Insight into the regulations of rice protein on the gluten-free bread matrix properties

Gluten-free bread (GFB) crumb was still crisp despite the structure of hydrocolloids. Rice protein (RP), the endogenous protein of gluten-free rice flour, could potentially eliminate the GFB textural disadvantages. Here, RP (0 g/100 g–5.0 g/100 g) replaced the rice flour to investigate their effect on GFB matrix properties by evaluating the dough rheology, crumb texture, bread physicochemical properties and microstructure, respectively. Results of rheological properties indicated the appropriate concentrations of RP enhanced the stored energy and viscoelastic properties of dough, but the excessive one would weaken the structural strength, which was evidenced by the remarkably decreased maximum development height of dough under stress (Hm) and advanced rupture time (Tx) of dough. As a result, the addition of RP positively improved the crumb matrix properties with an increase in springiness, resilience and hardness. Meanwhile, RP made the GFB matrix more moistening with reduced moisture loss and provided crust with pleasant color due to the Millard reaction. However, corresponding to the rheo-fermentation properties, RP had little effect on bread specific volume and even remarkedly decreased it when the RP concentrations exceeded 3.0 g/100 g. As revealed by the microstructure and protein profiles, the addition of RP formed a compacted structure and interacted with hydroxypropyl methylcellulose (HPMC) to enhance the matrix properties, but superfluous RP led to the RP aggregation and interfered with the network of HPMC to deteriorate the GFB structure.