Cocoa shell: an industrial by-product for the preparation of suspensions of holocellulose nanofibers and fat

Cocoa shell (CS) is a by-product of the chocolate industry with limited economic benefit and a high environmental impact. In this study, a new material for the food industry that consists of nanocellulose fibers with CS fat was successfully isolated (yield of approximately 7.12%). The material was characterized with attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR), solid-state ¹³C nuclear magnetic resonance (¹³C NMR), X-ray diffraction (XRD), fluorescence and atomic force microscopy (AFM). The XRD, ¹³C NMR, and ATR–FTIR results suggest that the structure of the cellulosic CS fibers can be interpreted as cellulose I_β. The crystallinity index (CrI) of an isolated sample was investigated by different methods with ATR–FTIR, ¹³C NMR, and XRD. According to the results, ¹³C NMR and XRD are the most adequate methods for quantifying the CrI of cellulosic samples in the presence of fat. In addition, the XRD results indicate that approximately 65 to 70% of the sample was crystalline. According to the fluorescence microscopy results, the cellulosic sample formed a suspension with fat, and the AFM results show that the cellulosic part of the sample had nanometric diameters between 30–80 nm with high aspect ratios. Consequently, a suspension of nanocellulose, hemicellulose, and fat was isolated from CS by chemical and mechanical treatments. The new material can be called a “suspension of holocellulose nanofibers and fat” owing to its composition and fiber diameters. The high aspect ratio of the nanocellulose fibers in the suspension resulted in an entangled network that stabilized the CS fat.