1,720,987 research outputs found
Perceived astringency in wine: A predictive model
No full textSensations perceived in the act of tasting are important determinants of consumer response to red wine. Astringency is a tactile stimulus that strongly influences wine acceptability. Astringency descriptors account for more than a half of the total terms in the mouth-feel wheel proposed for describing the sensory properties of red wine. The physiological mechanism of the astringency perception in wine is based on the reaction of phenolic compounds with salivary proteins and the consequent formation of insoluble astringent/protein complexes. The availability of in vitro assays to estimate the strength of the sensation induced by different phenolic compounds became crucial in order to optimise the processing conditions in relation to this important driver of wine acceptability and sensory quality. In this work recent advancements in predicting astringency induced by phenolic compounds are discussed and new and promising methods are presented. Critical points in collecting both sensory and chemical data are reviewed. In particular, the application of the "Astringency Mucin Index" (AMI) in predicting the astringency induced by grape and wine phenol extracts is shown. The results of the use of the AMI on commercial phenolic extract, seed phenolic extracts from 'Aglianico' grape, 18 'Sangiovese' experimental wines and 20 commercial 'Aglianico del Vulture' wines are presented. Future developments of methods capable of predicting astringency are discussed
Extra virgin olive oil bitterness evaluation by sensory and chemical analysis
Full text linkAn experimental investigation was performed on blend extra virgin olive oils (EVOO) from different cultivars and EVOO from different olive monovarieties (Coratina, Leccino, Maiatica, Ogliarola) with the aim to evaluate the possibility of estimating the perceived bitterness intensity by using chemical indexes, such as the total phenol content and the compounds responsible of oil bitterness measured spectrophotometrically at 225 nm (K225 value) as bitterness predictors in different EVOO. Therefore, a bitterness predictive model, based on the relationship between the perceived bitterness intensity of the selected stimuli and the chosen chemicals parameters has been built and validated. The results indicated that the oil bitterness intensity could be satisfactorily predicted by using the K225 values of oil samples
Prediction of perceived astringency induced by phenolic compounds II: Criteria for panel selection and preliminary application on wine samples
No full textIn the following work, subject saliva characteristics affecting panel astringency evaluation in phenolic mixtures were studied. Sixty subjects were selected on the basis of their salivary flow, haze developing capacity and protein concentration. Subjects rated the perceived astringency of tannic acid (TA), commercial procyanidin (PA) and grape seed extract (GSE) solutions with concentration values ranging from 0.42 to 1.4 g/L. Astringency intensity perception proved to be inversely related to saliva flow rate and haze developing capacity. No significant correlations were found between saliva protein concentration and intensity of astringency perception. A panel selected on the basis of subject similarity for flow rate and haze developing capacity rated the astringency intensity of set sample training solutions of TA, PA and GSE with concentrations ranging from 0.39 to 4.48 g/L. The reactivity of the same astringent solutions with mucin was measured in an in vitro assay and expressed in terms of Nephelometric Turbidity Units (NTU). Three predictive models described by a linear regression of astringency intensity vs. NTU were found. The possibility of a practical application of the proposed assay for optimization of wine production was evaluated on 18 experimental wines. A linear correlation was found between the intensity astringency ratings of wine samples and the in vitro assay response. © 2005 Elsevier Ltd. All rights reserved
Prediction of perceived astringency induced by phenolic compounds
No full textA method which can be used to estimate perceived astringency due to polyphenolic compounds is presented here. Thirty subjects were selected on the basis of them having similar salivary flows and they were trained to rate the perceived astringency of tannic acid and grape seed extract solutions. A scale of phenolic compound concentrations ranging from 0 to 3.2 g/L was selected in order to obtain an experimental curve describing the perceived intensity of the sensation. The same astringent solutions were added to a mucin solution in conditions resembling those present in the oral cavity. The formation of polyphenol-protein complexes was measured on the basis of the increasing turbidity of the reaction mixture and was expressed in terms of nephelometric turbidity units (NTU). Experimental curves describing NTU vs polyphenol concentration were obtained. Predictive models of astringency intensity vs NTU were produced. The predictive capacity of the models was checked by comparing the measured and predicted intensities of a set of samples prepared at phenolic compound concentration level varying from 0.94 to 2.13 g/L. © 2004 Elsevier Ltd. All rights reserved
Metataxonomic and metagenomic approaches for the study of undefined strain starters for cheese manufacture
No full textUndefined strain starters are used for the production of many traditional and artisanal cheeses. Composition of undefined starters depends on several factors, and the diversity in strains and species significantly affects cheese quality and features. Culture-dependent approaches have long been used for the microbial profiling and functionalities of undefined cultures but underestimate their diversity due to culturability biases. Recently, culture-independent methods, based on high-throughput sequencing (HTS), have been preferred, with a significant boost in resolution power and sensitivity level. Amplicon targeted (AT) metagenomics, based on 16S rRNA sequencing, returned a larger microbiota diversity at genus and, sometimes, at species levels for artisanal starters of several PDO cheeses, but was inappropriate for populations with high strain diversity, and other gene targets were tested in AT approaches. Shotgun metagenomics (total DNA) and metatranscriptomics (total RNA), although are more powerful in depicting diversity and functionality of undefined cultures, have been rarely applied because of some limitations (e.g., high costs and laboriousness, need for bioinformatics skills). The advantages of HTS technologies are undoubted, but some hurdles need to be still overcame (e.g., resolution power, discrepancy between active and inactive cells, robust analytic pipelines, cost and time reduction for integrated approaches) so that HTS become routinary and convenient for defining complexity, microbial interactions (including host-phage relationships) and evolution in cheeses of undefined starters
Use of by-products of the olive oil industry for bread fortification: Effect of health claims on consumer liking
No full textIn this study the possibility to utilize by-products of the olive oil industry for bread fortification was investigated. In particular, when using a specific decanter made by Pieralisi (Italy) for olive oil extraction it is possible to obtain a by-product having the physical consistency of a paté, whose polyphenols content is very high [about 9600 ppm (f.w.)] and that could find an use in the food industry. After several tests at industrial level to identify the maximum allowable addition of paté that would not cause technological problems in the production of a typical bread loaf, the dough fortification was carried out at 600 ppm. The cooking step caused a 14% polyphenols loss, but due to the water removal the final concentration in the bread was about 2600 ppm. The bread acceptability was then assessed in comparison with a traditional bread loaf using a panel of 110 consumers, giving no information about the bread characteristics. While the data showed higher preference of the traditional bread as far as color and general appearance, the fortified bread was preferred for taste and aroma. The test was then repeated giving the panelist information about the polyphenols content and their beneficial effects on the human health. In this case the fortified bread scored a higher acceptability vs the regular bread. The bread was also analyzed to assess the polyphenols bioavailability after baking and the results indicate that by eating 100 g of fortified bred the polyphenols daily intake would be about 4 times higher than the minimum quantity recommended by EFSA in order to exert a positive influence on consumers’ health. The overall results indicate that fortification of bread with phenolic compounds resulting from the production of olive oil is feasible and that consumers are positively influenced in their choice by the information received
Heating Performances of Tomato-Based Dressing Sauces Undergoing Moderate Electric Fields
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Biodegradable packaging and edible coating for fresh-cut fruits and vegetables
No full textThis work focuses on biodegradable packaging and edible coatings applied to fresh-cut fruits and vegetables and their effects on the product quality. Practical applications are mainly limited to the use of biodegradable materials that, however, do not allow full control of the product moisture loss. Better results can be achieved by the combined use of biodegradable packagings with edible coatings and recent research has shown that enrichment with silver-montmorillonite nanoparticles may be a promising technique. However, the actual utilization of these materials is still limited, due to the high costs of the raw materials and the limited production
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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