Comparison of Batch and Continuous Wet-Processing of Coffee: Changes in the Main Compounds in Beans, By-Products and Wastewater.

Gustavo A Figueroa Campos,Harshadrai M Rawel,Pedro Saravia Celis,Sorel Tchewonpi Sagu

doi:10.3390/foods9081135

Gustavo A Figueroa Campos, Harshadrai M Rawel + Show 2 more

Open Access

https://doi.org/10.3390/foods9081135

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Abstract

Many technical challenges still need to be overcome to improve the quality of the green coffee beans. In this work, the wet Arabica coffee processing in batch and continuous modus were investigated. Coffee beans samples as well as by-products and wastewaters collected at different production steps were analyzed in terms of their content in total phenols, antioxidant capacity, caffeine content, organic acids, reducing sugars, free amino group and protein content. The results showed that 40% of caffeine was removed with pulp. Green coffee beans showed highest concentration of organic acids and sucrose (4.96 ± 0.25 and 5.07 ± 0.39 g/100 g DW for the batch and continuous processing). Batch green coffee beans contained higher amount of phenols. 5-caffeoylquinic Acid (5-CQA) was the main constituent (67.1 and 66.0% for the batch and continuous processing, respectively). Protein content was 15 and 13% in the green coffee bean in batch and continuous processing, respectively. A decrease of 50 to 64% for free amino groups during processing was observed resulting in final amounts of 0.8 to 1.4% in the processed beans. Finally, the batch processing still revealed by-products and wastewater with high nutrient content encouraging a better concept for valorization.

Highlights

Coffee is one of the most widely produced and traded agricultural products
Total phenols and antioxidant capacity from the de-pulped coffee beans to the green coffee beans can be observed, depending on whether the cherries were processed in batch or in continuous workflow
High values of caffeine were obtained in coffee pulp (1.16 ± 0.02 and 1.09 ± 0.03 g/100 g dry weight (DW) for the batch and continuous processing, respectively), and caffeine was detected in the parchment of the batch process (Figure 2a)

Summary

Introduction

Coffee is one of the most widely produced and traded agricultural products. World production in 2019 was estimated at around 167 million 60-kg bags, with 95 million bags of Arabica (Coffea arabica) and 72 million bags of Robusta (Coffea canephora) [1]. Robusta coffee has a stronger and harsher taste with a high concentration of caffeine, while Arabica coffee, considered to be of higher quality, has a sweeter taste, with a higher amount of sugars and an excellent acidity evaluation [2]. Green coffee beans are rich in bioactive compounds such as caffeine, free amino groups, polyphenols and chlorogenic acids. They contain a number of functional biological properties such as stimulation of the central nervous system, myocardial stimulation and peripheral vasoconstriction [4]. These characteristics of green coffee beans have been subject of numerous works and interest from the nutraceutical and pharmaceutical industries [5]. Taking into account these different classifications, the composition and concentration of coffee constituents differ according to the type of coffee beans, the environmental conditions, soil type and geographical areas of cultivation [6,7]

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