Thermomechanical and Morphological Properties of Nanocomposite Films from Wheat Gluten Matrix and Cellulose Nanofibrils

Abstract

The aim of this investigation was the optimization of preparing gluten film containing cellulose nanofibrils (CNF). An optimization procedure using central composite design (CCD) with three factors (CNF, glycerol, and sodium dodecyl sulfate (SDS) concentrations) was used in order to investigate the effect of these parameters on the mechanical (tensile strength--TS, elongation at break--ε(b)) and thermal properties of gluten films and to establish a formulation to depict the relationship between the mentioned factors and mechanical properties. Through regression analysis, it was found that TS and ε(b) well fitted by quadratic polynomial equations (R² = 0.99 and 0.98, respectively) and the glycerol concentration was the most significant factor influencing them. The optimization was based on maximizing TS and ε(b). The optimum conditions determined using response surface methodology (RSM) were defined as: CNF concentration, 11.129 g/100 g, glycerol concentration, 35.440 g/100 g and SDS concentration, 6.259 g/100 g. The predicted responses for these film preparation conditions were a TS of 3.630 MPa and ε(b) of 86.033%. The verification experiments were conducted under optimal conditions to compare predicted and actual values of dependent variables. This experiment indicated that both predicted and actual values (TS of 3.721 MPa and ε(b) of 88.935%) almost coincide each other and therefore the estimated models were reasonable and of high accuracy to predict dependent variables values. The scanning electron microscopy (SEM) images showed non-agglomerated and well dispersed CNF in the gluten matrix. Differential scanning calorimetry (DSC) results indicated that there is not any significant difference (P > 0.05) between the glass transition temperature (T(g)) of optimum nanocomposite (-29.12 °C) and control film (-29.64 °C) and their thermogravimetric analysis (TGA) thermograms showed similar degradation behavior.

Wheat gluten–based coatings and films: Preparation, properties, and applications

“…Nanofillers possess a high geometrical aspect ratio and have the potential to reinforce the mechanical and barrier properties of nanocomposite film (Xu et al, 2019(Xu et al, , 2020. Rafieian et al (2014) optimized wheat gluten film formulation with cellulose nanofibrils, glycerol, and SDS through response surface methodology. The condition of 11.129/100 g cellulose nanofibrils, 35.440/100 g glycerol concentration, and 6.259/100 g SDS concentration resulted in the highest tensile strength and elongation at break, which were 3.63 MPa and 86.03%, respectively (Rafieian et al, 2014).…”

“…Rafieian et al (2014) optimized wheat gluten film formulation with cellulose nanofibrils, glycerol, and SDS through response surface methodology. The condition of 11.129/100 g cellulose nanofibrils, 35.440/100 g glycerol concentration, and 6.259/100 g SDS concentration resulted in the highest tensile strength and elongation at break, which were 3.63 MPa and 86.03%, respectively (Rafieian et al, 2014). There was no significant difference in the glass transition temperature and degradation behavior between films created under this condition and the control film, indicating that the addition of cellulose nanofibrils, glycerol, and SDS did not affect the thermal properties of wheat gluten-based films (Rafieian et al, 2014).…”

“…The condition of 11.129/100 g cellulose nanofibrils, 35.440/100 g glycerol concentration, and 6.259/100 g SDS concentration resulted in the highest tensile strength and elongation at break, which were 3.63 MPa and 86.03%, respectively (Rafieian et al., 2014). There was no significant difference in the glass transition temperature and degradation behavior between films created under this condition and the control film, indicating that the addition of cellulose nanofibrils, glycerol, and SDS did not affect the thermal properties of wheat gluten–based films (Rafieian et al., 2014). The optimal formulation for wheat gluten–based films with cellulose nanofiller (CNF) and carboxymethyl cellulose (CMC) was also determined: Overall, 1% wheat gluten, 0.686% CMC, and 8.549% CNF resulted in desirable water vapor permeability and mechanical properties (Bagheri et al., 2019).…”

Effect of tea polyphenols on the quality of Chinese steamed bun and the action mechanism

“…For differential scanning calorimetry (DSC) analysis, the sample (5.0 ± 0.5 mg) was added in an iron crucible, and then the crucible was sealed and heated from 40 to 180 • C with a rate of 5 • C/min by using a Polyma calorimeter (NETZSCH Ltd, Selb, Germany). Nitrogen gas was used as the purge gas with a flow rate of 20 ml/min, and vacant iron crucible was used as the reference (Rafieian et al, 2014).…”

The effect of carboxylated nanocrystalline cellulose on the mechanical, thermal and barrier properties of cysteine cross-linked gliadin nanocomposite

“…Wheat gluten (WG) is a renewable, biodegradable, and edible agropolymer with appropriate film-forming ability (Rafieian et al 2014b;Naji et al 2012). WG films, similar to other protein-based films, have appropriate barrier properties against O 2 and CO 2 at low and moderate relative humidities (RH) (Khwaldia et al 2010) and high selective CO 2 /O 2 permeability ratio in comparison with conventional oil-derived synthetic films (Gontard and Guilbert 2010).…”