Understanding cold maceration in red winemaking: A batch processing and multi-block data analysis approach

The phenolic extraction optimization during the winemaking process is of crucial importance. The main aim of cold maceration is to enhance phenolic extraction prior to the fermentation process. The pre-fermentative diffusion of phenolic substances takes place at low temperatures and in the absence of ethanol. Variable results are often reported for cold maceration applications, which are ascribed to grape composition at harvest. The influence of different cold maceration treatments was evaluated following batch process modelling combined with hierarchal multiblock analysis. The winemaking process was divided in three blocks, namely: cold maceration, alcoholic fermentation and malolactic fermentation. Batch evolution and batch level models were assessed using PLS quantified phenolic composition. A combined effect of high SO2 levels and enzyme additions seemed to have a significant positive influence on wine phenolic levels, regardless of grape characteristics. Batch modelling provides a better process understanding through the identification of the relevant process variables (phenolics). Moreover, hierarchal multiblock zooming capability was used to understand the effect of cold maceration during the different parts of the process as well as providing an overall effect of cold maceration applications.