New Approaches to Characterizing Food Microstructures
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New Approaches to
Characterizing Food Microstructures
Anne-Marie Hermansson, Maud Langton, and Niklas Lorén Introduction Many food-processing operations are designed to create the microstructure that gives the food product its characteristic properties. From milk we can produce different cheeses, yogurts, spreads, or whipped products where the properties are determined by the structure. Other examples of fabricated foods are cereal products such as pasta, meat products such as sausages, and so on. All of these products are based on colloidal structures such as gels, emulsions, foams, or combinations thereof. Microscopy provides the tools for describing how a particular structure is engineered, and, therefore, how it relates to the properties of the product. Approaches in which microscopy methods are combined with other techniques can promote the understanding of the structural role of individual components and their effect on the overall microstructure of complex food products. There are a number of microscopy techniques available, and each technique provides part of the information necessary for a full understanding of the microstructure of foods and other complex biomaterials. Microscopy covers length scales from 109 m to 103 m. Several microscopy techniques are required to cover this range, and different routes of preparation enable us to focus on specific information such as interactions between biopolymers, interfacial structures, and bulk structures. Combining techniques allows us to study the effect of a change in one biopolymer within a complex assembly and to follow how such a change can affect the behavior of the overall structure. This provides a tool for exploring the biophysical reasons behind relationships between structure and behaviors such as mechanical properties. New developments within microscopy, such as the digitization of images and the
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computer power to process image information, open up new avenues for research. The ability to follow dynamic events will steadily improve and attempts to characterize structures under in vivo conditions or with a minimum of preparation will increase. Studies under dynamic conditions give new insight into the kinetics of structure formation, rearrangement, and breakdown that are important for the processing and product development of foods as well as other structured products. Structure engineering can drive the development of new processes yielding tailor-made structures to give products the desired properties. This article will cover developments in microscopy techniques and approaches to the study of relevant states of aggregation and their structural role in more complex colloidal food systems. Recent results from
dynamic studies of biopolymer mixtures will also be presented.
Structural Levels The full characterization of the microstructure of a complex food structure such as an emulsion, foam, or mixed gel requires consideration of not only the sizes and distributions of dispersed and continuous phase regions, but also the fine structure within
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