Flavoring substances stimulate immune defenses

More than just a good flavor

Freising June 18, 2018

Not only do citric acid and spicy 6-gingerol from ginger add special flavors to food and beverages; both substances also stimulate the molecular defenses in human saliva. That is the result of a human clinical trial by a team from the Technical University of Munich (TUM) and the Leibniz-Institute for Food Systems Biology.

Human saliva is a complex, watery mixture made up of vastly different components. In addition to mucosal and immune cells, it contains a large number of molecules that perform a wide variety of biological functions. Not only does saliva play an important role in dietary intake, but it is also crucial to maintaining the health of one’s teeth, gums, and oral mucosa.

At the same time, it also represents the first bulwark against external pathogens. For this purpose, saliva contains various antimicrobial molecules, including the antibacterial lysozyme. These are part of the innate molecular immune system.

It has been proven that factors such as age, health, and what someone eats and drinks influence the composition of saliva. However, little is known about the effects of individual food constituents.

In order to learn more about this, a team of scientists led by Professor Thomas Hofmann, head of the Leibniz-Institute for Food Systems Biology at TUM, studied the influence of the following flavors on the composition of human saliva: citric acid (sour), the sweetener aspartame (sweet), iso-alpha acids (bitter), the flavor enhancer monosodium glutamate (umami), table salt (salty), 6-gingerol (spicy), and the substances contained in Sichuan pepper —hydroxy-alpha-sanshool (tingling) and hydroxy-beta-sanshool (numbing).

How the Molecular Defense System is Activated in Saliva

As the scientists first demonstrated by combining salivary flow measurements, proteome analyses and bioinformatic evaluations, all the substances under investigation modulate the protein composition of saliva to a greater or lesser extent.

Analyses of the biological function of the salivary proteins affected by modulation also showed that the changes triggered by citric acid and 6-gingerol activate the molecular defense system in saliva.

For example, 6-gingerol increased the activity of an enzyme that converts the thiocyanate contained in saliva into hypothiocyanite, approximately tripling the amount of the antimicrobial and fungicidal hypothiocyanite in saliva. The changes triggered by citric acid, on the other hand, caused lysozyme levels in saliva to increase tenfold.

Studies on bacterial cultures have shown for the first time that this increase is sufficient to almost completely prevent the growth of Gram-positive bacteria. Lysozyme acts against this type of bacteria by destroying their cell walls.

“Our new findings show that flavoring substances already display biological effects in the oral cavity that go far beyond their known sensory properties,” said Professor Hofmann from the Department of Food Chemistry and Molecular Sensory Science at TUM. The food chemist explains that one of the goals of food systems biology is to further investigate these using the latest analytical methods. In his opinion, this is the only way to find new approaches for the long-term production of food whose ingredient and function profiles are aligned with the health and sensory needs of consumers.

Publication: Matthias Bader, Andreas Dunkel, Mareike Wenning, Bernd Kohler, Guillaume Medard, Estela del Castillo, Amin Gholami, Bernhard Kuster, Siegfried Scherer and Thomas Hofmann: Dynamic Proteome Alteration and Functional Modulation of Human Saliva Induced by Dietary Chemosensory Stimuli, Journal of Agricultural and Food Chemistry 6/2018. DOI: 10.1021/acs.jafc.8b02092


Prof. Thomas Hofmann
Chair of Food Chemistry and Molecular Sensory Science
Leibniz-Institute for Food Systems Biology at TUM 
Mail: thomas.hofmann@tum.de 
Phone: +49 (89) 289-22201 
Phone 2: +49 (8161) 71-2902

The Leibniz-Institute for Food Systems Biology at TUM comprises a new, unique research profile at the interface of Food Chemistry & Biology, Chemosensors & Technology, and Bioinformatics & Machine Learning. As this profile has grown far beyond the previous core discipline of classical food chemistry, the institute spearheads the development of a food systems biology. Its primary research objective is to develop new approaches for the sustainable production of sufficient quantities of food whose biologically active effector molecule profiles are geared to health and nutritional needs, but also to the sensory preferences of consumers. To do so, the institute explores the complex networks of physiologically and sensorially relevant effector molecules along the entire food production chain in order to make their effects systemically understandable and predictable over the long term.

The Technical University of Munich (TUM) is one of Europe¹s leading research universities, with around 550 professors, 41,000 students, and 10,000 academic and non-academic staff. Its focus areas are the engineering sciences, natural sciences, life sciences and medicine, combined with economic and social sciences. TUM acts as an entrepreneurial university that promotes talents and creates value for society. In that it profits from having strong partners in science and industry. It is represented worldwide with the TUM Asia campus in Singapore as well as offices in Beijing, Brussels, Cairo, Mumbai, San Francisco, and São Paulo. Nobel Prize winners and inventors such as Rudolf Diesel, Carl von Linde, and Rudolf Mößbauer have done research at TUM. In 2006 and 2012 it won recognition as a German "Excellence University." In international rankings, TUM regularly places among the best universities in Germany.