However, researchers stressed that a more detailed analysis is required before it can be used in skin care products.
The study team, from Indonesia and Iran, argued that solid waste from the coffee de-pulping process threatens the environment as it produces organic pollutants.
On the flip side, evidence suggests that coffee by-products could provide added value owing to its potential as an antioxidant source.
They therefore conducted a systematic review was to evaluate the antioxidant activity of coffee by-products obtained from arabica and robusta pulp, and their processing methods.
One study in the review that compared robusta and arabica coffee pulp with aqueous extraction revealed higher antioxidant capacity in that of the arabica variant.
However, a different result was shown by another study comparing the antioxidant activities of coffee silverskin from both variants.
“The study found that coffee silverskin from robusta variant has higher antioxidant activity as suggested by DPPH, ABTS, and FRAP assays, they wrote.
“Higher antioxidant efficacies of robusta variant were also revealed by a study employing green coffee extract.”
They also found that the antioxidant activities could be affected not only by the variant, but also the extraction or brewing method.
The data suggested that aqueous extract was found to be the most common processing method used to obtain the antioxidant from various coffee by-products, followed by methanol and ethanol extract.
Moreover, each coffee by-product could have different levels of antioxidant activity, with coffee silverskin revealed to have the highest value.
In terms of its potential in cosmetics, they highlighted one study that showed the use of a coffee by-product in topical formulation had been reported.
The study in question added coffee pulp extract powder into a skin lotion formulation (at 0.125 %, 0.25 %, 0.5 % and 1 % by mass), and assessed the phenolic content, antioxidant activity and stability.
“All coffee pulp skin lotions were found to show good physical stability and considerably higher antioxidant activity (IC50 : 5,805 ppm – 55,776 ppm) compared to commercial lotions (IC50 : 505,018 ppm – 557,218 ppm),” the study noted.
This latest review concluded: “Coffee by-products contain bioactive compounds possessing antioxidant properties which could be used as additives in foods, beverages, and cosmetics. In particular, their benefits in skin care products require further investigation.”
Source: F1000 Research
“Coffee by-products as the source of antioxidants: a systematic review”
Authors: Kartini Hasballah, et al.