Suppression of sweetness: evidence for central mechanism for suppression of sweetness from sucrose by citric acid.

The underlying mechanisms of taste interactions in humans are not well understood, and three mechanisms have been proposed, namely a chemical interaction, a peripheral physiological, and a central mechanism. In the present study, it was investigated which of these mechanisms causes the suppression of sweetness by citric acid. This was investigated using a split-tongue gustometer that can stimulate the two sides of the tongue with different stimuli simultaneously, enabling a comparison of sucrose and citric acid presented either separately on each side of the tongue simultaneously or in a mixture on one side. Two studies were conducted using low (Study 1; n = 50) and high (Study 2: n = 59) concentrations of sucrose (2.5% (w/w) and 10% (w/w), respectively), and citric acid (0.14% (w/w) and 0.18% (w/w), respectively). In neither of the studies was there a significant difference in sweetness intensity ratings between the two conditions where sucrose and citric acid were presented either separately or in a mixture form. However, both showed significantly lower sweetness ratings than without citric acid indicating suppression of the sweetness of sucrose from citric acid. This provides strong evidence for a central mechanism for the suppression of the sweetness of sucrose by citric acid. This mechanism seems to be equal in high and low concentrations of both sucrose and citric acid.

Taste Interactions between Sweetness of Sucrose and Sourness of Citric and Tartaric Acid among Chinese and Danish Consumers.

Tastes interact in almost every consumed food or beverage, yet many aspects of interactions, such as sweet-sour interactions, are not well understood. This study investigated the interaction between sweetness from sucrose and sourness from citric and tartaric acid, respectively. A cross-cultural consumer study was conducted in China (n = 120) and Denmark (n = 139), respectively. Participants evaluated six aqueous samples with no addition (control), sucrose, citric acid, tartaric acid, or a mixture of sucrose and citric acid or sucrose and tartaric acid. No significant difference was found between citric acid and tartaric acid in the suppression of sweetness intensity ratings of sucrose. Further, sucrose suppressed sourness intensity ratings of citric acid and tartaric acid similarly. Culture did not impact the suppression of sweetness intensity ratings of citric or tartaric acid, whereas it did influence sourness intensity ratings. While the Danish consumers showed similar suppression of sourness by both acids, the Chinese consumers were more susceptible towards the sourness suppression caused by sucrose in the tartaric acid-sucrose mixture compared to the citric acid-sucrose mixture. Agglomerative hierarchical cluster analysis revealed clusters of consumers with significant differences in sweetness intensity ratings and sourness intensity ratings. These results indicate that individual differences in taste perception might affect perception of sweet-sour taste interactions, at least in aqueous solutions.

The Role of Intrinsic and Extrinsic Sensory Factors in Sweetness Perception of Food and Beverages: A Review.

When it comes to eating and drinking, multiple factors from diverse sensory modalities have been shown to influence multisensory flavour perception and liking. These factors have heretofore been strictly divided into either those that are intrinsic to the food itself (e.g., food colour, aroma, texture), or those that are extrinsic to it (e.g., related to the packaging, receptacle or external environment). Given the obvious public health need for sugar reduction, the present review aims to compare the relative influences of product-intrinsic and product-extrinsic factors on the perception of sweetness. Evidence of intrinsic and extrinsic sensory influences on sweetness are reviewed. Thereafter, we take a cognitive neuroscience perspective and evaluate how differences may occur in the way that food-intrinsic and extrinsic information become integrated with sweetness perception. Based on recent neuroscientific evidence, we propose a new framework of multisensory flavour integration focusing not on the food-intrinsic/extrinsic divide, but rather on whether the sensory information is perceived to originate from within or outside the body. This framework leads to a discussion on the combinability of intrinsic and extrinsic influences, where we refer to some existing examples and address potential theoretical limitations. To conclude, we provide recommendations to those in the food industry and propose directions for future research relating to the need for long-term studies and understanding of individual differences.