Understand and characterize draining of acid milk gels using Magnetic Resonance Imaging and Time Domain-Nuclear Magnetic Resonance

A novel dedicated device is introduced to enable investigation of the filtration draining process of different acid-induced milk gels using Magnetic Resonance Imaging (MRI). This approach allows the spatio-temporal resolution of serum content and distribution in gels throughout draining. Its application for the characterization of five acid gels formulated using reconstituted or fresh milk and using different thermal treatments and/or lactic starters indicates its large potential for a better understanding of acid-induced gel draining in dairy industry. Self-diffusion and relaxation measurements using Time Domain-Nuclear Magnetic Resonance (TD-NMR) were performed on the gels following filtration draining to validate and supplement the MRI results, while gels obtained through centrifugation were examined in view of correlating T2 relaxation times to the water content of gels. The presence of lipids in reconstituted milk or the substitution of a casein fraction by microparticulated denatured whey proteins were shown to impact the structure of gels and their serum holding capacity.