Which of the specialty grains has least amount of sugars in it? Also which "tech" parameter of grains shows sugar amount? In few words I want to brew rich beer but with low alcohol content, the best is 4-4.5% If I do Otter+Biscuit+Melanoidin in total for about 13lbs for 5gal I'll get pretty high alcohol content, is there any way to reduce ABV in one of two similar grain bills? I will be mashing at higher temps near 158 to get more unfermentables. (higher?) Maybe by using any special yeast?
Subbing one specialty grain for another is not going to have a significant impact on gravity. The extract potential among lightly kilned grains like biscuit, amber, and melanoiden doesn't vary much, according to the stats listed in Beersmith. It's not clear why you are locked into using 13 lbs for 5 gallons, but the biggest factor for getting lower ABV is to use less grain overall and get a lower gravity wort. Mashing high and choosing a less attenuative yeast will affect final gravity, which also plays into your ABV. I've never mashed higher than 156F. I tend to do this when I have a lower gravity wort to help retain some body. To choose a less attenuative yeast, first consider what style you are brewing and what yeasts are appropriate to the style. Then look at the attenuation stats and get some idea of which lower attenuators you might want to use. You didn't say what style you are brewing but the grist looks like it could be an English ale; WLP 002 is a good choice (or Wyeast 1968).
Along the lines of what pweiss909 said, Malt spec sheets aren't really going to tell you what you need to know. If you want high Final gravity relative to what would otherwise be average for a given Original gravity, you need some combination of the following... - very high (or very low) mash temp - short mash time - low attenuating yeast strain - grains that tend to yield more unfermentable dextrins That last factor above is sort of what you were asking about, but the spec sheets won't get you there. This spreadsheet might help.... Brewcipher One last thing...you can also replace some of your base malt with either maltodextrin or lactose (but add to the boil, not in the mash) to get a higher final gravity (and lower ABV) for the same original gravity. Of course, you have to decide if either of those ingredients fits your style.
Even without seeing your recipe I am sure the melanoidin and biscuit represent a small % of the total 13# grain bill. Swapping them in or out doesn't change things much. And thirteen pounds in 5.5 gallon batch probably puts you in the 6% range. You aren't looking at dropping the gravity too much to get back to 4.5% If you just take out 3-4# of base, you'll wind up with a similar beer to the original just a lower ABV. Maybe, you want to up your mash temp 2 degrees or so to keep some body after removing some base malt.
Try this out: 68% Munich-10 10% Biscuit 10% C-10 8% Special-B 4% Pale Chocolate Mash at 158-160 for 45 minutes add 0.5 lb maltodextrin/5 gallons at flameout use 1332, 1338, or 1968 (lowest attenuation yeast strains) This should have just enough diastatic power to get you there and will probably resemble a brown ale. Depending on your efficiency - you should get a 4% beer finishing up at about 1.032. Caution - this will probably be really freaking sweet.
Too little ABV and too much residual sugars is not a good combination for a beer shelf life. I think you don´t need to be worried about specialty malts, if your concern is ABV you just need to adjust your OG and FG to go where you want.If you like a beer with a 4.5 % ABV just use : 10 lbs of malts where 90% is a base malt, counting with an average of 68% of extraction efficiency and mashing for 60 min at 156 F you will end up with an OG of about 1048, fermenting with a low attenuative yeast your FG would be around 1015 , this way you are going to get a beer close to the one you desire.
Dilution might could be one solution. Add sterlized water to the bottling bucket to achieve your target ABV. Beer and Wine Journal's Chris Colby has the details here.
