Nineteen bovine muscles were removed from beef carcasses (n = 9). Muscles were trimmed free of fat, cut into 2.54 cm thick steaks, and were packaged in Styrofoam trays with polyvinylchloride overwrap. Steaks were assigned randomly to a day of retail display (0-, 1-, 2-, 3-, 4-, or 5-d). Steaks were evaluated over the course of retail display for objective measures of discoloration (metmyoglobin, oxymyoglobin, L*-, a*-, and b*-values), reducing ability (metmyoglobin reductase activity, resistance to induced metmyoglobin formation, and nitric oxide metmyoglobin reducing ability), oxygen consumption rate, oxygen penetration depth, myoglobin content, oxidative rancidity, and pH. Muscles were grouped according to objective color measures of discoloration. M. longissimus lumborum, M. longissimus thoracis, M. semitendinosus, and M. tensor fasciae latae were grouped as "high" color stability muscles, M. semimembranosus, M. rectus femoris, and M. vastus lateralis were grouped as "moderate" color stability muscles, M. trapezius, M. gluteus medius, and M. latissimus dorsi were grouped as "intermediate" color stability muscles, M. triceps brachi - long head, M. biceps femoris, M. pectoralis profundus, M. adductor, M. triceps brachi - lateral head, and M. serratus ventralis were grouped as "low" color stability muscles, and M. supraspinatus, M. infraspinatus, and M. psoas major were grouped as "very low" color stability muscles. Generally, muscles of high color stability had high resistance to induced metmyoglobin formation, nitric oxide reducing ability, and oxygen penetration depth and possessed low oxygen consumption rates, myoglobin content, and oxidative rancidity. In contrast, muscles of low color stability had high metmyoglobin reductase activity, oxygen consumption rates, myoglobin content, and oxidative rancidity and low resistance to induced metmyoglobin formation, nitric oxide metmyoglobin reducing ability, and oxygen penetration depth. Data indicate that discoloration differences between muscles are related to the amount of reducing activity relative to the oxygen consumption rate.

Charles University in Prague Faculty of Pharmacy in Hradci Králové Department of Pharmaceutical Botany and Ecology Candidate: Kamila Ambrožová Supervisor: PharmDr. Jana Karlíčková, Ph.D. Title of Thesis: Copper reducing activity of isoflavonoids Copper in our body appears only in trace amounts. Despite this fact is an important component of many enzymes, which are responsible for right function of the whole organism. The most important are antioxidant activity, collagen and conective tissue synthesis, formation of pigmentation and cell respiration. Main target of the organism is control the homeostasis of copper, because excess and deficiency of the element could be pathological. Increase level of copper can cause many of civilization diseases. Isoflavones are the plant metabolites of polyfenolic structure which can positively affect different processes in our body. Research is dedicated to anti-inflammatory and estrogenic effects, antioxidant and anticancer aktivity. The elimination and inactivation of radical elements is performed becase of ability of isoflavones to reduce transition elements or chelate them. The aim of this thesis was to determine the reducing activity of seven isoflavonoids - daidzein, genistein, biochanin A, genistin, glycitein, formononetin and prunetin. The highest reduction...

Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Botany and Ecology Candidate: Jakub Mísař Supervisor: PharmDr. Jana Karlíčková, Ph.D. Title of Thesis: Copper reducing effects of quercetin metabolites Copper is an essential trace element in particular due to its ability to easily convert between both redox forms: oxidized (Cu2+ ) and reduced (Cu+ ). Flavonoids are common components of the human diet and they can have positive influence on human health. They are converted into small phenolic acids during digestion by specific bacteria in the colon. Although effects of flavonoids have been extensively studied, the same is not true for their metabolites- phenolic acids. In this in vitro study, eight phenolic acids, which are known metabolites of commonly used flavonoid quercetin, were analyzed for their copper reducing activity at four (patho)physiologically relevant pHs. Simple spectrophotometric method based on an indicator bathocuproinedisulfonic acid disodium salt was used for the assessment reduction of copper ions. The degree of cupric reduction differed among tested compounds. All o- dihydroxycompounds were the most active and achieved 100% of cupric ion reduction in low compound to copper ratio. In conclusion, based on this study, it appears that...

Les bactéries lactiques, en particulier Lactococcus lactis sont utilisées en industrie agroalimentaire. Ces bactéries sont connues pour avoir une activité réductrice, désignant leur aptitude à abaisser le potentiel redox (Eh) d’un milieu. Le génome de L. lactis MG1363 code plusieurs protéines possédant un motif CXXC potentiellement liées à une activité redox. Pour comprendre le rôle des protéines de surface riches en cystéines, deux approches ont été utilisées. Par l’approche bioinformatique, notre intérêt s'est porté sur deux protéines de surface de fonctions inconnues et à motif CX2CX10CX2C : Llmg_0524 et Llmg_0526. Leurs gènes forment un opéron induit temporairement en début de croissance. Dans les deux protéines, le motif chélate un ion de zinc par les résidus cystéines, formant un complexe très stable. Nos données suggèrent que cet opéron contribue à l'intégrité de la paroi cellulaire et que le zinc participe à la stabilité des protéines. L'identification des protéines à thiols exofaciaux par une approche biochimique indique la présente d’AhpF à la surface de L. lactis. La délétion du gène ahpF entraîne une forte sensibilité du mutant au cumène hydroperoxyde, mais aucune au peroxyde d'hydrogène. Le cumène hydroperoxyde provoque une modification de la proportion en acide gras chez le mutant ahpF, le mécanisme de cyclopropanation contribue à sa survie en réponse à un stress oxydatif. La compréhension des fonctions impliquées dans l'activité réductrice des lactocoques permettra une meilleure maîtrise du Eh dans la fabrication des produits fermentés et un meilleur contrôle des flores pathogènes et d’altérations. Le projet Food-Redox a été financé par l'ANR. / Lactic acid bacteria, particularly Lactococcus lactis are used in dairy industry. These bacteria are known to have a reducing activity, indicating their ability to lower the redox potential (Eh) of a medium. L. lactis MG1363 genome encodes several proteins with a CXXC motif, potentially linked with a redox activity. To understand the role of proteins rich in cysteine located at the surface of L. lactis, two approaches were used, one bioinformatics and biochemical another. For bioinformatic approach, interest was focused on two proteins of unknown function and CX2CX10CX2C motif: Llmg_0524 and Llmg_0526. Their corresponding genes form an operon temporarily induces in early growth phase. In these two proteins, the pattern chelate a zinc ion via its cysteine residues. The zinc-cysteine complexe is very stable, it suggests a probable role in protein stability. Data suggest that this operon contributes to the cell wall integrity. The identification of exofacial thiol proteins by a biochemical approach indicates that AhpF is present at the surface of L. lactis. The ahpF gene deletion causes a strong sensitivity to the cumene hydroperoxide, but no sensibility for hydrogen peroxide. In the mutant ahpF incubation with cumene hydroperoxide modified fatty acid proportion, cyclopropanation mechanism thus contributes to the survival in response to oxidative stress. Understanding the lactococci functions involved in the reduction activity allows a better control of redox potentiel in the fermented food production and thus a better control of foodbornes microorganisms in these products. Food-Redox project is financially supported by the French National Research Agency.

Red bright color is an important quality attribute that influences beef purchasing and is affected by beef pH. Therefore, the aim of this study was to determine if high ultimate pH affected color stability of longissimus lumborum (LL) steaks from pasture-fed Nellore bulls and if HiOx atmosphere package improved the color stability of high pHu muscles. To achieve these objectives, 18 LL muscles from Nellore bulls were grouped into 3 pHu ranges: normal (n = 6; 5.40 < pHu <5.79), intermediate (n = 6; 5.80 < pHu <6.19) and high (n = 6; pHu > 6.20). All the muscles were cut into 2.5 cm steaks and packaged in 80% O2/ 20% CO2 (v/v) and then stored at 2 ± 1 ºC under dark conditions until day 5 and under fluorescent light until day 14 (the end of display-time). pH, gas composition, instrumental color, surface pigment, metmyoglobin reducing activity (MRA), oxygen consumption rate (OCR), and lipid oxidation were determined throughout display-time. High pHu steaks were darker (L*), redder (a*, a*/b*), with better tone (Hue), less metmyoglobin and higher MRA (p < 0.05) than normal pHu samples. HiOX MAP increased surface OMb during display time in pHu > 6.2 (p < 0.05), showing a bright-red color in high group. Intermediate group was less dark than high group and had longer color stability than normal group (p < 0.05). Therefore, High pHu had great color and lipid oxidation stability and desired color due to HiOx MAP under cold storage for 14 days and intermediate pHu had beneficial aspects presented in both other treatments. / A cor vermelho-brilhante da carne bovina é um atributo de qualidade essencial considerado no momento de compra pelo consumidor, sendo intrinsecamente afetada pelo pH final (pHf) da carne. Assim, esse trabalho objetivou determinar se o pHf alto da carne afetou a estabilidade de carne do músculo Longissimus lumborum (LL) de bovinos da raça Nelore macho inteiro criado a pasto e se a embalagem com atmosfera modificada com alta concentração de oxigênio melhorou a estabilidade de cor da carne com pHf alto. Para isso, 18 músculos LL de Nelore machos inteiros criados a pasto foram classificadas em 3 faixas de pHf: normal (n = 6; 5.40 < pHu <5.79), intermediário (n = 6; 5.80 < pHu <6.19) e alto (n = 6; pHu > 6.20), 48h pós abate. Todos os músculos foram então porcionados em bifes com 2,5 cm de espessura 72h pós abate, os quais foram embalados em atmosfera composta por 80 % O2/ 20% CO2 (v/v), sendo finalmente armazenados a 2 ± 1 ºC no escuro até o 5º dia de tempo de exposição. No 5º dia, as amostras iniciaram a exposição à luz fluorescente até o dia 14 do período. As análises de pH, composição gasosa das embalagens, cor instrumental, pigmentos superficiais, atividade redutora da metamioglobina (ARM), taxa de consume de oxigênio (TCO) e oxidação lipídica foram realizadas ao longo do tempo de exposição. Os bifes com pHf alto apresentaram cor mais escura (L*), vermelha (a*, a*/b*), com melhor tonalidade (hue), menor metamioglobina superficial e maior ARM (p < 0.05). A embalagem com alta concentração de oxigênio aumentou a proporção de oximioglobina (OMB) superficial ao longo do tempo de exposição (p < 0.05), evidenciando uma cor vermelho-brilhante no grupo alto. O grupo Intermediário se mostrou menos escuro o grupo alto e mais prolongada estabilidade de cor que o grupo normal (p < 0.05). Assim, considera-se que a pHf alto afetou a estabilidade de cor e de oxidação lipídica dos músculos e a coloração do grupo alto foi melhorada pela ação da embalagem com oxigênio. O pH Intermediário se mostrou vantajoso por apresentar benefícios presentes nos dois outros tratamentos.

Red bright color is an important quality attribute that influences beef purchasing and is affected by beef pH. Therefore, the aim of this study was to determine if high ultimate pH affected color stability of longissimus lumborum (LL) steaks from pasture-fed Nellore bulls and if HiOx atmosphere package improved the color stability of high pHu muscles. To achieve these objectives, 18 LL muscles from Nellore bulls were grouped into 3 pHu ranges: normal (n = 6; 5.40 < pHu <5.79), intermediate (n = 6; 5.80 < pHu <6.19) and high (n = 6; pHu > 6.20). All the muscles were cut into 2.5 cm steaks and packaged in 80% O2/ 20% CO2 (v/v) and then stored at 2 ± 1 ºC under dark conditions until day 5 and under fluorescent light until day 14 (the end of display-time). pH, gas composition, instrumental color, surface pigment, metmyoglobin reducing activity (MRA), oxygen consumption rate (OCR), and lipid oxidation were determined throughout display-time. High pHu steaks were darker (L*), redder (a*, a*/b*), with better tone (Hue), less metmyoglobin and higher MRA (p < 0.05) than normal pHu samples. HiOX MAP increased surface OMb during display time in pHu > 6.2 (p < 0.05), showing a bright-red color in high group. Intermediate group was less dark than high group and had longer color stability than normal group (p < 0.05). Therefore, High pHu had great color and lipid oxidation stability and desired color due to HiOx MAP under cold storage for 14 days and intermediate pHu had beneficial aspects presented in both other treatments. / A cor vermelho-brilhante da carne bovina é um atributo de qualidade essencial considerado no momento de compra pelo consumidor, sendo intrinsecamente afetada pelo pH final (pHf) da carne. Assim, esse trabalho objetivou determinar se o pHf alto da carne afetou a estabilidade de carne do músculo Longissimus lumborum (LL) de bovinos da raça Nelore macho inteiro criado a pasto e se a embalagem com atmosfera modificada com alta concentração de oxigênio melhorou a estabilidade de cor da carne com pHf alto. Para isso, 18 músculos LL de Nelore machos inteiros criados a pasto foram classificadas em 3 faixas de pHf: normal (n = 6; 5.40 < pHu <5.79), intermediário (n = 6; 5.80 < pHu <6.19) e alto (n = 6; pHu > 6.20), 48h pós abate. Todos os músculos foram então porcionados em bifes com 2,5 cm de espessura 72h pós abate, os quais foram embalados em atmosfera composta por 80 % O2/ 20% CO2 (v/v), sendo finalmente armazenados a 2 ± 1 ºC no escuro até o 5º dia de tempo de exposição. No 5º dia, as amostras iniciaram a exposição à luz fluorescente até o dia 14 do período. As análises de pH, composição gasosa das embalagens, cor instrumental, pigmentos superficiais, atividade redutora da metamioglobina (ARM), taxa de consume de oxigênio (TCO) e oxidação lipídica foram realizadas ao longo do tempo de exposição. Os bifes com pHf alto apresentaram cor mais escura (L*), vermelha (a*, a*/b*), com melhor tonalidade (hue), menor metamioglobina superficial e maior ARM (p < 0.05). A embalagem com alta concentração de oxigênio aumentou a proporção de oximioglobina (OMB) superficial ao longo do tempo de exposição (p < 0.05), evidenciando uma cor vermelho-brilhante no grupo alto. O grupo Intermediário se mostrou menos escuro o grupo alto e mais prolongada estabilidade de cor que o grupo normal (p < 0.05). Assim, considera-se que a pHf alto afetou a estabilidade de cor e de oxidação lipídica dos músculos e a coloração do grupo alto foi melhorada pela ação da embalagem com oxigênio. O pH Intermediário se mostrou vantajoso por apresentar benefícios presentes nos dois outros tratamentos.