Grapevine cane and stalks were considered for pyrolysis at 400 to 700 °C to produce biochar for increasing the water holding capacity of vineyard soil. Feedstocks were pyrolysed using a continuous feed reactor and the resulting biochars characterized in terms of physico-chemical properties, including water retention performance. Hydrophobicity was found in biochar from both feedstocks pyrolysed at 400 °C, but not at higher temperatures. At low soil matric potential, the pyrolysis temperature was the defining variable in determining water retention whereas at higher pressures, the feedstock was the more important variable. Available water content (AWC) of biochar increased with increasing pyrolysis temperatures, with optimal results obtained from grapevine cane at a pyrolysis temperature of 700 °C, which had an AWC 23% higher than a typical clay type soil. Principal component analysis showed variability in water retention of these biochars to be closely associated with the zeta potential, as well as the carbon and ionic content, suggesting that surface charge and hydrophobicity are key properties determining water holding capacity. Pure biochars were superior in water retention performance to typical sandy soils, and so biochar amendment of these soil types may improve water holding (particularly at field capacity). Further study with pot or field trials is recommended to confirm water retention behaviour and assess the feasibility of application under different viticultural scenarios.

Anthocyanins are polyphenolic compounds that provide pigmentation in plants as reflected by pH-dependent structural transformations between the red flavylium cation, purple quinonoidal base, blue quinonoidal anion, colourless hemiketal, and pale yellow chalcone species. Thermodynamically stable conditions of hydrated plant cell vacuoles in vivo correspond to the colourless hemiketal, yet anthocyanin colour expression appears in an important variety of hues within plant organs such as flowers and fruit. Moreover, anthocyanin colour from grape berries is significant in red winemaking processes as it plays a crucial role in determining red wine quality. Here, nonlinear ordinary differential equations were developed to represent the evolution in concentration of various anthocyanin species in both monomeric (chemically reactive) and self-associated (temporally stable) forms for the first time, and simulations were verified experimentally. Results indicated that under hydrating conditions, anthocyanin pigmentation is preserved by self-association interactions, based on pigmented monomeric anthocyanins experiencing colour loss whereas colour-stable self-associated anthocyanins increase in concentration nonlinearly over time. In particular, self-association of the flavylium cation and the quinonoidal base was shown to influence colour expression and stability within Geranium sylvaticum flower petals and Vitis vinifera grape skins. This study ultimately characterises fundamental mechanisms of anthocyanin stabilisation and generates a quantitative framework for anthocyanin-containing systems.

Field tests to evaluate in-line dosing with bentonite followed by centrifugation as an alternative to batch fining for protein haze control in white wine or juice were undertaken. The tests were performed at a commercial winery with a Sultana wine and Gordo (Muscat of Alexandria) juice and using two types of bentonite: Vitiben and SIHA-Active-Bentonite G. Fining performance was monitored by heat testing and quantification of heat unstable protein by HPLC. Heat test turbidity and heat unstable protein concentration decreased to stable values between 30 s and 2 min after bentonite injection. Sensory evaluation of Sultana wine fined with Vitiben by balanced reference duo-trio difference tests detected no difference between untreated, in-line dosed, and batch fined wine. Furthermore the volume of wine or juice occluded in lees can be substantially reduced by centrifugal compaction. However, incomplete separation of bentonite from wine or juice during centrifugation produced a carryover of 30% of the added bentonite into the clarified wine. This carryover problem may be mitigated, inter alia, by reducing operating flowrate through the centrifuge or using multiple centrifugation steps (in parallel or series). Therefore, inline dosing followed by centrifugation provides a rapid processing method for protein haze reduction in wine or juice with a decreased volume of lees. It can reduce significant value losses presently arising in the wine industry from batch fining and the resulting quality downgrades that occur in wine recovered from bentonite lees by rotary drum vacuum filtration.