A couple of questions -
1) I want to add body to a brew using maltodextrin. The local brew shop said that maltodextrin is the same as powdered corn sugar. Is this correct and if not, what is it's common name and where can I buy it?
2) One recipe I am keen to use said to add 250g lactose to my brew. Now I have read enough to know that lactose is pretty much unfermentable so that Og/FG should be equally affected, but can anyone tell me how to calculate how a given volume / weight of lactose will alter the OG/FG calculation?
Cobber
Most percieved body in a beer is related to the alcohol content. Lower ABV commercial beers (the early ones especialy) were thin and watery. Maltodextrin is a product of the enzymatic or acid hydrolosis of starch. This starch can have many origins including Corn, wheat, rice, sorghum, potato etc...
The enzymes alpha and beta amylase reduce the very long chains of unbranched glucose units that make up starch, into the three sugars of primary interest to the brewer
- Glucose = 1 Glucose unit (full name of the dried form Alpha-dextro glucose monohydrate - dextrose for short)
- Maltose = 2 glucose units
- Maltotriose = 3 glucose units
The extent to which the manufacturer of the product takes the reduction is expressed in dextrose equivalents "The DE rating of a maltodextrin syrup of DE43 means 1kg has the same fermentability of 430grames of dextrose. Band dried spray dried syrups are often sold in brewshops as "powdered corn syrup" although they may not be derived from corn starch. Corn starch is the prefered feed stock for in plants in north America. In Australia the imported chinese version is
mostly produced from wheat starch, so we could call it powdered wheat syrup and still be correct! Starch is Starch! A total conversion will yeild only glucose (well mostly) but by controling the process various other products are also available for use by the brewer. The Glucose, Maltose and Maltotriose are all used by the yeast in that order. The higher sugars such as Maltotetraose = 4 glucose units, Pentose = 5 glucose units and many more, are collectivly called dextrins and are unable to be used by yeast but have an impact on the level of perceived body. However if they are not being converted into ethanol, the best thing for body, it could be argued that adding maltodextrin alone replacing "x" other fermentable could
reduce percieved body.
Additionaly malt extract contains Limit dextrins . Limit dextrins are formed by the incomplete reduction of branched glucose structures called Amylo pectin. Our friend the enzymes that we get for free from barley are not able to break up the branches (the branches have Alpha 1-6 glycosidic bonds, not the easily cleaved alpha 1-4 bonds of starch). Importantly our enzymes are more or less active at different temperatures so our mashing temp will affect our finished body. For example 64 degree mash will yield a drier beer - 67c more body.
So where am I going here? To be honest, too the fridge...
OK where were we.. Yes, maltodextrin to add body. What is the beer you are trying to make? If you want body, make a full strength beer without adjuncts (an adjunct is anything other than Malted barley, water, hops and yeast) substitute the adjunct for liquid or dried malt extract. For the more pedantic brewers or the gluten intolerent add malts derived from other grains
Lactose (milk sugar) is used to sweeten beers like milk stouts is this where you are going?
Unfortunatly too many homebrew stores don't know what they sell in terms of analysis of their adjuncts. Just ask them if they know the DE of their corn syrup! Or the ratio of Glucose, Maltose ,Maltotriose .Mostly they will look like the probervial rabbit in the headlight!
I hate to sound like one of the pedantic, but why do you need to calculate the og/fg ratio. Will you be paying excise? Final gravity is what it is. What yeast are you using and what temperature profile? Temperature and yeast strain have a potentialy bigger impact on flavour profile/body than the addition of 250g of lactose.
The important thing for home brewers is not the the FG, but the end point of fermentation, that is - is the gravity stable. Test your brews, if you have the same gravity for 3 days in a row (sugars are no longer being converted) regardless of the measured gravity, its ready to Bottle/keg. For home brewers a refractometer is better than a hydrometer (insert flame war starter here) all we want to determine is the end point of fermentation. There is a good chance we will drink them at 4.8 or 4.7 ABV so what does it matter? We wont chuck them out if the abv is .3 out! Download
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