Melanoidins from Coffee Infusions. Fractionation, Chemical Characterization, and Effect of the Degree of Roast

Abstract

A method involving fractionation in ethanol aqueous solutions, anion exchange chromatography, and immobilized copper chelating chromatography was developed to obtain high molecular weight anionic melanoidin populations from coffee infusions. Six anionic fractions with different physicochemical properties (ethanol solubility and chelating ability) and chemical composition regarding carbohydrate as well as protein nature and content were isolated. Fractions with similar chemical composition were obtained for light-, medium-, and dark-roasted coffee infusions. These melanoidin fractions accounted for 30-33% of the cold-water soluble high molecular weight material, independently of the degree of roast in coffee. The nature and abundance of the different polysaccharides in each fraction were dependent on their ethanol solubility. The 50% ethanol insoluble melanoidin populations contained mostly galactomannan-like carbohydrates, and the fractions obtained with 75% ethanol contained mostly arabinogalactan-like carbohydrates. The melanoidin populations with chelating properties presented significantly lower carbohydrate content and, from these, the 75% ethanol soluble fractions were almost devoid of carbohydrate material. The results obtained suggest that the chelating ability of these coffee melanoidins is modulated by their carbohydrates.

Effect of pH and temperature on browning intensity of coconut sugar and its antioxidant activity

“…Our study also showed the same phenomenon where the total phenolics increased with increasing initial pH of coconut neera and the end point temperature of heating. The presence of phenolic groups in the melanoidin fraction with high molecular weight has also been found in coffee brew due to the role of chlorogenic acid in the formation of melanoidin (Nunes and Coimbra, 2007;Bekedam et al, 2008).…”

Influence of extraction process on antioxidant capacity of spent coffee

“…is normally used to remove fatty compounds in coffee before extraction of antioxidants or other coffee compounds, such as melanoidins, (Bekedam et al, 2008a;Nunes & Coimbra, 2007;Ramalakshmi et al, 2009;Rufian-Henares & Morales, 2008). However, this process might influence on the antioxidant capacity of remained coffee samples because some organic antioxidants can be also removed.…”

Effect of sugar addition (torrefacto) during roasting process on antioxidant capacity and phenolics of coffee

“…In The absorbance at 420nm has been commonly used to characterize melanoidins, which are mainly originated by Maillard Reactions during roasting process of coffee and other heat-treated foods (Morales, 2005;Nunes & Coimbra, 2007). However, it has been reported that melanoidins accounted for only 65 % of color potency of the high molecular weight fraction obtained from light roasted coffee, and for only 39 % from dark roasted coffee (Nunes & Coimbra, 2007).…”

“…In The absorbance at 420nm has been commonly used to characterize melanoidins, which are mainly originated by Maillard Reactions during roasting process of coffee and other heat-treated foods (Morales, 2005;Nunes & Coimbra, 2007). However, it has been reported that melanoidins accounted for only 65 % of color potency of the high molecular weight fraction obtained from light roasted coffee, and for only 39 % from dark roasted coffee (Nunes & Coimbra, 2007). Many other brown-colored products appear to be sugar (retro)aldolization/dehydratation and carbohydrate condensation products, which may or may not be attached to proteins or other structures of amino nitrogen in a similar way to the Maillard Reactions (Rizzi, 1997;Hofmann, 1999).…”