Maria Gilda Stivala, Margarita Villecco, and Pedro Aredes Fernandez* 
*Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Ayacucho 471, San Miguel de Tucuman, Tucuman 4000, Argentina (pedroaredes@fbqf.unt.edu.ar)

The lactic acid bacteria (LAB), mainly belonging to the genera Lactobacillus and Pediococcus, can produce alterations in wine including the ability to synthesize biogenic amines and exopolysaccharide. The low molecular weight phenolic fractions (LMF) were obtained from Malbec (M), Cabernet Sauvignon (C), and Tannat (T) wines from Cafayate, Argentine. The effect of LMF on the viability of L. hilgardii 6F and X1B and P. pentosaceus 12p, isolated from Argentinean wines, were assayed at an equal concentration to wine (1X) and concentrated two (2X) or four (4X) times in synthetic wine medium (SWM), pH 4.5. Additionally, the effect of some pure wine phenolic compounds (PC), such as gallic acid (G), protocatechuic acid (P), p-coumaric © acid, cafeic acid (F), and catechin (H), were assayed individually at a final concentration of 400 mg/L. At different times, samples were collected to determine cell viability in MRS-agar medium and the effect on cell membrane integrity was evaluated by electron microscopy. The composition of LMF obtained by liquid-liquid extraction with ethyl acetate was determined by HPLC-DAD, showing a total concentration of phenolic compounds of 316.7, 229.3, and 311.1 mg/L for M, C, and T wines, respectively. In the presence of LMF at 1X and 2X concentration, all fractions diminished the growth rate without cellular damage. At 4X concentration, LMF produced microbial cellular death and damaged cell integrity. Among the individual PCs tested, the greatest inhibition of L. hilgardii 6F, L. hilgardii X1B, and P. pentosaceus 12p occurred with caffeic and p-coumaric acids, including damage to cell integrity. P. pentosaceus was most sensitive to all LMF and PCs assayed. These results represent a promising approach to wine preservation by using PCs against LAB spoilage and, consequently, eliminating or reducing the use of SO2 in wineries.

Funding Support: CIUNT – Project PIUNT 26/D540. CONICET - Project PIP 627