Pulsed Electric Fields to Improve the Use of Non-Saccharomyces Starters in Red Wines

Abstract

New nonthermal technologies, including pulsed electric fields (PEF), open a new way to generate more natural foods while respecting their organoleptic qualities. PEF can reduce wild yeasts to improve the implantation of other yeasts and generate more desired metabolites. Two PEF treatments were applied; one with an intensity of 5 kV/cm was applied continuously to the must for further colour extraction, and a second treatment only to the must (without skins) after a 24-hour maceration of 17.5 kV/cm intensity, reducing its wild yeast load by up to 2 log CFU/mL, thus comparing the implantation and fermentation of inoculated non-Saccharomyces yeasts. In general, those treated with PEF preserved more total esters and formed more anthocyanins, including vitisin A, due to better implantation of the inoculated yeasts. It should be noted that the yeast Lachancea thermotolerans that had received PEF treatment produced four-fold more lactic acid (3.62 ± 0.84 g/L) than the control of the same yeast, and Hanseniaspora vineae with PEF produced almost three-fold more 2-phenylethyl acetate than the rest. On the other hand, 3-ethoxy-1-propanol was not observed at the end of the fermentation with a Torulaspora delbrueckii (Td) control but in the Td PEF, it was observed (3.17 ± 0.58 mg/L).

Microbial Decontamination by Pulsed Electric Fields (PEF) in Winemaking

“…Alternatively, the use of non-Saccharomyces strains for alcoholic fermentation and for the improvement of the sensorial profile of neutral varieties is becoming a new trend in winemaking. Certain studies have confirmed that non-Saccharomyces yeasts implant themselves better in PEF-treated must [31,32]. Consequently, higher levels of several specific metabolites of interest produced by non-Saccharomyces yeasts have been detected in wines obtained from PEF-treated musts.…”

Emerging Non-Thermal Technologies for the Extraction of Grape Anthocyanins

“…Average residence time 0.41 s ↑extraction Phenols +23% +25% after 7 days [ 52 ] Continuous Merlot grapes >30 kV/cm, 4.7–49.4 kJ/L Flow 500 kg/h ↑extraction ↑Phenols +23−162% Shortening of cold macerations +17−636% after 24 h [ 53 ] Continuous Rondinella grapes Square-wave pulses at 1.5 kV/cm, 1, 5 and 10 μs, 2, 10 and 20 kJ/kg, 400 Hz Flow 250 L/h ↑extraction ↑Phenols +37% +30% color intensity after fermentation [ 54 ] Continuous Grenache grapes Pulses of 5 kV/cm, 63.4 kJ/kg. 1800 µS (45 pulses of 40 µS) Average residence time 0.38 s. Temperature < 32 ± 2 Flow 120 kg/h ↑extraction ↑Phenols ×1.6 ×2.2 after 24 h [ 55 ] Ultrasounds Discontinuous Tannat grape pomace. US bath: 15−60 °C, 0−100 W, 5−50 min ↑extraction ↑Phenols +50% +50% [ 56 ] Discontinuous Red grape pomace US bath: 25 °C, 160 W, 40 kHz, 30 min, 0.4 W/mL, 720 J/mL ↑extraction +59% after 5 min [ 33 ] Discontinuous Monastrell grapes US bath: 18 °C, 40 kHz, 280 W, 90 min …”

“…Anthocyanin extraction increases in the range of 17–100% ( Table 1 ) depending on processing conditions and post-maceration time. The temperature is increased by only 2–15 °C [ 55 ], therefore it is easy to work at room temperature or under refrigerated conditions. In addition to improved anthocyanin and phenol extraction, PEFs can be used for gentle non-thermal pasteurization of the must, thus improving the implantation of non- Saccharomyces starters [ 55 ] and potentially reducing the use of SO 2 .…”

Non-Saccharomyces as Biotools to Control the Production of Off-Flavors in Wines

“…UHPH is capable of producing sterilization with the elimination of yeast, bacteria, and even spores, depending on the in-valve temperature [ 85 , 93 ]. Pulsed technologies (i.e., PEFs and PL) have shown an inactivation capacity around or above 2-log for wild yeasts in grapes [ 94 , 95 , 96 ]. The antimicrobial performance of PEFs can be greatly enhanced in combination with mild temperatures (50 °C) [ 97 ].…”

“…The inactivation of wild yeasts by emerging non-thermal technologies in grapes or grape must is a useful technology to facilitate the implantation of non- Saccharomyces starters that can be used to control off-flavor formation. Several non-thermal technologies have shown high efficiency in increasing the implantation of non- Saccharomyces yeasts, such as HHP [ 92 ] and PEFs [ 95 ]. The high effectiveness of UHPH also makes it a leading technology not only for improving yeast implantation, but also for reducing SO 2 levels due to its ability to inactivate oxidative enzymes [ 85 ].…”