by OzDistilling » Sun Dec 27, 2020 11:20 pm
Let me bore you with some basic Sugar Science.
Most of the yeasts that a distillery would use for a cane or beet sugar based wash is Saccharomyces cerevisiae, or SaccC. SaccC 'feeds' (more accurately metabolises) only monosaccharides, like glucose, fructose, and Galactose. Sucrose (cane or beet sugar) is a disaccharide, or dual sugar, combining one molecule of glucose and one of fructose. For SaccC yeasts to metabolise sucrose, it first must be split into its simple monosaccharide components. This splitting is called hydrolysis or inversion. Inversion is caused by subjecting sucrose solutions to heat, or adding a catalyst (an acid like sulphuric or citric) or an enzyme (invertase).
During natural SaccC fermentations, the yeast produces the enzyme invertase, that splits the sucrose first making it available for fermentation. But obviously the invertase must do its job first before the yeast can ferment the glucose and fructose.
Yeasts produce invertase in far larger quantities and much faster than needed, so the onset of inversion phase is usually very fast, and rarely does the lack of invertase, hence inversion, impact fermentation. During the inversion phase, the yeast is also doing other very important things, like reproduction. Forcing yeast into a premature stationary (fermentation) phase and depriving it off a adequate lag and growth phases, may lead to stuck ferments.
There is little empirical scientific evidence that supports the notion that 'pre-inverting' a sucrose wash via hydrolysis (addition of acid), or heat (boiling) promotes, better, faster or more compete fermentation.
Of all the articles that I have read that suggest this, none consider the factor that hydrolysis view the addition of an acid also lowers the pH. Often this hidden side effect of a lower pH is the real reason for a more robust fermentation. You should aim for a pitch pH level of around 7.0. Hard water sources of 8.5+ benefit from the inverted sugar, reducing its effective pH to around 7. The data is skewed.
So, my point is this. Why bother with inversion for your wash sugars, ket mother nature do it for you, and more cheaply.
However, I have not discussed the other aspects of inverted sugar (syrups). It is very beneficial to invert any sugar syrup you use for product sweetening etc. Inverted syrups do not crystallize easily and are more stable in ethanol. Sweetening a 25% ABV liqueur with just sucrose could lead to heat haze, or wall scale due to crystallization. Sweetening with an inverted syrup will prevent this. Inverted 'sucrose' syrups are 10-20% sweeter than inverted sucrose.
Best inversion recipe. For every kg of Sucrose, add 1 litre of water and 1 gm of citric acid. Heat to 70C or until mixture clears, do not heat about 75C or your making caramel. This recipe calls for slightly more C.Acid than required, but results in a syrup with a pH of aroun 4.5 whci has a much improved shelf life and resistance to microbial spoiling.