Well, as a complete newcomer to this board, let me jump right into this fray! While many meadmakers have had success with acid additions into the must at the start of fermentation, many others have suffered through sluggish or even stuck fermentations while using those (mostly older) recipes calling for early additions of acid. I can say without doubt, based on personal experience and much documented quantitative research, that there is often no good reason for acid additions pre-fermentation in virtually all mead recipes. In fact, I will support the position taken by John -- often a basic pH adjustment is in order. Research conducted on many available honeys shows that the average pH of honey is in fact in the range of 3.6 to 3.9. That research also tends to show that the gluconic acid - gluconolactone equilibrium within a typical mead must tends to hold pH at or near that of the original honey, unless water with an excess of alkalinity is used in the must. However, when acids are added at the start of fermentation, the equilibrium pH can be skewed lower. Also, there is not enough gluconic acid for that natural equilibrium to prevent the pH of honey must from going lower with just a slight addition of H+ ions. Results of studies by Lallemand (one of the largest commercial suppliers of oenologic yeasts) strongly argue that optimal fermentation kinetics occur when the must is kept between 3.4 and 4.0 pH. At pH levels of 3.2 and below, the yeast are excessively stressed and cannot clear the surplus of H+ ions within cells, leading to their eventual inability to sustain fermentation. At pH of 4.0 and above, the growth of spoilage organisms within the must is not sufficiently inhibited.
When a purely traditional mead must (i.e. honey and water only) is inoculated with yeast, the rapid production of CO2 results in some of the gas dissolving into solution within the must, becoming carbonic acid in the process and effectively dropping the pH of the must. Thus, without adequate buffers to keep the equilibrium pH in the desireable range of 3.4 to 4.0, the very act of fermentation can produce a byproduct that quenches the process.
The bottom line to this argument is that John is correct (although his numbers may be a bit off) -- rather than add acids in advance, in a mistaken belief that such additions will promote fermentation, instead add them as flavour adjuncts at the end of fermentation. If anything, an addition of Potassium Carbonate or Bicarbonate is instead called for.
When a purely traditional mead must (i.e. honey and water only) is inoculated with yeast, the rapid production of CO2 results in some of the gas dissolving into solution within the must, becoming carbonic acid in the process and effectively dropping the pH of the must. Thus, without adequate buffers to keep the equilibrium pH in the desireable range of 3.4 to 4.0, the very act of fermentation can produce a byproduct that quenches the process.
The bottom line to this argument is that John is correct (although his numbers may be a bit off) -- rather than add acids in advance, in a mistaken belief that such additions will promote fermentation, instead add them as flavour adjuncts at the end of fermentation. If anything, an addition of Potassium Carbonate or Bicarbonate is instead called for.
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