Microstructure–texture relationships of aerated sugar gels: Novel measurement techniques for analysis and control

Proper control of the texture properties of aerated foods demands accurate measurement tools. Aerated sugar gels with identical composition but different microstructures were produced by applying different mixing times of 2, 4 and 8 min. Compression test and acoustic emission measurements were carried out to characterize the mechanical properties of these foams. Significant differences in deformation properties and number of acoustic events were found depending on the foaming time, indicating differences in texture. Microstructural attributes such as bubble size and bubble number distributions of the different foams were measured based on micro- and nano-CT and were found to differ between the foams. Additionally, time and spatially resolved diffuse spectroscopy were used to evaluate their optical properties. While, as expected for foams with the same chemical composition, the absorption properties were not significantly different, a relationship between scattering and microstructural properties was found. The results show that microstructural properties affect the texture of aerated foams. Moreover, the latter can be measured nondestructively using time and spatially resolved diffuse spectroscopy.Industrial relevanceFood aeration is one of the fastest growing unit operations in the food industry (Zúñiga and Aguilera, 2008 and Zúñiga and Aguilera, 2009). Proper design and control of the texture properties of aerated foods demand accurate measurement tools of microstructural features.Food microstructure is defined as the spatial arrangement of structural components of food and their interactions. Structural elements include water and oil droplets, gas cells, fat crystals, strands, granules, micelles and interfaces. Changes in the microstructure during storage and processing can be significant and affect the macroscopic appearance, quality and perception of food. Due to the microscopic complexity, straightforward methodologies that link quality to food microstructure do not exist today, as opposed to many engineering materials with a well ordered microstructure, for which the relationship with macroscopic properties can be easily understood based on fundamental physics. The only way forward is to develop methods that measure directly the microstructural properties of foods.

► The structure–property relationships of sugar foams were studied. ► Nano-CT of foams was feasible down to a resolution of 0.5 μm. ► Optical properties obtained from resolved spectroscopy increased with mixing time. ► Acoustic emission measured texture of aerated foams affected by microstructure.