Figure out Potential SG and other metrics for a new ingredient

I'm running an experiment of making small batches of beer with a mix of 2-row malt and various starchy vegetables; for example, right now I have a half-gallon batch of parsnip ale in primary.

My question is, how do I figure out metrics like Potential SG, Protein, and Moisture % to add parsnip or other vegetables as new grains in BeerSmith2? I already checked the available add-ons, and didn't see anything that included vegetables.

SquidPope said:

My question is, how do I figure out metrics like Potential SG, Protein, and Moisture % to add parsnip or other vegetables as new grains in BeerSmith2? I already checked the available add-ons, and didn't see anything that included vegetables.

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Errrmmmm... true. Vegetables like parsnips are not an add on.

To get protein, look up the nutrition data and see how many grams of protein are in a serving, then scale this to a pound or kilo.

The easiest method to figure water content is to simply weigh the vegetable, then dehydrate it and weigh it again. The difference is water weight and should be expressed as a percentage of the starting weight. 

To figure the extraction, need a control. You must mash just pale malt to get an extract by weight. That is simply measuring the gravity after mashing one pound of grain and sparging to get 1 gallon of wort. Make sure the grain runs dry.

Then, adding 1 lb veg to a 1 lb grain mash, you'll sparge to get 1 gallon. The difference between the control and test is the gravity of the veg. If you were careful in the control to precisely measure the sparge volume to run dry, any water trapped in the grain/veg mash should be measured because it represents the water content of the veg.