MRI in Food Process Engineering

Abstract

Most foods (initial/final) and food components are disperse multiphase systems (suspensions, foams, emulsions, porous/dry/wet bulk solids). Aspects of the material properties essential for both consumer and producer are the structure (different length-scales) and flow behavior. The flow behavior is important for the design of process unit operations and sensory behavior of the final food product. The structure is correlated with various macroscopic properties like the storage/ageing behavior, phase separation (syneresis, sedimentation) [1,2], and the filtration/deformation/fiow/sensorial behavior. Correlations between the evolution of the stress and porosity, agglomeration, and flow-type are established for flowing foods (starch solutions [3], wheat dough [4]). It is, therefore, plausible to assume that the correlation between the structure and the rheology is generally valid. Materials with volume fractions of the disperse phase higher than 5 vol.% are usually opaque [5]. MRI offers the possibility to perform measurements non-invasively, non-destructively, and highly selective (in situ, online) in order to study the structure or trace structural changes or inner transport processes in different phases/states of aggregation (without preparations) during production, storage, transportation, and consumption (temporal, spatial, chemical resolved). Samples may be studied several times under identical or changed conditions, which is a great advantage (time saving, higher accuracy, interior surface) compared to preparative microscopy. The objective of MRI in food process engineering is to develop and check appropriate models and describe the system for a reliable process design, quality control, and process control, in order to forgo time-intensive trial and -error. Foods have often to be built up step by step from simple ingredients to complex systems in order (i) to study effects of single constituents and (ii) to quantify interactions between constituents. On the basis of the knowledge of the involved phenomena, new products/apparatus with improved process conditions can be developed economically [6].