The behavior of roasted coffee extract and its isolated high molecular weight fraction have been investigated as carbon steel corrosion inhibitors in HCl solution by weight loss measurements, potentiodynamic polarization curves, electrochemical impedance and scanning electron microscopy analysis. All results showed that the high molecular weight fraction, rich in melanoidins, present an important role in the inhibitory action of the roasted coffee extract in the acid corrosion of carbon steel.

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Exotic coffees may be defined as extravagant and unique coffees, primarily due to their production mode, including unusual bioprocessing or fermentation conditions associated with superior sensorial characteristics. The aim of the present study was to investigate the influence of bioprocessing and of growing conditions on flavor precursors of Jacu and Kopi Luwak exotic green coffees, respectively. Moreover, this is the first study to perform a detailed chemical analysis of these exotic coffees. Thirteen green Coffea arabica bean samples were obtained, five from Espírito Santo state, Brazil, and eight Kopi Luwak from different regions of Indonesia. Samples were analyzed regarding their proximate composition, chlorogenic acids (CGA), sucrose, alkaloids, triacylglycerols (TAG), diacylglycerols, free fatty acids, sterols, diterpenes and tocopherols. Scanning electron micrography confirmed bioprocessing of Jacu and Kopi Luwak coffee samples. Bioprocessing by the Jacu bird caused reductions of 69 and 28% in caffeine and CGA contents, respectively. The TAG profile of Jacu coffee was modified. TAG containing two saturated fatty acids were preferably hydrolyzed in detriment to those containing two unsaturated fatty acids. Other coffee components were not affected by the bird's digestion of the beans. Kopi Luwak coffee samples had a chemical composition in accordance with reported ranges for non-bioprocessed green C. arabica samples, except for caffeine (0.48 g/100 g) and CGA (5.09 g/100 g), which were found in low amounts. Crop year rather than location or post-harvest processing discriminated Kopi Luwak coffee samples, suggesting that weather conditions would be the most crucial aspect for their chemical composition, especially in terms of total lipids, ashes, total CGA, sucrose and proteins.

Maté(Ilex paraguariensis) is a plant rich in chlorogenic acids (CGA) used to prepare teas elaborated with untoasted or toasted leaves. The present study was the first to investigate the effect of increasing toasting degrees, during actual industrial conditions, on matéCGA contents, their incorporation into melanoidins, and their relationship between matémelanoidins and antioxidant activity (AA). CGA contents decreased by up to 91% during toasting, and two lactones were formed. Melanoidins contents increased 73% at the beginning of toasting and decreased thereafter. UV−vis spectroscopy and nuclear magnetic resonance spectroscopy indicated the presence of proteins, polysaccharides, and CGA in the backbone of matémelanoidins. The contents of caffeic and ferulic acids bound to matémelanoidins reached a maximum at the medium toasting degree (6.2/100 g), followed by a decay thereafter. The AA of matémelanoidins was mainly correlated with phenolics and nitrogen compounds incorporated into their structure.