EMPREGO DA TÉCNICA DE MEFS-HS/CG-EM PARA AVALIAÇÃO DO PERFIL QUÍMICO DA FERMENTAÇÃO DE LEVEDURAS SELVAGENS DO CERRADO SUL-MATO-GROSSENSE

Abstract

Currently, various yeast strains are employed in the brewing process to generate distinct profiles, including some originating from wild and extreme environments that contribute to complexity. The objective was to isolate yeast strains from the terroir of the South-Mato-Grosso Cerrado for potential application in craft beer production. Four points in a region at the boundaries of the municipalities of Campo Grande and Sidrolândia were chosen for collection. A total of 161 samples were collected: 18 insects (I), 38 soils (S), 41 trunks (T), 28 fruits (F), 13 flowers (FL), and 23 other sources such as fungi and webs (OT). The samples were collected in 50 mL Falcon tubes, and in the laboratory, inoculation was performed in YPM8E5 liquid medium (yeast extract 10 g/L, peptone 20 g/L, malt extract 40 g/L, high maltose 40 g/L, ethanol 5% (v/v)) with a relative density of 1.035. During seven days, samples showing bubble formation were plated on solid medium with antibiotics. From the selective inoculum, 21 growths were obtained on the plates, followed by fermentation tests using the stepwise propagation methodology. With a volume of 100 mL, sensory evaluations and sugar attenuation measurements were conducted. As a result, six samples demonstrated potential for commercial application, with two strains exhibiting fermentative capacity and relevant organoleptic profiles. These are S14 (collected from soil), presenting a sour aroma, honey and clove notes, sweet ester hints, and high gas formation, and T38II (collected from trunk), displaying a sour aroma profile with fruity esters, notes reminiscent of apple peel and grape skin, both with pH between 4 and 5, and fermentation attenuation of 62% for S14 and 50% for T38II. The two attenuated strains were evaluated by gas chromatography-mass spectrometry with solid-phase microextraction (SPME-GC-MS) to identify the chemical profile of the samples. Correspondence was found in the presence of ketones, alcohols, esters of organic acids, and hydrocarbons. The other four strains showed potential for the food industry due to the found organoleptic diversity. Based on source selection and obtained growths, it was noted that samples from soils and trunks have a higher likelihood of success in yeast isolation. It was also observed that wild microorganisms are generally producers of phenolic compounds (POF+) and organic acids, presenting organoleptic complexity and highlighting individuals' resistance mechanisms in the environment. With yeast evolution and domestication, this characteristic tends to be lost or expressed more prominently, as observed in Weiss-style beers.