Haemanalysis of tannins: The concept of relative astringency
Abstract
The astringency of tannins, that is their efficiency as precipitants of proteins, is determined by their reaction with the proteins of haemolysed blood and calorimetric determination of residual haemoglobin. The method is accurate and sensitive because of the narrow range of concentration of tannin between that required to initiate precipitation (the threshold concentration) and that for complete precipitation. ‘Relative astringency’ (RA) is the ratio of the concentration of the tannic acid to that of the tannin which effects the same degree of precipitation. The RA of certain esters of hexahydroxydiphenic acid and of certain procyanidins of known constitution has been determined and the results applied to the ellagitannins and/or leucoanthocyanins present in species of Shorea, Geranium and other plants. The homology of each of these classes of tannins is discussed in the light of the results.
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Study of the relationship between red wine colloidal fraction and astringency by asymmetrical flow field-flow fractionation coupled with multi-detection
2021, Food ChemistryMacromolecules including condensed tannins and polysaccharides impact wine taste and especially astringency. Asymmetrical Flow-Field-Flow-Fractionation (AF4) coupled to UV detection (UV), multi-angle light scattering (MALS) and refractive index detection (dRI) has been proposed to separate red wine colloids.
The present work aimed at relating AF4-mutidetection profiles with red wine astringency. Fifty commercial red wines characterized by a trained sensory panel were analysed by AF4-UV-MALS-dRI and UV–visible spectroscopy. The analytical data set was built by selecting the three variables most predictive of the astringency score from each table (UV, dRI, MALS, Mw distribution, and UV–visible spectra of whole wine, permeate and retentate A4F fractions) and analysed by principal component analysis. Red wine astringency was more related to variables extracted from the AF4 data than to UV- absorbance of the wine or permeate, confirming the relevance of AF4-multidetection for analysis of the colloidal fraction involved in this perception.
Description of the temporal dynamics in microbial community composition and beer chemistry in sour beer production via barrel ageing of finished beers
2021, International Journal of Food MicrobiologyCurrently, there is a strong interest in barrel ageing of finished, conventionally fermented beers, as a novel way to produce sour beers with a rich and complex flavour profile. The production process, however, remains largely a process of trial and error, often resulting in profit losses and inconsistency in quality. To improve product quality and consistency, a better understanding of the interactions between microorganisms, wood and maturing beer is needed. The aim of this study was to describe the temporal dynamics in microbial community composition, beer chemistry and sensory characteristics during barrel ageing of three conventionally fermented beers that differed in parameters like alcohol content and bitterness. Beers were matured for 38 weeks in new (two types of wood) and used (one type of wood) oak barrels. Beer samples were taken at the start of the maturation and after 2, 12 and 38 weeks. Microbial community composition, determined using amplicon sequencing of the V4 region of the bacterial 16S rRNA gene and the fungal ITS1 region, beer chemistry and sensory characteristics substantially changed throughout the maturation process. Likewise, total bacterial and fungal population densities generally increased during maturation. PerMANOVA revealed significant differences in the bacterial and fungal community composition of the three beers and across time points, but not between the different wood types. By contrast, significant differences in beer chemistry were found across the different beers, wood types and sampling points. Results also indicated that the outcome of the maturation process likely depends on the initial beer properties. Specifically, results suggested that beer bitterness may restrain the bacterial community composition, thereby having an impact on beer souring. While the bacterial community composition of moderately-hopped beers shifted to a dominance of lactic acid bacteria, the bacterial community of the high-bitterness beer remained fairly constant, with low population densities. Bacterial community composition of the moderate-bitterness beers also resembled those of traditional sours like lambic beers, hosting typical lambic brewing species like Pediococcus damnosus, Lactobacillus brevis and Acetobacter sp. Furthermore, results suggested that alcohol level may have affected the fungal community composition and extraction of wood compounds. More specifically, the concentration of wood compounds like cis-3-methyl-4-octanolide, trans-3-methyl-4-octanolide, eugenol and total polyphenols was higher in beers with a high alcohol content. Altogether, our results provide novel insights into the barrel ageing process of beer, and may pave the way for a new generation of sour beers.
Wine taste and mouthfeel
2021, Managing Wine Quality: Volume One: Viticulture and Wine QualityTaste and mouthfeel are essential elements of wine quality and major drivers for expert evaluation and consumer liking. Major taste qualities in wine are sweetness, sourness, and bitterness, contributed by different types of molecules, including sugars, organic acids, and ethanol, while mouthfeel encompasses a number of interrelated tactile sensations. The present chapter reviews current knowledge on the compounds and mechanisms responsible for wine taste and mouthfeel properties, with special emphasis on astringency elicited by phenolic compounds, and presents physicochemical and sensory analysis approaches involved in this research. It then includes a discussion on the impact of some viticulture and winemaking practices on wine composition and associated taste and mouthfeel properties.
Anti-inflammatory, analgesic activity, and toxicity of Pituranthos scoparius stem extract: An ethnopharmacological study in rat and mouse models
2020, Journal of EthnopharmacologyPituranthos scoparius is a medicinal plant that is used in traditional medicine in Algeria and other North African nations to treat several diseases such as asthma, rheumatism, measles, dermatoses, jaundice, and digestive disorders.
Aim of the study: The present investigation was designed to investigate an ethnobotanical survey about Pituranthos scoparius in Setif region, Algeria, and assess the acute toxicity, in vivo anti-inflammatory potential and analgesic effect of Pituranthos scoparius hydromethanolic stem extract (PSSE) in rats and mice models.
Acute toxicity of PSSE was carried out based on OECD guidelines 425. Both possible death and signs accompanying toxicity of animals were monitored for 14 days to establish the median lethal dose (LD50) of PSSE. Anti-inflammatory effect of the extract was evaluated using the xylene, croton oil-induced ear edema, and carrageenan-induced paw edema, whereas the analgesic activity was evaluated using acetic acid-induced abdominal constriction in mice model.
Data from the ethnopharmacological survey showed that 24.47% of people used this plant in traditional (folk) medicine. Results also revealed that PSSE contains high amounts of polyphenols, flavonoids, and tannins, and that the extract did not cause any deaths or changes in the behavior of treated animals; LD50 values were found to be higher than 5 g/kg BW. Additionally, no significant variations were observed in the alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) enzymes, or in the levels of urea and creatinine. Oral administration of PSSE at the doses of 100, 300, and 600 mg/kg produced a significant dose-dependent inhibition effect in both xylene and croton oil-induced ear edema in mice. Administration of PSSE at a dose of 100, 250, and 500 mg/kg significantly (P < 0.05) exhibited anti-edematogenic effect in the carrageenan-induced rat paw edema after 3 h. In acetic acid-induced writhing model, PSSE significantly (P < 0.05) reduced writhing at a dose of 500 mg/kg with 69.92% of inhibition.
Taken all together, PSSE is non-toxic, and exhibits potent anti-inflammatory and analgesic activities. Through the ethnomedicinal study, our findings highlight the medicinal use of PSSE in traditional medicine and as an additional source of natural and safe anti-inflammatory agents.
Invited review: Astringency in whey protein beverages
2020, Journal of Dairy ScienceAstringency is the sensation of mouth drying and puckering, and it has also been described as a loss of lubrication in the mouth. Astringency is perceived as an increase in oral friction or roughness. Astringency caused by tannins and other polyphenols has been well documented and studied. Whey proteins are popular for their functional and nutritional quality, but they exhibit astringency, particularly under acidic conditions popular in high acid (pH 3.4) whey protein beverages. Acids cause astringency, but acidic protein beverages have higher astringency than acid alone. Whey proteins are able to interact with salivary proteins, which removes the lubricating saliva layer of the mouth. Whey proteins can also interact directly with epithelial tissue. These various mechanisms of astringency limit whey protein ingredient applications because astringency is undesirable to consumers. A better understanding of the causes of whey protein astringency will improve our ability to produce products that have high consumer liking and deliver excellent nutrition.