Extracting Yeasts Flavor Advantage

Early man wasn’t inclined to gussy up his food: pound it into a paste, roast it on a stick and maybe clean it—that was it. A little serendipity in the form of natural wild yeast changed all that, turning hard, dried grain pastes into fluffy bread or, maybe more providentially, wetter ones into beer. Today’s food industry still prizes yeast’s fermentation abilities but has discovered another valuable function: Yeast can improve and enhance the flavor of a whole spectrum of foods.

Doing flavor a favor 

Those who’ve had the dubious pleasure of tasting yeast “vegetable extracts” like Marmite or Vegemite without being able to “speaka the language,” may shudder when contemplating yeast extract’s flavor. However, “The dose makes the poison,” or, in this case, delicious savory effects.

Yeast-extract spreads start with an ingredient described by The Food Chemical Codex as: “... the water-soluble components of the yeast cell, the composition of which is primarily amino acids, peptides, carbohydrates and salts. Yeast extract is produced through the hydrolysis of peptide bonds by the naturally occurring enzymes present in edible yeast or by the addition of food-grade enzymes.”

As a bonus, yeast extracts contain high levels of B vitamins, perhaps the reason for the staying power of the aforementioned spreads. But, adding small amounts of yeast extracts—typically less than 2%—provides “a mixture of free glutamic acid, nucleotides, minerals and peptides, which provide a multi-dimensional impact on flavor and mouthfeel, says Otis Curtis, business development manager, DSM Food Specialties USA, Inc., Eagleville, PA.

Process to product 

Manufacturers typically start out with high-protein strains of Saccharomyces cerevisiae or debittered brewers yeasts (Saccharomyces cerevisiae or Saccharomyces uvarum), but also use Torula yeasts, lactic yeasts, such as Kluyveromyces fragilis, and Candida utilis grown on various substrates. The strain and the media influence the compounds produced. “Molasses and sugar are the starting materials for the bakers yeast, along with some micronutrients, so the supply is not limited,” says David Adams, president, Savoury Systems International, Inc., Branchburg, NJ.

After a growth period, processors can initiate an autolysis process by modifying the temperature or providing an osmotic shock that causes the yeast to “self-destruct” with their own enzymes. “The autolysis process is similar to your stomach, as indigenous enzymes break down the yeast proteins under mild acid conditions,” says Adams. Control of pH, temperature and length of autolysis dictate the end result. Adding salt or additional proteases and peptidases also helps control the protein degradation and the resulting mixture of components. This greatly affects the flavor profiles of the yeast extracts.

After autolysis is complete, the insoluble cell walls are removed and the soluble components are concentrated and then undergo a short, high-temperature sterilization to inactivate remaining enzymes and stabilize the product. Ingredients called “autolyzed yeast” or “whole-cell yeast” still contain cell walls and other insoluble material.

The finished yeast extracts generally fall into one of the following categories: liquid yeast extracts (approximately 50% to 65% solids), viscous pastes (approximately 70% to 80%) and dried powders.

Souping-up flavor 

Ultimately, what’s left is a savory stew of flavor components—the protein-based compounds mentioned, as well as organic acids and mineral salts—the exact composition depends on the starting cultures, their nutrients and processing they encounter. These can act as flavor enhancers or as flavors in their own right while adding umami mouthfeel characteristics. Some combinations can mask bitterness or sourness and increase savory aroma, and some can add color or even provide antioxidants. Certain yeast extracts “provide authentic, direction flavor profiles, such as roasted chicken or boiled beef, which mimic the flavors developed during traditional culinary preparation techniques,” says Curtis. “The end effect is a more complex enhancement of flavor and impact, which is critical for providing consumers with satisfying food.”

Their high protein content, in the range of about 50% to 75%, makes yeast extracts valuable as building blocks for reaction flavors. The free amino acids react with reducing sugars to form Maillard reaction compounds with brown colors and flavors that characterize everything from caramel to meat to cheese to bread. According to Adams, numerous products with high active nucleotides for flavor enhancement “also contribute some brothy flavor but are fairly neutral for meat flavor, so they can be used in almost any savory application —chicken, poultry, beef, cheese, vegetable. Flavor bases can be developed by using these different building blocks of yeast extracts of this type, or strong, roasted ones that have been oven dried.”

Typically, yeast extracts enhance the flavors of savory baked items, such as bread, pizza and crackers; snack items, especially coatings; soups and broths; sauces; seasonings and condiments; salad dressings; and meat, seafood and vegetarian entrée products. They provide natural, clean-label tools for flavor enhancement, by minimizing or replacing less-consumer- friendly options, such as hydrolyzed vegetable proteins (HVPs), monosodium glutamate (MSG) and salt.

Yeast extracts’ flavor-enhancing proficiency comes in great measure from synergies between the 5' nucleotides and the free glutamates, which result in a 10X to 15X boost in flavor. These are stable to the heat encountered in most food processes; however, glutamate can be broken down by certain enzymes.

The flavor benefits extend to improvements in low-sugar, low-fat and low-salt formulations by masking bitterness, rounding out mouthfeel and enhancing flavors. Salt-free extracts only provide about 0.5% sodium by weight. “It is estimated that 80% of our sodium intake comes from process foods,” explains Curtis. “That means consumers can only do so much to control their sodium intake by restricting use of the beloved salt shaker. A high-nucleotide extract is a perfect solution which allows food processors to reduce sodium from 25% to 50%, depending on the application. We have seen interest in lower-sodium or healthier products, from soups to prepared meals.”

New ingredients contribute little to no flavor for more of a stealth enhancement. “With the more recent development of the higher nucleotide types, one can use a very low amount for enhancement —replacing MSG, etc.—so there is no interference with delicate flavor systems such as seafood or Oriental,” says Adams. “By modification of the fermentation, autolysis or drying, variations can be developed for many end products.”

Ultimately, as Adams points out, yeast extracts provide valuable benefits to consumers and processors: high protein, low fat (0.5%, with no trans fatty acids), kosher/halal/natural, vegetarian, nonallergenic, and nutritional benefits, plus abundant supply and extreme application versatility.