Berry Maturity (berry + maturity)

Distribution by Scientific Domains

Selected Abstracts

Impact of Harvesting and Processing Conditions on Green Leaf Volatile Development and Phenolics in Concord Grape Juice

M.M. Iyer
ABSTRACT:, The disruption of plant cell walls during fruit juice processing results in the enzymatic formation of herbaceous-smelling green leaf volatiles (GLVs). Our objective was to assess the impact of thermal processing conditions on resulting levels of GLVs (hexanal, trans -2-hexenal, hexanol, cis -3-hexenol, and trans -2-hexenol), total phenols, monomeric anthocyanins, and percent polymeric color in Concord grape juice. The effects of fruit maturity and stage of juice processing on juice GLV content was also assessed. Of the GLVs studied, only trans -2-hexenal routinely exceeded its published sensory threshold in finished juice. We observed an inverse linear correlation between berry maturity (total soluble solids) and trans -2-hexenal levels in finished juice (P,< 0.05, R 2= 0.91). Trans -2-hexenal was at a maximum immediately following crushing (569 ,g/kg, >30-fold over detection threshold [DT]), decreased to 100 ,g/kg following depectinization, pressing, and pasteurization, and to 32 ,g/kg following cold-stabilization. The loss of trans -2-hexenal could be explained primarily by its reduction to trans -2-hexenol, which increased from 53 ,g/kg after crushing to 500 ,g/kg after cold-stabilization. High temperature pretreatment of must immediately following crushing ("hot break") resulted in 5- to 6-fold higher concentrations of trans -2-hexenal in the final bottled juice as compared to conventional hot press. Contrary to expectations, no significant increase in phenolics and anthocyanins were observed in hot break conditions. These results indicate that hot break procedures may thermally inactivate enzymes responsible for transforming trans -2-hexenal under normal processing conditions and potentially alter the flavor qualities of the finished Concord juice. Different equivalent pasteurization regimes (82 to 93 °C) prior to bottling had no significant effect on GLV content of the finished Concord juices (P,> 0.05). Practical Application: Introducing new processing techniques to fruit juice production can potentially result in undesirable changes to organoleptic properties. We have observed significantly higher levels of trans- 2-hexenal, a potent herbaceous off-flavor, in Concord grape juice prepared with an initial high temperature heat treatment ("hot break"). Concord juice producers should be cautious in using hot break processing, especially with immature fruit, as it may result in persistence of green aromas in juice. [source]

A method for determination of fruit-derived ascorbic, tartaric, oxalic and malic acids, and its application to the study of ascorbic acid catabolism in grapevines

Abstract Background and Aims:, The majority of the acidity of a grapevine (Vitis vinifera L.) berry is a result of the accumulation of l -tartaric (TA) and l -malic acids (MA). TA is synthesised from l -ascorbic acid (Asc, vitamin C), the metabolism of which is poorly characterised in grapevines. In a distinct pathway, oxalic acid (OA) is also formed from Asc degradation. The aim of this study was to develop a single method whereby the distribution of Asc and its catabolites from fruit and vegetative sources could be determined. Methods and Results:, Effective recoveries of total Asc, TA, OA and MA were achieved with this extraction method, while chromatographic separation was accomplished with reversed-phase high-performance liquid chromatography (RP-HPLC). These results demonstrate that Asc and its catabolites TA and OA rapidly accumulate in immature berries, and that the Asc to dehydroascorbate ratio increases with berry maturity. Conclusions:, A method for the simultaneous analysis of Asc, TA, OA and MA in fruits is provided; moreover, we have demonstrated its use to study their distribution in fruits, rachis, leaves and roots. Significance of the Study:, This method enables accurate monitoring of the accumulation of Asc, permitting further research towards understanding acid metabolism during berry ripening. [source]

Studies on Colletotrichum acutatum and Greeneria uvicola: Two fungi associated with bunch rot of grapes in sub-tropical Australia

Abstract Vineyards in the Hunter Valley and Hastings Valley (sub-tropical NSW) were examined by unaided eye for visible symptoms of bunch rot diseases at berry maturity in 2003 (for a total of five varieties over seven vineyards). Grey mould (Botrytis cinerea) was evident in three vineyards, and ripe rot (Colletotrichum acutatum) was evident in four of those seven vineyards surveyed. Other bunch rots at six of the vineyards could not be readily identified by visual inspection. The incidence of fungi on grapevine reproductive structures (and potentially bunch-rot fungi) was then recorded for a Cabernet Sauvignon vineyard in the Hastings Valley during the 2004/5 and 2005/6 growing seasons, and outcomes are reported here in some detail. By berry maturity, C. acutatum and Greeneria uvicola (bitter rot) were the predominant pathogens isolated from those structures, and constitute the first such report of bitter rot fungi on wine grapes in Australia. Indeed, the frequency of latent infection by C. acutatum and G. uvicola increased with berry development during the growing season. Other fungi isolated included Alternaria spp., Botryosphaeria spp., Cladosporium spp., Epicoccum sp., Fusarium spp., Nigrospora spp., Pestalotia spp., Phomopsis viticola and Trichoderma spp. Isolation of B. cinerea from this vineyard was rare. Infection of various wine grape varieties in vitro with C. acutatum and G. uvicola at post veraison revealed all varieties to be susceptible over a range of temperatures (20,35oC). Based on laboratory studies, there was no infection of berries at a relative humidity (RH) < 50%, and infection diminished at 87% RH. Infection did occur if the berries were first incubated at 100% RH for 24 hours, and then transferred to an environment of lower humidity. [source]

Effects of ethephon, methanol, ethanol and girdling treatments on berry maturity and colour development in Cardinal table grapes

Abstract To hasten berry maturity and improve skin colour, the early-season table grape variety Cardinal was treated (post veraison) with a bunch + foliar spray using either 240 or 480 mg/L ethephon, as well as with 30% methanol, 30% ethanol (v/v); or by girdling. Treatment effects were evaluated in a randomised experimental design, with 10 replications of one plant per plot, down a single row. Ethephon at 480 mg/L applied twice, on July 2 when 5% of the berries showed colouring and on July 9 when 20% of the berries developed partial colour, increased total soluble solids, °Brix/titratable acidity and skin colour. Girdling, methanol and ethanol also increased total soluble solids and berry colouration and caused faster ripening. Ethephon at 480 mg/L was generally the most effective means of hastening ripening and improving colour. [source]