Effects of hydrolysis and bleaching conditions on the efficiency of cellulose microfibrils extraction from coffee parchment through a design of experiments

Abstract

Cellulose microribbons were isolated from coffee parchment through acid hydrolysis, alkaline hydrolysis, and bleaching. Factorial design experiments allowed studying the in uence of the chemical precursor concentrations and reaction times on the mass losses. TGA, SEM, XRD, and FT-IR techniques allowed characterized the coffee parchment hydrolyzed and bleached. Obtained results suggest that after acid hydrolysis, hemicellulose was the main fraction released from the coffee parchment, and after alkaline hydrolysis, lignin. Lignocellulosic compound dissolution produces a reduction/disappearance of some vibrational bands. This dissolution enhances the crystalline index and decreases the microrribons diameter. However, in coffee parchment, the microrribons are twisted giving the appearance of bers with a minor diameter. The design of the experiment results suggests that the main factors during acid and alkaline hydrolysis are the concentration of the chemical precursors. In the bleaching process, a variation in the factors does not signi cantly in uence the response variable. However, for brightness, the precursor concentration affects the cellulose quality. The optimal conditions for cellulose extraction from coffee parchment are 5% (v/v) of HNO3 by 2 h, 3%(m/v) NaOH by 1 h, and a 1:1 ratio of NaClO: CH 3 COOH by 45 min for bleaching. IntroducciónCoffee is one of the world's largest agricultural activities (Chain-Guadarrama et al. 2019). International Coffee Organization (ICO) reports in October 2022 a world coffee exports of 9.69 million bags (ICO 2022). The coffee industry generates a variety of by-products with distinct chemical compositions as coffee pulp, mucilage, parchment, husks, silverskin, and spent coffee grounds (Oliveira et al. 2021). Among all these agroindustrial wastes, coffee parchment (CP) is a material derived from the coffee threshing process. Its composition and high calori c value make it a cheap and eco-friendly biofuel due to its low content of heavy metals and ash (RODRIGUEZ and ZAMBRANO 2010;Wondemagegnehu et al. 2022). Moreover, its hypoglycemic and hypolipidemic properties make it a dietary supplement (Benitez et al. 2019). Moreover, for every 60 kg of coffee processed, 11 kg corresponds to coffee parchment (Bekalo and Reinhardt 2010;APUZZO III 2018;Benitez et al. 2019).CP is composed mainly of lignin (32-34%), hemicellulose (29-35%), and cellulose (12-45%) (Bekalo and Reinhardt 2010;Benitez et al. 2019). For that, coffee parchment is a potential source of cellulose by its cheapness and availability in coffee-producing countries. Cellulose is one of the most abundant and important organic compounds on earth, with a brous structure composed of crystalline and amorphous zones intertwined, making them very resistant and insoluble in water (Fenema and Tannenbaum 2010;Siqueira et al. 2010). Many natural resources have been employed to obtain cellulose, such as tomato plant (

Biocomposites of Cellulose Isolated from Coffee Processing By-Products and Incorporation in Poly(Butylene Adipate-Co-Terephthalate) (PBAT) Matrix: An Overview

“…Rodríguez et al [49] isolated cellulose microfibrils from coffee parchment through acid hydrolysis, alkaline hydrolysis and bleaching. An aqueous solution of 2.5 and 5% (v/v) of HNO 3 was applied by reflux heating for 60, 120, and 180 min for acid hydrolysis.…”