Maltodextrins are a group of mostly unfermentable carbohydrates produced by the partial hydrolysis of starch or glycogen. Maltodextrins typically impart little or no flavor upon the finished beer, but are important because they can be a valuable method for adding gravity and perceived body and mouthfeel to a beer.
This can be extremely helpful when you are brewing a heavy adjunct beer, such as a gluten free ale, that might have a thin or diminished body. Maltodextrin is often made from corn, and a typical composition will be .5% dextrose, 2.5% maltose, 3.5% maltotriose, 93.5% higher saccharides. You will want to consult your vendor for actual numbers.
Body in brewing terms is often described as the thickness or viscosity of a beer as judged by your mouth. The body of a beer is typically described as thin, medium or full. Different varieties of beer are assumed to have a specific body profile; for instance a light lager or pilsner would be expected to have a thin body profile, whereas a stout would have a full body. The term mouthfeel is oftentimes used synonymously with body.
Determining factors in defining and making up a beer’s body include proteins, carbonation level, unfermentable sugars such as maltodextrin, water profile, and alcohol level.
Apparent attenuation is the measurement of the percentage of sugars that have been converted to alcohol by the yeast in a beer. Apparent attenuation is equal to the original gravity minus the final gravity divided by the original gravity, showing the percentage of conversion. A typical apparent attenuation range is between 65 and 80%.
Apparent attenuation calculation example:
Original Gravity of sample beer = 1.06
Final Gravity of sample beer = 1.012
Calculation: 1.06 – 1.012 = .048
.048 / .06 = 80% Apparent Attenuation
There are a variety of ways to impact your apparent attenuation. Some of these include the type of yeast you use, the amount of yeast you pitch, your mash temperature(s), your grain bill composition, and your mash PH. If you are doing extract brewing, then the primary impacts will come from your yeast and any unfermentable sugars that you may add, such as maltodextrin.