Hydroxypropyl methylcellulose hydrocolloid systems: Effect of hydroxypropy group content on the phase structure, rheological properties and film characteristics

This work investigates the structure, processability, and film performance of hydroxypropyl methylcellulose (HPMC) hydrocolloids affected by hydroxypropy substitution degree and blending with hydroxypropyl starch (HPS). The hydroxypropylation of HPMC could increase inter-chain hydrogen bonding, thereby promoting its gelation, and improve film-forming, but reduce the mechanical properties of the films. HPMC-HPS mixed hydrocolloid system showed a typical "sea-island" morphology with the continuous phase changing with blend ratio. The content of hydroxypropy groups of HPMC affected the compatibility between HPMC and HPS, the morphology of the discrete phase, and the rheological properties of the blends. The fluid-like HPS enhanced the gel strength of HPMC when they had better compatibility. With a higher degree of hydroxypropy substitution, blend films exhibited a much denser structure, better oxygen barrier property, and appropriate mechanical properties. The knowledge obtained from this work could guide the development of edible packaging materials with desired properties and functionality.