Poster Presentation 23rd International Society of Magnetic Resonance Conference 2023

In situ monitoring of milk fermentation process by advanced NMR techniques (#345)

Xiaoqi Shi 1 , Qing Zeng 2 , Yanqin Lin 1
  1. Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen
  2. The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

Introduction: Milk is fermented to ease the burden of lactose intolerance. Varying fermentation durations can effectively regulate the levels of lactose and lactic acid in milk, consequently influencing its fermentation degree and flavor profile1. This enables the milk to cater to a wider range of consumers' preferences and ensure greater nutritional value. NMR technology has the capability to monitor the reduction of lactose and the production of lactic acid in real-time and non-destructively during the fermentation process. However, due to the complexity of its structure and coupling network, the 1D 1H spectrum fails to offer sufficient resolution. Moreover, the acquisition time required for a 2D spectrum increases exponentially, thereby compromising the transient nature of the monitoring process.

Aims and Methods: In this work, the milk fermentation process was monitored in situ using advanced NMR techniques. Pure Shift Yielded by Chirp Excitation (PSYCHE) sequence acquired a series of pure shift spectra with multiplets collapsing into singlets2. The Gradient-Enhanced Multilet-Selective Targeted-Observation NMR Experiment (GEMSTONE) sequence was used to selectively excite a specific proton in the overlapping area of the milk3. The lactose and lactic acid contents in two spectra were quantified, allowing for the calculation of the fermentation rate of milk.

Results: During milk fermentation, the characteristic peaks of lactose and lactic acid were separated in the overlapping peaks. The results indicate that lactose reduction and lactic acid production happen concurrently. Lactose decreased by about 30% within 12 hours. As the fermentation of milk progresses, the rate at which it occurs gradually decelerates. The results obtained from the PSYCHE and GEMSTONE studies exhibit a fundamental consistency.

Conclusions: By in situ quantifying lactose and lactate in overlapping peaks, it reflects the rate and degree of fermentation of milk during the fermentation process, so that the fermentation time of milk can be set according to different needs.

  1. Parvez S, Malik K A, Ah Kang S, et al. Probiotics and their fermented food products are beneficial for health. Journal of applied microbiology. 2006, 100(6): 1171-1185.
  2. Foroozandeh M, Adams R W, Meharry N J, et al. Ultrahigh‐resolution NMR spectroscopy. Angewandte Chemie International Edition. 2014, 53(27): 6990-6992.
  3. Kiraly P, Kern N, Plesniak M P, et al. Single‐scan selective excitation of individual NMR signals in overlapping multiplets. Angewandte Chemie International Edition. 2021, 60(2): 666-669.