An NMR Metabolomics Approach to Investigate Factors Affecting the Yoghurt Fermentation Process and Quality

Abstract

A great number of factors can influence milk fermentation for yoghurt production such as fermentation conditions, starter cultures and milk characteristics. It is important for dairy companies to know the best combinations of these parameters for a controlled fermentation and for the desired qualities of yoghurt. This study investigates the use of a 1H-NMR metabolomics approach to monitor the changes in milk during fermentation from time 0 to 24 h, taking samples every hour in the first 8 h and then at the end-point at 24 h. Three different starter cultures (L. delbrueckii ssp. bulgaricus, S. thermophilus and their combination) were used and two different heat treatments (99 or 105 °C) were applied to milk. The results clearly show the breakdown of proteins and lactose as well as the concomitant increase in acetate, lactate and citrate during fermentation. Formate is found at different initial concentrations depending on the heat treatment of the milk and its different time trajectory depends on the starter cultures: Lactobacillus cannot produce formate, but needs it for growth, whilst Streptococcus is able to produce formate from pyruvate, therefore promoting the symbiotic relationship between the two strains. On the other hand, Lactobacillus can hydrolyze milk proteins into amino acids, enriching the quality of the final product. In this way, better insight into the protocooperation of lactic acid bacteria strains and information on the impact of a greater heat treatment in the initial matrix were obtained. The global chemical view on the fermentations provided using NMR is key information for yoghurt producers and companies producing starter cultures.

Effect of fumaric acid on the growth of Lactobacillus delbrueckii ssp. bulgaricus during yogurt fermentation

“…thermophilus was consumed during coculture with Lb. bulgaricus (Trimigno et al, 2020), supporting that fumaric acid functions as a symbiotic substance between these species. We also confirmed that the addition of fumaric acid to the coculture of Lb.…”

“…thermophilus was rapidly consumed during coculture with Lb. bulgaricus (Trimigno et al, 2020). These reports suggest that fumaric acid functions as the symbiotic substance between Strep.…”

“…thermophilus and Lb. bulgaricus have revealed candidates functioning in symbiosis (Herve-Jimenez et al, 2009;Sieuwerts et al, 2010;Trimigno et al, 2020). Some studies demonstrated that Strep.…”

Application of the Metabolomics Approach in Food Authentication

“…Certain parameters can affect milk fermentation and desirable yogurt qualities, such as fermenting conditions, starter crops, and milk characteristics. Trimigno et al [83] conducted a metabolomic NMR approach to research the yogurt fermentation process and how NMR can detect yogurt quality. The breakdown and a concomitant increase of proteins and lactose during fermentation were also observed.…”

Foodomics: Analytical Opportunities and Challenges

“…111 Despite its relatively low sensitivity, this technology is highly reproducible, rapid, and no preliminary sample separation is required, and it has been implemented to screen the metabolic profile of the blue mussel (Mytilus edulis) and the Manila clam (Ruditapes phlippinarum), 112 to discriminate the geographical origins of agave species and grape varieties, 113 to determine the metabolomic profiling of acerola clones at different ripening stages, 114 to evaluate the rheological characteristics of sponge cake after in vitro digestion, 115 or to investigate milk fermentation during yoghurt production when different heat treatments of milk and starter cultures are employed. 116 In all of these studies, advanced statistical tools played a critical role for compound identification and the discovery of significant metabolites. For instance, the statistical total correlation spectroscopy (STOCSY) was used by Aru et al to identify mytilitol as an integral part of the metabolome of R. philippinarum and M. edulis, but also to suggest that the distribution of this metabolite is species-specific and dependent on the geographical origin of the sample.…”