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This study addresses the interactions of coffee storage proteins with coffee-specific phenolic compounds. Protein profiles, of Coffea arabica and Coffea canephora (var robusta) were compared. Major Phenolic compounds were extracted and analyzed with appropriate methods. The polyphenol-protein interactions during protein extraction have been addressed by different analytical setups [reversed-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), and Trolox equivalent antioxidant capacity (TEAC) assays], with focus directed toward identification of covalent adduct formation. The results indicate that C. arabica proteins are more susceptible to these interactions and the polyphenol oxidase activity seems to be a crucial factor for the formation of these addition products. A tentative allocation of the modification type and site in the protein has been attempted. Thus, the first available in silico modeling of modified coffee proteins is reported. The extent of these modifications may contribute to the structure and function of "coffee melanoidins" and are discussed in the context of coffee flavor formation.
Can satiety be measured?
(2001)
An energy-controlled study on a Western diet composed of 45% fat, 40% carbohydrate and 15% protein by energy was carried out. The study consisted of four test phases having a length of 9 days in each case, where 8 healthy free- living subjects were adjusted to individual energy requirements at maintenance level. Between the tests, wash-out phases of 4-5 months were inserted to avoid adaptation effects. By using a standard breakfast of constant composition, satiety was evaluated by applying the concept of categorical comparison, which was based on the common fact, that the perception between two meals is changed and usually a set of sensations can be discriminated. These were termed very full and full (just after finishing a meal), appetite and hungry (just before the next meal). These sensations were used as categories on a categorical scale. The evaluation of satiety was performed such that on each day of the four test phases the subjects had to select over a period of 4 h every 30 min one category out of the four, what corresponded to the individual sensation at that time. This procedure was followed by a mathematical treatment of data such that the individual judgements were transformed into a numerical system. As a result, the time course of satiety was available characterizing the time-dependent change of the interoception after consuming the test meal. Using this concept highly reliable results were obtained as demonstrated by the comparison of the four test series.