South Africa Wine Research Projects

3. OENOLOGY RESEARCH COMPLETED PROJECT

PROCESS CONTROL AND MONITORING OF PHENOLIC COMPOSITION DURING ALCOHOLIC FERMENTATION

WW JT 19-02 Dr Jose-Luis Aleixandre-Tudo, South African Grape and Wine Research Institute,

Stellenbosch University Date completed: 2023

AIM AND INDUSTRY RELEVANCE: Many factors influence the extraction of phenolic compounds during the fermentation process. Temperature, punch down and pump over frequencies, oxygen addition through aeration or mi cro-oxygenation, the presence or absence of skins, and cold and post-maceration techniques, among others, can promote significant changes in the levels and the composition of phenolic compounds in the resulting wines. The analysis of fermenting samples using conventional meth ods, such as spectrophotometric approaches or HPLC analysis, is not always possible due to time, personnel, facilities or budget constraints. Using spectroscopy with chemometrics would provide a rapid, reliable and simple way of monitoring the extraction of phenolic compounds during this process. This project aimed to establish a process control system to forecast and monitor red wine fermentations using grape data and real-time measurements. The following results were obtained: • Mid-infrared spectroscopy was the most suitable technique for this application. • A multiple-tank sampling system was implemented. • Rough filtration provided high-quality spectral data. • First principal modelling accurately predicted the progression of red wine fermentations. • Time-specific prediction models were obtained. • A multivariate monitoring system display was successfully implemented. The monitoring system, a key outcome of this project, has been successfully implemented. It can forecast red wine fermentations from grape compositional data, allowing for the early iden tification of process deviations and the implementation of mitigation practices. This real-time monitoring of red wine fermentations is a significant step towards ensuring consistent product quality in the wine industry.

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SOUTH AFRICA WINE RESEARCH 2024