An Evaluation of the Use of Coffee Silverskin Particles and Extracts as Additives in Wheat Flour/Glucose Mixtures to Produce Bioactive Films for Food Packaging

The scientific community’s interest in finding an alternative to the term “wastes” for coffee by-products is steadily increasing. The substantial presence of polyphenols, caffeine, and tannins in these wastes could result in the contamination of water and soil, as they exhibit harmful effects on a range of plants, microorganisms, and aquatic organisms. However, these identical antioxidants can extensively be utilized in food packaging applications. In the context of active packaging, the development of bioactive food packaging films based on natural products and coffee industry wastes is of significant importance according to circular economy principles. In this study, the effect of coffee silverskin particles, i.e., waste of the coffee roasting process, and coffee silverskin aqueous extracts on the properties and antioxidant activity of wheat flour-based films with glucose for food packaging applications were evaluated. In addition, chemical structure identification, optical and morphological analysis, color measurements, and physico-chemical characterization of the films were performed, determining their water absorption, film solubility, and degree of swelling. Furthermore, the oxygen and water vapor transition rate and their antioxidant activity were also measured, and it was found that increasing the addition of coffee silverskin particles and aqueous extracts affected the properties of the films. The biocomposite films of wheat flour and glucose with coffee silverskin particles produced in this work exhibited higher tensile stress at break and Young’s modulus compared with wheat flour film with no additives. However, a decrease in elongation at break was observed with increasing addition of the silverskin due to the transition from a pure elastomeric material to a crosslinked one following the formation of hydrogen bonds between the additive and the matrix, which was also found in the FTIR spectra. This work offers a new use of wheat flour and coffee silverskin as an inexpensive biocomposite material to produce multifunctional active films for food packaging applications.