Nopal cladodes flour (Opuntia ficus-indica): characterization and application as a new reinforcement and antioxidant biopolymer on starch-based films.

Abstract

This thesis studied important issues related to the incorporation of the nopal (Opuntia ficus-indica) cladodes flour (NC) in a cassava starch matrix for the development of a sustainable plastic film. Thus, this study aimed to evaluate the influence of the alkaline treatment applied to NC on the film properties as well as to compare the functional efficacy of NC to propolis extract and lignin addition. NC was obtained by grinding and sieving process. The resulting fractions (NC-45, NC-80 and NC-120 mesh sieve) were characterized in terms of chemical composition (XRD and FT-IR), morphology (SEM), content of total phenolics and antioxidant activity (DPPH and ABTS). The FTIR spectra of the NCs showed bands related to the presence of proteins, fibers, lipids, sugars and pectin. The presence of crystallites related to calcium salts, cellulose and hemicellulose peaks were evidenced by XRD. Due to the morphological and chemical characteristics, NC-120 was the chosen fraction. The NC-120 was subjected to an alkaline treatment at different pHs (7, 8, 9, 10, 11 and 12) and subsequently added to the polymeric matrix of cassava starch; glycerol added as a plasticizer. The presence of NC-120 affected starch-starch interactions (SEM) and the thermal stability (DSC). NC-120 incorporation was compared to propolis extract and lignin performance. According to multivariate statistics, NC-120 affected the mechanical properties in a similar way to the addition of lignin and propolis extract, however NC-120 was better incorporated into the cassava starch matrix, providing films with more hydrophobic surface and greater antioxidant activity, attesting its potential as a reinforcing and antioxidant biopolymer (88.43% radical inhibition by the DPPH method). The films obtained did not present antimicrobial activity, nevertheless due to the high antioxidant activity and hydrophibicity modification capacity, NC-120 has a high potential for incorporation in active packaging systems.