THE ROLE OF MINERAL NUTRITION ON YIELDS AND FRUIT QUALITY IN GRAPEVINE, PEAR AND APPLE

ABSTRACT Fertilization of temperate fruit trees, such as grapevine ( Vitis spp.), apple ( Malus domestica), and pear ( Pyrus communis) is an important tool to achive maximum yield and fruit quality. Fertilizers are provided when soil fertility does not allow trees to express their genetic potential, and time and rate of application should be scheduled to promote fruit quality. Grapevine berries, must and wine quality are affected principally by N, that regulate the synthesis of some important compounds, such as anthocyanins, which are responsible for coloring of the must and the wine. Fermenation of the must may stop in grapes with low concentration of N because N is requested in high amount by yeasts. An N excess may increase the pulp to peel ratio, diluting the concentration of anthocyanins and promoting the migration of anthocyanins from berries to the growing plant organs; a decrease of grape juice soluble solid concentration is also expected because of an increase in vegetative growth. Potassium is also important for wine quality contributing to adequate berry maturation, concentration of sugars, synthesis of phenols and the regulation of pH and acidity. In apple and pear, Ca and K are important for fruit quality and storage. Potassium is the most important component of fruit, however, any excess should be avoided and an adequate K:Ca balance should be achieved. Adequate concentration of Ca in the fruit prevents pre- and post-harvest fruit disorders and, at the same time, increases tolerance to pathogens. Although N promotes adequate growth soil N availability should be monitored to avoid excessive N uptake that may decrease fruit skin color and storability

White wine protein analysis by capillary zone electrophoresis

Capillary zone electrophoresis was evaluated as a method for the analysis of wine proteins. Seven wines from three different varieties, Chardonnay, Sauvignon blanc, and Muscat of Alexandria, were used in this systematic analysis of the effect of variables of capillary electrophoresis conditions on wine protein profiles. While there was some differences in the magnitude of protein peaks as a function of vintage and winemaking conditions, each of the varieties displayed a distinct and distinguishable protein profile. If wine is analyzed directly, both proteinaceous and nonproteinaceous UV-absorbing materials are detected. The protein fraction can be obtained from wines by ultrafiltration and analyzed separately. Resuspension of the retentate proteins following ultrafiltration under conditions allowing sample stacking yielded the greatest number and sharpest separation of peaks. The electrophoresis running buffer impacted protein profiles and number of peaks, as expected. Protein peaks were found to be protease-sensitive, suggesting that wine proteins are not intrinsically resistant to protease degradation. Hazes induced by heat/chill treatment effectively stripped the wines of protein content. Capillary zone electrophoresis represents an excellent tool in the analysis of wine proteins and has the potential to differentiate wine varietals

Assessment of the Brettanomyces bruxellensis metabolome during sulphur dioxide exposure

Brettanomyces bruxellensis displays a high degree of genotypic and phenotypic polymorphism and is the main yeast species involved in wine spoilage. The innate resistance of 108 B. bruxellensis strains to the antimicrobial agent SO2 used in winemaking was investigated. Nineteen strains (17.6%) were sensitive to SO2 , failing to grow at the lowest concentration tested (0.1 mg L-1 molecular SO2 ). Twenty-nine strains (26.8%) grew at 0.1 mg L-1 , 42 strains (38.9%) grew at 0.2 mg L-1 , and 16 strains (14.8%) were able to grow as high as 0.4 mg L-1 mol. SO2 . Two strains able to grow in the presence of 0.6 mg L-1 mol. SO2 were further studied by GCMS-TOF analysis to define the metabolic response to SO2 treatment. Two hundred and fifty-three intracellular metabolites were detected. The main effect observed was a decrease in cytoplasmic levels of polyols and an increase in levels of some amino acids, alanine, glutamic acid, glycine, proline, 5-oxoproline, serine and valine, which were significantly accumulated in the presence of SO2 . No alteration in the pentose phosphate pathway was observed, suggesting NADPH usage could be diverted to other pathways. Finally, a change in metabolites involved in the glycerophospholipid pathway (glycerol-3-phosphate and myo-inositol) was also found

Discrepancy in glucose and fructose utilisation during fermentation by Saccharomyces cerevisiae wine yeast strains

Copyright © 2009 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reservedN.J. Berthels, R.R. Cordero Otero, F.F. Bauer, J.M. Thevelein, I.S. Pretoriu