BIOPROSPECTING OF NON-CONVENTIONAL PATAGONIAN YEASTS FOR NON- ALCOHOLIC OR LOW ALCOHOL BEERS PRODUCTION (NABLAB)

ROMERO ROJAS, MACARENA DANAE; BURINI, JULIETA; LIBKIND, DIEGO

Chapadmalal

Congreso; XVIII Congreso de la Sociedad de Microbioloogía General; 2023

SAMIGE

In the brewing process, yeasts play a key role at the organoleptic level of the finished product due to the multiplicity of aroma and flavour compounds that they produce during fermentation. At this point, native (non-conventional) yeasts result in a tool for brewing diversification and innovation, including the production of non-alcoholic or low-alcohol beers (NABLAB), also granting regional identity to the products.The objective of this work was to evaluate the fermentative performance and organoleptic profile of non-conventional yeasts isolated from natural environments of the Andean-Patagonian region of Argentina, to assess their potential as brewing starters for the production of NABLAB.The fermentations were carried out in tubes with 35 ml of Congress wort (10°Bx), 0,3 ppm of zinc and 20 ppm of oxygen, at 20 °C. The pitching rate used was 0.75 x 106 cells/ml/°P. Native yeasts studied belong to the genera Hanseniaspora, Lachancea, Metschnikowia, Pichia and Torulaspora. Commercial strains of these genera, as well as American Ale yeast (US-05), English Ale yeast (S-04) and S. eubayanus type strain (EUBY®) were used as controls. Fermentation kinetics was evaluated in 46 strains (5genera, 20 species) by weight loss of the system (CO2 release) during 7 days. Fermentation rate (μ), theoretical alcohol (TA), pH and apparent attenuation (AA) were recorded. In addition, a sensory mapping based on aroma properties was carried out with a trained sensory panel, with emphasis on the sensory detection of on-flavors and off-flavors.Of all strains tested, 35 were discarded for presenting an attenuation higher than 25%, high levels of off-flavors and/or no on-flavors.11 isolates belonging to 4 genera were selected due to their physicochemical and aromatic qualities: three Hanseniaspora (TA: 0,69 % v/v; pH: 4,71 - 4,73; AA: 12,6%), four Lachancea (TA: 0,70 - 1,22 % v/v; pH: 4,28 - 4,60; AA: 12,5 - 22,3%), two Pichia (TA: 0,01 - 0,52 % v/v; pH: 4,58 - 4,80; AA: 0,27 - 9,54%) and two Torulaspora (TA: 0,86 - 1,30 % v/v; pH: 4,52 - 4,59; AA: 15,7 - 23,3 %). All the selected strains had a μ less than 0.007 h-1. Among these yeasts, Pichia hampshirensis CR10-23 produced less alcohol (0,01% v/v) while Torulaspora sp. SR10-E1 presented the highest levels of alcohol (1,30% v/v). Hanseniaspora sp. CRUB 232 had the most interesting aromatic attributes, like flowers, banana, stone and tropical fruits, red apple and pears. All isolates of the genus Metschnikowia were discarded due to their unpleasant aromas of rotten eggs, old fruit, cheese, and expired yoghurt.For the development of starters from the selected yeasts, studies will continue on a larger scale, deepening in the evaluation and analysis of their fermentative behavior at a fermentation level and sensory attributes.