Effect of oxidoreduction potential on aroma biosynthesis by lactic acid bacteria in nonfat yogurt

Abstract

The aim of this study was to investigate the effect of oxidoreduction potential (Eh) on the biosynthesis of aroma compounds by lactic acid bacteria in non-fat yogurt. The study was done with yogurts fermented by Lactobacillus bulgaricus and Streptococcus thermophilus. The Eh was modified by the application of different gaseous conditions (air, nitrogen, and nitrogen/hydrogen). Acetaldehyde, dimethyl sulfide, diacetyl, and pentane-2,3-dione, as the major endogenous odorant compounds of yogurt, were chosen as tracers for the biosynthesis of aroma compounds by lactic acid bacteria. Oxidative conditions favored the production of acetaldehyde, dimethyl sulfide, and diketones (diacetyl and pentane-2,3-dione). The Eh of the medium influences aroma production in yogurt by modifying the metabolic pathways of Lb. bulgaricus and Strep. thermophilus. The use of Eh as a control parameter during yogurt production could permit the control of aroma formation.

Redox Potential: Monitoring and Role in Development of Aroma Compounds, Rheological Properties and Survival of Oxygen Sensitive Strains During the Manufacture of Fermented Dairy Products

“…The authors also demonstrated that oxidative Eh conditions clearly increased the production of aroma compounds [51]. These results are consistent with the bibliography.…”

“…Furthermore, during storage, different profiles were observed for the four aromas depending on the Eh conditions [51]. Under oxidizing conditions (+170 to +245 mV), the concentration of acetaldehyde was relatively stable during storage, which is in accordance with the literature [9,55,56] and the concentration of dimethyl sulphide was also stable.…”

“…It has also been reported that Cheddar has a reducing Eh and is an indicator of the establishment of the conditions required for the formation of aroma compounds [67]. As shown previously, Eh can modify the metabolic pathways of aroma production by lactic bacteria [51]. Kieronczyk et al [49] demonstrated that reducing Eh conditions can stimulate carboxylic acid production in cheese, while oxidative Eh conditions improve the production of volatile sulphur compounds and aldehydes.…”

“…However, the Eh of the medium has not yet been considered, although it is supposed to affect bacterial metabolism [49,50]. Martin et al [51] determined to what extent Eh can affect the metabolic pathways involved in the production of aroma compounds in Lb. bulgaricus and S. thermophilus.…”

“…Firstly, the authors focused on the impact of these different Eh conditions on the biosynthesis of these four aromas by bacteria after one day of storage [51]. In the standard yoghurt (made in ambient air), diacetyl was observed in the highest concentrations, and acetaldehyde the lowest.…”