One of the drinks I made for my nine rounds of high concept modernist cocktails presentation featured a special edition Yellow Chartreuse where the acacia honey was “removed” and swapped for pungent, full flavored dandelion honey. I had also done this in the past with Green Chartreuse where the non-aromatic white sugar was replaced with palm sugar jaggery creating a sort of white, coconut Chartreuse. I even went further by re-distilling Der Lachs Danzig Goldwasser and using it to fortify a strawberry liqueur.
This is really fun stuff but all the while I referred to it as a rendering and noted some limitations. One of the big limitations is that a small percentage of aroma is left behind in the pot when you re-distill, but why?
First I should point out that the above liqueurs I am manipulating are the product of distillation and not infusion with a small exception for the honey quotient of Yellow Chartreuse which is added after distillation. One of the visiting food scientists at the presentation contested this distillation assertion based on some of his experiences with a vacuum still. The assertion was based on vacuum distilling chartreuse and finding significant amounts of aroma left behind. His experience raises some questions that hopefully I can answer but the experience does not indicate infusion. Even if these particular liqueurs were infused, distillation would separate most of the volatile aroma. If significant non-volatile compounds were left behind in the pot, like gustatory-bitterness or gustatory-acidity, you would have an infusion on your hands but in each case there is nothing, just gustatory-sweetness from the sugar.
What we are both encountering is the fixative effect of the sugars added to the distillate which turns it into a liqueur. Sugar has a capacity to hold on to aroma compounds and keep them from volatilizing. Fixatives are a wild subject that I am only unraveling in tiny pieces. In the context of this modernist cocktail-centric distillation, the fixative effect is working against our rendering, but in many other cases the fixative effect can be used to our advantage.
A great paper, Trehalose Addition to Dehydrated Strawberry Puree by D. Komes et al., explains how food scientists put the fixative effect to work quite well. Trehalose is a miracle sugar that I had first heard about a year ago from a friend who is my science mentor. I sourced some back then but so far haven’t used it. Trehalose is the sugar that allows the desert to bloom after 50 years without rain. It was even added to cosmetics as a preservative before they figured out it was actually functioning as the active ingredient. I didn’t see at first investigation how trehalose would fit into my culinary inquiries. Trehalose is used in Modernist Cuisine (full text search tool), but not regularly and not with an explanation.
The linked paper is concerned with dehydrating strawberry puree. When you dehydrate the puree alone, near all the volatile aroma is lost. When you add sucrose before dehydration, significantly more aroma is kept and when you add trehalose instead of sucrose, an astonishing amount of aroma is kept. The volatile aroma just doesn’t evaporate with the water like you would think. The strawberry experiment parallels the re-distillation of liqueurs with significant sugar contents. Sugar holds on to some of the aroma during vacuum distillation as well as typical atmospheric distillation where the heat is dramatically higher.
Explaining the Chartreuse re-distillation phenomenon has exposed a whole new area of exciting inquiry. There must be countless fixative applications in pastry where trehalose would be helpful. I bet there are also applications for chefs trying to push the limits of dry aging meats. Can new vacuum/pressure techniques allow us to quickly apply fixatives like trehalose? (Modernist Cuisine has great pressure marinading advice) Trehalose is only recently economically viable and you will definitely hear more about it in the future.