Abstract
The aim of this study is to analyze the properties of a series of polysaccharide composite films, such as apparent density, color, the presence of functional groups, morphology, and thermal stability, as well as the correlation between them and their antimicrobial and optical properties. Natural antioxidants such as anthocyanins (from cranberry; blueberry and pomegranate); betalains (from beetroot and pitaya); resveratrol (from grape); and thymol and carvacrol (from oregano) were added to the films. Few changes in the position and intensity of the FTIR spectra bands were observed despite the low content of extract added to the films. Due to this fact, the antioxidants were extracted and identified by spectroscopic analysis; and they were also quantified using the Folin-Denis method and a gallic acid calibration curve, which confirmed the presence of natural antioxidants in the films. According to the SEM analysis, the presence of natural antioxidants has no influence on the film morphology because the stretch marks and white points that were observed were related to starch presence. On the other hand, the TGA analysis showed that the type of extract influences the total weight loss. The overall interpretation of the results suggests that the use of natural antioxidants as additives for chitosan-starch film preparation has a prominent impact on most of the critical properties that are decisive in making them suitable for food-packing applications.
Highlights
Chitosan is a cationic polysaccharide that is a suitable packaging material due to its biocompatibility, biodegradability, non-toxicity, film-forming and antimicrobial properties.This polymer is currently used in food packaging, agriculture, biomedical science and cosmetics.It can be used as a transparent film or coating to improve food quality and to extend its shelf life.Chitosan is one of the most abundant natural biopolymers with proven antimicrobial, antioxidant, and antifungal/viral properties [1,2,3].Materials 2018, 11, 120; doi:10.3390/ma11010120 www.mdpi.com/journal/materialsStarch is a biodegradable and thermoplastic polymer formed mainly by two polysaccharides: amylose and amylopectin
It should be noted that, regarding the % weight loss at 135 ◦ C, the results suggest that the antioxidants coming from beetroot, blueberry and pitaya are more thermally stable than thymol and carvacrol from oregano
The Fourier Transform Infrared Spectroscopy (FTIR) spectra are similar, because both chitosan and starch have cyclic structures and multiple –OH bonds which are typical of saccharides, water, carboxylic acids, antioxidants, etc
Summary
Chitosan is a cationic polysaccharide (obtained from the deacetylation of chitin, coming from the shells of crustaceans and insect exoskeletons) that is a suitable packaging material due to its biocompatibility, biodegradability, non-toxicity, film-forming and antimicrobial properties.This polymer is currently used in food packaging, agriculture, biomedical science and cosmetics.It can be used as a transparent film or coating to improve food quality and to extend its shelf life.Chitosan is one of the most abundant natural biopolymers with proven antimicrobial, antioxidant, and antifungal/viral properties [1,2,3].Materials 2018, 11, 120; doi:10.3390/ma11010120 www.mdpi.com/journal/materialsStarch is a biodegradable and thermoplastic polymer formed mainly by two polysaccharides: amylose and amylopectin. Chitosan is a cationic polysaccharide (obtained from the deacetylation of chitin, coming from the shells of crustaceans and insect exoskeletons) that is a suitable packaging material due to its biocompatibility, biodegradability, non-toxicity, film-forming and antimicrobial properties. This polymer is currently used in food packaging, agriculture, biomedical science and cosmetics. Starch is a biodegradable and thermoplastic polymer formed mainly by two polysaccharides: amylose and amylopectin In recent research, this polymer is considered to be a promising agent for applications such as food packaging due to its biodegradability and flexibility [3]. According to Jiang et al [4], the starch from rice is convenient for preparing chitosan-starch films because of its relatively small particle size (2–8 μm) and its hypoallergenic quality, which make it an appropriate material for food industry utilization
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