RESUMEN
A time-domain 1 H nuclear magnetic resonance relaxometry method was elaborated for the rapid microstructural characterization of mozzarella cheese. For this purpose, there is a strong need to know how the experimentally determined T2 relaxation time distribution can be related to specific constituents in mozzarella. In this study, a detailed investigation is offered for fresh and aged low-moisture mozzarella cheese, often applied as a pizza cheese, by application of both a conventional Carr-Purcell-Meiboom-Gill (CPMG) sequence and a free-induction decay CPMG (FID-CPMG) sequence. The relaxation behavior was further elucidated by addition of deuterium oxide and by mild heat treatment of samples. The relaxation times of water protons in mozzarella were found to range from a few microseconds to some tens of milliseconds (in aged mozzarella) or to about hundred milliseconds (in fresh mozzarella). The upper limit of the T2 distribution can even be extended to the seconds range upon releasing water protons from the mozzarella matrix using a mild heat treatment or upon addition of deuterated water. Both stimuli also provided evidence for the absorption of water into the cheese matrix. The potential release and uptake of water demonstrated that mozzarella acts as a very dynamic system during production and storage. The detected differences in the behavior of the water fraction between fresh and aged low-moisture mozzarella might be utilized to study the influence of either production and/or storage conditions on the cheese ripening process.
RESUMEN
Elucidating the composition of waxes is of utmost importance to explain their behavior in liquid oil structuring. The chemical components (hydrocarbons - HCs, free fatty acids - FFAs, free fatty alcohols - FALs and wax esters - WEs) of natural waxes were analyzed using HPLC-ELSD and GC-MS followed by evaluation of their oil structuring properties. The gel strength, including the average storage modulus and oscillation yield stress, displayed a negative correlation with FALs and a positive correlation with HCs, FFAs and WEs. The components dictating the gel strength are HCs, FFAs and WEs in a descending order of importance. The consistency of the oleogels increased with the increasing amount of FFAs and HCs and the decreasing amount of WEs and FALs. The presence of more WEs results in a strong but brittle gel with a high initial flow yield stress. We believe these results might be useful in selecting the right waxes to combine in certain fat-based food products.