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ABV Changes When You Add Fruit

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Most people believe that when you add fruit to fermenting wort, the ABV of the resulting beer will dramatically increase due to the amount of sugar added with the fruit. Well, that is probably not going to be what happens. The problem with above logic is that they are considering the amount of sugar added with the fruit but they are disregarding the amount of water in the fruit.

So how do you calculate the ABV change when you add fruit to wort?

You will need 4 pieces of information:

1. The weight of the fruit you are adding.
This weight should exclude pits, seeds, stems, etc. Of course this will no be a perfect weight because there may still be things like pulp that cannot be removed but generally the weight is very low compared to the total weight of the fruit added.

2. The Brix of the fruit. The easiest way to get this is with a refractometer but if you don’t have one of those then you may be able to get the info off of the label of the container. Or as a last resort fine the percentage of sugar in the fruit via a Google search. This will probably be pretty close but an actual measurement is definitely better.

3. The OG of the beer you are adding the fruit to. This is the ORIGINAL GRAVITY and NOT the current gravity.

4. The weight of the beer. Granted, you probably didn’t weigh the beer when you pitched the yeast but you can still get the figure if you know how many gallons of wort you started with.
The weight of the beer can be calculated this way:
OG * Volume * weight of a gallon of water (8.36 pounds)
So if I started with 5.5 gallons of 1.055 wort then the weight would be 1.055 * 5.5 *8.36 = 54.8 pounds

Once you gather the above information you use this formula to calculate the ABV change:

(Weight of the beer from #4 * Brix/Plato of the beer + weight of the fruit addition * Brix/Pato of the fruit / Weight of the beer + weight of the fruit addition)

To keep you from having to look up the Brix if you don’t have a refractometer just use the following table

Specific
Gravity Brix
0.990 0.00
0.991 0.00
0.992 0.00
0.993 0.00
0.994 0.00
0.995 0.00
0.996 0.00
0.997 0.00
0.998 0.00
0.999 0.00
1.000 0.00
1.001 0.26
1.002 0.51
1.003 0.77
1.004 1.03
1.005 1.28
1.006 1.54
1.007 1.80
1.008 2.05
1.009 2.31
1.010 2.56
1.011 2.81
1.012 3.07
1.013 3.32
1.014 3.57
1.015 3.82
1.016 4.08
1.017 4.33
1.018 4.58
1.019 4.83
1.020 5.08
1.021 5.33
1.022 5.57
1.023 5.82
1.024 6.07
1.025 6.32
1.026 6.57
1.027 6.81
1.028 7.06
1.029 7.30
1.030 7.55
1.031 7.80
1.032 8.04
1.033 8.28
1.034 8.53
1.035 8.77
1.036 9.01
1.037 9.26
1.038 9.50
1.039 9.74
1.040 9.98
1.041 10.22
1.042 10.46
1.043 10.70
1.044 10.94
1.045 11.18
1.046 11.42
1.047 11.66
1.048 11.90
1.049 12.14
1.050 12.37
1.051 12.61
1.052 12.85
1.053 13.08
1.054 13.32
1.055 13.55
1.056 13.79
1.057 14.02
1.058 14.26
1.059 14.49
1.060 14.72
1.061 14.96
1.062 15.19
1.063 15.42
1.064 15.65
1.065 15.88
1.066 16.11
1.067 16.34
1.068 16.57
1.069 16.80
1.070 17.03
1.071 17.26
1.072 17.49
1.073 17.72
1.074 17.95
1.075 18.18
1.076 18.40
1.077 18.63
1.078 18.86
1.079 19.08
1.080 19.31
1.081 19.53
1.082 19.76
1.083 19.98
1.084 20.21
1.085 20.43
1.086 20.65
1.087 20.88
1.088 21.10
1.089 21.32
1.090 21.54
1.091 21.77
1.092 21.99
1.093 22.21
1.094 22.43
1.095 22.65
1.096 22.87
1.097 23.09
1.098 23.31
1.099 23.53
1.100 23.75
1.101 23.96
1.102 24.18
1.103 24.40
1.104 24.62
1.105 24.83
1.106 25.05
1.107 25.27
1.108 25.48
1.109 25.70
1.110 25.91
1.111 26.13
1.112 26.34
1.113 26.56
1.114 26.77
1.115 26.98
1.116 27.20
1.117 27.41
1.118 27.62
1.119 27.83
1.120 28.05
1.121 28.26
1.122 28.47
1.123 28.68
1.124 28.89
1.125 29.10
1.126 29.31
1.127 29.52
1.128 29.73
1.129 29.94
1.130 30.15

The Brix of various of fruits.

Apple 13.3
Apricot 14.3
Black currant 15.0
Blackberry 10.0
Black raspberry 11.1
Blueberry 14.1
Boysenberry 10.0
Carob 40.0
Cherry 14.3
Cranberry 10.5
Date 18.5
Dewberry 10.0
Elderberry 11.0
Fig 18.2
Gooseberry 8.3
Grapefruit 10.2
Guava 7.7
Lemon 8.9
Lime 10.0
Loganberry 10.5
Mango 17.0
Naranjilla 10.5
Orange 11.8
Papaya 10.2
Passion Fruit 15.3
Peach 11.8
Pear 15.4
Pineapple 14.3
Plum 14.3
Pomegranate 18.2
Prune 18.5
Quince 13.3
Raisin 18.5
Raspberry 10.5
Red currant 10.5
Strawberry 8.0
Tangerine 11.5

Example:

Lets say I started with 5.5 gallons of 1.055 wort (13.55 brix using the above chart). I am adding 10 pounds of raspberries (10.5 brix) to the wort (using the other above chart).

1. Weight of the fruit = 10 pounds
2. Brix of the fruit = 10.5
3. OG of the wort = 1.055
4. Weight of the beer = 48.5 pounds (1.055 * 5.5 * 8.36)

So the formula works out to: ((48.5 * 13.55) + (10 * 10.5))/ (48.5 + 10)

(657.175 + 105) / 58.5 = 13.03 Brix.

13.03 Brix is ~1.053 so adding the fruit LOWERED the OG by .0002 points.

So what happens if we use the above numbers but start with an OG of 1.050?

1. Weight of the fruit = 10 pounds
2. Brix of the fruit = 10.5
3. OG of the wort = 1.050
4. Weight of the beer = 48.28 pounds (1.050 * 5.5 * 8.36)

So the formula works out to: ((48.28 * 12.37) + (10 * 10.5))/ (48.5 + 10)

(597.22 + 105) / 58.5 = 12.0 Brix which is about 1.048. So it lowered the OG by .007 points

So what happend if we add a fruit with a lot of sugar in it like figs? Side note, I have me a beer using a fig addition and it’s awesome!

Same as the first example but the Brix of the fruit is 18.2.

1. Weight of the fruit = 10 pounds
2. Brix of the fruit = 18.5
3. OG of the wort = 1.055, Brix is 13.55
4. Weight of the beer = 48.5 pounds (1.055 * 5.5 * 8.36)

So the formula works out to: ((48.5 * 13.55) + (10 * 18.5))/ (48.5 + 10)

(657.175 + 185) / 58.5 = 14.4 Brix or about 1.059 OG. So the figs increased the OG about 4 points.

As a general rule the addition of fruit will not have a significant affect on the gravity of the wort so the ABV is usually not that much different with or without the fruit addition.