Remigio López-Solís

This comparative literature review evaluated the polyphenolic profiles in seeds, skins, and wines of nine Vitis vinifera L. cultivars. The data compilation revealed that total tannins and catechin exhibited comparatively more homogeneous phenolic profiles in seeds than skins, suggesting differential tissue regulation of specific phenolic biosynthetic pathways within the berry. However, this pattern did not extend to total phenols or epicatechin. Furthermore, the results confirmed wide inter- and intra-cultivar polyphenolic variations, with intra-cultivar dispersion frequently reaching a magnitude comparable to, or exceeding, that observed between cultivars. These variations are likely related to the multifactorial effect of environmental, genetic, and cultural contexts on polyphenol concentration in grapes and wines due to methodological differences (extraction protocols, various quantification techniques and winemaking practices) and biological factors (edaphic and climatic conditions). Furthermore, this high inter- and intra-cultivar variability leads to overlapping concentration ranges, preventing strict varietal categorization. This demonstrates that each study represents only a snapshot of specific environmental and agricultural conditions. Consequently, this review underscores that standardized analytical protocols, rigorous experimental designs, and robust biological replication are essential to distinguish between experimental noise and biological variability, reinforcing the value of comprehensive phenolic profiles for genotypic characterization and targeted winemaking decisions.

Wine fining comprises any operation resulting in the cleaning, stabilisation and improvement of the organoleptic characteristics of wine. Fining agents, such as certain proteins of varying electrical charges, interact physicochemically with wine polyphenols in ways not yet fully understood with diverse effects on wine attributes. In this study, four widely used protein fining agents (casein, ovalbumin and two gelatins) were compared for their ability to interact with three different types of phenolic-rich solutions: a tannic acid solution, a wine grape seed extract and seven different varietal wines. A phenolic characterisation of both the seed extract and all the wines was carried out. The interaction between the protein fining agents and the phenolic solutions was evaluated by diffusion and precipitation tests on cellulose membranes and protein staining. All four protein fining agents interacted to differing extents by producing soluble and insoluble complexes with the tannic acid, grape seed extract and wines. In the wines, the interactions were found to not only depend highly on the protein composition of the fining agent, but also on the chemical composition of the wine. Notwithstanding, the observed phenolic differences between the wines could not fully account for the differential interactions between wine and the fining agents, thus indicating that the wine matrix as a whole may play a role in those interactions.

Morphological features of tear microdesiccates on glass surfaces have been associated with tear fluid status. Tear-film lipids play a critical role in the pathophysiology of some ocular surface disorders. Tear microdesiccates display 4 distinctive morphological domains (zones I, II, III, and transition band). In this study, we investigated the lipid location in tear microdesiccates. Tear from individual healthy eyes (assessed by symptoms, signs, and slit-lamp examination) was collected using absorbing minisponges. One-µL aliquots were allowed to dry under ambient conditions on microscope slides. Tear microdesiccates were examined by various transmitted light microscopy methods. Tear lipids were located both by partition experiments using 2 lipophilic dyes (Oil red O and Nile blue A) mixed with tear fluid under conditions preserving morphological features of microdesiccates and by assessing the effect of 2 solvents markedly differing in polarity (water and ethanol) on the morphology of particular domains of preformed microdesiccates. During desiccation, both Nile blue A and Oil red O became preferentially located in the outermost domain of tear microdesiccates (zone I) without affecting the formation of major fern-like crystalloids (zones II and III). Low volumes of water drastically affected fern-like crystalloids, whereas the gross morphology of zone I was maintained. Contrarily, ethanol, a less polar solvent, was a fixative for fern-like crystalloids, although it markedly affected the bulk of zone I by extracting liquid droplets out of microdesiccates and visibilizing some filamentous subcomponents. Zone I is a hydrophobic domain, whereas zones II and III are highly hydrophilic domains of tear microdesiccates. Zone I represents a lipid-rich structure.

Wine is an acidic beverage; its pH (2.9–3.8) is critically important to its organoleptic properties. During degustation, wine interacts with K_a = 6.1). Few data are available on whether the buffering capacity of saliva may alter the pH of wine and thus its sensorial properties. In this study both in vitro and in vivo approaches were conducted to measure pH in mixtures of representative red and white wines with human saliva. Continuous additions of microvolumes of either wine to a definite volume (3 mL) of saliva in vitro resulted in a progressive and steep decline in the pH of the wine/saliva mixture. Thus, a few microliters of either wine (<0.27 mL) was sufficient to reduce the pH of saliva by 1 pH unit. Further additions of wine to saliva lowered the pH to that of the corresponding wine. In the in vivo assay, definite volumes (1.5–18 mL) of either wine were mixed for 15 s with the mouth saliva of individual healthy subjects before pH determination in the expectorated wine/saliva mixtures. Compared to saliva, pronounced decreases in pH were observed, thus approaching the pH of wine even with the smallest volume of wine in the assay. Altogether, these results demonstrate that the buffering capacity of wine prevails over that of saliva and that during degustation the pH of the wine/saliva mixture in the mouth is, at least temporarily, that of the corresponding wine.

Tear desiccation on a glass surface followed by transmitted-light microscopy has served as diagnostic test for dry eye. Four distinctive morphological domains (zones I, II, III and transition band) have been recently recognized in tear microdesiccates. Physicochemical dissimilarities among those domains hamper comprehensive microscopic examination of tear microdesiccates. Optimal observation conditions of entire tear microdesiccates are now investigated. One-μl aliquots of tear collected from individual healthy eyes were dried at ambient conditions on microscope slides. Tear microdesiccates were examined by combining low-magnification objective lenses with transmitted-light microscopy (brightfield, phase contrasts Ph1,2,3 and darkfield). Fern-like structures (zones II and III) were visible with all illumination methods excepting brightfield. Zone I was the microdesiccate domain displaying the most noticeable illumination-dependent variations, namely transparent band delimited by an outer rim (Ph1, Ph2), homogeneous compactly built structure (brightfield) or invisible domain (darkfield, Ph3). Intermediate positions of the condenser (BF/Ph1, Ph1/Ph2) showed a structured roughly cylindrical zone I. The transition band also varied from invisibility (brightfield) to a well-defined domain comprising interwoven filamentous elements (phase contrasts, darkfield). Imaging of entire tear microdesiccates by transmitted-light microscopy depends upon illumination. A more comprehensive description of tear microdesiccates can be achieved by combining illumination methods.

Purpose: Tear desiccation on a horizontal glass surface followed by low-resolution light microscopy has been used as an expeditious diagnostic aid to evaluate patients suspected of dry eye. The presence of fern-like crystalloids in the dry specimen is the only feature taken into consideration. We demonstrate that different morphological domains of tear microdesiccates can be separated based on distinctive physicochemical properties. Methods: Healthy subjects (Ocular Surface Disease Index questionnaire, laboratory tests, and slit-lamp examination) and 74 young adults from a random student population were recruited as volunteer tear donors. Single tear samples were taken from individual eyes (n = 154) using absorbing polyurethane minisponges. From each sample, aliquots were allowed to desiccate simultaneously on microscope slides positioned either horizontally or vertically followed by comparative dark-field microscopy. Results: Vertical desiccation of each tear sample resulted in highly reproducible top-to-bottom stratification. Particular layers in any vertical microdesiccate represented morphological domains of the corresponding horizontal microdesiccate. Major fern-like crystalloids located at the center of Rolando type I horizontal microdesiccates became concentrated in a prominent layer at the bottom of vertical microdesiccates. Often, these fern-like crystalloids were more vigorous than those of the horizontal counterpart. A number of tear samples from the random population showed no ability to form fern-like crystalloids either by vertical or horizontal microdesiccation. Other prominent layers in vertical microdesiccates represented less noticeable circularly distributed morphological domains of the corresponding horizontal specimens. Conclusions: Microdesiccation of tear fluid on a vertical glass surface causes top-to-bottom stratification of diverse tear components. A more comprehensive expeditious tear assessment is feasible.

Fern-like crystalloids form when a microvolume of tear is allowed to dry out at ambient conditions on a glass surface. Presence of crystalloids in tear “microdesiccates” is used to evaluate patients with Dry-Eye disease. This study aims to examine morphologically the desiccation process of normal tear fluid and to identify changes associated with accelerated tear evaporation. Tear microdesiccates from healthy (Non-Dry Eye) and Dry Eye subjects were produced at ambient conditions. Microdesiccate formation was monitored continuously by dark-field video microscopy. Additionally, accelerated desiccation of tear samples from healthy subjects was conducted under controlled experimental conditions. Particular morphological domains of tear microdesiccates and their progressive appearance during desiccation were compared. In normal tear microdesiccates, four distinctive morphological domains (zones I, II, III and transition band) were recognized. Stepwise formation of those domains is now described. Experimentally accelerated desiccation resulted in marked changes in some of those zones, particularly involving either disappearance or size reduction of fern-like crystalloids of zones II and III. Tear microdesiccates from Dry Eye subjects may also display those differences and be the expression of a more synchronous formation of microdesiccate domains. Morphological characteristics of tear microdesiccates can provide insights into the relative rate of tear evaporation.

Desiccation of human tears on glass surfaces results in fern-like crystalloids. This phenomenon has been associated with tear normality (Tear Ferning Test, TFT) and is used as a diagnostic aid to evaluate patients with Dry-Eye disease. However, TFT is focused on the assessment of only a minor fraction of desiccated tear samples and considers only the relative abundance and density of fern-like crystalloids. The aim of this study was to characterize morphologically entire desiccated micro volumes of tears from healthy donors. Tear samples were collected from 23 healthy young adult volunteers. Tear aliquots (1-3 μL) were allowed to dry on glass surfaces under ambient conditions of temperature (15-25°C) and relative humidity (40-45%). Dry samples were analyzed by dark-field microscopy. Morphometric data were acquired with Image J software. Tear volume was positively correlated with both area and time of desiccation. Morphological features of multiple microdesiccates produced from a single subject displayed striking similarities whereas tear microdesiccates from different healthy subjects displayed consistent differences but shared a common general design. This design may be mostly represented by the occurrence of four distinctive zones, named as zones I, II, III and Transition band. The main features of these zones are described.

Summary: Grape seed and skin proanthocyanidins undergo significant changes during grape maturation. Those changes have been associated with a decreased astringency of grapes collected at later maturation stages. We have now compared the ability of proanthocyanidin‐rich extracts from Carménère grape seeds collected at two stages of berry development (veraison vs. harvest) both to interact with salivary proteins and to produce astringency. Interaction of proanthocyanidins with the salivary protein was assessed by analysing the concentration‐dependent effect of seed extracts both on inducing salivary protein precipitation and on restricting diffusion of the salivary protein on cellulose membranes. Seed extracts from grapes collected at veraison compared with those of grapes collected at harvest displayed a higher ability both to interact with the salivary protein fraction and to produce astringency. As a whole, our observations show that astringency is closely dependent on the magnitude of the interactions between proanthocyanidins and the salivary protein fraction.