Phytochemical Profiling and Potential Application of Sarawak Liberica Coffee Silverskin

Nick Laurence, Buyong (2024) Phytochemical Profiling and Potential Application of Sarawak Liberica Coffee Silverskin. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Liberica coffee is the minority species variety of the Coffea family. Internationally, this variety only consisted of 1% of the coffee variety cultivated worldwide. Despite that, this variety is the major species (73%) planted in Malaysia compared to the other varieties. During the roasting of the coffee bean, multiple by-products are produced mainly the coffee silverskin (CS). CS is thin tegument layer outside of the coffee bean, that was generated when treated with high heat intensity. When the coffee production is exponential, this creates an excess of the waste that have multiple potential of application in the industries such as cosmetic, healthcare, and food products. In the recent years, numerous studies had been done on the CS, regarding its beneficial bioactive compounds, as these had shown some promising benefits in multiple industries such as the food production, pharmaceuticals, medicine, and human health. However, most of these studies only focused on the majority variety of the coffee family, thus leaving a knowledge gap on the Liberica CS. As one of the main Liberica cultivators in South-east Asia, the CS variety of the Liberica originate from Sarawak, Malaysia piques the interest in this study. The result showed that, the CS have a high phenolic content in methanol extract and high flavonoid content in ethanol extract, 15.24 ± 0.65 mg GAE/g and 25.14 ± 0.59 mg QE/g, respectively. The DPPH activity was also found to be highest as in the ethanol extract (83.85 ± 1.78%), concurred by the results in the FRAP assay as the highest reduction was also in ethanol extract (11.40 ± 18.57 μmol FSE/g). In terms of the caffeine content, the amount was the highest calculated in the methanol extract with 26.86 ± 5.77 mg/g (1.77 ± 0.38%) of the dry weight of the CS. From the CG-MS employment, the CS was identified to contain 30 bioactive compounds, where four compounds (5-Hydroxymethylfurfural, D-allose, Caffeine, 1,6-Anhydro-β-D-glucofuranose) identified to be the major constituent in the CS, while the rest are in trace amount. In this study, the CS did not exhibit any antimicrobial effects on both Gram-positive and Gram-negative bacteria. In conclusion, the study shows that Sarawak Liberica CS does contain high beneficial bioactive compounds such as phenolic and flavonoid, while exhibit a significant antioxidant property. The CS may lack in antimicrobial ability, but the high caffeine content of the CS makes it a potential valuable by-product for the industries.

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