Whey protein aerated gels as matrices for controlled mineral release in simulated gastric conditions

Aerated whey protein gels were obtained using a cold gelation process induced by Ca2+, Mg2+ or Fe2+. A new product was manufactured with different rheological and microstructural properties. Non-aerated and aerated gels behaved as strong gels with storage moduli several times higher than loss moduli. The aerated gel obtained using Fe2+ ions was the most transparent and a fractal structure of air bubbles was observed. Aerated gels induced by Ca2+ and Fe2+ ions were stable for 41 days when stored at 7 degrees C. For Mg2+ induced aerated gels, a decrease in an average bubble size was found to be caused by canals in the air/gel interface. Release of the ions was performed in simulated gastric conditions and compared to acid-induced hydrolysis. For Mg2+ and Ca2+ induced gels, diffusion mechanism was responsible for ion release from the gel and aerated gel matrix, and for Fe2+ induced gels the release was a complex process, which involved both diffusion of iron ions and the process of relaxation of the gel matrix. More intensive ion release was found in simulated gastric conditions in comparison to hydrolysis in acid, and for aerated gels in comparison to non-aerated gels. The total release of ions from the non-aerated and aerated gels in the artificial stomach lasted several hours, allowing the use of these matrices for the release of active substances in the lower gastrointestinal tract (non-aerated gels) and as matrices floating in the stomach (aerated gels). Aerated gels with Fe2+ or Mg2+ ions could be used for supplementation of the human body with these important microelements. (C) 2014 Elsevier Ltd. All rights reserved.