Influence of Fermentation Time on the Phenolic Compounds, Vitamin C, Color and Antioxidant Activity in the Winemaking Process of Blueberry (Vaccinium corymbosum) Wine Obtained by Maceration.

Flavonoid compounds, including anthocyanins and flavan-3-ol derivatives, total tannins, total vitamin C and resveratrol were analyzed by HPLC in blueberry fruits, their skin and pulp, as well as in wines produced from them. Two wines were elaborated, with different times of fermentation. The fruit analysis provided information on the distribution of bioactive compounds in the berries, showing that the skin had the highest concentrations of all compounds. The winemaking process needed a maceration stage to extract these compounds from skins to wine. This maceration process increased the concentration of all compounds and the antioxidant activity values measured by the DPPH assay, but long maceration times decreased the compounds and the antioxidant activity, due to the phenolic compounds that were involved in several reactions, such as polymerization, copigmentation, degradation, formation of pyranoanthocyanins and reactions between anthocyanins and tannins. The sensorial analysis of wines showed that partial fermentation wine had better characteristics than total fermentation wine, although both wines had a high acidity.

Enhance Wine Production Potential by Using Fresh and Dried Red Grape and Blueberry Mixtures with Different Yeast Strains for Fermentation.

Red grapes and blueberries are known for their high content of bioactive compounds and antioxidant properties. In Mediterranean winemaking, traditional sun-drying can be replaced by controlled-airflow-chamber-drying, which provides better quality, higher phenolic content, and increased antioxidants. This study aimed to increase the sugar content and phenolic compounds of the must by drying the fruits to fifty per cent of their original moisture content. Two musts were prepared: the first one was prepared by combining fresh red grapes and dried blueberries (M1), while the other was created using dried red grapes and fresh blueberries (M2), followed by fermentation at 25 °C with M05 Mead and X5 yeast strains. The M2 must showed the highest levels of phenolic compounds, red color (A520), total anthocyanins, and antioxidant activity. During fermentation, the anthocyanin content increased mainly in the dried blueberry macerates, where it increased between 4- to 5.5-fold. More bioactive compounds were extracted from the wines produced using yeast inoculation despite the shorter maceration times. A sensory analysis demonstrated consumers' acceptance of the wines in terms of color, flavor, and aroma. In conclusion, the use of red grapes in the production of blueberry red wine proved to be effective, providing higher sugar and must yields, while the dried fruits improved the fermentable sugar content obtaining wines with an alcoholic content between 10 and 11% (v/v). The higher levels of bioactive compounds increased the antioxidant capacity of the resulting red fruit wines.

Surface energy transfer in hybrid halide perovskite/plasmonic Au nanoparticle composites.

The incorporation of plasmonic metal nanoparticles (NPs) into the multilayered architecture of perovskite solar cells (PSCs) has been a recurrent strategy to enhance the performance of photovoltaic devices from the early development of this technology. However, the specific photophysical interactions between the metal NPs and the hybrid halide perovskites are still not completely understood. Herein, we investigate the influence of Au NPs on the photoluminescence (PL) signal of a thin layer of the CH3NH3PbI3 hybrid perovskite. Core-shell Au@SiO2 NPs with a tunable thickness of the SiO2 shell were used to adjust the interaction distance between the plasmonic NPs and the perovskite layer. Complete quenching of the PL signal in the presence of the Au NPs is measured together with the gradual recovery of the PL intensity at a thicker thickness of the SiO2 shell. A nanometal surface energy transfer (NSET) model is employed to reasonably fit the experimental quenching efficiency. Thus, the energy transfer deactivation is revealed as a detrimental process occurring in the PSCs since it funnels the photon energy into the non-active excited state of the Au NPs. This work indicates that tuning the distance between the plasmonic NPs and the perovskite materials by a silica shell may be a simple and straightforward strategy for further improving the efficiency of PSCs.

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.