Rice starch-alginate systems gelatinised by high hydrostatic pressure (HHP) as dysphagia-oriented matrices

The rheological, mechanical and structural properties of conventional and waxy rice starch-alginate composite gels formed by heat (90 +/- 1 degrees C, 20 min) and high hydrostatic pressure (500 MPa at 20 +/- 3 degrees C for 20 min) were investigated to explore the feasibility of these matrices as novel dysphagia-oriented foods. Amylose containing rice starch composite samples processed by HHP exhibited a rheological pattern typical of weaker networks with more fluid-like behaviour among all formulations (G' = 300-1200 Pa, tan delta = 0.10-0.20), which was considered favourable for dysphagia patients. HHP gelatinisation led to marked short-term retrogradation of normal starch gels, as reflected by the significantly higher values of gel firmness (72 +/- 4 g) (p < 0.05). However, this phenomenon was significantly attenuated by the presence of alginate (10-15 g) (p < 0.05). The texture profile analysis (TPA) parameters of all formulations were within the range recommended for texture-modified food products for dysphagia patients. HHP treatment indicated a positive effect on the long-range and short-range ordered structure of the composite gels, which was further confirmed by the SEM micrographs. The international dysphagia diet standardization initiative (IDDSI) tests indicated that only amylose-containing starch-alginate composites produced by HHP could be classified as level 5. These results provide insights into the potential benefits of utilising HHP to produce starch-alginate composites for the development of the novel soft gel-type dysphagia food matrices.