Abstract
As an important functional material in food industry, intelligent packaging films can bring great convenience for consumers in the field of food preservation and freshness detection. Herein, we fabricated pH-sensing films employing hydroxypropyl guar (HPG), 1-butyl-3-methylimidazolium chloride (BmimCl), and anthocyanin (Anth). Besides, the effects of adding cellulose nanocrystals (CNC) into the composite films upon the films’ structures and physicochemical properties are elucidated. The addition of CNC promoted more compact film structures. Moreover, CNC dramatically improved several properties of the pH-sensing films, including the distinguishability of their color changes, sensitivity to pH, permeability to oxygen and water vapor, solvent resistance, durability, and low-temperature resistance. These results expand the application range of pH-sensing films containing CNC in the fields of food freshness detection and intelligent packaging.
Highlights
To produce hydroxypropyl guar (HPG)/cellulose nanocrystals (CNC)/IL/Anth film-forming solutions, 0.6 g of HPG was dissolved in 60 mL of deionized water at room temperature by stirring at 400 rpm for 5 h
The pH-sensing films were cut into squares of 2 cm × 2 cm, and squares of the cut film were stored under room lights (25 ◦ C; relative humidity (RH): 60%)
Good mechanical properties are among the basic requirements for the films to be used as packaging
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. To immobilize natural pH dyes, a number of natural and biodegradable polymers, including starch [3], chitosan [8], guar gum [9], and cellulose [10], have been studied. Among these biopolymeric materials, polysaccharides have been considered among the most promising, because they are abundant, biodegradable, inexpensive and exhibit good film-forming ability. CNC films exhibit excellent mechanical strength, optical transparency, and oxygen barrier properties. They can be used as a reinforcing agent for biopolymeric materials, providing improved physicochemical properties. We studied the solvent resistance, temperature resistance, light resistance, and durability of the pH-sensing films
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