Effects of Citric Acid on Structures and Properties of Thermoplastic Hydroxypropyl Amylomaize Starch Films

Abstract

Hydroxypropyl amylomaize starch (HPAS) films were prepared by hot press. The effects of initial pH of HPAS on the mechanical properties, molecular interaction, structure, and cross-linking degree of the resultant films were investigated. A weak acidic condition was suitable for cross-linking of citric acid and HPAS by reactive extrusion. The film of HPAS with an initial pH of 5.66 had the maximum tensile strength of 7.20 MPa and elongation-at-break of 94.53%, and the weight average molecular weight of HPAS increased to 4.17 × 105 g/mol. An appropriate initial pH facilitated the formation of diester bonds between HPAS and citric acid during extrusion, but too low initial pH levels resulted in hydrolysis of starch molecules and reduced the mechanical properties.

Synthesis and detailed characterization of sustainable starch‐based bioplastic

“…The bioplastics were produced by solution casting method with 10%, 30%, and 50% of CA (% wt of starch used) 17,18 . Briefly, all bioplastics were prepared with 18 g of RS and PS in the ratio of 1:1 (w/w), and 5 mL of glycerol.…”

Native and modified biodegradable starch‐based packaging for shelf‐life extension and safety of fruits/vegetables

“…Remarkably, only a 5% addition of STMP increased the maximum TS and lowest elongation (Sharma et al ., 2021). The inclusion of citric acid in hydroxypropyl amylomaize starch‐based film showed the highest TS and elongation‐at‐break of 7.20 MPa and 94.53%, respectively, at a pH level of 5.66, which might be due to the creation of crosslinking bonds between starch and citric acid during the process of extrusion (Qin et al ., 2019). Biodegradable starch‐based film incorporation with citric acid treated at 85 °C reduced the WVP and structural integrity of the film as compared to film treated at 75 °C (Seligra et al ., 2016).…”

Functionality and Applicability of Starch-Based Films: An Eco-Friendly Approach

“…The intensity of acetylation significantly influenced the water vapor permeability of high amylose starch films, once the acetylated starch films with 0.42 and 0.72 of substitution degree had a lower WVP than the acetylated starch films with DS = 0.24 [67]. Further, Zamudio-Flores et al ( 2007) [68] performed a dual modification of banana starch. The authors oxidized the banana starch at three different levels and acetylated it.…”