Extraction of oligosaccharides and phenolic compounds by roasting pretreatment and enzymatic hydrolysis from spent coffee ground

ABSTRACT

Spent coffee ground (SCG) is the waste generated during the preparation of instant coffee and is the sourceof industrially valuable organic compounds. In this article, SCG was pretreated by roasting at 150°C for 30minutes and heated with water at 90°C for extracting carbohydrates and phenolic compounds, after which1.0% (w/w) β-mannanase was applied for the hydrolysis of pretreated SCG. SCG is characterized in terms ofits total sugar content by the anthrone–sulfuric assay and phenolic compounds by Folin−Ciocalteu’s procedure.In this study, the total sugar increased by 14.79% (w/w) by the roasting process, and subsequently enzymatichydrolysis increased the total sugar yield up to 17.43% (w/w) compared to the untreated SCG, i.e., 10.24%(w/w). The reducing sugar was estimated by the dinitrosalicylic acid method and the end product increased to106.10 (mg Glucose/g) from the initial content 5.32 (mg Glucose/g raw SCG). The total phenolic compoundincreased to 291.86 (mg Gallic acid/g lyophilized material), which was a 6.39-fold increase compared to thenative SCG (45.68 mg Gallic acid/g). These results point to the valuable compounds present in SCG, can beenhanced by combining the roasting pretreatment and enzymatic hydrolysis, and can be utilized in the foodand biotech industries.