Flavor Preferences Conditioned by Dietary Glutamate

Abstract

Our understanding of the molecular basis of umami taste and its appetitive qualities has been greatly aided by studies in laboratory rodents. This review describes methods for testing responses to the prototypical umami substance monosodium glutamate (MSG) in rodents. Two techniques, forced exposure to MSG and 2-bottle choice tests with ascending concentrations, were used to evaluate the responses to the taste of umami itself, and 2 other methods used oral or postoral MSG to modify the responses to other flavors. Intake and preference for MSG are enhanced in mice by experience with MSG and with other nutrients with positive postoral effects. In addition, flavor preferences are enhanced in mice and rats by gastric or intestinal MSG infusions via an associative learning process. Even mice with an impaired or absent ability to taste MSG can learn to prefer a flavor added to an MSG solution, supporting the notion that glutamate acts postorally. The more complex flavor of dashi seasoning, which includes umami substances (inosinate, glutamate), is attractive to rodents, but dashi does not condition flavor preferences. Details of the postoral glutamate detection process and the nature of the signal involved in learned preferences are still uncertain but probably involve gastric or intestinal sensors or both and vagal transmission. Some findings suggest that postoral glutamate effects may enhance food preferences in humans, but this requires further study.

The Reproduction Rate of Peptide Transporter PEPT-1 Deficient C. elegans Is Dependent on Dietary Glutamate Supply

“…L-Glutamate belongs to the non-essential amino acids in mammals and in C. elegans (Vanfleteren, 1980 ; Braeckman et al, 2009 ), and its role as neurotransmitter and modulator of behavior has been described in numerous studies (Zheng et al, 1999 ). Furthermore, its role as taste enhancer by activation of umami taste receptors in mammals is discussed (Ackroff and Sclafani, 2016 ). In this study, we were able to show that supplementation of bacterial food with L-glutamate, D-glutamate and L-glutamine did not change the feeding behavior of ad libitum fed pept-1 C. elegans , and thus a generally increased nutrient supply leading to an improved metabolic status in this amino acid deficient strain could be excluded under the given experimental conditions.…”

Brazilian Nutritional Consensus in Hematopoietic Stem Cell Transplantation: Adults

“…(135) It has gained attention because it is one of the last tastes or flavors to be discovered, and is therefore known as the fifth taste, in addition to the other four: sweet, sour, salty and bitter. (138) Because it activates specific receptors for glutamate and its byproducts, taste-m-GLUR4 (a metabotropic receptor of glutamate) seems to be one of the most preserved tastes during gustatory changes inherent to prolonged exposures to chemotherapy toxicity. (135) einstein (São Paulo).…”

“…Umami can be composed of, in addition to glutamate, other salts such as disodium guanilate and inosinate, naturally present in foods like cheese, tomato and fish. (138) It affects the salivary flow, promoting better dilution of the chemical compounds from foods in the oral cavity. In Brazil, a study showed that it is identified, even at low thresholds, by children diagnosed with leukemia and lymphomas undergoing conditioning chemotherapy, (135) which makes it a possible alternative that should get more attention from those in the field of dietary management.…”

Yeast Extracts: Nutritional and Flavoring Food Ingredients

“…The yeast extracts have been described and used principally as food nutritional and flavoring ingredients, are also progressively used as functional ingredients in functional foods and food complements, and are more marginally used in skin conditioning, skin protection, and as cosmetic and personal care products. , They are also used as a nutritional source in microbial growth media for their content in nitrogen, amino acids, vitamins, nucleic acids, minerals, and carbohydrates. No toxic symptoms or lesions were observed in rats receiving an acute, subchronic, or chronic oral dried fermentate preparation of Saccharomyces cerevisiae .…”