Microwave-assisted methanolysis of green coffee oil

Abstract

Optimisation of a microwave-assisted methanolysis was performed to obtain cafestol and kahweol directly from green coffee oil (Coffea arabica). A two-factor (the methanolysis period and temperature), three-level, factorial experimental design (3(2)) was adopted. The methanolysis procedure was performed under microwave irradiation, using closed vessel and accurate fast responding internal fibre-optic temperature probe. The effects on the responses were measured by HPLC. After 3 min of microwave irradiation (hold time) at 100°C, with 500 mg of green coffee oil, a yield higher than 99% was obtained. The yield of this reaction is 26% after 2h when working under conventional heating. The methods described in the literature lead to long reaction times, poor yields and formation of side products. The microwave-assisted technique proved to be faster, avoided undesired side products and gave better conversion, when compared to conventional heating process.

Analytical methods applied for the characterization and the determination of bioactive compounds in coffee

“…Use of mass spectrometry for analyte detection is another option possible in HPLC analysis, which gives additional selectivity. Oigman et al [89] analyzed kahweol and cafestol using LC-HRMS after microwave methanolysis of coffee samples. Latest research showed that for the determination of diterpenes in green coffee samples the 10-min-long microwave-assisted extraction was considerably less time consuming than the 4-h-long traditional Soxhlet extraction, while amount of extracted diterpenes was similar [90].…”

New approaches on the analyses of thermolabile coffee diterpenes by gas chromatography and its relationship with cup quality

“…The utilization of a short extraction time can result in incomplete leaching of the analytes from the matrix surface [21]. However, prolonged exposure to hot conditions may result in the formation of artifacts due to their thermolability [16,18,[22][23][24]. Similarly, alkaline hydrolysis employs strong bases, for example NaOH and KOH that can ϱ be very aggressive for labile compounds such as the furokaurane diterpenes of coffee [24,25].…”

“…However, prolonged exposure to hot conditions may result in the formation of artifacts due to their thermolability [16,18,[22][23][24]. Similarly, alkaline hydrolysis employs strong bases, for example NaOH and KOH that can ϱ be very aggressive for labile compounds such as the furokaurane diterpenes of coffee [24,25]. Iso-and dehydrated diterpenes are described as degradation products, commonly associated with the heating process of the coffee bean, and are especially found in roasted coffees [13,26].…”

Lattice Boltzmann simulation of cafestol and kahweol extraction from green coffee beans in high-pressure system

“…Cafestol and kahweol are diterpenes that have been studied in view of anti-inflammatory, antioxidant, and hepatoprotective effects (Oigman et al, 2012). Epidemiological evidences have also assigned lower risks of colorectal cancer thanks to kahweol consumption (Giovannucci, 1998).…”