Nano-/microstructure of extruded Spirulina/starch foams in relation to their textural properties

Abstract

This work reports on an in-depth characterization of the nano-and microstructure of extruded starch foams loaded with the microalga Spirulina (1, 5 and 10 wt.%), as well as the implications of Spirulina incorporation on the textural properties of the foams. Due to the gelatinization process occurring during extrusion, the crystalline and lamellar structures originally present in the starch granule were disrupted, resulting in very amorphous foams.Moreover, the crystalline structure of the fatty acids present in the raw microalga was lost during processing. The presence of Spirulina intracellular components induced the formation of more thermally-stable V-type crystallites through complexation with amylose, hence producing slightly more crystalline foams (XC~5-9%) than the pure extruded starch (XC ~3%). This affected the microstructure of the hybrid foams, which showed more densely packed and well-connected porous structures. Microstructural changes had an impact on the texture of the foams, which became harder with greater Spirulina loadings. The foams underwent very limited re-crystallization upon storage, which was further reduced by the presence of Spirulina. Interestingly, the free fatty acids from Spirulina re-crystallized and the resistant starch content in the 10% Spirulina foam increased, which could potentially be interesting from a nutritional perspective. These results show the potential of extrusion cooking to produce healthier snack foods and highlight the suitability of advanced characterization tools such as neutron tomography and small angle X-ray scattering to investigate food structure.

An Overview of Ingredients Used for Plant-Based Meat Analogue Production and Their Influence on Structural and Textural Properties of the Final Product

“…However, with the optimization of the extrusion process, it was concluded that at low moisture, high temperature and high screw speed, it is possible to partly substitute soy with spirulina to produce meat-like structures. Martinez-Sanz et al [118] produced foams containing starch and spirulina powders using extrusion cooking with an aim to analyze their micro-and nanostructure. The microstructure of the hybrid foams containing both starch and spirulina had more densely packed and well-connected porous structures, which, in consequence, also affected texture-samples with higher spirulina concentrations exhibited higher hardness.…”

Applications of Plant Polymer-Based Solid Foams: Current Trends in the Food Industry

“…In Martínez-Sanz [34], foams were produced by extrusion cooking using Spirulina at 0, 1, 5, and 10 wt.% mixed with corn starch. During extrusion, starch granules are ruptured as they are subjected to high shear, pressure, and temperature.…”

“…The presence of protein can disrupt the pore walls of the expanding melt, which results in reduced expansion and smaller sized, denser cell structures. On the other hand, protein content can increase the number of pores of starch-based extrudates at certain levels, as a result of a greater number of nucleation sites [34].…”

Latest advances in imaging techniques for characterizing soft, multiphasic food materials

“…The authors quantified both the water migration and protein fibre contraction through image analysis of the 3D tomogram. NT has also been applied to investigate several starch/microalgae foam samples, providing an in-depth characterization of the porous microstructureand to assess the effect of different formulation on the porosity, void distribution and connectivity (Martínez-Sanz et al, 2020). Neutron tomography represents a unique and promising technique to investigate food materials, however is limited by the accessibility to a dedicated neutron source facility to perform such experiments.…”