Application of mild pulsed electric fields on starter culture accelerates yogurt fermentation

Abstract

The goal of this work was to investigate the influence of pulsed electric fields (PEF) operational parameters on a mixture of Streptococcus thermophilus DIL 5218 and Lactobacillus delbrueckii subsp. bulgaricus DSMZ 20081 T with regards to the culture's acidification capability in reconstituted skim milk medium. We investigated the effects of field strength, pulse frequency and total number of pulses by use of design of experiments and a two-level full factorial design. The responses were the cell counts of the two microorganisms after PEF application, the pH lag phase λ pH , the maximum pH change rate µ max , the maximum pH change and the oxidation/reduction potential (ORP). The application of PEF on the mixed culture accelerated the acidification of milk by an average of 12 min in an approx. 160 min lasting control λ pH. In contrast the maximum pH change rate µ max and the maximum pH change decreased slightly in fermentations with PEF-treated cultures. Furthermore, a significantly faster decrease of the oxidation/reduction potential (ORP) already within the first 30 min and a lower final ORP was observed in milk fermented with PEF-treated culture. The total number of pulses applied was the most influencing factor in most of the responses measured. We hypothesized that the reason for the enhanced performance of the PEF-treated culture was a combination of an oxidative stress response of S. thermophilus DIL 5218 and an enhanced proteolytic phenotype in L. delbrueckii subsp. bulgaricus DSMZ 20081 T .

Pulsed electric field processing in the dairy sector: A review of applications, quality impact and implementation challenges

“…Dairy culture strains ( Streptococcus thermophilus DIL5218 and Lactobacillus delbrueckii subsp. bulgaricus DSMZ 20081 T) when inoculated in reconstituted skim milk, and when PEF was applied (strength = 1 kV cm −1 , 3 cycles of 50 pulses and 4 Hz frequency) yoghurt fermenting time reduced by 12 min (Chanos et al ., 2020). According to the study, the application of PEF can result in cellular stress and expedite LAB metabolism, thereby enhancing fermentation efficiency.…”

Use of Modern Technologies in the Production of Fermented Products

“…Проведено исследование влияния низкоинтенсивного PEF в процессе производства ферментированных молочных напитков. P. Chanos [43]. Было отмечено, что PEF может вызывать клеточный стресс и ускорять метаболизм LAB, улучшая их работу во время ферментации.…”

Potential applications of pulsed electric field in cheesemaking

“…Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in co-culture were treated by PEF and then used to carry out the fermentation (Chanos et al 2020). The authors hypothesised that PEF treatment of the co-culture would allow Str.…”