Use of chemically treated nopal cladodes as additive in the cassava starch composite films

Nopal cladodes (NC) are considered a source of fibers and bioactive compounds with high antioxidant properties, so their application as biofiller and bioactive agent in starch films has generated interest. To improve NC incorporation into starch film, NC was chemically treated at different pH values (7, 8, 9, 10, 11, and 12). The physical, mechanical, and active properties of cassava starch/NC composite films were evaluated. Increasing the alkaline treatment of NC, the composite films were more homogeneous, less hydrophilic, more elongable and less mechanically resistant. Thus, alkaline NC treatment at pH 12 yielded the most elongable (72.3%) and hydrophobic (contact angle = 71.8 degrees), but the leastmechanically resistant (1.7 MPa) cassava starch/NC film. Meanwhile, alkaline treatment of NC at pH 11 provided films with better functional properties and antioxidant properties, as measured by DPPH center dot (74.6%) or ABTS(center dot+) (16.6 mu m Trolox/g of film) radical scavenging, as well as hydrophobic surface (64.6 degrees) and improved mechanical resistance (2.5 MPa). Nevertheless, the composite cassava starch/NC films obtained here did not exhibit anti-microbial activity. In conclusion, chemical treatment improved the performance of NC to be used as an additive to produce starch composite films less hydrophilic and with antioxidant property that can help to preserve foods sensitive to oxidation (e.g., nuts and dehydrated fruits). Highlights center dot NC flour contains phenolic compounds, protein, lipids, carbohydrate and fibers. center dot Compounds removed in the NC treatment affected the properties of films. center dot Alkaline NC treatment contributed to increase the elongation of composite film. center dot Alkaline NC treatment decreased the hydrophilicity of composite film. center dot NC treated at pH 11 yielded films with suitable properties for food packaging.