Applying Chemistry to Solve Protein Flavoring Issues

Originally Published: November 10, 2014
Last Updated: March 3, 2021
Peach and tropical-type flavors can offset astringency in whey-based beverages, as in this peach smoothie.

November 7, 2014 – One need not be an industry veteran to know the consumer’s bottom line is taste—and its close companion is flavor. Yet, as more proteins find their way into everything from sports beverages to energy bars, product developers are applying chemistry to solve protein flavoring issues for these in-demand ingredients that present challenges.

Robert J. McGorrin, Ph.D., department head and Jacobs-Root Professor, Food Science & Technology, Oregon State University, opened a door onto those challenges as he presented strategies for overcoming them, in his discussion, “Applying Chemistry to Solve Protein Flavoring Issues.”

Prefacing his talk with the acknowledgment that flavor can make or break a product’s commercial success and consumer acceptance, McGorrin quickly got down to explaining how and why product flavor goes wrong—whether by way of heat, processing, oxidation, pH fluctuations or interactions with other ingredients—namely, proteins.

It’s not that proteins themselves contribute unwanted flavors— although volatile impurities in protein ingredients (and amino acids) certainly can. Rather, it’s what happens when proteins bind, absorb, release or otherwise react with constituents of the product matrix—flavor ingredients, in particular. The off-notes that result are infamous among product developers, and McGorrin presented an inventory of classic flavor defects attributable to common protein sources and ingredients.

For instance, alcohol- and ketone-containing flavors might form hydrophobic bonds with the beta-lactoglobulin proteins in whey. While these bonds are largely reversible, more permanent covalent bonds can form between aldehydes, like the benzaldehyde responsible for cherry flavor, and the amino acid dipeptide aspartame in, say, an artificially sweetened soda. When this happens, McGorrin explained, what’s known as a Schiff base forms, and over the soda’s shelflife at room temperature, both the cherry character and its sweetness can disappear.

By analogy, the same types of Schiff reactions can occur between flavors and proteins. McGorrin also noted that sulfur-containing flavors, like mercaptans and thiols, can form disulfide bonds with the amino acids cysteine and methionine, yielding burnt-rubber and cabbage off-notes, particularly in retorted beverages. And, there are more reactions where those came from, all with sufficiently complex chemistry. As a rule of thumb, he said, flavor-binding strength and propensity are related to protein type, with soy and whey binding more readily than gelatin, casein or corn, generally speaking.

Bringing matters back to the benchtop, McGorrin turned his focus to protein-boosted products—beverages in particular. He noted they are on the more challenging end of the formulation spectrum because of their high water activity (Aw) and being part of a “dynamic” product medium. Because protein beverages are normally thermally processed, flavors often change during heating, or are lost by reactions with other ingredients (flavor “scalping”).

However, beverages also often have advantages in regards to flavor stability, since they are usually refrigerated. McGorrin quoted colleagues who say formulators often have to use flavors “by the bucket-load”—upwards of four to 10 times the normal amount—to counter act losses and changes that take place in beverages formulated for high-protein content. He then laid out four hypothetical challenges that high-protein formulations often face, and several strategies to address them:

1. Flavor congruency: When dealing with general protein off-flavors, consider following what McGorrin calls a flavor congruency approach—the formulation equivalent of “If you can’t beat ‘em, join ‘em.” In other words, if the challenge is an earthy pea protein or a beany soy protein, select a flavor profile that’s supposed to include those “off” notes, like peanut or nut flavors. Or simply co-opt the off-flavor as part of the intended profile. In this case, a green note in a soy protein could round out a “jammy” strawberry into a more true-to-fruit flavor.

2. Soy’s bitterness: When soy proteins encounter low pH levels, bitterness results. McGorrin credited vanilla and peach flavors with masking both that bitterness and soy’s notorious beany notes. And, if the beverage can be processed either with high shear or nano-processing, he added, the improved emulsion stability will contribute creaminess and improve flavoring efficiency.

3. Bitter blocking: Another way of addressing bitterness, McGorrin went on, is to counterbalance it with increased sweetness. However, in an era of calorie restriction, that may not be an option. The solution here, he said, is to use bitter blockers that “distract” the senses from the bitterness. He listed sodium chloride, monosodium glutamate and adenosine monophosphate as examples, but noted that flavor houses can build proprietary solutions.

4. Avoiding astringency: When whey beverages drop below a certain pH—3.5 is often the cutoff—they can become astringent, which is the sensation that comes from the interaction of saliva proteins with constituents in the drink. One hedge against this is to raise pH—but that introduces protein-stability and beverage clarity issues. Alternatively, McGorrin suggested adopting a tropical flavor profile, such as mango, pineapple and coconut, all of which can overcome bitterness. Peach, citrus and apple can also counteract some astringency, he added.

Regardless of the challenge or solution, McGorrin recommended working with suppliers early and often in the R&D process. While one doesn’t have to disclose deep formulation secrets, data about moisture content, pH, heat processing, storage conditions, percentage protein, and the addition of other vitamins, minerals and high-intensity sweeteners can help flavor partners put together a successful and efficient flavor solution that cuts time to market and makes good on both the promise of protein and a company’s promise to its consumers.

Robert J. McGorrin, Ph.D., Department Head & Jacobs-Root Professor, Food Science & Technology, Oregon State University,, 

The summary above is an excerpt from the “2014 Protein Trends & Technology Seminar Magazine: Formulating with Proteins”