Protein Flavoring Problems: The Whys, Wherefores & Solutions

Originally Published: June 25, 2017
Last Updated: June 25, 2021
Protein Flavoring Problems: The Whys, Wherefores & Solutions. A benzaldehyde compound can have an almond flavor or cherry flavor when bound with protein.

From a food or beverage product developer’s point of view, does it make more sense to match the flavor to the protein or the protein to the flavor? This is only one of the questions addressed by renowned University of Minnesota flavor expert, Gary Reineccius, Ph.D., during his discourse on the art and science of flavor titled “Protein Flavoring Problems: The Whys, Wherefores & Solutions.”

“Flavor” is a holistic response to chemical stimuli contributed by specific combinations of selected and highly reactive aroma chemicals (ca.11,300 have been identified in nature); non-volatile tastants (salty, sweet, sour, bitter, umami); and chemesthetic signals (e.g., heat of peppers and cooling of menthol). These combined chemical stimuli provide a pattern of signals to the brain that then are perceived as flavor.

This same constellation of sensory signals must be rigorously managed throughout a food’s manufacturing, storage, handling and preparation processes to ensure that, in the end, “the balance of a product’s sensory inputs meets our expectations,” said Reineccius.

PRotein Flavoring Problems: The Whys, Wherefores & Solutions - Chart of Benzaldehyde (Cherry/Almond) binding by type of protein.

Different proteins bond with different flavors differently. In this experiment, whey and soy quickly stripped volatile benzaldehyde (cherry or almond flavor) molecules from model protein bar system stored at very high temperatures. Thus no levels are shown in the graph above. Equivalent concentrations of rice or pea proteins allowed for better retention of this flavor, in this one case. [Click on image for downloadable PDF]

Proteins in food are very reactive systems, he continued. Proteins can trap flavors in multiple ways through hydrophobic, hydrophilic or ionic reactions; or through covalent bonding with amino acid side chains to prevent their volatilization and sensory detection in the nose and mouth.

Reineccius proceeded to catalog some of the reaction pathways whereby protein-flavor interactions impact product quality. For example, the oxidative decomposition of residual phospholipids resulting in grassy, beany flavor-notes in soy and other legumes is well-known.

Phospholipids are especially difficult to separate from legume proteins during processing, but he noted that the University of Wisconsin had recently been granted a patent on the use of cyclodextrins to strip phospholipids from plant protein streams. Heat and oxidation create their own sensory off-notes for animal proteins, such as in Maillard browning reactions in milk proteins during storage.

So, what are good strategies for dealing with the challenges of protein-flavor binding or off-flavor development? Reineccius counseled a methodical approach. The first step is to identify the off-flavor notes. Next, try to link the identified off-flavors to specific processing steps. Ask oneself if there are practical fixes to the process, storage and/or handling conditions responsible for Maillard browning reactions, oxidation or protein hydrolysis.

If the creation of off-flavor compounds is unavoidable, can the solubility or volatility properties of the identified off-flavor compounds be used to remove them (e.g., solvent extraction, adsorption or heat-stripping)? “You don’t want to have to design a flavor system around the off-flavor notes, if you can avoid it,” said Reineccius. He was highly skeptical of flavor-masking agents. “There has been some progress with this approach for bitterness, but I have yet to see success in truly masking off-odors.”

Another approach is to select proteins based on their flavor reactivity. Different proteins absorb/chemically react with specific flavor compounds at different rates. Thus, there may be an opportunity to pair specific flavors with certain proteins.

“Often, one flavor compound characterizes, is absolutely key, to a product’s flavor profile (additional components round out or complete the flavor profile),” said Reineccius. Benzaldehyde, for example: “When tart, we perceive benzaldehyde as cherry; if not tart, it’s almond.” He described how one of his students used protein bars—fortified with whey, soy, pea and rice protein and stored at 45˚C—to document how benzaldehyde binding was significantly greater for pea and whey proteins than it was for rice or soy proteins. Hence, one might opt for rice instead of whey protein in cherry- or almond-flavored products. [See chart “Benzaldehyde (Cherry/Almond) Binding by Proteins.”]

“Here is my advice, said Reineccius: “When working on a project that involves protein and flavor interactions, work closely with people that have experience in this area, because it (flavor chemistry) is still an art. Otherwise, if we depend only on science to tell us what we need to know, we are in trouble. We have much to learn yet.”

“Protein Flavoring Problems: The Whys, Wherefores & Solutions,” Gary Reineccius, Ph.D., Professor and Past Department Head, Dept. of Food Science & Nutrition, University of Minnesota, greinecc@umn.edu

This presentation was given at the 2017 Protein Trends & Technologies Seminar — Technical Program: Formulating with Proteins.

Click here for access to the PowerPoint presentation of Protein Flavoring Challenges by Gary Reineccius, Ph.D., Professor and Past Department Head, Dept. of Food Science and Nutrition, Univeristy of Minnesota.

Click to see the list of past and future Protein Trends & Technologies Seminars.