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The chromophore release and identification method isolates well-defined chromophoric substances from different cellulosic matrices, such as highly bleached pulps, cotton linters, bacterial cellulose, viscose or lyocell fibers, and cellulose acetates. The chromophores are present only in extremely low (ppm to ppb) concentrations. The concept of primary and secondary chromophores is introduced, with primary chromophores arising only from the polysaccharides inherent to cellulosic materials. Secondary chromophores also include atoms from the chemicals used to process the cellulose. Most primary chromophores belong to one of three compound classes: hydroxy-[1,4]-benzoquinones, hydroxy-[1,4]-naphthoquinones, and hydroxyacetophenones. Among them, three individual compounds dominate: 2,5-dihydroxy-[1,4]-benzoquinone, 5,8-hydroxy-[1,4]-naphthoquinone, and 2,5-dihydroxyacetophenones, amounting to more than 80 % of the total isolated chromophores in most cases. In lignin-free cellulosics, these three compounds can thus be regarded as key chromophores. The prevalence of these molecules is due to both exceptionally strong resonance stabilization, as reflected in delocalized double bonds, and their ready reformation from carbohydrate degradation products by recondensation reactions. The findings that (a) most chromophores in lignin-free cellulosic materials belong to only three compound classes and that (b) three chromophore compounds make up the bulk of the chromophore mixtures are foundational for future bleaching research: Based on this knowledge, specific searches for optimized bleaching conditions can now concentrate on these compounds and still cover the vast majority of chromophores.

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The fruit fly Drosophila melanogaster has been increasingly recognized as an important model organism in nutrition research. In order to conduct nutritional studies in fruit flies, special attention should be given to the composition of the experimental diets. Besides complex diets, which are often based on maize, yeast, sucrose, and agar, Drosophila can be also fed chemically defined diets. These so-called holidic diets are standardized in terms of their macro- and micronutrient composition although the quantitative nutrient requirements of flies have yet not been fully established and warrant further investigations. For instance, only few studies address the fatty acid, vitamin, mineral, and trace element requirements of fruit flies. D. melanogaster may be also of interest in the field of nutritional medicine. Diet-induced diabetes and obesity models have been established, and in this context, often, the so-called high-fat and high-sugar diets are fed. However, the composition of these diets is not sufficiently defined and varies between studies. A consensus within the scientific community needs to be reached to standardize the exact composition of experimental complex and holidic diets for D. melanogaster in nutrition research. Since D. melanogaster is an established valuable model system for numerous human diseases, standardized diets are also a prerequisite to conduct diet-disease interaction studies. We suggest that a comprehensive approach, which combines deep phenotyping with disease-related Drosophila models under defined dietary conditions, might lead to the foundation of a so-called fly clinic.