Search

Vitis vinifera L. cv. País is an ancestral Chilean grape undervalued due to its undesirable oenological characteristics. In this study, steam extraction for the production of grape juice, a new product, according to our knowledge, is proposed as an alternative for the valorization of this fruit. The effect of the extraction time on the composition and antioxidant capacity of País grape juice obtained was evaluated, as well as the change in the phenolic profile during storage. The soluble solid values and total polyphenol and total anthocyanin content increased with the extraction time. However, a residence time of the juice in the extraction device higher than 10 min led to thermal degradation of anthocyanins and flavonols. The most abundant phenolic compound identified and quantified by HPLC-DAD in the País grape juice was cinnamic acid. The storage of juices had a greater effect on anthocyanin and flavonol losses than the residence time of the juice in the extraction device. The antioxidant capacity of juice measured by ABTS and ferric reducing power assays ranged from 3 to 5 mmol trolox/L and from 10 to 18 mM Fe2+/L, respectively. In summary, steam extraction is a viable method to produce País grape juice with antioxidant capacity. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol) (PVA) displays ice recrystallization inhibition (IRI) properties as many antifreeze proteins found in cold tolerant organisms. The molecular architecture and composition (molecular weight and distribution of pendant OH and acetate groups) have been studied to improve the antifreezing properties of PVA, suggesting that the molecular architecture of PVA plays an important role in IRI activity. The present work deals with the preparation of PVA microparticles using an alkaline treatment. The effect of PVA molecular weight on the morphology and antifreezeing properties of PVA microparticles was investigated. The antifreezeing property of PVA microparticles on the susceptibility of flower bud tissues to freeze damage was also evaluated. The alkaline treatment of an aqueous PVA solution produced stable polymer chain aggregates with spherical shapes. The average size of the PVA microparticles increased significantly with the increasing molecular weight of the PVA macromolecule precursor. The PVA microparticles inhibited the growth of ice crystals and blocked ice growth at concentrations as low as 0.01 % w / v . The effect of impeding ice crystal growth by preventing the joining of adjacent ice crystals is attributed to the larger size of the PVA particles adsorbed on the ice surface compared to the aggregated PVA macromolecules in saline solution. The thermal hysteresis activity of PVA macromolecules and microparticles was not detected by differential scanning calorimetry analysis. The PVA microparticles reduced the incidence of freeze injuries in flower bud tissues by 55% and their application, considering the low toxicity of PVA, has a high potential for freeze protection in fruit crops.