Dados do Trabalho

Título

SCREENING OF HYDROTHERMAL TREATMENT WITH CITRIC ACID APPLIED TO COFFEE PROCESSING RESIDUES USING THE TAGUCHI METHOD

Introdução

Residual coffee husk (RCH) from the wet processing of coffee is a by-product that represents an important agro-industrial waste stream. Hydrothermal pretreatment (HTP) applied for the biorefinery of agro-industrial wastes has been successfully explored. Citric acid is a non-toxic and biodegradable additive, capable of efficiently separating hemicellulose from lignocellulosic biomass. This study explored the potential of TPH together with citric acid to produce a hemicellulose-free residual biomass from RCH, yielding celooligosaccharides (COS) and xylooligosaccharides (XOS) and phenolic compounds (PC) in liquid form.

Material e Métodos

A pressurized reactor with a 2 L stirred tank was used to process 40 g of DCP with a solid-liquid ratio of 4%. Screening Taguchi design with L4 orthogonal array (23-1) was carried out, with three factors and two levels: temperature (140-150 °C), time (20- 60 min) and citric acid (0%-1%). The main components of the residual biomass, such as cellulose, hemicellulose and lignin, were analyzed, as well as their crystallinity index (CI).

Resultados e Discussão

In the liquid fraction, the content of sugars and phenolic compounds was analyzed by high performance liquid chromatography, and COS and XOS were estimated by additional hydrolysis. The most influential factor on residual biomass was temperature, decreasing hemicellulose content and increasing lignin and cellulose, while decreasing the crystallinity index (with less processing time). In the liquid fraction, TPH was able to produce a higher magnitude of XOS (>30 g/kg) when citric acid was used with longer processing time; phenolic components increased with higher temperature and shorter processing time (>0.9 g/kg); COS were maximal (>30 g/kg), when processed in shorter time and without the presence of citric acid.

Conclusão

These results demonstrate that high-value products can be obtained from agro-industrial wastes, in addition to the potential of TPH and citric acid; however, it is essential to improve the process conditions to optimize the utilization of the residual biomass.