Intelligent modified corn starch films with spray-dryer encapsulated grape and beetroot extracts

Grape residue and beetroot juice are alternative sources for the extraction of various compounds of interest, such as anthocyanins and betalains, respectively. These can act as intelligent colorants in bioactive packaging, which may undergo a color change due to pH variation, allowing for the monitoring of food freshness. The objective of this work was to evaluate the effect of adding spray-dryer encapsulated grape and beetroot extracts¹ on the mechanical, functional, and intelligent properties of modified corn starch films. Films were prepared with 4% modified corn starch (A), 30% glycerol (g/100g starch), with and without the addition of 20% grape (U) or beetroot (B) particles (g/100g starch) using the casting method². The films were characterized for their mechanical properties³ using a TA.TX Plus texture analyzer (TA Instruments, United States), as well as for moisture and solubility². The UV/visible light barrier properties were determined using a UV/visible spectrophotometer (Lambda 25 UV/Vis, PerkinElmer, USA) between 200 and 800 nm. Their color-changing capacity was evaluated by immersing the films in solutions at different pH levels (2-12). The U and B films exhibited lower tensile strength (7.1 ± 0.8 and 1.7 ± 0.3 MPa, respectively) than the control films (10.0 ± 2.0 MPa). However, the films containing B were significantly more elongated (39.8 ± 5.5%) and more soluble (30.02 ± 1.63%) than the corn starch films without extract (6.5 ± 0.2% and 23.07 ± 3.54%, respectively). The films with added particles absorbed 20.55 ± 5.67 (U) and 16.145 ± 0.27 (B) at 280 nm, and 46.64 ± 1.68 (U) and 46.12 ± 2.03 (B) at 600 nm. Both films showed a color change with pH variation. The wettability of the corn starch film surfaces was not significantly altered by the addition of the encapsulated extract (A: 70.04 ± 4.79°; U: 65.36 ± 9.63° and B: 67.61 ± 8.51°). The produced films with added encapsulated extracts have the potential to act as intelligent packaging for foods with low moisture content.