Effect of acetic anhydride, citric acid and cellulosic fibers on the properties of starch nanocomposite film for egg storage

Abstract

The effect of cassava starch modifications on the properties of lignin-nanofiber-filled thermoplastic starch composite films was investigated for the extension of egg shelf-life. Starch was extracted from cassava and modified with acetic anhydride (AA), citric acid (CA) and dual modification with the two (AA/CA). Similarly, lignin and nanofibers were prepared from bamboo. Starch nanocomposite films were then produced by casting method from native and modified starch with lignin and nanofibers as fillers. The nanocomposite films were also optimized and characterized for water barrier, mechanical, thermal, and biodegradability properties. The packaging effect of starch nanocomposite films on egg quality parameters measured in terms of internal & external characteristics (egg weight, albumen height, yolk index, haugh height), biochemical changes, microbial studies and shelf life of the stored eggs were determined afterwards. The result showed that water absorption capacity of the modified starch films were significantly lowered (p<0.05) compared to that of thermoplastic starch (TPS) and native starch films. Tensile strength, Percent elongation and Young’s modulus values of 14 MPa, 30.08 % & 20.50 MPa respectively were recorded for TPS while 18 MPa, 45.24 % & 23.03 MPa were obtained for native starch film. The corresponding values of these parameters significantly increased (p<0.05) to 21.50 MPa, 49.12 % & 26.53 MPa; 20.36 MPa, 48.60% & 25.25 MPa; and 21.51 MPa, 48.53% & 25.52 MPa for starch film modified with AA, CA and AA/CA respectively. TGA of the films showed that the modified films are more thermally stable than the TPS and native starch. Degradation was most rapid in native starch films especially pure TPS film and slower in modified starch nanocomposite films with starch mixture being the slowest. Results also showed that the starch nanocomposite films preserved the internal and external qualities of eggs up to 10wks at ambient temperature (AT) and 20 wks under refrigeration. Microbial growths were observed in the control samples at ambient temperature and under refrigeration. However, no growth was recorded for eggs stored with the starch nanocomposite films at ambient temperature and under refrigeration. It can thus be concluded that, modification with AA, CA and AA/CA improved the physicochemical properties of starch. Addition of fillers further improved the properties (water barrier, mechanical property and thermal stability) of the starch nanocomposite films. The modified films were also biodegradable and extended the shelf life of eggs beyond that of the controls. Therefore, the modified films are recommended for egg storage.