Soy Sauce: Little Black Dress in a Bottle

If the belt on your R&D budget hasnt tightened already, its bound to start pinching soon. While formulators always aim to trim the fat, now more than ever they require the product-development equivalent of the little black dress, an ingredient thats functional, economical and versatile.

That little black dress may already be hanging in your test-kitchen closet, but its more amber than black, and its more liquid than lace. Its soy sauce, which in any of its process-friendly forms enhances flavor, balances flavor profiles, and coexists peacefully in clean-label and even reduced-sodium formulations.

Great taste in the making

The natural brewing process for soy sauce hasnt changed much in the past 2,500 years. In its specifics, however, modern soy sauce fermentation is a tightly controlled practice.

At Kikkoman, it starts with the inoculation of a blend of American-grown soybeans and wheat with the seed mold Koji aspergillus, says Mike Evans, vice president, sales and marketing, Kikkoman Sales USA, Inc., San Francisco. After several days of maturation, the resulting culture, called a koji, is mixed with a salt brine to form a mash known as a moromi. The moromi ferments for several months, during which osmophilic lactic acid bacteria and yeasts turn the wheat and soybeans into a reddish-brown, semiliquid mature mash. Then a sequence of pressing, filtering, pasteurization and refining hones this mash into finished soy sauce.

With the moromi tied up for months in fermentation, natural brewing will never qualify as a quick-turnaround process. But during that 6-month maturation, soy sauce develops the complex fingerprint that accounts for its character and functionality.

The defining quality of a stellar soy sauce lies in its flavor balance, Evans says. And that flavor balance is a direct result of fermentation.

The elements of enjoyment

The savory sweetness and complex richness of brewed soy sauce results from fermentation and a combination of ingredients. Among these is salt, which tops out at between 12% and 18% in a naturally brewed product. This salt comes from the brine, not from the fermentation, but its essential to the process, as it creates an optimal osmotic environment for the bacteria and yeasts.

Those yeasts feed on at least a dozen different sugars liberated from wheat starch by moromi enzymes, generating ethanol and other aromatic alcohols in the process. Some of those alcohols react with other portions of the sugars to produce more than 10 different organic acids, including lactic and succinic. A finished soy sauce will have a pH of about 4.8, and 1.0% lactic acid, which helps temper the sauces saltiness and introduces a pleasing tang. Organic acids interact with the ethanol to produce the aromatic esters that give a fine soy sauce its bouquet.

Other important elements in a brewed soy sauce include the peptides and amino acidsglutamic acid, aspartic acid, lysine, alanine, glycine and tryptophanproduced by the enzymatic denaturation of soybean protein. Total nitrogen content, an indicator of protein, is about 1.65% weight per volume in a brewed soy sauce. Glutamic acid is the main amino acid responsible for umami, the savory fifth taste that gives soy sauce its well-rounded profile. The ratio of glutamic acid to total nitrogen is 0.65 in a brewed sauce. Scientists purport this glutamate works synergistically with the sauces salt to create an even greater flavor-enhancing effect. In fact, formulators can use soy sauce to replace some of their formulation salt. At very low use levels, soy sauce can also bring in a real umami kickwithout a characterizing soy-sauce flavor, Evans says. Taking into account other formulation adjustments, a number of product developers Ive worked with have found it a useful tool for reducing the sodium chloride levels of their products.

Soy sauces amino acids also participate with sugars in the Maillard reaction, creating the soy sauces trademark light-amber color. Color clarity and depth are important indicators of soy sauce quality, and many of the components that participate in color reactions also contribute to flavor. Oxygen exposure can darken soy sauce, so users should heed their suppliers advice to keep any open product sealed and refrigerated.

Alternative routes

Not all soy sauces are products of the natural brewing process. The most-common alternative production method is chemical hydrolysis using hydrochloric acid to break down soybean proteins to amino acids. When maximum hydrolysis is reached, the mixture is cooled to halt the reaction, then neutralized, filtered, mixed with active carbon and purified.

Because many nonbrewed sauces contain no wheat ingredientsand because no fermentation occurs to free up sugarscorn syrup is often added. Other ingredients found in chemically hydrolyzed soy sauces include hydrolyzed corn and soybean proteins, citric acid for tartness, and monosodium glutamate for umami.

Chemical hydrolysis is a quicker production method, but it yields a soy sauce without the organoleptic complexity of naturally brewed. The low glutamic acid content leads some manufacturers to add glutamate-rich ingredients like wheat gluten to boost totals; meanwhile, the amino acid tryptophan is almost entirely absent. The main organic acid in fermented soy sauce is lactic, while formic takes the lead in chemically produced. And chemical hydrolysis can trigger secondary reactions that produce unwanted byproducts like dimethyl sulfide, hydrogen sulfide and furfural, all of which have strong aromas.

Soy sauce is a versatile ingredient with proven process stability. It withstands retort and pasteurization temperatures without flashing off of aromatic volatiles, and stores for up to 18 months unopened at room temperature. Durable, practical, adaptable: It really is a little black dress in a bottle.

Debbie Carpenter is senior marketing manager, foodservice & industrial, Kikkoman Sales USA, Inc., San Francisco.