Determination of volatile compounds during deterioration of African opaque beer using a stir bar sorptive extraction technique and gas chromatography-high resolution mass spectrometry

Abstract

Opaque beer traditional to African communities undergoes quick deterioration and is consumed within 7 days of its production. The current study has utilized a stir bar sorptive extraction technique followed by GC-HRT determination to trace variations of 84 volatile compounds in four opaque beers commonly brewed in South Africa over the 7-day shelf life period. The major fruity esters were observed to increase up to Day 4 and eventually decreasing until Day 7 where their levels were finally lower than Day 1. Aldehydes reduced drastically and were less than 50% on Day 2 and becoming almost undetectable at Day 7. The common beer alcohols (phenylethyl alcohol and 3-methyl-1-butanol) decreased during beer shelf life while phenolics with undesirable medicinal tastes (creosol and p -cresol) increased up to 24-fold by Day 7. This study might open future research perspectives around opaque beer traditional to African rural communities.

Nutritional Compositions of Optimally Processed Umqombothi (a South African Indigenous Beer)

“…In beer, fat content is negligibly present in the form of fatty acids, thus having a minimal contribution to the energy value of the beverage [32][33][34]. Since fat is considered a trace constituent in beer, these findings were in line with other studies [3,33,[35][36][37]. A fat content of 0% in umqombothi was also reported by [4].…”

Presence of Carbonyl Compounds in Beers - A Brief Review

“…The presence of carbonyl compounds in beers, in particular aldehydes and ketones, significantly influence the sensory properties of the beverage, especially flavor and smell, which are the result of mixtures of these compounds in different concentrations. [14]. In addition, in the human body, carbonyls can interact with DNA forming some types of compounds that can promote mutations, increasing the risk of cancer in some parts of the body, causing damage to human health [15].…”

Discrimination and quantification of volatile compounds in beer by FTIR combined with machine learning approaches

“…People worldwide love beer owing to its various tastes, physicochemical properties, and flavor ( Almeida, Aparecida, Lima, Suarez, & Andrade, 2018 ; Alves et al, 2020 ; Betancur, Motoki, Spence, & Velasco, 2020 ). The flavor of beer is characterized by the presence of dozens of volatile organic compounds, including alcohols, esters, fatty acids, carbonyl compounds, sulfur compounds, furanic compounds, monoterpenols, and volatile phenols, constituting the unique flavor of each beer at different concentrations ( Gagula et al, 2020 ; Ncube, Dube, & Nindi, 2020 ). Some of these compounds are pleasant, and their concentrations should be kept stable; however, some have undesirable properties that should be reduced to a minimum ( Dong et al, 2014 ; Liu et al, 2023 ).…”

“…Some of these compounds are pleasant, and their concentrations should be kept stable; however, some have undesirable properties that should be reduced to a minimum ( Dong et al, 2014 ; Liu et al, 2023 ). Providing consumers with stable-quality beer is extremely essential, and regular beer analysis is warranted to track, minimize, and correct the concentrations of volatile organic compounds in beer ( Betancur et al, 2020 ; Gagula et al, 2020 ; Ncube et al, 2020 ).…”