The Combined Effect of Pressure and Temperature on Kefir Production—A Case Study of Food Fermentation in Unconventional Conditions

Abstract

Food fermentation under pressure has been studied in recent years as a way to produce foods with novel properties. The purpose of this work was to study kefir production under pressure (7–50 MPa) at different temperatures (17–32 °C), as a case study of unconventional food fermentation. The fermentation time to produce kefir was similar at all temperatures (17, 25, and 32 °C) up to 15 MPa, compared to atmospheric pressure. At 50 MPa, the fermentation rate was slower, but the difference was reduced as temperature increased. During fermentation, lactic and acetic acid concentration increased while citric acid decreased. The positive activation volumes (Va) obtained indicate that pressure decreased the fermentation rate, while the temperature rise led to the attenuation of the pressure effect (lower Va). On the other hand, higher activation energies (Ea) were observed with pressure increase, indicating that fermentation became more sensitive to temperature. The condition that resulted in a faster fermentation, higher titratable acidity, and higher concentration of lactic acid was 15 MPa/32 °C. As the authors are aware, this is the second work in the literature to study the combined effect of pressure and temperature on a fermentative process.

Identification of the Microbiota in Coconut Water, Kefir, Coconut Water Kefir and Coconut Water Kefir-Fermented Sourdough Using Culture-Dependent Techniques and Illumina–MiSeq Sequencing

“…Ribeiro et al (2020) [34] and Irigoyen (2005) [35] reported that the pH of kefir was between 4.2 and 4.6, similar to this study, and corresponded to the overall titratable acidity values of the kefir grains. The lactic acid concentration of kefir grains in this study was, however, lower than that reported by Ribeiro et al (2020) [34] for milk kefir grains, which had a lactic acid concentration of 4 mg/g. This could be due to the fact that water kefir grains were used in this study instead of milk kefir grains.…”

“…Kefir grains had a pH of 4.56 ± 0.6, TTA of 6.14 ± 0.12, D-lactic acid concentration of 0.16 ± 0.03 g/L and L-lactic concentration of 0.55 ± 0.05 g/L. Ribeiro et al (2020) [34] and Irigoyen (2005) [35] reported that the pH of kefir was between 4.2 and 4.6, similar to this study, and corresponded to the overall titratable acidity values of the kefir grains. The lactic acid concentration of kefir grains in this study was, however, lower than that reported by Ribeiro et al (2020) [34] for milk kefir grains, which had a lactic acid concentration of 4 mg/g.…”

Biotecnología del kéfir: una revisión sobre las aplicaciones y sus perspectivas futuras

“…comerciales(Nikolaou et al, 2017(Nikolaou et al, , 2019 Nikolaou et al, 2020a; Nikolaou et al, 2020b; Nikolaou et al, 2020c). En la Fig.5se resumen las aplicaciones del kéfir.Mejorando el rendimiento del kéfirEn el proceso de mejorar las características del kéfir, se ha ensayado cambiar el pH del sustrato(Arévalo & Quispe, 2008;Laureys et al, 2019), modificar la temperatura(Putri et al, 2020), la presión(Ribeiro et al, 2020), la concentración inicial del inóculo(Apar et al, 2017), evaluar la presencia de CO2(Kök-Taş et al, 2013), usar fermentación secundaria(Yıldız-Akgül et al, 2018) e incluso, añadir extractos de plantas en búsqueda de mayores beneficios(Aiello et al, 2020).Al evaluar el efecto del pH en la producción del kéfir, se observa que los cambios en el pH óptimo (4,4) generan un decremento en el crecimiento de la biomasa(Arévalo & Quispe, 2008). Cuando existe amortiguación del pH se presentan altas concentraciones de carbohidratos totales residuales y bajas concentraciones de metabolitos.…”