@article{RohnPetzkeRaweletal.2006, author = {Rohn, Sascha and Petzke, Klaus-J{\"u}rgen and Rawel, Harshadrai Manilal and Kroll, J{\"u}rgen}, title = {Reactions of chlorogenic acid and quercetin with a soy protein isolate - Influence on the in vivo food protein quality in rats}, series = {Molecular nutrition \& food research : bioactivity, chemistry, immunology, microbiology, safety, technology}, volume = {50}, journal = {Molecular nutrition \& food research : bioactivity, chemistry, immunology, microbiology, safety, technology}, publisher = {Wiley}, address = {Weinheim}, issn = {1613-4125}, doi = {10.1002/mnfr.200600043}, pages = {696 -- 704}, year = {2006}, abstract = {Plant phenolic compounds are known to interact with proteins producing changes in the food (e.g., biological value (BV), color, taste). Therefore, the in vivo relevance, especially, of covalent phenolprotein reactions on protein quality was studied in a rat bioassay. The rats were fed protein derivatives at a 10\% protein level. Soy proteins were derivatized with chlorogenic acid and quercetin (derivatization levels: 0.056 and 0.28 mmol phenolic compound/gram protein). Analysis of nitrogen in diets, urine, and fecal samples as well as the distribution of amino acids were determined. Depending on the degree of derivatization, the rats fed with soy protein derivatives showed an increased excretion of fecal and urinary nitrogen. As a result, true nitrogen digestibility, BV, and net protein utilization were adversely affected. Protein digestibility corrected amino acid score was decreased for lysine, tryptophan, and sulfur containing amino acids.}, language = {en} } @article{RawelFreyMeidtneretal.2006, author = {Rawel, Harshadrai Manilal and Frey, Simone K. and Meidtner, Karina and Kroll, J{\"u}rgen and Schweigert, Florian J.}, title = {Determining the binding affinities of phenolic compounds to proteins by quenching of the intrinsic tryptophan fluorescence}, series = {Molecular nutrition \& food research : bioactivity, chemistry, immunology, microbiology, safety, technology}, volume = {50}, journal = {Molecular nutrition \& food research : bioactivity, chemistry, immunology, microbiology, safety, technology}, number = {8}, publisher = {Wiley}, address = {Weinheim}, issn = {1613-4125}, doi = {10.1002/mnfr.200600013}, pages = {705 -- 713}, year = {2006}, abstract = {The noncovalent binding of selected phenolic compounds (chlorogenic-, ferutic-, gallic acid, quercetin, rutin, and isoquercetin) to proteins (HSA, BSA, soy glycinin, and lysozyme) was studied by an indirect method applying the quenching of intrinsic tryptophan fluorescence. From the data obtained, the binding constants were calculated by nonlinear regression (one site binding; y = Bx/k + x). It has been reported that tannins inhibit human salivary amylase and that these complexes may reduce the development of cariogenic plaques. Further, amylase contains two tryptophan residues in its active site. Therefore, in a second part of the study involving 31 human subjects, evidence was sought for noncovalent interactions between the phenols of green tea and saliva proteins as measured by the fluorescence intensity. Amylase activity was determined before and after the addition of green tea to saliva of 31 subjects. Forty percent of the subjects showed an increase in amylase activity contrary to studies reporting only a decrease in activity. The interactions of tannin with amylase result in a decrease of its activity. It still remains to be elucidated why amylase does not react uniformly under conditions of applying green tea to saliva. Further, in terms of using phenols as caries inhibitors this finding should be of importance.}, language = {en} } @article{GoetzChmielewskiGoedekeetal.2017, author = {Goetz, Klaus-Peter and Chmielewski, Frank M. and Goedeke, Kristin and Wolf, Kristine and Jander, Elisabeth and Sievers, Steven and Homann, Thomas and Huschek, Gerd and Rawel, Harshadrai Manilal}, title = {Assessment of amino acids during winter rest and ontogenetic development in sweet cherry buds (Prunus avium. L.)}, series = {Scientia horticulturae : an international journal sponsored by the International Society for Horticultural Science}, volume = {222}, journal = {Scientia horticulturae : an international journal sponsored by the International Society for Horticultural Science}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0304-4238}, doi = {10.1016/j.scienta.2017.05.001}, pages = {102 -- 110}, year = {2017}, abstract = {This study examined changes in sweet cherry buds of 'Summit' cultivar in four seasons (2011/12-2014/15) with respect to the nitrogen (N) content and the profile of eight free amino acids (asparagine (Asn), aspartic acid (Asp), isoleucine (Ile), glutamine (Gln), glutamic acid (Glu), arginine (Arg), alanine (Ala), histidine (His)). The presented results are to our knowledge the first under natural conditions in fruit tree orchards with a high temporal resolution from the dormant stage until cluster development. The N content in the buds from October, during endo- and ecodormancy until the beginning of ontogenetic development was a relatively stable parameter in each of the four seasons. The N accumulation into the buds began after 'swollen bud' and significant differences were visible at 'green tip' with an N content of 3.24, 3.12, 3.08, 2.40 which increased markedly to the mean of 'tight' and 'open cluster' by 3.77\%, 3.78\%, 3.44\% and 3.10\% in 2012-2015, respectively. In the buds, levels of asparagine were higher (up to 44 mg g\&\#8722;1 DW\&\#8722;1) than aspartic acid (up to 2 mg g\&\#8722;1 DW\&\#8722;1) and aspartic acid higher than isoleucine (up to 0.83 mg g\&\#8722;1 DW\&\#8722;1). Levels of glutamine were higher (up to 25 mg g\&\#8722;1 DW\&\#8722;1) than glutamic acid (up to 20 mg g\&\#8722;1 DW\&\#8722;1). The course of the arginine content was higher in 2011/12 compared to 2012/13, 2013/14 and 2014/15 which showed only slight differences. The alanine content in the buds was denoted in the four seasons only by relatively minor changes. The histidine content was higher in 2011/12 and 2012/13 compared to 2013/14 and 2014/15 which showed a comparable pattern. For 6 amino acids (Asn, Asp, Ile, Glu, Arg, Ala), the highest content was observed in 2012/13, the warmest period between swollen bud and open cluster. However in 2014/15, the season with the lowest mean temperature of 8.8 °C, only the content of Gln was the lowest. It was not possible to explain any seasonal differences in the amino acid content by environmental factors (air temperature) on the basis of few seasons. From none of the measured free amino acids could a clear determination of the date of endodormancy release (t1) or the beginning of the ontogenetic development (t1*) be derived. Therefore, these amino acids are no suitable markers to improve phenological models for the beginning of cherry blossom.}, language = {en} } @article{EggertRawelNikfardjametal.2006, author = {Eggert, Kai and Rawel, Harshadrai Manilal and Nikfardjam, Martin S. Pour and Kroll, J{\"u}rgen}, title = {Interactions between lysozyme and wine components}, series = {Deutsche Lebensmittel-Rundschau : DLR}, volume = {102}, journal = {Deutsche Lebensmittel-Rundschau : DLR}, number = {10}, publisher = {Behr}, address = {Stuttgart}, issn = {0012-0413}, pages = {472 -- 478}, year = {2006}, abstract = {The addition of lysozyme amounting to 1000 mg/l wine does neither effect its total phenol content (Folin-Ciocalteu-Method), nor wine colour (measured by extinction at 512 nm) nor its antioxidative capacity (TEAC-Assay). No covalent binding of wine phenols to the enzyme was observed during lysozyme addition, although non-covalent interactions are possible. Lysozyme activity is not influenced by the presence of malvidin-3-glucoside and resveratrol in model experiments, whereas pH and ethanol content produce a corresponding alteration in lysozyme activity. With regard to red wine, a significant effect was noted in the presence of wine components.}, language = {de} } @article{FigueroaCamposSaguTchewonpiSaraviaCelisetal.2020, author = {Figueroa Campos, Gustavo A. and Sagu Tchewonpi, Sorel and Saravia Celis, Pedro and Rawel, Harshadrai Manilal}, title = {Comparison of batch and continuous wet-processing of coffee}, series = {Foods}, volume = {9}, journal = {Foods}, number = {8}, publisher = {MDPI}, address = {Basel}, issn = {2304-8158}, doi = {10.3390/foods9081135}, pages = {19}, year = {2020}, abstract = {Many technical challenges still need to be overcome to improve the quality of the green coffee beans. In this work, the wet Arabica coffee processing in batch and continuous modus were investigated. Coffee beans samples as well as by-products and wastewaters collected at different production steps were analyzed in terms of their content in total phenols, antioxidant capacity, caffeine content, organic acids, reducing sugars, free amino group and protein content. The results showed that 40\% of caffeine was removed with pulp. Green coffee beans showed highest concentration of organic acids and sucrose (4.96 ± 0.25 and 5.07 ± 0.39 g/100 g DW for the batch and continuous processing). Batch green coffee beans contained higher amount of phenols. 5-caffeoylquinic Acid (5-CQA) was the main constituent (67.1 and 66.0\% for the batch and continuous processing, respectively). Protein content was 15 and 13\% in the green coffee bean in batch and continuous processing, respectively. A decrease of 50 to 64\% for free amino groups during processing was observed resulting in final amounts of 0.8 to 1.4\% in the processed beans. Finally, the batch processing still revealed by-products and wastewater with high nutrient content encouraging a better concept for valorization.}, language = {en} } @misc{EggertRawelPawelzik2011, author = {Eggert, Kai and Rawel, Harshadrai Manilal and Pawelzik, Elke}, title = {In vitro degradation of wheat gluten fractions by Fusarium graminearum proteases}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {877}, issn = {1866-8372}, doi = {10.25932/publishup-43510}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-435102}, pages = {697 -- 705}, year = {2011}, abstract = {Fusarium spp. infection of cereal grain is a common problem, which leads to a dramatic loss of grain quality. The aim of the present study was to investigate the effect of Fusarium infection on the wheat storage protein gluten and its fractions, the gliadins and glutenins, in an in vitro model system. Gluten proteins were digested by F. graminearum proteases for 2, 4, 8 and 24 h, separated by Osborne fractionation and characterised by chromatographic (RP-HPLC) and electrophoretic analysis (SDS-Page). Gluten digestion by F. graminearum proteases showed in comparison with gliadins a preference for the glutenins whereas the HMW subfraction was at most affected. In comparison with a untreated control, the HMW subfraction was degraded of about 97\% after 4 h incubation with Fusarium proteases. Separate digestion of gliadin and glutenin underlined the preference for HMW-GS. Analogue to the observed change in the gluten composition, the yield of the proteins extracted changed. A higher amount of glutenin fragments was found in the gliadin extraction solution after digestion and could mask a gliadin destruction at the same time. This observation can contribute to explain the frequently reported reduced glutenin amount parallel to an increase in gliadin quantity after Fusarium infection in grains.}, language = {en} } @article{MenendezRawelSchwarzenbolzetal.2006, author = {Menendez, Orquidea and Rawel, Harshadrai Manilal and Schwarzenbolz, Uwe and Henle, Thomas}, title = {Structural changes of microbial transglutaminase during thermal and high-pressure treatment}, doi = {10.1021/Jf0522863}, year = {2006}, abstract = {The activity of microbial transglutaminase (MTG) and the corresponding secondary structure, measured by circular dichroism (CID), was analyzed before and after treatment at different temperatures (40 and 80 degrees C) and pressures (0.1, 200, 400, 600 MPa). Irreversible enzyme inactivation was achieved after 2 min at 80 degrees C and 0.1 MPa. Enzyme inactivation at 0.1, 200, 400, and 600 MPa and 40 degrees C followed first-order kinetics. The enzyme showed residual activity of 50\% after 12 min at 600 MPa and 40 degrees C. Mobility of aromatic side chains of the enzyme molecule was observed in all temperature- and/or pressure-treated samples; however, high-pressure treatment at 600 MPa induced a loss of tertiary structure and a significant decrease in the alpha-helix content. The relative content of beta- strand substructures was significantly increased after 30 min at 600 MPa and 40 degrees C or 2 min at 0.1 MPa and 80 degrees C. We conclude that the active center of MTG, which is located in an expanded 8-strand domain, is resistant to high hydrostatic pressure and pressure-induced inactivation is caused by destruction of cc-helix elements with a corresponding influence on the enzyme stability in solution}, language = {en} } @article{RohnRawelRoberetal.2005, author = {Rohn, Sascha and Rawel, Harshadrai Manilal and Rober, M. and Kroll, J{\"u}rgen}, title = {Reactions with phenolic substances can induce changes in some physico-chemical properties and activities of bromelain - the consequences for supplementary food products}, issn = {0950-5423}, year = {2005}, abstract = {Bromelain was allowed to react with phenolic compounds. The activity and selected physico-chemical properties of the resulting derivatives were characterized. In vitro experiments showed that the proteolytic activity of bromelain was inhibited. Bromelain also serves as a food protein, because food stuffs based on pineapple contain relatively high concentrations of bromelain. In vitro digestion of bromelain derivatives with the main proteolytic enzymes of the gastrointestinal tract was also adversely affected. A covalent attachment of the phenolic compounds was identified at the tryptophan, free amino (lysines and N-terminal) and thiol groups of bromelain. A decrease in solubility of the derivatives was observed. The isoelectric point was shifted to lower pH values and high molecular weight fractions were identified. All effects observed depended on the reactivity of the phenolic substances. Two supplementary food products containing both bromelain and quercetin were also tested in terms of their proteolytic activity and digestibility}, language = {en} } @article{RawelRohnKroll2005, author = {Rawel, Harshadrai Manilal and Rohn, Sascha and Kroll, J{\"u}rgen}, title = {Characterisation of 11S protein fractions and phenolic compounds from green coffee beans under special consideration of their interactions - A review}, issn = {0012-0413}, year = {2005}, abstract = {The intention of this study was to increase the knowledge on the composition and structure of coffee bean proteins and the changes induced in them especially with regard to their interactions with the phenolic compounds also present. For this purpose green coffee beans were extracted by means of standard methanol extraction to quantify the chlorogenic acid content. Different solubilisation buffers were applied to extract the protein fractions with or without prior fat removal. The protein samples thus obtained were analysed by different methods (RP-HPLC, SDS-PAGE and SELDI-TOF- MS). Preliminary model studies were performed to characterize the interactions between the isolated green coffee protein fractions and chlorogenic acid (the major phenolic compound in coffee beans) with the intention of fulfilling the ultimate goal of characterizing such reactions in roasted coffee. The results show that the content of chlorogenic bound covalently to the protein increases. A reaction with the nucleophilic protein side chains (tryptophan, cystein and lysine) was recorded. Cross-inked protein polymers were also detected, whereby the a-chain was found to be more reactive. These reactions effect the solubility of the coffee bean proteins, the latter in turn becoming more acidic in nature. The secondary structure was affected only slightly as determined by circular dichroism. The in-vitro tryptic digestibility was also influenced, where again the cc-chain seems to be more susceptible. The observed polymerisation due to derivatisation by chorogenic acid declines the digestion. Similar digestion behaviour was also observed during tryptic hydrolysis of roasted coffee compared to that of green coffee, roasting allowing more stronger denaturation caused by the accompanying Maillard reaction. The derivatised green coffee bean proteins were found to have moderate antioxidative capacity}, language = {en} } @article{RawelMeidtnerKroll2005, author = {Rawel, Harshadrai Manilal and Meidtner, Karina and Kroll, J{\"u}rgen}, title = {Binding of selected phenolic compounds to proteins}, issn = {0021-8561}, year = {2005}, abstract = {In the context of this study, the noncovalent binding of selected phenolic compounds (chlorogenic, ferulic, and gallic acids, quercetin, rutin, and isocluercetin) to different proteins (human serum albumin, bovine serum albumin, soy glycinin, and lysozyme) was studied with direct (Hummel- Dreyer/size exclusion chromatography) and/or indirect methods (fluorescence absorbance properties of the binding components). In the latter case, the measurement of the phenol binding was achieved by exploiting the intrinsic fluorescence emission properties of cluercetin as a probe. From the data obtained, the binding constants and the number of binding sites were calculated. The binding parameters were influenced by different factors, where, e.g., increasing temperature and ionic strength as well as decreasing pH cause a diminished binding. The structures of the proteins as determined by circular dichroism indicate changes in the tertiary structure with the secondary structure remaining intact}, language = {en} }