Adding value from coffee waste: low oxidized sterols in silverskin

Coffee production with imported beans has doubled in Canada since 2003. From this > 125,000 t of waste is generated most of which ends up in landfill. A significant component of the waste is as the pulp (cascara) and silverskin. In 2019, the Happy Goat Company roasted 50 t of green coffee beans yielding 300kg silverskin which will greatly increase in 2021. Silverskin teas have 3-6 times more caffeine than coffee beans and are rich in total phenolics, antioxidant capacity and phytosterols. There is good evidence of their safety. However, the coffee roasting process creates oxidized phytosterols in the silverskin which are somewhat toxic. Phytosterol Oxidation Products (POPs) have been reported in silverskin in several studies. We have a unique opportunity to examine POPs in silverskin considering a number of variables. These will include process, roast degree and the roast profile. When the final best conditions are chosen, measurement of caffeine, total antioxidant capacity and total flavonoids with be conducted in the final product and in the silverskin-derived beverages. The goal is to reduce waste from the roastery and add some value for the farmers in Ethiopia and Guatemala who produce coffee for the company.

Faculty Supervisor:

David McMullin;David Miller


Kimberlynn MacDonald


Happy Goat Coffee Company




Service industry


Carleton University



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