Improved red wine process efficiency and product quality through enhanced phenolic extraction by Controlled Phenolic Release (CPR) and Berry Pricking

Abstract

Two novel approaches to Pinot Noir winemaking were investigated; Controlled Phenolic Release (CPR) by microwave maceration of must, and Accentuated Cut Edges (ACE) (initially referred to as ‘berry pricking’) to increase diffusion from grape skins. Industry engagement was achieved through Distributed Industry Trials conducted in working wineries, and wines were subjected to full chemical and sensory analysis. The novel wines were phenolically and sensorially acceptable. Each process demonstrated a relatively short payback period, and ACE moved to follow-on investigation (VIN 1501). CPR improved extraction efficiency, but human factors and the existence of competing technologies suggested CPR was unlikely to be developed further at this time.

Summary

This project investigated two novel approaches to Pinot Noir winemaking; Controlled Phenolic Release (CPR) by microwave maceration of grape must and Accentuated Cut Edges (ACE) (initially referred to as ‘berry pricking’) processing to increase diffusion from grape skins.

Chemical and sensory analysis of the Pinot Noir wines yielded significant differences associated with each novel maceration treatment. Wines made with microwave maceration (CPR) and fermented on skins showed differences in phenolics concentration out to two years post-bottling, with up to two-fold higher tannin concentration, and higher anthocyanin and total phenolics concentration.

In a comparison of seven different maceration treatments including CPR on skins, CPR with early pressing, ultrasound maceration and standard winemaking processes, phenolic, tannin and monosaccharide composition of Pinot Noir wines was shown to vary by maceration treatment. The most notable in terms of impact on wine chemistry, were the two CPR treatments and the ultrasound treatment. CPR wines with early pressing were similar to control wines in terms of phenolics concentrations, although they had approximately half the time on skins. Formal sensory appraisal of CPR with early pressing wines showed they had unique sensory characteristics that were, on average, preferred to control wines. While the relative impact of CPR treatments was the main focus of much of this project, the impact of ultrasound treatment on the composition of wines was also investigated.

ACE maceration involves the cutting of grape skins into smaller fragments than is usual, consequently increasing the rate of extraction of colour and flavour components from the broken edges of the grape skins. The procedure was demonstrated to increase the rate of phenolic extraction to such an extent that pressing the grape solids off prior to the end of fermentation with fermentation completed in a smaller tank was investigated. This is referred to as Press Early (PE) ACE maceration or ‘PEACE maceration’.

Phenolics analysis showed that ACE maceration caused a dramatic increase in the extraction of colour and tannin in the first two days of fermentation. Six months after bottling, the average increase in tannin and stable pigment concentration, relative to conventionally made wine, was 45% for ACE wines, while for the PEACE wines the concentrations were 35% and 30% respectively. Sensory panelists judged PEACE wines to be superior in phenolic composition relative to their control and ACE counterparts and described them as having more fruity and floral attributes than the control wines.

The ACE maceration technique in combination with early press off has considerable potential as a technique to help commercial winemakers manage compressed vintages, by reducing the time in the fermentation tank by 25 to 50%.

The business case for each of the novel processes examined in this project with Pinot Noir winemaking demonstrated payback periods of approximately four years for CPR and less than 12 months for ACE. CPR was found to produce sensorially preferred wines in approximately half the time of standard winemaking processes, and has the potential to generate more strongly extracted wines from low colour and tannin fruit. However, human factors (e.g. OHS and operator familiarity, local capacity for design and maintenance of units) and established technologies that may offer similar extraction efficiencies (e.g. standard thermovinification, Flash Release) mean that microwave maceration is unlikely to be developed further at this time.