Fig. 1
Characterisation of (a) model foods and (b) ready-to-swallow in vivo food boli. The parameters analysed include water content, textural attributes (i.e., firmness, cohesion work, adhesion work, and maximum adhesive force), and shear viscosity at the relevant oral shear rate (50s− 1). Additional parameters such as insalivation ratio (Hw), food oral processing (FOP) time derived from US recordings (n = 10), and the stimulated salivary flow rate are reported for in vivo food boli. Averaged data along with corresponding standard deviations are shown. Model foods were subjected to three repetitions (n = 3), while food boli were analysed through three repetitions across three different panellists (n = 3 × 3). Statistical significance (p < 0.05) between datasets is denoted by letters. Water content varied between foods, with ASS at the lowest and SS the highest. VL was the most spreadable, requiring less compression work (similar to SS), while ASS resisted the most, needing double the compression work compared to VL. Adhesion varied, having both VL and SS similar adhesive properties while ASS had over twice the adhesion work and force. At relevant oral conditions, VL and ASS showed similar flow abilities (1.1 and 1.4 Pa.s, respectively). SS exhibited higher resistance (2.1 Pa.s), featuring distinct shear thinning phases between 50–100 s− 1 (shear viscosity profiles of both foods and boli are included in Supplementary Information). After oral processing, food boli spreadability improved, with over 80% firmness decrease for VL and ASS, and around 60% for SS. Compression effort reduced over 85% for VL and ASS, and approximately 50% for SS. Adhesion forces decreased by over 90% for VL and ASS, and approximately 60% for SS. This reduction contributed to a notable decrease in adhesion work, exceeding 90% for VL and ASS, and around 40% for SS. Flow resistance varied, with VL showing the most significant decrease to 0.1 Pa.s, followed by ASS with a 60% reduction and SS with a 36% decrease. Food-to-saliva ratio, FOP time, and estimated salivary flow rate showed no significant differences among food boli.
