Optimization of microwave-assisted water solvent extraction and phytochemical-antidiabetic evaluation of coffee pulp | |
| Author | Hakim, Muhammad Eriansyah Al |
| Call Number | AIT Thesis no.FIBNH-26-01 |
| Subject(s) | Extraction (Chemistry) Coffee Bioactive compounds |
| Note | A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Food Innovation, Nutrition and Health |
| Publisher | Asian Institute of Technology |
| Abstract | Coffee pulp (Coffea canephora), an underutilized by-product of coffee processing, contains a range of bioactive compounds associated with antioxidant and antidiabetic properties. This study assessed extraction efficiency, optimized microwave-assisted extraction (MAE) parameters, and investigated the phytochemical profile together with the antidiabetic activity of coffee pulp extracts. A preliminary comparison of extraction methods showed that maceration at 70°C for 30 min produced the highest total phenolic content (TPC) of 26.12±1.27 mg GAE/g and the strongest antioxidant activity, with DPPH IC₅₀ of 166.43±4.09 µg/mL. In contrast, MAE at 30, 60, and 90 s resulted in lower TPC values of 14.90±0.84, 19.46±0.47, and 19.39±0.78 mg GAE/g, respectively, but improved total flavonoid content (TFC). The highest TFC was obtained at 60 s (62.29±1.89 mg QE/g), followed by 90 s (54.83±2.67 mg QE/g) and 30 s (42.59±1.12 mg QE/g). A similar trend was observed for total soluble sugar (TSS), which increased under MAE and reached the highest value at 60 s (227.37±9.31 mg GE/g), compared with 193.35±7.56 mg GE/g at 30 s and 221.99±4.17 mg GE/g at 90 s, while maceration yielded 126.44±5.17 mg GE/g. Extraction yield also increased with longer MAE duration, reaching 24.73±0.34% (30 s), 27.47±0.90% (60 s), and 33.20±0.82% (90 s). These findings indicated that extraction performance was highly dependent on MAE conditions, supporting the need for further optimization. Optimization using response surface methodology (RSM) with a face centered central composite design (FCCD) identified the optimal MAE conditions as 90 s extraction time, 87.58% microwave power cycle (rounded to 90% to suit the microwave equipment), and a 1:20 solvent-to-sample ratio. Under these conditions, recovery of bioactive compounds markedly improved, with TPC increasing to 45.39±2.44 mg GAE/g and TFC to 134.05±4.10 mg QE/g. The optimized extract also showed significantly enhanced antioxidant activity, with DPPH IC₅₀ of 94.20±6.30 µg/mL, together with an extraction yield of 27.57±1.30%, confirming the effectiveness of multivariate optimization in improving extract quality. LC-HRMS analysis revealed several major compounds in both conventional and optimized extracts, including citric acid, chlorogenic acid, and 4,5-dicaffeoylquinic acid. The optimized MAE extract exhibited the strongest antidiabetic inhibitory activity, with IC₅₀ values of 1.34±0.10 mg/mL for α-amylase and 3.99±0.44 µg/mL for α-glucosidase. In comparison, maceration at 70°C for 30 min showed IC₅₀ values of 3.12±0.37 mg/mL and 5.03±0.25 µg/mL, while acarbose showed 5.39±0.74 mg/mL and 10.12±1.01 µg/mL, respectively. Overall, optimized MAE using water as a green solvent effectively enhanced the recovery of bioactive compounds and improved biological activity, highlighting the potential of coffee pulp as a sustainable functional ingredient with promising antioxidant and antidiabetic applications. |
| Year | 2026 |
| Type | Thesis |
| School | Faculty of Food, Agriculture and Natural Resources (2026) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Food Innovation, Nutrition and Health (FINH)/Former code name = FI |
| Chairperson(s) | Anal, Anil Kumar; |
| Examination Committee(s) | Darniadi, Sandi;Ghimire, Anish; |
| Scholarship Donor(s) | Her Majesty the Queen’s Scholarships (Thailand); |
| Degree | Thesis (M. Sc.) - Asian Institute of Technology, 2026 |
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