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Relating food structure to texture and sensory properties

Nesli Sozer discusses structure in cellular solid foods and how this can be related to texture-sensory properties, with an emphasis on cereal products

Introduction

In food structure characterisation, the word “cell” refers to open space filled with air surrounded by a liquid or solid phase. Cellular solid foods can be classified under four different categories based on their structure (open vs closed; thick vs thin; uniform vs non-uniform), processing method of formation (fermentation-baking; extrusion-puffing; freeze drying), texture (soft vs brittle; weak vs strong; elastic vs plastic) and hygroscopicity (physically stable vs tendency to absorb/lose moisture) (1).

Texture is a key quality attribute for many of the cellular solid food materials such as bread, cakes, crackers and extruded snacks. The structure of the food matrix and the cellular architecture influences appearance, texture perception, as well as flavour release. The mechanical failure of cellular foods is related to polymer properties of the cell wall material, processing steps, ingredients and the interaction of all these factors. Understanding the structure-texture relationship of food products is a challenge due to non-homogeneities within the food matrix. Cellular solid foams with identical densities can exhibit different mechanical responses due to discrepancies in the cellular architecture at the micro scale. The changes in the average cell size, cell size distribution, average cell wall thickness, number of cells, cell shape and spatial distribution of cells in the foam matrix are important structural parameters affecting the mechanical response of the solid foams.

There is an increasing demand from the food industry to quantitatively relate mechanical properties to changes in the structure of solid food foams. Until now, food engineers focused on advanced food processing technologies that would enable formulation and production of safe and high quality foods concentrating on the properties at the macro scale. However, most of the structural elements, for example, starch, proteins, plant cell walls, protein fibres, oil droplets, food polymer networks, which contribute to physical, textural and rheological properties are below 100 μm in scale (2). Thus, the next era of food research should be to understand the impact of these structural components on the aforementioned properties in order to be able to fulfill the ever increasing consumer demands.

Previously, solid mechanics theories have been applied by researchers to define the fundamental mechanical behaviour of bread and extrudates (3). Microscopy, magnetic resonance imaging, computer vision techniques, porosimetry, and X-ray computed tomography are some of the several techniques which have been used to study food microstructures.

This paper provides brief information on the concepts of structural architecture in cellular solid foods and how it can be related to texture-sensory properties with an emphasis on cereal products...

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