Abstract

The repurposing of by-products and the reduction of waste from food processing streams is an ever-increasing area of interest. Brewer’s spent yeast (BSY) is a prevalent by-product of the brewing industry. The spent yeast cells are removed at the end of the bulk fermentation. A small amount of it is used to start the next batch of fermentation; however, the majority of the spent yeast is discarded. This discarded yeast is high in nutrients, in particular proteins, vitamins and minerals, as well as containing functional and biologically active compounds such as polyphenols, antioxidants, β-glucans and mannoproteins. At present, BSY is mainly used in animal feed as a cheap and readily available source of protein. This review explores alternative, value-added applications for brewer’s spent yeast including nutritional ingredients, functional food additives as well as non-food applications. A major challenge in the utilization of BSY in food for human consumption is the high level of RNA. An excess of RNA in the diet can lead to an increase in uric acid in the bloodstream, potentially causing painful health conditions like gout. This issue can be overcome by RNA degradation and removal via additional treatment, namely heat treatment and enzymatic treatment. There is potential for the use of BSY ingredients in various food applications, including meat substitutes, bakery products and savory snacks.

Highlights

  • Yeast is a single-celled organism used in beer manufacture for the transformation of sugars from grain to alcohol

  • While many potentially exciting technologies have been investigated, few have been implemented on an industrial scale, with animal feed being the main outlet for Brewer’s spent yeast (BSY) currently

  • This study showed that the hops acids in the BSY protected proteins from degradation by hyper ammonia producing bacteria (HAB) [49]

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Summary

Introduction

Yeast is a single-celled organism used in beer manufacture for the transformation of sugars from grain to alcohol. Yeast extracts formed by the breakdown of the yeast cell membrane can be used as additives in food products as a source of free amino acids, peptides or for their antioxidant properties [2]. Compounds such as β-glucans and mannoproteins can be derived from BSY. These have many functional uses in food products such as textural stabilization, as well as potential health benefits [4]. BSY could be utilized by a wide variety of industries in the production of nutritional supplements, functional food ingredients and other value-added products

Use of Yeast in Brewing and Fermentation—An Overview
A Brief Overview of Fermentation
Pitching
Yeast Viability
Flocculation
Production of Yeast Extract
Modification of Yeast Extract
Protein
Mineral and Vitamin Content
Phenolic Compounds
Glutathione
BSY Applications
Brewer’s Spent Yeast as an Enzyme Source
Functional Food Applications
Reducing Agents
Health and Nutritional Applications
Flavor-Enhancing Ingredient
The RNA Issue—Purines
Meat Substitute Applications
Fermentation Substrate
Biofuels—Methane Production
Biosorption Agent
Findings
Conclusions
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