Why Adding Gypsum to The Mash

       The main function of adding gypsum (CaSO4-2H2O) to the mash is to improve the water quality of the brewing water and the pH of the mash, so that the enzymes can give full play to their functions under suitable pH conditions, and also to make the pH of the wort closer to the isoelectric point of certain proteins when boiling, so as to promote their coagulation. Gypsum regulates pH on the principle that decomposed, free phosphate from malt phytates can create a balance of ionic mixtures.
Calcium ions in gypsum can form first, second and third phosphates with the negatively charged phosphate ions mentioned above, where the third phosphate is insoluble and forms a precipitate. If calcium ions are present in excess, then the above equilibrium shifts to the right, with the constant formation of calcium phosphate precipitates and the constant release of hydrogen ions (H+), with three hydrogen ions released per one molecule of phosphoric acid, thus lowering the pH of the mash and offsetting the rise in pH due to the presence of carbonate (CO32-).

      Gypsum is not added arbitrarily, as the addition of gypsum results in the formation of calcium phosphate precipitates and the loss of large amounts of phosphoric acid (or phosphate), which, along with its salts, is a buffering substance for the wort and a nutrient needed by the yeast. Secondly, adding gypsum in excess leaves behind large amounts of sulphate (SO42-) ions, which can form sulphates with ions such as sodium, potassium and magnesium. Excessive sulphates (e.g. magnesium sulphate, etc.) can have an effect on the taste of the beer, e.g. causing vulgar bitterness, astringency or even after-bitterness.

       Calcium chloride is used in the case of insufficient chloride ions (C1-) in the brewing water, because the presence of the right amount of chloride ions activates the yeast, promotes the action of enzymes and gives a softer flavour to the beer, while its calcium ions (Ca2+) have a similar effect to the calcium in gypsum. Brewing water if the content of chloride ions more than 60mg / L, generally not suitable for the use of calcium chloride, but if you have to use, add the chlorine ions and the total amount of the original chlorine ions in the water is not more than 100mg / L, but also not to have a great impact.

       It should be noted that calcium ions or some enzyme protectants, such as α-amylase, etc., in the α-amylase action of the site to add or the presence of a certain amount of calcium ions, will be conducive to the enzyme action.

       Add gypsum is generally added in the paste pot and saccharification pot at the time of pitching, and the quantity added can be calculated according to the formula introduced in some current professional books, or according to the mash (brewing water and malt quality index), but the effect of adding it in the boiling pot is not too great, and it is prone to cause flavour side effects. It is important to note that the composition and content of the inorganic salts in the brewing water must be understood, and if the carbonate content is very low, or if it contains a lot of calcium sulphate hardness, gypsum can be added sparingly or not at all. Add calcium chloride can also be added directly to the paste pot or saccharification pot can also be added before the first water should be dissolved, mixing, and filter out the insoluble residue, to be added after a little cold.