An industry-focused study conducted by New Zealand researchers analysed the holding temperature of Sauvignon blanc machine-harvested grapes and the effect on the concentration of grape thiol precursors and that of free thiols in the resultant wines.
A study conducted by Australian researchers over two vintages, 2019 and 2020, explored the effects of aeration timing, amount and duration on Chardonnay fermentations and aroma profiles. Whereas certain aeration regimes delivered positive outcomes, others delivered negative outcomes.
The pre-fermentation phase during the vinification of white and rosé wines significantly increases the quality of the wines, but also carries the risk of oxidation and the development of spoilage microorganisms. These risks may result in loss of quality.
Healthy grapes have a complex microbial ecology including filamentous fungi, yeasts and bacteria. The variety and population of microorganisms present on the grape surface will depend on many factors. However, high sugar concentrations on the berry surface of damaged grapes will especially favour the increase of undesirable microorganisms, such as acetic acid bacteria and wine spoilage yeasts. These microbes are transferred to the must during processing and can have a profound influence on wine composition, flavour and quality. Populations can increase with extended duration of pre-fermentation operations, such as grape transportation, cold soaking, cold storage of juices or grape dehydration. Winemaking strategies to reduce the population of unwanted microbes usually include the use of sulphur dioxide. With the increasing demand for low sulphur dioxide wines, alternative strategies such as bioprotection are explored.
One of the non-Saccharomyces yeasts studied is Metschnikowia pulcherrima. This article will focus on the antagonistic activity of a specific strain, M. pulcherrima LEVEL2 Guardia™, on other wine yeast species for bioprotection applications.