María Blanch

Fructo-oligosaccharides in table grapes and response to storage.

Fructo-oligosaccharides (FOS) have been recognized as health food ingredients with a protective effect against environmental stresses in plants. We have analyzed the profiles of individual FOS in Cardinal table grape pulp, until now undetected, and quantified their changes in response to low temperature and high CO2 levels. FOS separation and quantification was carried out using anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD), and the glucose, fructose and sucrose content of the grapes was also determined. Five FOS were identified and quantified: 1-kestose, neokestose, nystose, nystose b and kestopentaose. While in non-treated table grapes the endogenous FOS remained at steady state levels during storage at 0°C, exposure to 20% CO2 for 3days significant increases the levels of 1-kestose and kestopentaose, members of the inulin series. Considering the competitive advantage afforded by CO2-treated grapes, this transitory FOS accumulation could provide protection against damage caused by low temperature storage.

Increasing Catechin and Procyanindin Accumulation in High-CO2-Treated Fragaria vesca Strawberries

This paper deals with the impact of low temperature and high CO2 levels on flavonols, proanthocyanidins, and anthocyanins, synthesized via branched pathways from common precursors, in strawberries (Fragaria vesca L.). Flavonoids were identified with Q-TOF equipment and quantified by HPLC-quadrupole. Proanthocyanins B1 and B3 accumulated in CO2-treated strawberries, whereas in untreated (air) fruit, flavonoid production was redirected toward anthocyanin accumulation with a sharp decrease in catechin and procyanidin B3 levels. Moreover, in CO2-treated fruit, mainly in those with 20% CO2, anthocyanin accumulation did not decline. Due to its antifungal activity, catechin induction in CO2-treated strawberries could explain the capacity of high CO2 treatments to reduce fungal decay. Ascorbic acid content increased in 40% CO2-treated fruits, whereas in those treated with 20% CO2 an increase in flavonol content was observed. Despite these differences, similar antioxidant capacities were found in untreated and CO2-treated Mara de Bois strawberries.

Effects of High CO2 Levels on Fermentation, Peroxidation, and Cellular Water Stress in Fragaria vesca Stored at Low Temperature in Conditions of Unlimited O2

To better understand the tolerance of strawberries (Fragaria vesca L.) to high CO2 in storage atmospheres, fermentation and cellular damage were investigated. Fruits were stored for 3 and 6 days at 0 °C in the presence of different CO2 levels (0, 20, or 40%) with 20% O2. Changes in pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) gene expression and in fermentative metabolites, as well as in bound water and malondialdehyde (MDA) concentrations, were analyzed. In strawberries stored without added CO2, up-regulation of PDC and ADH was not associated with an increase in fermentative metabolites. By contrast, moderate ethanol fermentation in fruits exposed to 20% CO2 seems to be essential to maintain fruit metabolism, reducing both lipid peroxidation and cellular water stress. However, if the CO2 concentration increases (40%), the excess acetaldehyde and ethanol produced were closely correlated with a decrease in bound water and production of MDA.

Metabolic Responses of Sugarcane Plants Upon Different Plant–Pathogen Interactions

Abstract Sugarcane plants, subjected to environmental stress, mechanical injuries, or infection by pathogens, produce glycoproteins containing heterofructans, composed of a fairly extensive domain of β-1,2-fructofuranoside chains in which galactitol units intercalated. They could act as signaling molecules for cell recognition, able to discriminate between beneficial endophytes and bacterial or fungal pathogens. Infection mechanisms and disease progress are very different for different pathogens. Xanthomonas albilineans produces a gum, a xanthanlike polymer, which obliterates the xylem elements producing desiccation and leaf yellowing, and this disease has been termed “leaf scald.” Sporisorium scitamineum, on the other hand, uses stomata to penetrate the host tissues or secretes hydrolytic enzymes of cell wall polymers, which enable mycelial entry through any point on the surface of the plant. Pathogen spores also secrete quorum signals that increase the number of cells in the inoculum. However, some of the glycoproteins produced by infected cane act as false quorum signals. Then the probability of inhibiting germination increases by increasing the aggregation of the teliospores caused by noxious false signals. Alternatively, infection of sugarcane plants by smut teliospores elicits lignification by activating monolignol production. Lignin deposits increase in the cell walls of the infected plant and impede the entry of the pathogen. Teliospores must displace on the wet surface of the plant, either to find a natural way of entry or to be grouped by the effect of quorum sensing. The displacement occurs by successive contractions and relaxations of the actomyosin complex that composes the cytoskeleton.