DETERMINACION DE PARAMETROS DE LETALIDAD MICROBIANA DE MICROORGANISMOS CONTAMINATES EN CERVEZA ARTESANAL RELEVANTES PARA EL PROCESO DE PASTEURIZACION

LATORRE, M. ; SANTOS, M.V.; LIBKIND, D.; RANALLI, N.

SAN CARLOS DE BARILOCHE

Workshop; IWOBY 2nd Intenational Workshop on Brewing Yeasts; 2021

UNCO, Fundación CRELTEC, CONICET

Pasteurization has become an attractive alternative for the craft brewing sector since 2020 when the pandemic initiated in march. The advantages of applying a correct pasteurization process in cans and bottles are several; the beverage achieves a better shelf life, it follows a clean-label formulation without the use of food preservatives, in-package pasteurization there are no aseptic filling conditions to be maintained downstream and most importantly, there is no need for a cold chain transportation and distribution. Since pasteurization is a thermal process it can affect flavor and quality therefore it must be carefully done and monitored. In order to avoid over pasteurized beer the assessment of spoilage microorganisms such as diastatic strains of Sacharomyces cerevisiae should be carried out. The ability to survive and/or grow as well as the thermal resistance in a specific beer environment is an important aspect to be considered. The lethality parameters for the thermal inactivation of diastaticus which corresponds to the reference decimal reduction time D (in units of minutes) and thermal resistance constant Z (in units of ⁰C) are both parameters used to calculate the minimum pasteurization units (one pasteurization unit (PU) equals to 1 min at 60 ⁰C) and the number of logarithmic cycles reduced during the process. In our research group we studied the identity and genetic diversity of 32 isolates of S. cerevisiae obtained from contaminated beers, and 66% of these yeasts belonged to diastatic strains. Therefore the aim of this work were : a) to assess the ability of S. cerevisiae diastatic strains to survive and grow in an specific beer style (IPA beer with IBU>20) during a 7-30 day period, b) to test their thermal resistance capabilities by submitting these strains to a thermal treatment of 60 ⁰C during 30 seconds and c) to determine the lethality parameters (D and Z) of the isolates that reached the best performance in a) and b) by using the capillary tube method. The information on spoilage microorganisms of beer is of importance for food scientist and engineers in order to correctly establish adequate operating conditions and optimize the pasteurization process.