ANTIMICROBIAL EFFECT OF MAQUI EXTRACTS ON PEAR CIDER SPOILAGE YEASTS.

GONZALEZ FLORES MELISA; VICTORIA KLEINJAN; GARRIDO MAKINISTIAN FRANCISCO; RODRIGUEZ MARIA EUGENIA; FRANCESCHINIS LORENA; SALVATORI DANIELA; LOPES CHRISTIAN ARIEL

Los Cocos- Cordoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

SAMIGE

Berries extracts have been used in the fermented beverage industry (such as beer, apple or pear ciders) as functional ingredients, colorants or antimicrobials. Particularly, the maqui berry (Aristotelia chilensis) extract has been used to obtain colored ciders, however, its antimicrobial potential has not been evaluated in this beverages.In this work, the antimicrobial effect of the maqui on spoilage microorganisms (MOs), isolated from pear ciders, was evaluated, including the yeasts; Zygosaccharomyces parabailii (Zp), Brettanomyces bruxellensis (Bb) and B. custersianus (Bc) and an acetic bacteria Acetobacter sp. (Ac).These 4 MOs were individually inoculated in 5% w/v maqui extract (5g of fresh maqui in 100mL of extraction liquid). Two extraction liquids were used; i) fermented pear must, containing 2g/L of sugar, without sulphite (essay1), ii) pear cider, containing 30g/L of sugar, 400mg/L of total sulphite (essay2), both with 5% v/v of ethanol, sterilized by filtration. In addition, all Mo were inoculated in dilutions of these extracts with their respective extraction liquid (1/10; 1/5; extraction liquid without maqui).A third essay was also carried out with extract ii, without sterilization, in the 1/10 dilution and without maqui (pear cider). All fermentations were carried out in 35mL and growth was followed by OD and the amount of CO2 lost daily. In the final stage of the incubation process (4 months) the number of forming colonies units FCU and cells/mL were quantified.A better growth at higher concentrations of maqui in the Zp yeast was observed (essay1), which could be due to the contribution of nitrogen and sugars from the maqui extract (it provides 40% and 2% more of nitrogen and sugars respectively). However, in presence of an excess of sugars (essay2), the antimicrobial effect of the maqui on the yeast can be observed (in addition to the effect of the sulphite), which involve, a significant reduction in the maximum growth, in the 1/10 and 1/5 dilutions and total growth inhibition in maqui extract without dilutions.The Bb and Bc yeasts presented a similar behavior, both decreased their growth kinetics when maqui was added (essay1), while this effect, was not so pronounced, in sulphite presence (essay2). These yeasts tolerate a maximum of 400mg/L of sulphite, being sublethal the concentration already present in the cider used.The Ac bacteria, was not affected by the maqui in essay1, growing with the same kinetics in all the conditions used. On the other hand, in the essay2, there was no growth due to the effect of sulphite.In 1 and 2 essays, for all conditions and Mo used, coherence between the decrease in maximum growth (OD), maximum production of CO2 and cells/mL and FCU of the final incubation stage, was observed.In essay3 (without sterilization), individually inoculating the 4 Mo and comparing with the condition without inoculating Mo, a decrease in maximum growth about 10% (for Zp) and 50-40% (for Bb and Bc) was observed when maqui was added. In the control, without inoculating Mo, growth was also observed, although it was reduced by 90% in the presence of maqui.In conclusion, the maqui extract has an antimicrobial effect on spoilage yeast of pear ciders; Zp, Bb and Bc. In addition, it helps to reduce the growth of microorganisms naturally present in this beverage after 4 months of incubation.