Inactivation of Brettanomyces bruxellensis by High Hydrostatic Pressure technology

Highlights

• Brettanomyces bruxellensis inactivation by HHP depends on treatment condition.

• HHP was also influenced by wine conditions and strains.

• High pH and ethanol wines shortly treated at 100 MPa inactivated B. bruxellensis.

• B. bruxellensis inactivations at 200 MPa were fairly variable.

• Every wines treated at 300 MPa managed a complete inactivation of B. bruxellensis.

Abstract

High Hydrostatic Pressure (HHP) technology was tested on two strains of Brettanomyces bruxellensis isolated from Rioja red wines for analyzing the microbial inactivation reached in different oenological conditions. With this purpose, these strains were inoculated in synthetic wine with different pH and ethanol content. The inactivations reached with 100 MPa, 200 MPa and 300 MPa applied from one to seven minutes were tested just after the treatment and after a week.

Current consumers demand quality, free-additive wines. This has made oenological industry search alternative non-thermal technologies. The present results supported that high pH and high ethanol wines shortly treated at 100 MPa made B. bruxellensis undetectable. Moreover, low pH and low ethanol wines content should be at least treated at 200 MPa, and wines with intermediate ethanol content should be carefully analyzed in terms of strain composition before applying HHP. Finally, treatments at 300 MPa managed a complete inactivation regardless of oenological conditions.

Introduction

Winemaking is a complex microbiological and chemical procedure in which the sulphur dioxide addition is the main manner to ensure the wine microbial stability (Ribéreau-Gayon, Dubourdieu, Donèche, & Lonvaud-Funel, 2007).

The employment of sulphur dioxide in vinification is usually aimed to prevent wine oxidation and to ensure the inactivation of most of the wine-borne spoilage microorganisms. Actually, the use of sulphur dioxide occurs in different stages as, for instance, in must, after alcoholic fermentation, after malolactic fermentation and during the ageing in wood barrels and bottles. Specifically, the ageing of wine in wood barrels is the most complex stage because the solid sulphur dioxide has to be burnt inside the barrel, generating an inadequate and non-safe atmosphere for winery workers.

The sanitation of wood barrels is an important problem in wineries if sulphur dioxide could not be burnt inside the recipient (González-Arenzana et al., 2013). In fact, there are several spoilage microorganisms as yeasts, lactic acid bacteria and acetic acid bacteria that are able to survive in wine till ageing causing problems in wine quality (Bartowsky, 2009, Malfeito-Ferreira, 2014). Anyway, the genus of yeast Brettanomyces is actually one of the boldest microorganisms in winemaking, mainly during the ageing and during the storage stages (Sturm et al., 2014, Wedral et al., 2010). The anamorphic yeast Brettanomyces bruxellensis is a non-spore forming and the teleomorphic species Dekkera bruxellensis is spore-forming. Both yeast species have the ability of getting developed in wines and even surviving into the natural wood pores of barrels. They are considered potentially dangerous microorganisms because they could generate undesirable phenolic volatile compounds. For this reason, the inactivation of this species during ageing has been described as a complicated process, more when the future use of sulphur dioxide is being currently questioned (Romano et al., 2008, Romano et al., 2009). Taking into consideration all these information, alternative and new technologies should be investigated, in order to both reduce the sulphur dioxide addition and avoid the infection of wood barrels.

In modern times, there is an increasing concerning about quality healthy food containing low chemical levels. In oenology, this situation is causing an important demand of ecological wine, free of sulphites (Pozo-Bayón, Monagas, Bartolomé, & Moreno-Arribas, 2012).

It is widely known that some beverages as juices or wines are not prepared to be treated by thermal methods because some organoleptic qualities as taste, colour and flavour are completely sensitive to high temperature. The employment of natural substances (García-Ruiz et al., 2013) or different technologies, as pulsed electric field (PEF) (Puértolas, López, Condón, Raso, & Álvarez, 2009), microwaves applied to wood (González-Arenzana et al., 2013), High Hydrostatic Pressure (HHP) (Morata et al., 2012), etc., have been studied in the winery context including B. bruxellensis.

Among them, HHP is considered a promising and attractive technology that is transferred uniformly and instantly in food without heating the system (Mok et al., 2006). The HHP produces the volume reduction of the biological unit causing structural alterations in biomolecules, lipid membranes, protein structure, cell division, etc. (Balny et al., 2002, Bartlett, 2002, Mentré et al., 1999, Winter and Jeworrek, 2009). Hence, HHP could be useful to achieve non-thermal pasteurization and to improve life extension of food products without substantial modification of nutritional, functional and organoleptic properties of foods. Currently, a whole range of products such as fruit juices, (Barba et al., 2014, Buzrul, 2012), garlic (Kim, Kim, Kim, Noh, & Choi, 2014) or table olives (Pradas et al., 2012) have been subjected to HHP. The antiseptic effect of HHP in wines has been demonstrated and described in certain studies (Delfini et al., 1995, Puig et al., 2003). Furthermore, investigations about how HHP affects wine and grape quality have been published since 1994, concluding that this application could be interesting for pasteurization and for increasing the extractability without varying the organoleptic qualities (Buzrul, 2012, Lonvaud-Funel et al., 1994, Morata et al., 2015). The present study was targeted to describe the B. bruxellensis inactivation, with different ethanol content and pH, after being submitted to HHP from one to seven minutes at 100 MPa, 200 MPa and 300 MPa.