Development of biodegradable films based on blue corn flour with potential applications in food packaging. Effects of plasticizers on mechanical, thermal, and microstructural properties of flour films

• Thermoplastic flour films were obtained from blue corn flour.
• The effect the plasticizers on film's properties were researched.
• The mechanical and water resistance properties the films were improved.
• The sorbitol-plasticized flour films revealed better adhesion between phases.
• The ATR analysis confirms the chemical linkages between sorbitol and the biopolymer.

In the present study, blue corn flour films were developed. The cereal grain’s total composition (excluding the pericarp) is used to obtain the films. The plasticizing effects of two different polyols such as glycerol and sorbitol on the mechanical, thermal, and microstructural properties of flour films were researched. The results showed that films plasticized with sorbitol had better mechanical properties and less affinity for water than those plasticized with glycerol. The sorbitol-plasticized films were more rigid and did not lose their integrity when immersed in water. The ATR-FTIR spectra of blue corn flour plasticizer with sorbitol showed the presence of the additional band at 1745 cm−1 characteristic of the vibrational carbonyl peak, which confirms the chemical linkages between sorbitol and a polymeric matrix. The effect of the plasticizer on the glass transition temperature (Tg) was characterized using differential scanning calorimetry (DSC). Tg decreased as the plasticizer content increased. Plasticized glycerol films showed lower Tg values than those with sorbitol. SEM observations showed that it was necessary to add plasticizer to maintain film integrity. The sorbitol-plasticized flour films revealed better adhesion between phases, and these films showed a compact structure.