Pathway no 6 : ACID HYDROLYSE of STARCH
A starch mash is hydrolysed when subjected to high acidity. The acidic hydrolysis of starch has been industrialised during the 19th century to produce food-grade glucoses by the action of hydrochloric acid on cheap starch (potato, manioc). The brewing pathway No. 6 proceeds by chemical, not enzymatic, means, even though the acidity of the wort comes from, for example, lactic acid bacteria. Many traditional beers around the world are brewed with this technique: kwas (Russia), braga (Eastern Europe), Buza (Bulgaria, Romania), African raw grain beers (no malt), cassava beers without amylolytic ferments (Amazonia, tropical Africa), carob beers (South America, Native Americans in California and Colorado), sago beers (South East Asia, Borneo, Papua New Guinea), etc.
How to acidify a brew without resorting to lactic fermentation? Add to the mash or wort acidifying berries (cranberry, redcurrant, argouse, etc.), acidic vegetable juices (e.g. sorrel, lemon, etc.) or an acidified acetic beer, the leftover from a previous brew.
In the production of beer, this method alone very rarely contributes to the release of sugars from the starch.
A) The lactic acid is too weak and the method too long if it acts alone with a pH 4.5.
B) Too high an acidity is incompatible with the subsequent work of the yeasts.
C) Acetic fermentation involves the degradation of alcohol, a process that is incompatible with the purpose of the brewery.
In fact, the brewing pathway no. 6 often cooperates with other traditional techniques for brewing sour beers known in Europe, Africa or Asia. A sour wort hastens the hydrolysis of the starch.
A starchy slurry can be converted into simple sugars by a strong acid medium (pH < 4). This purely chemical technique is applied in industry to produce cheap glucose.
It is a method that characterises the brewing of kwas in Russia and braga in Central Europe, a simple infusion of breaded cereals with the addition of sour berries or fruits. It is also used to brew beer with the pith of the sago tree in Indonesia.
More generally, the involvement of lactic acid fermentation in traditional brewing methods around the world implies that acid hydrolysis plays a role in the preparation of beers.
Some examples of brewing starting with an acid phase, generally lactic: sake (rice-Japan), Berliner Weisse, Gose and Lichtenhainer (wheat-barley/Germany), kaffir beer (sorghum/South Africa), Lambic (wheat-barley/Belgium), kvas (rye/Russia), braga old acidic beers from Central Europe.
The pathway no 6 is also used to make dried acidic dough in the form of long-life bread patties.This ancient technique (Mesopotamia, Egypt) leads to the baking of breads (bakery) or to the soaking of the dried bread patties (brewery), a preliminary step to the brewing of more or less sour beers. The current vogue for artisanal beers is bringing acidulous beers back in the mainstream. The brewing of these sour beers is based on fully controlled industrial ingredients (malts, laboratory yeasts and lactobacillus, industrial corrective food products, etc.). The acidity is used to enrich a range of tastes. "Sour beers" have little to do with the brewing method No. 6 which uses acid mashing as the main means of starch hydrolysis instead of malting.
The hydrolysis of starch by voluntary acidification of the mash or wort is not to be confused with their normal acidification resulting from the metabolism of microorganisms (sour pH worts). Generally speaking, any infusion or decoction intended for brewing is slightly acidic or tangy, regardless of the methods chosen to hydrolyse the starch.
Traditional or industrial beers are therefore themselves somewhat sour. This feature makes the identification of pathway no. 6 problematic in historical documents describing the brewing processes of indigeneous beers.
In addition, this brewing technique comes into play, sometimes unintentionally, when beverages consist of several ingredients: starch, honey, milk, berries or fruits. This is notably the case for pastoralist peoples (Africa, Central Asia) who are ordinary milk drinkers and occasional beer drinkers when they can afford to buy grain or drink beer from farmers. This is also the case with the traditional non-alcoholic beverages of African and Asian Muslims. These drinks may spontaneously ferment after a few hours and become haram.