Investigating Physicochemical and Antifungal Characteristics of Soy Protein Isolate Edible Films with Eucalyptus Tannin

The use of natural active compounds in edible films is a suitable approach for active packaging production. The objective of this study was to investigate physicochemical and antifungal characteristics of soy protein isolate edible films containing eucalyptus tannin extract.

Tannin extract was prepared from eucalyptus leaves and then added to soy protein isolate films in three concentrations of 1, 2.5 and 5%. The antifungal activity against Aspergillus niger was evaluated,, along with the assessment of moisture sorption isotherms using Guggenheim-Anderson-de Boer (GAB), model permeability to water vapor and antioxidant activity of the films by inhibiting DPPH free radicals.

The fitted moisture absorption experimental data demonstrated that the GAB provided accurate predictions of moisture absorption isotherms with a good fit to the water activity (R2 > 0.92). Based on the results of principal component analysis (PCA), three major components accounted for 96% of the variance of the physicochemical parameters. Antioxidant activity using the DPPH method increased significantly from 6.43 (in the control sample) to 56.92% (in the sample containing 5% tannin), while the vapor permeability decreased particularly at high loading contents of tannin, compared to the control films. Samples containing eucalyptus tannin included good antifungal activities against Aspergillus niger and increasing quantities of tannin in the samples led to significant increases in the inhibition of fungal activity (p < 0.05).

The use of natural additives such as eucalyptus tannin extract in biodegradable films can improve the functional performance of soy protein isolate film and help to increase the shelf life of food products due to their antifungal and antioxidant characteristics.