Anthocyanin evolution and color changes in red grapes during their chamber drying

Designing Novel LiDAR-Detectable Plate-Type Materials: Synthesis, Chemistry, and Practical Application for Autonomous Working Environment

Plate-type hollow black TiO2 (HL/BT) with a high NIR reflectance was fabricated for the first time as a LiDAR-detectable black material. A TiO2 layer was formed on commercial-grade glass by using the sol-gel method to obtain a plate-type structure. The glass template was then etched with hydrofluoric acid to form a hollow structure, and blackness was further achieved through NaBH4 reduction, which altered the oxidation state of TiO2 to black TixO2x-1 or Ti4+ to Ti3+ and Ti2+. The blackness of the HL/BT material was maintained by a novel approach that involved etching prior to reduction. The thickness of the TiO2 layer was controlled to maximize the NIR reflectance when applied as paint. The HL/BT material with a thickness of 140 nm (HL/BT140) showed a blackness (L*) of 13.3 and high NIR reflectance of 23.6% at a wavelength of 905 nm. This is attributed to the effective light reflection at the interface created by the TiO2 layer and the hollow structure. Plate-type HL/BT140 provides excellent spreadability, durability, and thermal stability in practical paint applications compared with sphere-type materials due to the higher contacting area to the applied surface, making it suitable for use as a LiDAR-detectable inorganic black pigment in autonomous environments.

Synthesis of LiDAR-Detectable True Black Core/Shell Nanomaterial and Its Practical Use in LiDAR Applications

Light detection and ranging (LiDAR) sensors utilize a near-infrared (NIR) laser with a wavelength of 905 nm. However, LiDAR sensors have weakness in detecting black or dark-tone materials with light-absorbing properties. In this study, SiO2/black TiO2 core/shell nanoparticles (SBT CSNs) were designed as LiDAR-detectable black materials. The SBT CSNs, with sizes of 140, 170, and 200 nm, were fabricated by a series of Stöber, TTIP sol-gel, and modified NaBH4 reduction methods. These SBT CSNs are detectable by a LiDAR sensor and, owing to their core/shell structure with intrapores on the shell (ca. 2−6 nm), they can effectively function as both color and NIR-reflective materials. Moreover, the LiDAR-detectable SBT CSNs exhibited high NIR reflectance (28.2 R%) in a monolayer system and true blackness (L* < 20), along with ecofriendliness and hydrophilicity, making them highly suitable for use in autonomous vehicles.

Effect of carob variety and roasting on the antioxidant capacity, and the phenolic and furanic contents of carob liquors

BACKGROUND

The production of the traditional carob liquor from Algarve (Portugal) depends on numerous factors such as carob processing, variety and maceration conditions. An experimental design with 36 runs was created to evaluate the effect of the roasting temperature, particle size, variety of carob and time of maceration on several parameters of carob liquors as gallic acid and total phenolic content, the furanic composition (furfural and 5-(hydroxymethyl)furfural), browning index and in vitro antioxidant capacity.

RESULTS

The results revealed that carob variety was the independent variable with the greatest effect on antioxidant capacity, total phenolic and gallic acid content. In particular, AIDA liquors presented the highest results, mainly those prepared with unroasted carob. Meanwhile, Galhosa and Mulata liquors showed the greatest concentrations when the carob pulp was roasted at 150 °C. The furanic composition and browning index were greatly influenced by the carob roasting degree.

CONCLUSION

The levels of the main toxic furanics present in carob liquors, furfural and 5-(hydroxymethyl)furfural, suggest a safe consumption of these beverages even in samples of carobs with the maximum roasting degree. The smallest carob particle size favoured the highest phenolic extraction, while the longest maceration periods decreased the concentration of the toxic furanic compounds studied. © 2018 Society of Chemical Industry.

Coloring biology in grape skin: a prospective strategy for molecular farming

Grapevine is one of the earliest domesticated fruit crops that has been widely prized and cultivated for its fruit and wine. Grapes exhibit a wide range of colors, ranging from the green/yellow to the dark blue tones according to the amount and composition of anthocyanin. During the last decades, many studies regarding the genetic control of the grape color in European, American and Asian cultivars have been well documented. DNA binding genes for several transcription factors, such as MYBA1 and MYBA2 haplotype compositions at the color locus are the key determinant of anthocyanin diversity and grape skin color development. Retrotransposon in the MYBA1 promoter region and mutation in MYBA2 coding sequence resulted in a white-skinned grape. The MYB haplotypes affect the ratio of tri/di-hydroxylated anthocyanins and methylated/non-methylated anthocyanins through the regulation of several structural genes involved in the anthocyanin biosynthesis, resulting in diverse colored tones. The present review provides an overview of the current state of the molecular mechanisms underlying the genetic regulations of the anthocyanin accumulation and diversification in grapes. The hypothesized models described in this review is a step forward to potentially predict the color diversification in different grape cultivars, which translate the advances in fundamental plant biology toward the application of grape molecular breeding.

Effect of Drying on the Phenolic Content and Antioxidant Activity of Red Grape Pomace

Winemaking by-products are considered to be a rich source of bioactive compounds. Grape pomace is susceptible to microbial degradation due to the degree of residual moisture, so the drying of this pomace for conservation is considered to be an essential first step. Previous studies concerning the way in which drying affects winery by-products have produced contradictory results. In this study, a new methodology for drying grape pomace in a climatic chamber has been evaluated. Five red grape pomace varieties were dried in a climatic chamber at 40 °C and 10% relative humidity and the phenolic content and antioxidant activity of the dried and wet pomace samples were compared. The results indicate that this drying process is both feasible and beneficial because significant increases in the extractability of phenolic compounds and antioxidant activity were achieved.

Bioactive Compounds of Chamber-Dried Blueberries at Controlled Temperature and Wines Obtained from Them

The effects of chamber drying under controlled temperature and moisture conditions and fermentation process on blueberry juices to obtain three wines were studied in this work. Drying was carried out with a view to increase the sugar content and obtain wines with an ethanol content similar to a commercial grape wine or to obtain sweet wines. Analyses included color parameters; browning index; and anthocyanin, flavonols, flavan-3-ol derivatives, and tannin concentrations, as well as vitamin C concentration and antioxidant activity. Based on the results, drying increases color and the concentration of anthocyanins and tannins most probably by the effect of dehydration of the berries and diffusion of the colored compounds from the skin to the pulp due to the structural alterations in their skin. In addition, drying decreases flavonols, flavan-3-ol derivatives, and vitamin C concentrations. The browning index, anthocyanins, and tannins decreased with the fermentation time, and vitamin C was constant with the fermentation time. The sensory analysis showed that the wines with the best sensory characteristics were those with residual sugar, partial fermented wines 1 and 2.

Pre-drying and submerged cap winemaking: Effects on polyphenolic compounds and sensory descriptors. Part I: BRS Rúbea and BRS Cora

In contrast to the most worldwide used grape varieties, wine production in Brazil is mainly devoted to the elaboration of table wines from American grapes and hybrids. These grapes show initial disadvantages such as low soluble solids content in their optimal stage of ripening and poor color quality. Based on this, the Brazilian Agency EMBRAPA Grape and Wine has developed BRS type cultivars in order to enhance the quality of the table wines. This study analyzed the phenolic composition and sensory profile of BRS Rúbea and BRS Cora red wines elaborated by traditional and two alternative winemaking technologies: grape pre-drying and submerged cap of chaptalized musts. Pre-dried wines presented low concentrations of anthocyanins/pyranoanthocyanins and flavonols, suggesting that they were partially degraded by the thermal treatment (60°C). These wines were described as bitter and full-bodied because of their higher flavan-3-ols content, suggesting that these compounds were not greatly influenced by thermal degradation. Submerged cap was described as persistent to the palate and with an intense violet hue due to its high anthocyanin and flavonol concentrations. The antioxidant capacity presented a weak relationship with the anthocyanins and stilbenes, but was intensely related to the % of galloylated flavan-3-ols.

Influence of different withering conditions on phenolic composition of Avanà, Chatus and Nebbiolo grapes for the production of 'Reinforced' wines

The impact of postharvest withering rates on the phenolic composition of 'reinforced' wines produced with partially dehydrated grapes was evaluated. The study was performed on winegrape varieties with anthocyanin profiles differently constituted of di- and tri-substituted forms. Dehydration induced limited changes in the anthocyanin profile of berry skins. Nevertheless, the greatest abundance of total anthocyanins and their more stable forms (malvidin-3-glucoside and acylated glucosides) corresponded to the wines made from slow withered Chatus grapes, which were in turn the darkest. In contrast, the wines made from withered Avanà grapes did not meet good chromatic characteristics due to low contents of total anthocyanins and high ratios between di- and tri-substituted forms. Nebbiolo wines showed intermediate values of this ratio, and therefore of clarity and color intensity. The fast process is recommended because higher percentages of galloylated flavanols in the seeds of slow withered Nebbiolo grapes may have a negative influence on wine astringency.

Effect of temperature on the anthocyanin extraction and color evolution during controlled dehydration of Tempranillo grapes

In this paper, the influence of temperature during the controlled dehydration of Tempranillo red grapes has been studied. Two experiments at fixed temperatures of 30 and 40 °C, and a third experiment alternating temperatures of 40 and 15 °C every 12 h were carried out. The must from grapes dried at 40 °C presented the reddest color, and the highest anthocyanin concentration and antioxidant activity. A possible hypothesis could be that the high temperature induced a continuous water evaporation from the grapes, preventing the oxygen entry. At the same time, the dehydration resulted in broken skins, which facilitated the transfer of colored compounds to the pulp, increasing the red color of the musts. However, when the temperature dropped, oxygen could penetrate through the skin and the browning reactions started. As a result, the must obtained from gra pes dehydrated by alternating high and low temperatures presented the least anthocyanin content and the least red color.