Investigating High Hydrostatic Pressure Processing as a Tool for Studying Yeast during Red Winemaking

Abstract

The application of high hydrostatic pressure (HHP) to inactivate microorganisms in a grape must (crushed grapes), coupled with autoclavable microscale fermentors, was investigated as a potential tool for studying the impact of yeast on red wine aroma and flavor. A Pinot noir grape must was inoculated with Saccharomyces cerevisiae, Brettanomyces bruxellensis, Kluveromyces thermotolerans, Lactobacillus hilgardii, Oenococcus oeni, and Acetobacter aceti at ~1 × 10⁵ cfu/mL and subjected to HHP treatment for 10 min at 551 MPa (5510 bar). After HHP treatment no viable cells were detected in the grape must. Autoclavable microscale fermentors were then used to conduct replicate fermentations of HHP-treated and untreated Pinot noir grapes producing sufficient wine for chemical and sensory analysis. No differences were observed in fermentation rate between treatments, and variability between replicates was very low. No significant differences in color or hue were observed, but wine produced from HHP-treated grapes contained higher total phenolics. Sensory analysis of the wines by a trained panel revealed that other than a slight increase in overall fruit aroma there were no significant differences between any aroma and flavor descriptors. Results suggest that HHP processing of grapes, in conjunction with autoclavable microscale fermentors, could be used to conduct experimental red wine fermentations without the influence of native yeast and bacteria present on grapes and fermentation equipment.