Bioactive coconut protein concentrate films incorporated with antioxidant extract of mature coconut water

Coconut is a very important fruit worldwide. Coconut milk cake and mature coconut water (CW) are the by-products from coconut processing. Therefore, it is of interest to exploit coconut milk cake and CW as a source of protein and antioxidant, respectively. In particular, antioxidant compounds from CW were extracted using a solvent (acetone and diethyl ether) and the evaporation compared with coconut water concentrate (CWC) which was extracted using evaporation. CWC had a 4-times higher total phenolic content than that of CW. Even though the solvent extract had a higher total phenolic content than the evaporation-only extract, the antioxidant capacity of the solvent extract of CWC and the evaporation-only (CWC) was not significantly different. Moreover, using CW as a solvent also reduced the amount of glycerol needed to form a satisfactory coconut protein film. The use of CW as a solvent and the incorporation of CWC significantly increased the film solubility and water vapor permeability but improved the film mechanical properties. The total phenolic content and antioxidant capacity increased in protein films incorporated with CWC and using CW as a solvent. Fourier transform infrared spectroscopy showed interactions among the antioxidant compounds from CW, CWC and protein. The formation of a polyphenol-protein complex doubled the film elongation. Thus, the coconut protein film produced using CW as a direct solvent and incorporated with CWC can provide an environmentally friendly active packaging material for agricultural and food product applications.