Differentiation of roasted and soluble coffees through physical fractionation of selected essential and nonessential metals in their brews and exploratory data analysis

• Brews of ground roast and soluble coffee were fractionated in 5 molecular weight cut-offs.
• Molecular weight “>100 k Da” and “<5 k Da” metals fractions being the most distinctive.
• Molecular weight “>100 k Da” and “<5 k Da” metals fractions having the highest discriminating power in PCA and LDA.
• Metals bioaccessibilities indirectly assessed based on their fractionation patterns.

An analytical scheme for physical fractionation of Al, Ba, Ca, Co, Fe, K, Mg, Mn, Na, Ni, Sr and Zn in ground roasted and soluble coffees brews was proposed. It was based on ultrafiltration through five ultrafiltration membranes having molecular weight cut-offs of 5, 10, 30, 50 and 100 kDa. The highest “>100 kDa” and the lowest “<5 kDa” molecular weight fractions were established to differentiate the studied coffees brews the most. Al, Cu, Fe and Ni were mostly associated with the “>100 kDa” fraction, while Co, K, Mg and Na – with the “<5 kDa” fraction. For Ba, Ca, Mn, Sr and Zn, “>100 kDa” and “<5 kDa” fractions contributions were equally accounted. The physical fractionation pattern of selected metals was convenient for discovering important features of brews of both coffee types and differences between them by principal component analysis and then classifying them by linear discriminant analysis.

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