrew's
alternative method would allow you to determine the proportion of the
total juice in the fruit which has been extracted and thus to obtain a
true measure of efficiency.
Claude's point on the weight of the juice is interesting.

Simon

[jez....@btinternet.com]

Simon,

I love making notes and keeping records of my cider, and the processes - to ensure some kind of consistency and standard practice in my cider making (plus to help identify things that aren't so good). However, measuring the percentage yield is only really a rough science for me, hence weight of apples vs litres of juice will tell me approximately what to expect.

So, with my metal 'Ray' press loaded with 35kg of apples I can expect to achieve between 65-70% yield using a 12 ton bottle jack and a Fruit Shark mill. Also, cider varieties yield less than desert apples (whether this is due to size difference - don't know). That's one of the things I like about the egremont - so close to being a cider apple, yet more juicy:-)

I find the chart in Andrews book useful as a comparison - but each press behaves in a slightly different way. It would be interesting to me to know what Ray, or others using varieties of Rays design, are getting.

I have always been impressed, though, with the amount of juice Stephen Hayes gets from his Vigo rack and cloth press though! He just puts the pomace on and it seems to just surrender!

All the best

Jez
Sent from my BlackBerry® wireless device

[dave]

I know what amount of juice to expect from the varieties I press.
Crispin gives an incredible amount of juice and Spartan very little,
with various other varieties in between.
There must be a point where a higher percentage yield rate does become
less favourable. I'm not so sure that squeezing every last drop of
juice out of the seeds is going to be a good thing, and I also think
that some of the less favourable flavours from part of the core are
not wanted. Whether a press is ever going to be that efficient is a
different matter.