Spent Yeast from Brewing Processes: A Biodiverse Starting Material for Yeast Extract Production

Lisa Striegel,Mathias Hutzler,Friedrich Felix Jacob,Frank-Jürgen Methner,Michael Rychlik

doi:10.3390/fermentation5020051

Abstract

Spent yeast from beer manufacturing is a cost-effective and nutrient-rich starting material for the production of yeast extracts. In this study, it is shown how physiologically important ingredients in a yeast extract are influenced by the composition of the spent yeast from the brewing process. In pilot fermentations, the time of cropping (primary fermentation, lagering) of the spent yeast and the original gravity (12 ˚P, 16 ˚P, 20 ˚P) of the fermentation medium was varied, and four alternative non-Saccharomyces yeast strains were compared with two commercial Saccharomyces yeast strains. In addition, spent yeast was contaminated with the beer spoiler Lactobacillus brevis. The general nutrient composition (total protein, fat, ash) was investigated as well as the proteinogenic amino acid spectrum, the various folate vitamers (5-CH3-H4folate, 5-CHO-H4folate, 10-CHO-PteGlu, H4folate, PteGlu) and the biological activity (reduction, antioxidative potential) of a mechanically (ultrasonic sonotrode) and an autolytically produced yeast extract. All the investigated ingredients from the yeast extract were influenced by the composition of the spent yeast from the brewing process. The biodiversity of the spent yeast from the brewing process therefore directly affects the content of physiologically valuable ingredients of a yeast extract and should be taken into consideration in industrial manufacturing processes.

Highlights

Beer production generates large quantities of spent yeast during the fermentation and lagering process
We showed how the total folate content was allocated between the different folate vitamers (5-CH3 -H4 folate, 5-CHO-H4 folate, 10-CHO-PteGlu, H4 folate, PteGlu) in the fermentation medium or in the relevant spent yeast and how it could be transferred to the yeast extract
This study showed showedthat thatthe thebiodiversity biodiversityofofspent spent yeast from brewing process means it substantially influence the composition of physiologically important ingredients in the resulting yeast can substantially influence the composition of physiologically important ingredients in the resulting extract

Summary

Introduction

Beer production generates large quantities of spent yeast during the fermentation and lagering process. Following primary fermentation, this equates to about 0.7–1.1 kg compressed yeast per hectoliterfinished beer [1]. According to the current state of brewing technology, spent yeast after primary fermentation is only used in small quantities to pitch the batch [2]. Is generated (0.5–0.9 kg compressed yeast per hl finished beer), together with precipitated turbidity particles and “barm beer” [1]. The spent yeast from the brewing process is suitable for use as an efficient starting material to produce yeast extract [1,3]. Yeast extract is generally defined as the soluble content of a yeast

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