ABSTRACT
The sensory properties and appropriateness of cornelian cherry (Cornus mas L.) for processing is very closely related to its ripening stage, recognizable by firmness and skin colour to some extent. Due to the non-uniform ripening on the trees the quality of the fruits offered on the market depends very much on the harvest-method. Today, processors, who usually do not buy fresh fruits but frozen fruits or puree on the market, don`t have a suitable means for the accurate quality assessment of the raw material they need for the processing of high-quality products. The results of this work show for the first time that from the selected parameters (carbohydrates, organic acids, phenols) only flavonols, especially kaempferol-3-glucoside is appropriate to determine the stage of ripeness of cornelian cherries properly independent from species, provenance and crop year. Kaempferol 3-O-glucoside of about 1.75 mg/Kg in wild genotypes and of about 0.80 mg/Kg in most big cornelian cherry species can serve as a reference for sufficient ripeness and therefore for high fruit quality.
ABSTRACT
Red wine is rich in phenolic compounds, which chiefly determine its characteristic taste. One of its major phenolic acid constituents for which an astringency, yet no clear contribution to bitter taste has been reported, is gallic acid (GA). In previous studies, we have demonstrated bitter-tasting constituents to regulate cellular proton secretion (PS) as a key mechanism of gastric acid secretion via activation of bitter taste sensing receptors (TAS2Rs). Here, we hypothesized a contributing role of GA to the red wine-stimulated effect on PS in human gastric tumor cells (HGT-1 cells). Sensory analyses revealed that 10 µM GA as the lowest concentration tested more bitter than tap water, with increasing bitter ratings up to 1000 µM. In HGT-1 cells, the concentration of 10 µM GA evoked the most pronounced effect on PS secretion, either when added to cells as in-water solution or when spiked to a red wine matrix. GA-spiking of Zweigelt and Blaufränkisch red wine samples up to a concentration of 10 µM resulted in an equally stimulated PS, whereas the non-GA-spiked wine samples demonstrated contrary effects on PS, indicating a functional role of GA on PS. Involvement of TAS2R4 in the GA-induced PS was verified by means of an HGT-1 homozygote CRISPR-Cas9 TAS2R4 knockout approach. Moreover, gene expression analyses revealed GA to increase TAS2R4. These results demonstrate a functional role of TAS2R4 in GA-evoked PS as a key mechanism of gastric acid secretion aiding digestion. Moreover, our data provide mechanistic insights, which will help to produce stomach-friendly red wines.
