Tailor-made porous solid foods

A method of controlling the porosity of cellular solid foods and its dependence on solids content were investigated. Freeze-dehydration of cold-set alginate gels was used to produce tailor-made porous solids. Gels were composed of sodium alginate, corn starch, oil and other additives necessary to induce gelation. Porosity values were derived from particle and bulk densities utilizing a helium pycnometer and a volumetric displacement method. To achieve a wider range of porosities, the gels were immersed in sucrose solutions of 10 to 60°Bx. Gel porosity after drying decreased from 0.85 to 0.42 and 0.07 after immersion in the 30 and 60°Bx solution for 183 and 158 h, respectively. Similarly, after immersing gels containing an additional 5% soy oil, porosity decreased to 0.36 and 0.04 after 165 and 158 h, in 30 and 60°Bx solution, respectively. Preparation and formulation play a significant role in porosity, and they can both be utilized to control its value within the range 0.85-0.04. SEM micrographs revealed changes in the original cellular solid, characterized by numerous large void spaces, to a denser and more uniform appearance of the specimen after immersion in the 60°Bx sucrose solution. The dry gel system with controlled porosity provides a novel tool for the production of tailor-made cellular-solid foods.