delta H

"... I'm talking an astringent, harsh, almost chemical or metalic, bitter burning flavor." That doesn't sound like botanicals to me. I'd look at the base spirit (which can be hard to clean up if you don't have the correct gear), your water (are you treating your water, at every point - still charge dilution, and distillate dilution), or maybe your still (dissolving gaskets, residual cutting oil, etc - try brushing out your condenser/parrot and see if there is crap in it).

We don't do R&D on anything smaller than a 12 gallon still - and even that needs tweaking to go to 100gal+.

I'd highly suggest that the problem is likely the neutral. Do you make your own, and what equipment do you have to do so? If you are toting, do you rectify it - if not you'd be surprised by the fores/heads that remain in column-produced GNS that are relatively easy to pull off with a batch pot and column. Now, if you are satisfied with the spirit (and we only make gin out of spirit we'd be happy selling as vodka/soju, in terms of quality), then the botanicals can be a thing. Generally speaking, there are some 'hot' spices, like pepper (of various types), ginger, cassia - overdoing those can be unpleasant (though it can be good in a mixed drink - how is your product going to be used - we make a gin to mix and a couple gins to sip, they are very different profiles). Vapor is generally less harsh than macceration, and with vapor (if you have a good setup), you can decide when a batch is done by taste before you pull the laties out in the distillate.

There are a few more natural (and naturalish) colors you might try, some beet/vegetable extracts, carmic acid, they tend to sort red-purple (hibiscus, beet) and red-orange (carmic acid) - a little red-purple seems to look more pink to me than a little red-orange. Most of the natural colorants in the pink-red-purple spectrum are going to fade to yellow-orange-brown over time. The more you have of a pigment, the longer that takes (the oxidizing pigment acts as an antioxidant for the remaining, pulling o2 and ROS out of solution),. So red will last a lot longer than pink, in the acceptable range. Pink can fade to a nearly pee-like color of yellow, which is unappealing. Dark glass helps but then you lose the marketing advantage (see absinthe discussions re green vs brown) We decided that pink with natural was not doable (unless the product sold and was consumed very quickly, like 1-2 months tops from addition). My supposition is that pink color in a clear glass bottle is synthetic food coloring.

So thermostability means that the protein does not unfold (e.g., cooked egg whites don't uncook when cooled). Generally speaking reactions happen faster at higher temp, but it if the fold gets slightly floppy the catalysis might not work as well. Related, but not identical concepts. And yeah, mash can still be gummy at high temps, but the gummy is the issue more than the beta glucans. So if you can pump and ferment it with no issues, the tiny loss of sugar isn't always worth chasing.

In a past life I was a protein chemist at a big enzyme manufacturer - specifically high-temp engineering of carbohydrate hydrolases. Key point about "high temperature" enzymes is that thermoactivity (optimal catalytic temperature) is not the same thing as thermostability - also note that both are impacted by small changes in pH. And the will depend on the specific enzyme (and expression host) you are using in various products, and that gets technical quickly. That said, roughly: 1) Probably not. and 165 f is enough to gel the starch in most grains (not all, though). 2) Do a multistep mash, use it at a permissive temp for the glucanase. 3) Yes, but how much more is highly dependent on mash and fermentation conditions. So is it worth it is the question, really.

We just won a "best in class" for our flavored gin - which is the same spirit and proof as the base gin (prior to botanical infusion). We're about 5 batches in on production, and while it does taste better at 100% the same botanicals as the non-flavored version, it also is easier to make them the same, so you can split the distillate depending on sales needs (flavored vs not flavored. That said, I don't know what extract you plan on using - though infusing dry or fresh botanicals into a gin is pretty easy, just need a light filter after. We do that for Amari we make as well. Any reason you are going with an extract over not?

The point of charcoal 'filtration' is adsorption (surface binding) to remove 'contaminants' from the liquid phase, which could be nasties left in the vodka - or it could mean the oils from the botanicals in your gin. So, don't do that.

Plates and reflux allow more control over the temperature and composition of the vapor. Running just a pot still means the vapor temp/composition is determined by the ABV in the kettle charge, but that that changes over the run, and as such as does the vapor. Is it better? Sort of depends what you are trying to do. Does allow you to run to lower kettle ABV. I can't imagine why you would do this if not for vapor extraction, though.

We produce a number of "floral" gins, a few under our brand name and some contract - I hear we just won a best in class for one of them. Regardless, we make a lot of gins, all of them include at least some flower component, even our London dry (which we don't call a london dry). But even in our most floral gin, one of which is even named after a flower, by weight, the flowers are a tiny proportion of the gin botanical charge. And, as mentioned earlier, these are all vapor extracted botanicals. Flowers are tough, not unlike getting the balance correct on spicy components (cassia, ginger, cubeb, grains of p, black/white pepper, etc.). Overuse of of specific floral components is key flaw in some of the worst gin expressions I've tasted. Too much rose can go perfume.Too much lavender can go towards laundry detergent (no coincidence, laundry, lavender, and lavage all are the same root word). Chamomile is a bit safer to play heavy if you feel so compelled, elderflower is a common one (sort of a honey flavor in the gin). In the end, though, the best suggestion I have is to use a small still to develop your formulas, so you can dispose of less successful experiments that have less cost in time, spirit, and botanicals. Years ago we did about 4 or so experiments a day, lots of strange things. Some don't get used in gin for a reason. Some good memories, those little experiments.

+1 on using electric rather than flame on a small setup. Even a cheap (cycling) electric hotplate is fine, as long as your boiling flask is in a sandbath (a larger flask with sand in it) which will even out the heating of the internal boiler a lot. You can also, in the short term, get around the lack of an integral thermometer in the still by using an infrared thermometer and aiming it at the top of the stillhead. If you do that use some black tape to aim at on the outside of the glass, and calibrate it with water first to make sure the boiling point is correct. (I'll note that Much of my experience is labwork unrelated to ethanol, but similar principles apply.) I would also recommend not running all the way to dry. If you run to 100C (which you should run directly into a graduated cylinder), then add water to the initial volume (or half of the initial volume, etc) you can very easily calculate the %EtOH. This also lets you pick the most accurate range of your hydrometer, if you'd like.

gamma amylase (γ-amylase) is also alpha-glucosidase (AG, or sometimes AMG or limit amylase). Basically it is an exoamylase that cleaves soluble a1-4 glucose polymers down to glucose (if you care, by attack at the non-reducing end of the oligo). Depending on the specific enzyme, sometimes you will also have 1-6 hydrolase activity (amylopectinase, useful on things like rice). In barley malt, the major exoamylase is beta-amylase which makes maltose (glucose-a14-glucose). Most recombinant/exogenous/microbial enzyme exoamylase products are AG.

I suppose I could take a line on the copper and Alzheimer's disease (ironically, I have published in PNAS and the paper was about copper biochemistry), but medical isn't my area of specialty and I've see enough of hypotheses about AD over the years to know to stay out of that mess. However, if one is going to worry about copper in a still, the issue to consider is the ethylcarbamate (urethane) level in the product. Ethyl carbamate is really quite carcinogenic, and is going to be present in rather high levels in certain distillates made from cane and types of fruit (http://www.ncbi.nlm....pubmed/11409971). There is certainly a strong argument for stainless heads/condensers/parrots/etc. in the final distillation. Copper catalyzes a lot of reactions, including the formation of ethyl carbamate... though ethly carbamate is effectively not volatile (in a beverage still setting), so doing a stripping run in copper (or having copper in reflux path of a rectifying run) would likely be a good thing (assuming the last condenser was not copper). Unrelated - I am very confused when I see talk on "non-GMO corn" or "gluten free" on a bottle of spirits. I suppose I could see being opposed to GMOs in general, but DNA doesn't go over a still any better than gluten does.

+1 on the likelihood of carbonates from the dilution water - regardless of what the salts are (likely Ca++ and Mg++ carbonates in this case), as (less polar than water) ethanol concentration increases ions in solution will become less soluble, so things that were perfectly soluble in the initial water will precipitate as the solution becomes less polar. Probably you have high-mineral water, and if your cleaning water is close to saturation it won't be able to effectively dissolve the precipitate. Citric acid is a good suggestion of a cheap divalent cation chelator. Or use better water for dilution.

Some Malt Extract is actually just lautered malt mash that is boiled down. Alternatively, some mashes for these are malt+enzymes (which is still technically malt extract), and some are barley plus enzymes (which is usually called "brewers extract" or something without the word "malt"). Malt extract is an odd thing. If it is boiled down to concentrate there will be a lot of unfermentable sugars/oligosaccharides (good or bad in a beer, but bad in a spirit wash) an some loss of malt flavor (with possible gain of toasty flavor from the boil). If it is vacuum concentrated it should be more fermentable but might have significant flavor loss. Also, as an important note, yeast grown up on a diet of glucose don't do well in fermentation of a high-maltose mash. That means that if one uses a malt extract that had AG enzyme added (all malto-oligos to glucose) to grow up a yeast culture to pitch, then one must at AG to the wash. Conversely, if you want to use malt enzyme only mashing, then you need to grow that yeast up on a starter that didn't have AG in it (you need maltose around of the yeast won't express the transport/metabolism system for it - glucose is the "preferred" carbon source for yeast and most things). Basic point, if you make starter cultures (and you should, it is easy, just need a stirplate and a day), you should make the wash for the starter the same as what you are fermenting rather than risk issues with LME.