How can I figure out a beer's nutrition facts when I've homebrewed?
It's not a sum of the ingredients any more, is it?
So when I say "beer's nutrition facts" I means values like calories, carbs, proteins, vitamins, etc.
You can work out the approximate amount of calories if you think about what the major contributors to the brew are. Calories will come from carbohydrates (in the form of dissolved sugars) and alcohol (ethanol).
Ethanol has 7 kcal/g, so assuming an approximate density of 1 g / ml (i.e. water)* you can get the alcohol contribution from the alcohol by volume of your brew (ABV). I.e., 5% ABV = 45 kcal per 100 ml (5 * 7 = 45 kcal).
In terms of carbohydrates, you'll need to know the amount of dissolved unfermented sugar in your brew. Sucrose has about 3.9 kcal /g. So, if for example you have 5% sugars dissolved in your brew then sugars will give 20 kcal per 100m (5 * 3.9 = 19.5 kcal).
This will give you a total of 65 kcal per 100 ml.
How do you work out all this from your OG and FG? Well, I found this page which looks useful:
I imagine protein content can be calculated in a similar fashion.
Nutrition schmutrition. Beer is good for ya!
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Here is a link to a recipe calculator that I use to generate the US food label for my freelance recipes.
Using it with this link to adjust the amount of residual carbs should give you a decent estimate:
Note that the proteins are going to be fairly soluble in the alcohol so you can reasonably assume total extraction. The fats are another issue, but probably minimal. I'd ignore any residual yeast, if you clarify your brew, and fiber from the grains/fruit (hard to estimate soluble fiber).
So, here is an example. I brewed a batch of pear cider. Putting in the raw ingredients (58 pounds of pears, 1 oz yeast for 53 12 oz servings), I get the following nutritional facts from the recipe calculator:
User Entered Recipe
Amount Per Serving Calories 261.1 Total Fat 1.8 g Saturated Fat 0.1 g Polyunsaturated Fat 0.4 g Monounsaturated Fat 0.4 g Cholesterol 0.0 mg Sodium 0.2 mg Potassium 555.3 mg Total Carbohydrate 66.8 g Dietary Fiber 10.6 g Sugars 0.0 g Protein 1.8 g Vitamin A 1.8 % Vitamin B-12 0.0 % Vitamin B-6 4.0 % Vitamin C 29.4 % Vitamin D 0.0 % Vitamin E 11.0 % Calcium 4.9 % Copper 25.0 % Folate 7.7 % Iron 6.1 % Magnesium 6.6 % Manganese 16.8 % Niacin 2.2 % Pantothenic Acid 3.1 % Phosphorus 4.9 % Riboflavin 10.4 % Selenium 6.3 % Thiamin 5.9 % Zinc 3.5 %
Since I juiced the pears, I remove the fiber data (not a lot of fiber dissolves). I remove the fat data (not very soluble) and the carbohydrate calorie data, substituting the data from the Dave's calculator (note that in my case, there is very little sucrose - thus no sugars listed in nutrition label, the remaining carbs being the fructose that is converted to alcohol and in the SG calculations, so multiply the original carbs by the remaining "solids" after attenuation - see Dave's SG). So the adjusted label looks like this:
User Entered Recipe
53 Servings (12 oz servings)
Amount Per Serving Calories 187 Total Fat 0 g Saturated Fat 0 g Polyunsaturated Fat 0 g Monounsaturated Fat 0 g Cholesterol 0.0 mg Sodium 0.2 mg Potassium 555.3 mg Total Carbohydrate 12.0 g Dietary Fiber 0 g Sugars 0.0 g Protein 1.8 g Vitamin A 1.8 % Vitamin B-12 0.0 % Vitamin B-6 4.0 % Vitamin C 29.4 % Vitamin D 0.0 % Vitamin E 11.0 % Calcium 4.9 % Copper 25.0 % Folate 7.7 % Iron 6.1 % Magnesium 6.6 % Manganese 16.8 % Niacin 2.2 % Pantothenic Acid 3.1 % Phosphorus 4.9 % Riboflavin 10.4 % Selenium 6.3 % Thiamin 5.9 % Zinc 3.5 %
Until the software vendors have worked out the rules for combining ingredients to work out the nutritional stats via software, you'll need to send a sample off to a lab, where they will burn your 'product' and analyse the ash.
Depending on what nutritional information you are looking for, some of the brewing software packages will get you there. However, to truly know some of the protein and salt levels you need to know your water chemistry, you need the spec sheet from the malt, you need to know the residual yeast content, you need detailed analysis from the hop manufacturer... many variables.
And no its not just the sum of its parts anymore, primarily as a function of carbohydrates are concerned.