ID: 2259

• Title:
  Controlling Microorganisms in Wine through PEF Application: Inactivation of B. bruxellensis and impact on Wine Profile.
  
  Authors:
  

  Aguiar Macedo, Mafalda - EnergyPulse Systems, EPS, Lisbon, Portugal
  Teotónio Pereira, Marcos - EnergyPulse Systems, EPS, Lisbon, Portugal
  Redondo, Luís Manuel - Pulsed Power Advanced Applications Group from Lisbon Engineering Superior Institute, GIAAPP/ISEL
  Silva, Carlos - Carlos Silva Vinhos, Unip. Lda. Viseu, Portugal

  
  
  Abstract:
  Bruxellensis/Dekkera is a common occurrence in various food matrixes, such as wine, cider and beer, being able to benefit or negatively impact the final product. It is highly undesirable in the wine industry, considering its ability to convert hydroxycinnamic acids and p-coumarate in volatile phenols (e.g. 4-ethylguaiacol and 4-ethylphenol), usually bestowing off-flavour taints typically described “horsey�, “barnyard�, “bandaid�, “pharmaceutical�, and “smokey�.
  
  Thus, it is essential to avoid the sensorial and economic impacts of B. bruxellensis as early and as effectively as possible. This can be achieved by preventing the occurrence and development of this spoilage yeast with corrective or preventive approaches. Traditional approaches, such as raking and fining, and others, more technological, such as opting for lower pH and residual sugar content, higher concentration of molecular SO2, the use of DMDC and chitosan application are some of the most usual.
  
  Recently, the application of Pulsed Electric Fields (PEF) as a strategy for microbial control has been proposed due to its capability to inactivate microorganisms, through an exclusively physical, non-thermal and continuous process that results in the electroporation of pathogenic and spoilage microorganisms. Being already used in food liquid products, as milk and juices, laboratory studies have shown the successful application of PEF in wine for yeast inactivation which might represent a major achievement for the wine industry.
  
  With this work, the main objective was focused on an comprehensive literature research regarding microbial control resorting to PEF, at laboratory scale, and assess the optimal PEF parameters to apply at a semi-industrial scale. . The PEF system being used can process up to 500 L/h of wine, including a continuous co-axial PEF treatment chamber and pulse generator, enabling the application of electric fields up to 15 kV/cm. It also comprised of DN25 pipes, a pump, flowmeter, heat exchanger and inline thermometers, enabling the control of the initial and final wine temperatures, and pressure valve, which enables operation up to 6 bar. Electrical efficiency and economic study are also presented.
  
  Red wine previously contaminated with B. bruxellensis, was analyzed to assessment the level of contamination through the employment of flow cytometry with fluorescent in situ hybridization (RNA-FISH), pre and prior the application of PEF. In addition, basic oenological parameters and a comparative sensory analysis were conducted to assess possible alterations caused by the selected PEF protocol (15kV/cm, 35kJ/Kg).
  
  Results demonstrated that, after treatment, B. bruxellensis was undetected, being the initial population of 2500 viable cells/m (DL=<150 viable cells/ml). Total Yeast Count also decreased 80.66%.
  
  After treatment, PEF treated wine presented no significative differences regarding Total Acidity, pH and %Ye. A significant increase of Anthocyanins, Total Phenols, Colour intensity and Turbidity was determined. At sensory level, significant differences were not found between both wines; however it is worth mentioning that the majority of the tasting panel attributed an higher global evaluation to PEF treated wine.
  
  Keywords:
  B. bruxellensis, spoilage yeasts, wine, Pulsed Electric Fields
  
  Refs:
  
  
  Topic 1:
  10. Food safety and food preservation
  
  Topic 2:
  11. Agricultural crops and farming