Making Of Soy Sauce
Traditional Method To Make Soy Sauce
Firstly, it begins with the mash mix. This involves soaking soybeans in water until the beans are around 60% moisture. Then they are cooked in a pressure cooker for around 45 minutes. Flour is then added to the cooked soybeans. The spores of aspergillus is then added into the soybean (and wheat) to be mix together. The resultant mash is then spread onto plastic trays to a depth of 3 to 5cm. After laying out on plastic trays, the koji is then left to ferment in a warm room at 25°C to 28°C for 48 hours, resulting in a yellow-greenish gunk due to the growth of the Aspergillus mould. This gunk needs to be constantly stirred, to dissipate any irregular heat spots in the mash arising during the fermentation process.This fermentation stage is very important because it is when the Aspergillus mould starts generating the various enzymes which will eventually digest the proteins and carbohydrates in soybeans .
As a result of the enzymes created by the Aspergillus mould, the starches and proteins in the soybeans are on the way to be broken down into sugars and peptides. The mix is now ready for the introduction of other bacterium and yeasts for the next stage, which is called brine fermentation.This is when brine at 20g salt (sodium chloride) per 100ml is added to the fermented koji. After the treatment with Aspergillus, this watery mix should be very mildly acidic, with a pH of around 6.5. This mixture is then transferred to large fibre tanks with internal temperature control coils to continue fermentation at a reduced temperature of 15°C for 30 days or until the pH drops from the original 6.5 to 5.0. The pH falls (or acidity increases) because pediococcus halophilus is fermenting the sugars into lactic acid. During the entire brine fermentation process, the Aspergillus mould is also salt-tolerant and continues to produce enzymes and breaking down soy starches and proteins in the watery sludge into simple sugars, peptides and amino acids.This causes an amino acid-glycosidic reaction which results in the production of dark reddish-brown compounds called melanoidins due to the Maillard reaction.The second stage of brine fermentation involves the addition of the yeasts zygosaccharomyces rouxii and candida to the tanks and then slowly increasing the temperature of the mixture to 28°C until alcoholic fermentation begins. This means the yeasts are converting sugars into ethanol.
This fermentation stage lasts around 3 months during which more of the brine bacteria and yeasts may be added to maintain the fermentation process.The combination of lactic acid, ethanol, melanoidins, simple sugars, peptides, amino acids and other fermentation by-products is what gives fermented soy sauce its unique flavors, color, aromas and other characteristics.After a few months, the fermented soy mixture is now ready for the final processes of pressing, filtration and bottling as soy sauce. Most modern soy sauces will also undergo pasteurisation at around 70-80°C for a few minutes before bottling. The fermented watery mixture is now transferred from the brine fermentation tanks into vertical presses which will separate the sauce from the residue. The sauce is then filtered and clarified further by sedimentation or centrifugation as necessary. Before bottling, quality control checks would be done at the factory to assess not just the sensory attributes of the soy sauce (taste and aroma) but also the pH, amino acid content, saltiness, colour, microbial contamination levels, ethanol content, et cetera.