**4. Pulsed electric fields (PEFs)**

Pulsed electric fields (PEFs) are a non-thermal technology with a high potential in the extraction of phenolic and aromatic compounds from grapes [11–13] and also in the elimination of microorganisms [10, 14]. This technology uses high intensity voltages (10–40 kV) producing strong electric fields of 1–30 kV/cm. However, it can be considered a non-thermal technology because these high intensity fields are applied in ultra-short periods of a few microseconds which usually produce a temperature increase of only a few degrees Celsius.

Typical pulses are produced as bipolar square waves because of their higher efficiency compared to other types of waves. Exponential decay waves can also be used, but the energy transferred and the effectiveness of electroporation is lower for the same field intensity.

**35**

**Figure 8.**

*Emerging Technologies to Increase Extraction, Control Microorganisms, and Reduce SO2*

PEFs are applied to food products in a treatment chamber using two electrodes built with inert metals. The location of the electrodes is usually in two consecutives sections of the pipeline separated by an isolating section. In this design, the electrodes from the treatment chamber, keeping the same diameter of the pipeline through which the crushed grapes are pumped. The force lines of the electric field

The effect of PEFs on the cell is the electroporation which increases the permeability of the cell membrane in microorganisms and plant cells. This increase in permeability is due to the formation of pores. The electric field strength required to produce the electroporation depends on the size of the cells, with intensities below 10 kV/cm and specific energies below 10 kJ/kg being sufficient to produce this effect in grape skin cells. However, higher electric fields (>10 kV/cm) and specific energies (>50 kJ/kg) are required for the electropora-

In wine technology, electroporation is a powerful tool to increase the extraction of pigments and tannins, thus reducing maceration times (**Figure 8**). The skin contact time when crushed grapes are processed by PEFs can be reduced by 2–3 times in comparison with the unprocessed grapes, also allowing to finish the fermentation in the absence of solids which allows a cleaner and more controlled fermentation. The low temperature increase protects the aroma compounds and facilitates the preser-

Moreover, PEF can be applied continuously to the crushed grapes during the pumping from the crusher to the tank (**Figure 9**). Industrial devices can process more than 10 t/h. PEF industrial treatments decrease maceration times, thus increasing the availability of the fermentation facilities. In addition, the equipment is moderate in size, it requires little space in the winery, and the energy inputs

The use of PEFs to control microorganisms in grapes needs higher field intensities due to the smaller size of the microbial cells [45, 46]. These field intensities produce an inactivation ranging from 0.6 to 4.94 log cycles for several wine spoilage yeasts and lactic acid bacteria [46]. PEFs can be used as a powerful non-thermal tool to control indigenous microorganisms, thus helping to decrease

*Color intensity and degree of pigment extraction in musts obtained from untreated (right) and PEF-treated* 

*(left) grapes (*V. vinifera *L. cv. Garnacha) after 1 h of maceration.*

required are low compared to other traditional techniques.

*DOI: http://dx.doi.org/10.5772/intechopen.92035*

are tangential to the flow direction.

tion of microbial cells [12].

vation of the varietal aroma.

SO2 levels.

*Emerging Technologies to Increase Extraction, Control Microorganisms, and Reduce SO2 DOI: http://dx.doi.org/10.5772/intechopen.92035*

PEFs are applied to food products in a treatment chamber using two electrodes built with inert metals. The location of the electrodes is usually in two consecutives sections of the pipeline separated by an isolating section. In this design, the electrodes from the treatment chamber, keeping the same diameter of the pipeline through which the crushed grapes are pumped. The force lines of the electric field are tangential to the flow direction.

The effect of PEFs on the cell is the electroporation which increases the permeability of the cell membrane in microorganisms and plant cells. This increase in permeability is due to the formation of pores. The electric field strength required to produce the electroporation depends on the size of the cells, with intensities below 10 kV/cm and specific energies below 10 kJ/kg being sufficient to produce this effect in grape skin cells. However, higher electric fields (>10 kV/cm) and specific energies (>50 kJ/kg) are required for the electroporation of microbial cells [12].

In wine technology, electroporation is a powerful tool to increase the extraction of pigments and tannins, thus reducing maceration times (**Figure 8**). The skin contact time when crushed grapes are processed by PEFs can be reduced by 2–3 times in comparison with the unprocessed grapes, also allowing to finish the fermentation in the absence of solids which allows a cleaner and more controlled fermentation. The low temperature increase protects the aroma compounds and facilitates the preservation of the varietal aroma.

Moreover, PEF can be applied continuously to the crushed grapes during the pumping from the crusher to the tank (**Figure 9**). Industrial devices can process more than 10 t/h. PEF industrial treatments decrease maceration times, thus increasing the availability of the fermentation facilities. In addition, the equipment is moderate in size, it requires little space in the winery, and the energy inputs required are low compared to other traditional techniques.

The use of PEFs to control microorganisms in grapes needs higher field intensities due to the smaller size of the microbial cells [45, 46]. These field intensities produce an inactivation ranging from 0.6 to 4.94 log cycles for several wine spoilage yeasts and lactic acid bacteria [46]. PEFs can be used as a powerful non-thermal tool to control indigenous microorganisms, thus helping to decrease SO2 levels.

#### **Figure 8.**

*Color intensity and degree of pigment extraction in musts obtained from untreated (right) and PEF-treated (left) grapes (*V. vinifera *L. cv. Garnacha) after 1 h of maceration.*

*Chemistry and Biochemistry of Winemaking, Wine Stabilization and Aging*

and 4-log for aerobic and lactic acid bacteria in the must [8]. All these wild microorganisms remained undetected in the must after UHPH processing at 300 MPa (inlet temperature 20°C, in-valve 98°C, outlet 26°C, and in-valve time 0.02 s) [8]. Therefore, UHPH is a powerful technology for eliminating indigenous microorganisms and facilitating the use of modern biotechnologies, such as the use of non-*Saccharomyces* or yeast-bacteria co-inoculations [2]. Simultaneously, microbial

*Color evolution in the control and UHPH musts after 2 days at room temperature in the absence of SO2. White* 

UHPH technology has also shown high efficiency in enzyme destruction. The intense impact and shear forces that the fluid undergoes when pumped through the valve produce a molecular depolymerization that reduces colloidal particles, microorganisms, and enzymes to small fragments. In the case of cells and spores, it causes microbial death, and in the case of enzymes, it causes denaturalization and inactivation. In musts processed by UHPH, a reduction in oxidase activity higher than 90% has been observed for polyphenol oxidase (PPO) enzymes [8]. In addition, the fragmentation effect of colloidal particles can increase the nutrient availability for alcoholic fermentation, which can have positive impact on the production

When measuring the color intensity in white grape musts, the value was lower in UHPH than in the unprocessed controls. This is an indication of a paler color that can be correlated with low oxidation by PPO enzymes [8]. The same results have been observed when white musts were kept at room temperature under oxidation conditions and without SO2: the UHPH musts remained pale and the controls quickly browned (**Figure 7**). UHPH is a key technology for reducing sulfites in must by controlling oxidative enzymatic activities which lead to browning and aroma degradation.

Pulsed electric fields (PEFs) are a non-thermal technology with a high potential in the extraction of phenolic and aromatic compounds from grapes [11–13] and also in the elimination of microorganisms [10, 14]. This technology uses high intensity voltages (10–40 kV) producing strong electric fields of 1–30 kV/cm. However, it can be considered a non-thermal technology because these high intensity fields are applied in ultra-short periods of a few microseconds which usually produce a

Typical pulses are produced as bipolar square waves because of their higher efficiency compared to other types of waves. Exponential decay waves can also be used, but the energy transferred and the effectiveness of electroporation is lower

control facilitates the reduction of SO2 content.

of fermentative aroma [8].

*must of* Vitis vinifera *L. cv. Muscat.*

**Figure 7.**

**4. Pulsed electric fields (PEFs)**

for the same field intensity.

temperature increase of only a few degrees Celsius.

**34**

**Figure 9.**

*PEF experimental unit to process the crushed grapes at a flow of 3 t/h to improve the polyphenols extraction in the maceration-fermentation stage of red winemaking.*
