Retrograded Resistant Starch Improves Emulsion Stability and Emulsion Gel Properties Stabilized by Myofibrillar Proteins Without Degrading In Vitro Protein Digestibility

The objective of this study was to investigate the effects of retrograded resistant starch (RS3) (0, 2%, 4% and 6%; w/v) on the emulsion gel properties stabilized by myofibrillar proteins (MPs) and in vitro protein digestibility of the gels. The RS3 was prepared from corn or potato starch using the gelatinization–ultrasound–retrogradation method. The results showed that the addition of RS3 decreased the surface hydrophobicity (p < 0.05) and increased the fluorescence intensity of MPs, indicating enhanced protein–protein interactions. More stable emulsions stabilized by MP/RS3 mixtures were formed, along with higher electronegativity, a smaller droplet size and reduced creaming index. These changes promoted the formation of better gel networks with the oil droplets evenly dispersed, thus improving gel strength, water holding capacity (WHC) and texture, especially at the concentration of 6% RS3 added. The gel force results indicated that the addition of RS3 enhanced the hydrophobic interaction and disulfide bonds between MPs. LF-NMR and MRI data further confirmed that RS3 addition facilitated the migration of free water to immobilized water. Furthermore, the incorporation of RS3 caused a relatively lower pepsin digestibility but did not change the overall in vitro protein digestibility of the gels. This paper provides a method to produce high-quality low-GI meat products without degrading protein digestibility.