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Brazil is a country with strong agricultural production, annually producing a large amount of lignocellulosic residues. The valorization of these residues as ingredients for the food industry aims at environmental, social, and economic sustainability. Coffee hull is a by-product generated by the coffee industry that can be used to produce new food ingredients with high added value. This study aimed to obtain a multifunctional fiber-rich ingredient from a coffee hull using a one-step process based on reactive extrusion with alkaline hydrogen peroxide or sulfuric acid. For this purpose, we submitted a coffee hull to extrusion with sulfuric (1% and 3%) acid or alkaline hydrogen peroxide (1% and 3%) in one-step processes. Then, the obtained materials were characterized through their physicochemical and techno-functional properties. All treated samples had an increase in their cellulose and insoluble dietary fiber contents and also presented an increase in their porosity as observed by scanning electron microscopy. The sample modified with 3% alkaline hydrogen peroxide (AHP3) had the highest cellulose content (45.17%), insoluble dietary fiber (78.20%), density (3.54), water absorption capacity (1.96 g/g), and oil absorption capacity (0.86 g/g). All samples had thermal stability from room temperature to 300 °C and in all samples, the crystallinity indexes decreased after treatment. Reactive extrusion was effective in modifying the coffee hull. Our study proposes a green route to obtain a higher value-added product from lignocellulosic waste, with some advantages including short reaction times, low reagents concentrations, little or no effluent generation, and the possibility of scaling to industrial scale.

In this study, a better knowledge of the influence of cross-linking mechanism on the mechanical properties of starch films is presented. Thus, waxy starch and cassava starch films, cross-linked with trisodium trimetaphosphate (STMP), were produced and characterized concerning their morphology, transport, and mechanical properties. Starch cross-linking was verified by RAMAN spectroscopy and by iodine binding capacity (IBC) values, which were determined by color analysis of digital images. Although cross-linking affects the morphology and crystallinity of the films, it was not observed a relationship between the mechanism of the cross-linking reaction of the starch chain (amylose-amylopectin and amylopectin-amylopectin) and the transport properties. The lower Young Modulus and IBC value and the higher elongation at break observed for cross-linking cassava starch films relative to control and waxy films indicate that cross-linking mechanism influences the mechanical properties of starch films and should be considered to tailor the final properties of packaging and biobased products.