CHARACTERIZATION OF BIOACTIVE COMPOUNDS AND QUALITY ATTRIBUTES IN VACCINIUM SPP. DURING DEVELOPMENT RIPENING AND STORAGE.
Creators: name: COCETTA, GIACOMO
Publisher: name: Universit� degli Studi di Milano
Year: 2012

description: Blueberries belong to the genus Vaccinium , a widespread genus with over 200 species of evergreen and deciduous woody plants varying in size from dwarf shrubs to trees. Blueberry possesses one of the highest antioxidant capacities in berries due to the high contents of anthocyanin pigments; it is also a moderate source of ascorbic acid (AsA). It is accepted that the content of phenolics and ascorbic acid in berries is not only affected by genetic differences and pre-harvest environmental conditions, but also by the degree of maturity at harvest. In postharvest, different storage conditions may also strongly influence antioxidant capacity of this produce and there are many factors who contribute to improve fruit quality maintenance such as temperature, gas concentration and cultivar. The aim of these studies is to improve the product quality, by acquiring a better understanding about the evolution of bioactive compounds during maturation and storage and to define the optimal conditions to extend the shelf life of fresh produce while ensuring both commercial and nutraceutical quality. The work consists in the identification and evaluation of antioxidant compounds (such as phenolics and ascorbic acid) of potential use for their functional and bioactive properties during maturation and ripening and under different pre- and postharvest conditions in different blueberry cultivar and species. ? Shelf-life trials were performed along three years in order to test different controlled atmosphere (C.A.) conditions on three blueberry varieties (?Brigitta?, ?Legacy? and ?Duke?). Analyses on phenolic compounds and ascorbic acid content were performed, moreover, we performed analyses aiming to estimate the oxidative status of fruits during storage, by measuring the malondyhaldeide content expressed as TBARs equivalents. We have individuated the storage conditions that guarantee both the longest shelf life and the highest phenolic content during storage. Among the considered varieties, ?Brigitta? showed the best attitude to C.A. storage with the lowest degradation rate, and the highest quality keeping during the storage period. ? Benzothiadiazole (BTH) is a functional analogue of salicylic acid that acts as an elicitor of the phenolic metabolism and of systemic acquired resistence (SAR). Pre-harvest treatments with BTH were performed on two different varieties (?Duke? and ?Brigitta?) during fruit development and ripening. We measured ascorbic acid content, total phenols, total anthocyanins and total flavonoids at four different stages of maturation and ripening. We also measured APX, DHAR, MDHAR and GR enzymatic specific activities. A substantial positive effect of BTH treatment on phenolics and ascorbic acid content was observed in blueberry with different behavior depending on the cultivar studied. A positive effect was also observed on the activity of the enzymes involved in ascorbate recycling. ? Pre-harvest treatments using the phytohormone Methyl Jasmonate (MeJa) were performed. Plants from two cultivar (?Blue Ray? and ?Duke?) were treated with a MeJa solution. Berries nearly expanded after colour breaking were picked 3, 6, 9 and 24 hours after treatment for molecular analyses. After one week from the treatment all fruit from the plants were picked up and stored at -80�C. The whole experimental plan was repeated for two growing seasons. Total RNA was extracted from tissues for gene expression analyses on key enzymes of the phenylpropanoid pathway. Our results showed that the treatment was effective in stimulating the expression of some of the key genes in phenylpropanoids metabolism (such as CHS and PAL). We measured the changes in levels of different classes of phenolic compounds by HPLC. Data obtained from transcripts and metabolite analyses resulted to be well-paralleled and allowed us to make comparisons and observe good correlations in the so called gene-to-metabolite networks for secondary metabolism in blueberry. However more detailed analyses, for example on the regulatory factors of this pathway remains to be performed as an interesting challenge for future analyses. ? Ascorbic acid (AsA) accumulation and the expression of the genes encoding the enzymes of the main AsA biosynthetic and recycling routes as well as the activities of the enzymes involved in AsA recycling were investigated for the first time during the development and ripening of bilberry (Vaccinium Myrtillus) fruit. The results showed that the AsA level was highest in unripe green berries but decreased slightly during the maturation. This was supported by the expression data of the genes encoding the key enzymes in the main AsA biosynthetic route, particularly in the early ripening stages. Activities of the studied enzymes were mainly consistent with the AsA levels. In over-ripe berries, both AsA content and gene expression were markedly higher in skin than in pulp.