Semi-Continuous Fermentation of Onion Vinegar and Its Functional Properties.

Sulhee Lee,Young-Seo Park,Gwi-Gun Park,Jin-A Lee,Jae-Kweon Jang

doi:10.3390/molecules22081313

Abstract

For the fermentation of vinegar using onion, acetic acid bacteria and yeast strains with high fermentation ability were screened. Among them, Saccharomyces cerevisiae 1026 was selected as a starter for ethanol production and Acetobacter orientalis MAK88 was selected as a vinegar producer. When the two-stage fermentation of onion vinegar was performed at 28 °C, the titratable acidity reached 4.80% at 24 h of fermentation. When semi-continuous fermentation proceeded to charge-discharge consisting of three cycles, the acetic acid content reached 4.35% at 48 h of fermentation. At this stage, the fermentation efficiency, acetic acid productivity, and specific product formation rate were 76.71%, 17.73 g/(L·d), and 20.58 g/(g·h), respectively. The process in this study significantly reduced the fermentation time and simplified the vinegar production process. The content of total flavonoids and total polyphenols in onion vinegar were 104.36 and 455.41 μg/mL, respectively. The antioxidant activities of onion vinegar in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic) acid (ABTS+) radical scavenging activity, and reducing power were 75.33%, 98.88%, and 1.28, respectively. The nitrite scavenging abilities of onion vinegar were 95.38 at pH 1.2. The onion vinegar produced in this study showed higher organoleptic acceptability than commercial onion vinegar.

Highlights

Vinegar is a typical fermented food with a history of more than 10,000 years; it is produced by biological transformation via microorganisms [1]
Strain No MAK88, which was isolated from Korean traditional rice wine, exhibited high acid production (3.51%) and a good growth rate when cultured in onion juice, and thereby was selected as a starter for acetic acid fermentation
Resistance to acid or alcohol during fermentation is an important property for a good starter, because acid or alcohol produced during fermentation might hamper the growth and thereby the fermentation ability of the starter

Summary

Introduction

Vinegar is a typical fermented food with a history of more than 10,000 years; it is produced by biological transformation via microorganisms [1]. Many fermentation processes have been developed to increase the rate of biological reactions that aerobically transform ethanol into acetic acid for the industrial production of vinegar [3]. In the ethanol oxidation step, acetic acid bacteria convert ethanol to acetic acid via acetaldehyde [4]. This oxidation process is important for aerobic fermentation by two sequential reaction mechanisms using membrane-bound alcohol dehydrogenase and aldehyde dehydrogenase linked to the respiratory chain [5]. At the end of acetification, acetic acid bacteria are resistant to acetic acid, but begin to assimilate acetate and CO2 via the tricarboxylic acid (TCA) cycle This phenomenon is called ‘overoxidation’ and can limit the fermentation of acetic acid [6]

Methods

Results

Conclusion