The wastes of coffee bean processing for utilization in food: a review

Abstract

A few million cubic tons of waste are generated annually as a result of coffee processing. As a beverage, coffee in itself is a rich source of melanoidins, phenolic compounds, and other phytonutrients which confer a wide range of health benefits. These wastes generated every year are usually discarded as landfill mass, mixed with animal fodder, or incinerated. Coffee wastes, due to their high content of tannins and caffeine, can degrade the soil quality and induce carcinogenicity when mixed with animal fodder. This review aims to identify the potential of coffee silver skin and spent coffee grounds, both generated as a result of the roasting process and instantization processes. Coffee husk and coffee flour are also well-known for their excellent bioactive roles. The proximate composition of coffee silverskin indicates a rich dietary fibre source and finds wide applications in bakery and other allied food products. This process could generate a value-added product and alleviate the disposing quality of remnant spent coffee grounds. Companies are exploring novel ideas of producing coffee flour obtained from drying and milling of coffee cherries for applications in day-to-day food products. Coffee and coffee waste combined with its high concentration of fibre, colorant pigments, and antioxidant compounds, has immense potential as a functional ingredient in food systems and needs to be explored further for its better utilization.

Keywords: Antioxidant activity; Caffeine; Coffee silverskin; Dietary fibre; Prebiotics; Spent coffee grounds.

Fig. 1

Generalized structure of the coffee berry

Fig. 2

By-products generated during wet processing of coffee

Fig. 3

Valorisation of coffee waste for non-food applications

Fig. 4

a Antioxidant activities measured using DPPH method of different spent coffee grounds (SCG). b Antioxidant activities measured using ferric thiocyanate (FTC) method of different SCG extract on the 6th day of incubation period. c Antioxidant activities of different SCGs measured using thiobarbituric acid (TBA) method. Values are expressed as mean ± standard deviation. The same alphabets (a, b, c) in bars are not significantly different (p < 0.05) (Source: Zainol et al. 2020)