Insight into the formation mechanism of soy protein isolate films improved by cellulose nanocrystals

• Mechanism of cellulose nanocrystals (CNC) to improve film properties was proposed. • Adding CNC restricted water mobility and improved the viscoelasticity of films. • Incorporation of CNC enhanced hydrophobic and hydrogen bonding interactions. • CNC-induced conformational modifications promoted to form stronger film structures. • The obtained nanocomposite films can be used for pork and strawberry preservation. This study aimed to evaluate the effects of cellulose nanocrystals (CNC) on the basic properties of soy protein isolate films, and especially to propose the corresponding formation mechanism. Tensile strength, barrier properties, and water resistance were effectively improved after the formation of nanocomposite films. Incorporating CNC could restrict water mobility and improve the viscoelastic properties of films. Appropriate content of CNC (0.50% and 0.75%) promoted the construction of a more homogeneous and compact film structure, which may be attributed to the CNC-induced conformational modifications and the enhanced hydrophobic and hydrogen-bond interactions. While excessive CNC (1.00%) was not conducive to the integrity and continuity of film structures, resulting in the weakened functional properties. The obtained films were able to decrease total viable counts and total volatile basic nitrogen of stored pork, and extend the shelf-life of strawberry. This work offers a theoretical basis for the application of CNC in packaging industry.