In our Apple Pressing section we discuss several different press types with different efficiencies, and If you do much research on apple presses or read blogs that are about fruit pressing, you will come across people referring to press efficiency. “ I get 65% – 75% efficiency using my 12 ton bottle jack on my rack and cloth press” or my vego press gets me 72% efficiency. What do these people mean and how do you calculate press efficiency?
Typically speaking when efficiency is discussed with apple presses it is referring to the yield gained from pressing your fruit, i.e. “How much juice am I getting from this bushel (42 – 48 lbs) of apples?”
There are several different ways to determine the efficiency of your cider press. The method I first used was to weigh the apples prior to milling and pressing and then calculating the weight of the finished juice. When we bought our apples, I was given the weight of what I had bought, as that was how they calculated the price. This gave me a starting point. Firsts I needed to know how much apple juice weighed. I figured out what the water weight was (1 gallon is approximately 8.33lbs). However we know that apple juice is more dense than regular water because it has suspended solids in it. (That is why a hydrometer can work to calculate sugar.) Doing some poking around on the internet I came up with 8.7 lbs for a gallon of apple juice, but this number will vary depending on the apple variety that is being juiced. So if we have 48 lbs of apples and pressed 3.4 gallons of juice at 8.7 lbs per gallon out of that bushel
3.4 gal X 8.7 lbs= 29.58 lbs of juice.
To get a percent efficient we need to divide our yield by the starting amount.
29.58 lbs / 48 lbs gives us %61.6 percent efficiency.
This calculation does not take into account the raw solids that can not be pressed to make juice, stems, seeds, fiber etc., as getting %100 of the juice would still leave these materials behind. Andrew Lea, author of the fantastic book Craft Cider Making (get it at Amazon if you don’t already have it) is a prolific contributor on the Cider Workshop-Google Groups and he has stated that to get true efficiency you could use a method similar to what I described then “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.”
You would need to take extraordinary measures to get %100 of the juice from an apple, a feat that truly would not be worth the cost. In most cases, the method that I described above would work most efficiently.
What are your experiences? How do you calculate press efficiency? Please let me know in the comments section.