Effect of UV-C Irradiation on Quality from Fresh Grapes var. Bordô

Abstract The effect of irradiation through UV-C on the content of phenolic compounds, antioxidant activity, color, and texture profile was evaluated in Bordô variety grapes. Grapes were subjected to stress by irradiation at time of 0.5, 1.0, 4.0, 10 and 30 min that correspond at doses of 0.1, 0.3, 1.0, 2.4, and 7.2 kJ m-2, respectively. The total phenolic and anthocyanins content, antioxidant activity, color and texture of the grapes were evaluated after storage at 22 ºC for 24 and 48 h. In general, samples irradiated did not show an increase in total phenolic content, anthocyanin compounds and antioxidant activity. Hue and Chroma values indicated that the color of grapes did not change when irradiated. Texture profile analysis suggested that UV-C treatment delayed grapes softening.

Effect of temperature and relative humidity on stability following simulated gastro-intestinal digestion of microcapsules of Bordo grape skin phenolic extract produced with different carrier agents.

The stability of microparticles of Bordo grape skin aqueous extract, produced by spray-drying and freeze-drying using polydextrose (5%) and partially hydrolyzed guar gum (5%), was evaluated under accelerated conditions (75 and 90% relative humidity, at 35, 45, and 55°C for 35days) and simulated gastrointestinal digestion. The temperature had a significant effect on the reduction of phenolics content, with retentions varying from 82.5 to 93.5%. The retention of total monomer anthocyanins were in the range of 3.9-42.3%. The antioxidant activity had a final retention of 38.5-59.5%. In the simulated gastrointestinal digestion, a maximum release was observed for the phenolic compounds in the intestinal phase (90.6% for the spray-dried powder and 94.9% for the freeze-dried powder), as well as the antioxidant activity (69.4% for the spray-dried powder and 67.8% for the freeze-dried powder). However, a reduction of monomeric anthocyanins was observed in the intestinal phase.

Microencapsulation of grape (Vitis labrusca var. Bordo) skin phenolic extract using gum Arabic, polydextrose, and partially hydrolyzed guar gum as encapsulating agents.

Bordo grape skin extract was microencapsulated by spray-drying and freeze-drying, using gum arabic (GA), partially hydrolyzed guar gum (PHGG), and polydextrose (PD) as encapsulating agents. Total phenolics and total monomeric anthocyanin, antioxidant activity, color, moisture, water activity (aw), solubility, hygroscopicity, glass transition temperature (Tg), particle size, and microstructure of the powders were evaluated. The retention of phenolics and anthocyanins ranged from 81.4% to 95.3%, and 80.8% to 99.6%, respectively, while the retention of antioxidant activity ranged from 45.4% to 83.7%. Treatments subjected to spray-drying had lower moisture, aw, and particle size, and greater solubility, while the freeze-dried samples were less hygroscopic. Tg values ranged from 10.1 to 52.2°C, and the highest values corresponded to the spray-dried microparticles. The spray-dried particles had spherical shape, while the freeze-dried powders showed irregular structures. The spray drying technique and the use of 5% PHGG and 5% PD has proven to be the best treatment.