Optimal Design Approach Applied to Headspace GC for the Monitoring of Diacetyl Concentration, Spectrophotometric Assessment of Phenolic Compounds and Antioxidant Potential in Different Fermentation Processes of Barley

Badr Bouhcain,Fouad El Mansouri,Hammadi El Farissi,Francesco Cacciola,Joaquim C G Esteves Da Silva,Miguel Palma Lovillo,Jamal Brigui

doi:10.3390/app12010037

Abstract

The present study aimed to validate a control method on the gas chromatography system (GC) based on the experimental design strategy, to examine the changes and correlation between the fermentation process and the quality of alcoholic and non-alcoholic beer product, especially the formation of diacetyl. On the other hand, spectrophotometric methods were applied to the determination of polyphenols content and the potential antioxidant activity of beer during different fermentation processes. with this aim, three modes of barley fermentation were used, specifically classical fermentation, stopped fermentation and thermal process. The results showed that the different fermentation modes had a major impact on diacetyl production. The highest concentration was obtained using stopped fermentation 0.36 mg/L, the lowest concentration value 0.07 mg/L was detected using the thermal process. Monitoring the increase of oxygen concentration between fermentation, filtration, and filling of the final product (32, 107, 130 ppm, respectively) has a significant impact on the concentration of diacetyl. The obtained results of spectrophotometric analysis showed that the total antioxidant activity changed during beer fermentation process and demonstrate that the extend of the antioxidant activity was very much dependent on the total polyphenolic content with a higher value in Hopped wort (13.41%, 65 mg GAE 100 mL−1, 28 mg CE 100 mL−1) for antioxidant potential, total phenolic content, and total flavonoids content, respectively, whereas the lowest values was detected in Non-alcoholic beer using thermal process (7.24%, 35 mg GAE 100 mL−1, 10 mg CE 100 mL−1) for antioxidant potential, total phenolic contents, and total flavonoids contents, respectively. Based on the results achieved, we reveal the impact of the fermentation process on the nutritional value of the final product.

Highlights

Beer is one of the first-born and popular fermented drinks in mankind’s history, The process by which beer is brewed has not changed significantly since its discovery thousands of years ago and the production of this beverage can be considered as very traditional and remain still the same, without important variations ever since its earliest origin
The results show that the concentration of diacetyl increases between the stop of fermentation and the release of the final product, with the concentration of diacetyl at the last day of fermentation is equal to 12 μg/L this concentration increases up to 160 μg/L in the final product
Increasingly important role in beer flavor analysis, observed the non-alcoholic stoppingand fermentation beer (NABS), with a higher free related radical chemical in analysis of beer is essential is widely used in various research areas scavenging capacity than alcoholic beer by using classical fermentation (ABC)

Summary

Introduction

Beer is one of the first-born and popular fermented drinks in mankind’s history, The process by which beer is brewed has not changed significantly since its discovery thousands of years ago and the production of this beverage can be considered as very traditional and remain still the same, without important variations ever since its earliest origin. Various groups of compounds have been shown to play an important role in the flavor characteristics [3], e.g., esters, higher alcohols, aldehydes, ketones, organic acids), which contribute to the last sensorial character of beer [4]. Interesting topics are the reduction of diacetyl, dimethyl sulfide (DMS) or hydrogen sulfide and an enhanced production of sulfur dioxide or esters [6] They are originated from two amino acids namely valine and leucine, and are responsible for toffee, butterscotch, honey and vanilla-like off-flavors when they are present at concentrations higher than their threshold values (>0.1–0.4 mg/L) [7,8]. They may play the most important role in the final flavor [9]

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Conclusion