No abstract

The effects of water, sorbitol and a sucrose fatty acid ester (SE) on the water sorption behaviour and thermal and mechanical properties of pullulan-based edible ®lms as well as the physiological responses of fruit coated with pullulan have been studied. Incorporation of sorbitol or SE in pullulan ®lms resulted in lower equilibrium moisture contents at low to intermediate water activities (a w ), but much higher moisture contents at a w > 0.75; estimates of monolayer values (within 4.1± 5.9 gH 2 O kg À1 solids) were given by application of the Brunauer±Emmett±Teller (BET) and Guggenheim±Anderson±DeBoer (GAB) models. A single glass±rubber transition (T g ), attributed to the polysaccharide component, was detected by calorimetry and dynamic mechanical thermal analysis (DMTA) at a sorbitol level of 15±30% DM. With both tests the strong plasticising action of water and polyol was evident in the thermal curves, and the T g vs moisture content data were successfully ®tted to the Gordon±Taylor empirical model. Multifrequency DMTA measurements provided estimates for the apparent activation energy of the glass transition in the range of Ä 300±488 kJ mol À1. With largedeformation mechanical testing, large decreases in Young's moduli (tensile and three-point bend tests) were observed as a result of water-and/or polyol-mediated glass-to-rubber transition of the polymeric ®lms. In the moisture content range of 2±8%, increases in¯exural modulus (E) and maximum stress (s max ) with small increases in moisture content were found for ®lms made of pullulan or pullulan mixed with 15% DM sorbitol; a strong softening effect was observed when the water content exceeded this range. Addition of sorbitol increased the water vapour transmission rate of the ®lms, whereas addition of SE had the opposite effect. Application of a pullulan/sorbitol/SE coating on strawberries resulted in large changes in internal fruit atmosphere composition which were bene®cial for extending the shelf-life of this fruit; the coated fruit showed much higher levels of CO 2 , a large reduction in internal O 2 , better ®rmness and colour retention and a reduced rate of weight loss. In contrast, similar studies on whole kiwifruits showed increased levels of internal ethylene, which caused acceleration of fruit ripening during storage.

The last step of ascorbic acid (AA) biosynthesis is catalysed by the enzyme L-galactono-1,4-lactone dehydrogenase (GalLDH, EC 1.3.2.3), located on the inner mitochondrial membrane. The enzyme converts L-galactono-1,4-lactone to ascorbic acid (AA). In this work, the cloning and characterization of a GalLDH full-length cDNA from melon (Cucumis melo L.) are described. Melon genomic DNA Southern analysis indicated that CmGalLDH was encoded by a single gene. CmGalLDH mRNA accumulation was detected in all tissues studied, but differentially expressed during fruit development and seed germination. It is hypothesized that induction of CmGalLDH gene expression in ripening melon fruit contributes to parallel increases in the AA content and so playing a role in the oxidative ripening process. Higher CmGalLDH message abundance in light-grown seedlings compared with those raised in the dark suggests that CmGalLDH expression is regulated by light. Finally, various stresses and growth regulators resulted in no significant change in steady state levels of CmGalLDH mRNA in 20-d-old melon seedlings. To the authors' knowledge, this is the first report of GalLDH transcript induction in seed germination and differential gene expression during fruit ripening.

Grafting enhances pulp texture and bioactive composition. Potential suppression of sugar content as a result of grafting is minimized at full commercial maturity. Brief postharvest ambient storage enhances pulp lycopene and chroma, especially in early-picked fruit, notwithstanding the depletion of monosaccharides and citrulline and a limited deterioration of texture. © 2015 Society of Chemical Industry.

No abstract

No abstract

No abstract

No abstract