RESUMO
Lupinus mutabilis has protein (32.0-52.6 g/100 g dry weight) and lipid (13.0-24.6 g/100 g dry weight) contents similar to soya bean (Glycine max). The Ω3, Ω6, and Ω9 contents are 1.9-3.0, 26.5-39.6, and 41.2-56.2 g/100 g lipid, respectively. Lupins can be used to fortify the protein content of pasta, bread, biscuits, salads, hamburgers, sausages, and can substitute milk and soya bean. Specific lupin protein concentrates or isolates display protein solubility (>90%), water-absorption capacity (4.5 g/g dry weight), oil-absorption capacity (3.98 g/g), emulsifying capacity (2000 mL of oil/g), emulsifying stability (100%, 60 hours), foaming capacity (2083%), foaming stability (78.8%, 36 hours), and least gelation concentration (6%), which are of industrial interest. Lupins contain bitter alkaloids. Preliminary studies on their toxicity suggest as lethal acute dose for infants and children 10 mg/kg bw and for adults 25 mg/kg bw. However, alkaloids can also have medical use for their hypocholesterolemic, antiarrhythmic, and immunosuppressive activity. Bitter lupins can be detoxified by biological, chemical, or aqueous processes. The shortest debittering process requires one hour. This review presents the nutritional composition of lupins, their uses (as food, medicine, and functional protein isolates), toxicology, and debittering process scenarios. It critically evaluates the data, infers conclusions, and makes suggestions for future research.
Assuntos
Lupinus/química , Lupinus/toxicidade , Sementes/química , Alcaloides/análise , Proteínas Alimentares/administração & dosagem , Manipulação de Alimentos/métodos , Alimentos Fortificados , Humanos , Lipídeos/análise , Micronutrientes/análise , Valor Nutritivo , Proteínas de Plantas/análise , Proteínas de Plantas/química , PaladarRESUMO
Mung bean (Vigna radiata (L.) R. Wilczek) has been intensively researched; scattered data are available on various properties. Data on physical, chemical, food processing, and nutritional properties were collected for whole mung bean grains and reviewed to assess the crop's potential as food and to set research priorities. Results show that mung bean is a rich source of protein (14.6-33.0 g/100 g) and iron (5.9-7.6 mg/100 g). Grain color is correlated with compounds like polyphenols and carotenoids, while grain hardness is associated with fiber content. Physical properties like grain dimensions, sphericity, porosity, bulk, and true density are related to moisture content. Anti-nutrients are phytic acid, tannins, hemagglutinins, and polyphenols. Reported nutrient contents vary greatly, the causes of which are not well understood. Grain size and color have been associated with different regions and were used by plant breeders for selection purposes. Analytical methods require more accuracy and precision to distinguish biological variation from analytical variation. Research on nutrient digestibility, food processing properties, and bioavailability is needed. Furthermore, the effects of storage and processing on nutrients and food processing properties are required to enable optimization of processing steps, for better mung bean food quality and process efficiency.
Assuntos
Grão Comestível , Manipulação de Alimentos/métodos , Valor Nutritivo , Disponibilidade Biológica , Carotenoides , Fibras na Dieta , Proteínas Alimentares , Ferro da Dieta , Ácido Fítico , TaninosRESUMO
BACKGROUND: Exposure to palatable food odors influences appetite responses, either promoting or inhibiting food intake. Possibly, food odors are appetizing after a short exposure (of circa 1-3 min), but become satiating over time (circa 10-20 min). OBJECTIVE: To investigate the effect of odor exposure on general appetite and sensory-specific appetite (SSA) over time. DESIGN: In a cross-over study, 21 unrestrained women (age: 18-45 years; BMI: 18.5-25 kg m(-2)) were exposed for 20 min to eight different odor types: five food odors, two nonfood odors and no-odor. All odors were distributed in a test room at suprathreshold levels. General appetite, SSA and salivation were measured over time. RESULTS: All food odors significantly increased general appetite and SSA, compared with the no-odor condition. The nonfood odors decreased general appetite. All effects did not change over time during odor exposure. Savory odors increased the appetite for savory foods, but decreased appetite for sweet foods, and vice versa after exposure to sweet odors. Neither food odors nor nonfood odors affected salivation. CONCLUSIONS: Palatable food odors were appetizing during and after odor exposure and did not become satiating over a 20-min period. Food odors had a large impact on SSA and a small impact on general appetite. Moreover, exposure to food odors increased the appetite for congruent foods, but decreased the appetite for incongruent foods. It may be hypothesized that, once the body is prepared for intake of a certain food with a particular macronutrient composition, it is unfavorable to consume foods that are very different from the cued food.
Assuntos
Apetite/fisiologia , Ingestão de Alimentos/fisiologia , Odorantes , Salivação/fisiologia , Saciação/fisiologia , Adolescente , Adulto , Análise de Variância , Comportamento de Escolha , Estudos Cross-Over , Sinais (Psicologia) , Comportamento Alimentar , Feminino , Preferências Alimentares/fisiologia , Humanos , Pessoa de Meia-Idade , Odorantes/análise , Fatores de TempoRESUMO
This review paper discusses opportunities for intelligent packaging for monitoring directly or indirectly quality attributes of perishable packaged foods. The possible roles of intelligent packaging as a tool in supply chain management are discussed as well as the barriers to implement this kind of technology in commercial applications. Cases on pasteurized milk and fresh cod fillets illustrate the application of different intelligent packaging concepts to monitor and estimate quality attributes. Conditions influencing quality (e.g., temperature-time) can be monitored to predict the quality of perishable products when the initial quality is known and rather constant (e.g., pasteurized milk). Products with a highly variable initial quality (e.g., fresh fish) require sensors monitoring compounds correlated with quality.
Assuntos
Contaminação de Alimentos/prevenção & controle , Embalagem de Alimentos/métodos , Conservação de Alimentos/métodos , Animais , Técnicas Biossensoriais , Peixes , Microbiologia de Alimentos , Carne/análise , Carne/microbiologia , Leite/química , Leite/microbiologia , Pasteurização/métodos , TemperaturaRESUMO
Characterization of variation of experimental results is achieved by repeating experiments. Frequently, results are averaged before data are analysed but that may not be the best practice because valuable information is then lost. Three other ways to analyze repetitions are: (1) each experiment is analyzed on its own (no pooling of data), (2) all experiments are analyzed together in one go (complete pooling), (3) data are analyzed together while allowing for similarities as well as differences in the result (partial pooling). Multilevel modeling uses partial pooling by partitioning variance over more than one level. Level 1 consists of the measurements themselves; higher levels consist of groups or clusters of measurements (repetitions, experiments at various temperatures, at various pH values, etc.) and parameters are analyzed both at the population and at the group/cluster level. The approach is applied to a case study in which heat-induced isothermal degradation of ascorbic acid was studied with 15 repetitions in an aqueous solution, making it a two-level study. The data were analyzed using averaging and complete pooling, complete pooling without averaging, no-pooling at all, and partial pooling. The kinetic model was established by letting the data decide about the order of the reaction, while this was compared to a model where the order was fixed at 1 (first-order model). Results show that both averaging with complete pooling, as well as complete pooling without averaging, strongly underestimate variation. The no-pooling technique overestimates variation, while partial pooling partitions variation over the levels and thus gives a better impression of the variation involved. The kinetics of ascorbic acid appear to be subject to strong variation when each experiment is considered separately because it is a compound that is very sensitive to all kinds of experimental conditions. With multilevel modeling it appeared to be possible to characterize the uncertainties involved much better than with single level modeling. A Bayesian analysis was performed, in which parameters are allowed to be variable, which is useful because multilevel modeling leads to characterization of variation of parameters. The Bayesian method allows to visualize the posterior distribution of parameters, thereby giving more insight in their behaviour. Also, a Bayesian analysis focuses more strongly on predictive accuracy of models, including multilevel models. The predictive accuracy of 4 models describing the same ascorbic acid data was compared and the multilevel model with reaction order estimated from the data performed by far the best in this regard. The pros and cons of multilevel modeling are discussed and it is concluded that multilevel modeling is to be preferred whenever the data allow to perform such an analysis.
Assuntos
Tecnologia de Alimentos , Temperatura Alta , Ácido Ascórbico/química , Teorema de Bayes , CinéticaRESUMO
In Africa, nutrient intake deficiencies are widespread. We, therefore, investigated the potential contribution of cowpea dishes to the ingestion of several macro- and micronutrients. Processors and consumers were interviewed and cowpea dishes analyzed. Energy, protein, iron, zinc, and calcium contents ranged from 1647 to 2570 kJ, 10 to 25 g, 1 to 35 mg, 1.5 to 3.0 mg, 38 to 380 mg per 100 g d.w., respectively. The iron and calcium contents were highest in dishes containing leaves. The consumption of these dishes should be promoted along with research on how to further decrease the associated antinutritional factors of traditional cowpea dishes.
Assuntos
Dieta , Ingestão de Energia , Fabaceae/química , Manipulação de Alimentos/métodos , Frutas/química , Desnutrição/prevenção & controle , África/epidemiologia , Cálcio/análise , Cálcio da Dieta/análise , Proteínas Alimentares/análise , Humanos , Ferro da Dieta/análise , Desnutrição/epidemiologia , Valor Nutritivo , Folhas de Planta , Prevalência , Zinco/análiseRESUMO
Variation observed in heat inactivation of Salmonella strains (data from Combase) was characterized using multilevel modeling with two case studies. One study concerned repetitions at one temperature, the other concerned isothermal experiments at various temperatures. Multilevel models characterize variation at various levels and handle dependencies in the data. The Weibull model was applied using Bayesian regression. The research question was how parameters varied with experimental conditions and how data can best be analyzed: no pooling (each experiment analyzed separately), complete pooling (all data analyzed together) or partial pooling (connecting the experiments while allowing for variation between experiments). In the first case study, level 1 consisted of the measurements, level 2 of the group of repetitions. While variation in the initial number parameter was low (set by the researchers), the Weibull shape factor varied for each repetition from 0.58-1.44, and the rate parameter from 0.006-0.074 h. With partial pooling variation was much less, with complete pooling variation was strongly underestimated. In the second case study, level 1 consisted of the measurements, level 2 of the group of repetitions per temperature experiment, level 3 of the cluster of various temperature experiments. The research question was how temperature affected the Weibull parameters. Variation in initial numbers was low (set by the researchers), the rate parameter was obviously affected by temperature, the estimate of the shape parameter depended on how the data were analyzed. With partial pooling, and one-step global modeling with a Bigelow-type model for the rate parameter, shape parameter variation was minimal. Model comparison based on prediction capacity of the various models was explored. The probability distribution of calculated decimal reduction times was much narrower using multilevel global modeling compared to the usual single level two-step approach. Multilevel modeling of microbial heat inactivation appears to be a suitable and powerful method to characterize and quantify variation at various levels. It handles possible dependencies in the data, and yields unbiased parameter estimates. The answer on the question "to pool or not to pool" depends on the goal of modeling, but if the goal is prediction, then partial pooling using multilevel modeling is the answer, provided that the experimental data allow that.
Assuntos
Análise de Dados , Microbiologia de Alimentos , Temperatura Alta , Viabilidade Microbiana , Modelos Estatísticos , Salmonella , Teorema de Bayes , Contagem de Colônia Microbiana , Cinética , Salmonella/fisiologiaRESUMO
Forest food resources contribute significantly to food supply in areas where they grow. Three fermented baobab foods were studied: Dikouanyouri (from seeds, pH = 6.5); Tayohounta (from seed kernels, pH = 7), and Mutchayan (from baobab pulp and sorghum, pH = 4.2). Bacillus spp. (8.5 and 9.5 Log cfu /g) and lactic acid bacteria (8.9 and 8.4 Log cfu /g,) dominate in Dikouanyouri and Tayohounta, respectively. In Mutchayan, lactic acid bacteria (8.1 Log cfu/g) and yeasts (7.2 Log cfu/g) predominated. The arbitrary index of protein cleavage increases from 2.3% (unfermented products) to 13.7% in Dikouanyouri and 21.3% in Tayohounta, indicating significant protein degradation. Mutchayan is the most frequently consumed product.
Assuntos
Adansonia , Bactérias/isolamento & purificação , Dieta , Proteínas Alimentares/metabolismo , Microbiologia de Alimentos , Preparações de Plantas , Leveduras/isolamento & purificação , Adansonia/microbiologia , Bacillus/isolamento & purificação , Benin , Comportamento Alimentar , Fermentação , Manipulação de Alimentos/métodos , Abastecimento de Alimentos , Frutas , Humanos , Concentração de Íons de Hidrogênio , Lactobacillus/isolamento & purificação , Preparações de Plantas/administração & dosagem , Preparações de Plantas/metabolismo , SorghumRESUMO
Several authors have published about baobab food products. Data on macronutrients, micronutrients, amino acids, and fatty acids were collected from literature for pulp, leaves, seeds, and kernels of the baobab tree. The results show that baobab pulp is particularly rich in vitamin C; consumption of 40 g covers 84 to more than 100% of the Recommended Daily Intake (RDI) of pregnant women (19-30 years). The leaves are particularly rich in calcium (307 to 2640 mg/100 g dw), and they are known to contain good quality proteins with a chemical score of 0.81. The whole seeds and the kernels have a relatively high lipid content, 11.6 to 33.3 g/100 g dw and 18.9 to 34.7 g/100 g dw, respectively. The pulp and leaves exhibit antioxidant properties with a higher activity in the pulp than in the leaves. Reported nutrient contents of different baobab parts show a large variation, which may have arisen from various factors. Three recommendations are given for future research: 1. More attention should be given to accuracy and precision of analytical methods, 2. Research about digestibility and bioavailability of baobab products is needed, 3. The effect of storage and processing on the nutritional value of baobab products needs to be assessed.
Assuntos
Adansonia/química , Ácidos Graxos/análise , Frutas/química , Minerais/análise , Valor Nutritivo , Proteínas de Plantas/análise , Aminoácidos/análise , Animais , Digestão , Análise de Alimentos , Humanos , Folhas de Planta/química , Óleos de Plantas/química , Proteínas de Plantas/química , Sementes/química , Especificidade da EspécieRESUMO
Moderate intensity Pulsed Electric Fields (PEF) was studied for microbial inactivation as an alternative to high intensity PEF or to classical thermal pasteurization. The process is characterized by the application of electric pulses, allowing an increase of the product temperature by the ohmic heat generated by the pulses. A systematic evaluation of the effect of parameters electric field strength (E) and pulse width (τ) on the inactivation of Escherichia coli, Listeria monocytogenes, Lactobacillus plantarum, Salmonella Senftenberg and Saccharomyces cerevisiae in orange juice was carried out in a continuous flow system. A wide range of conditions was evaluated, and both E and τ were shown to be important in the efficacy to inactivate micro-organisms. Remarkably, PEF conditions at Eâ¯=â¯2.7â¯kV/cm and τâ¯=â¯15-1000⯵s showed to be more effective in microbial inactivation than at Eâ¯=â¯10â¯kV/cm and τâ¯=â¯2⯵s. Inactivation kinetics of the tested PEF conditions were compared to an equivalent thermal process to disentangle non-thermal effects (electroporation) from thermal effects responsible for the microbial inactivation. At standard high intensity PEF treatment a non-thermal inactivation at Eâ¯=â¯20â¯kV/cm and τâ¯=â¯2⯵s pulses was observed and attributed to electroporation. Non-thermal effects could also be resolved with moderate intensity PEF at Eâ¯=â¯2.7â¯kV/cm and pulse width between τâ¯=â¯15-1000⯵s. Microbial inactivation at these moderate intensity PEF conditions was studied in more detail at different pH and medium conductivity for E. coli and L. monocytogenes in watermelon juice and coconut water. Under moderate intensity PEF conditions the effectiveness of treatment was independent of pH for all evaluated matrices in the pH range of 3.8-6.0, whereas under high intensity PEF conditions the pH of the product is a critical factor for microbial inactivation. This suggests that the inactivation proceeds through a different mechanism at moderate intensity PEF, and speculations for this mechanism are presented. In conclusion, moderate intensity PEF conditions at Eâ¯=â¯2.7â¯kV/cm and pulse width of 15-1000⯵s has potential for industrial processing for the preservation of fruit juices and pH neutral liquid food products.
Assuntos
Eletricidade , Microbiologia de Alimentos , Conservação de Alimentos/métodos , Sucos de Frutas e Vegetais , Viabilidade Microbiana , Fenômenos Fisiológicos Bacterianos , Contagem de Colônia Microbiana , Temperatura Alta , Concentração de Íons de Hidrogênio , Saccharomyces cerevisiae/fisiologiaRESUMO
This study aimed to characterize the number of Salmonella on chicken breast filet at the retail level and to evaluate if this number affects the risk of salmonellosis. From October to December 2005, 220 chilled raw filets (without skin) were collected from five local retail outlets in The Netherlands. Filet rinses that were positive after enrichment were enumerated with a three-tube most-probable-number (MPN) assay. Nineteen filets (8.6%) were contaminated above the detection limit of the MPN method (10 Salmonella per filet). The number of Salmonella on positive filets varied from 1 to 3.81 log MPN per filet. The obtained enumeration data were applied in a risk assessment model. The model considered possible growth during domestic storage, cross-contamination from filet via a cutting board to lettuce, and possible illness due to consumption of the prepared lettuce. A screening analysis with expected-case and worst-case estimates for the input values of the model showed that variability in the inputs was of relevance. Therefore, a Monte Carlo simulation with probability distributions for the inputs was carried out to predict the annual number of illnesses. Remarkably, over two-thirds of annual predicted illnesses were caused by the small fraction of filets containing more than 3 log Salmonella at retail (0.8% of all filets). The enumeration results can be used to confirm this hypothesis in a more elaborate risk assessment. Modeling of the supply chain can provide insight for possible intervention strategies to reduce the incidence of rare, but extreme levels. Reduction seems feasible within current practices, because the retail market study indicated a significant difference between suppliers.
Assuntos
Contaminação de Alimentos/análise , Carne/microbiologia , Saúde Pública , Medição de Risco , Salmonella/isolamento & purificação , Animais , Galinhas , Contagem de Colônia Microbiana , Qualidade de Produtos para o Consumidor , Microbiologia de Alimentos , Humanos , Método de Monte Carlo , Intoxicação Alimentar por Salmonella/epidemiologiaRESUMO
A new primary model has been developed, using Gaussian distributed populations and Eyrings rate constant for the transition state, to describe inactivation kinetics of enzymes and micro-organisms subjected to heat and chemical treatment. The inactivation of both enzymes and micro-organisms could be associated with the irreversible transition to an inactivated state, as suggested by the Lumry-Eyring model for protein denaturation and enzyme inactivation. The characteristic inactivation model parameters, standard activation enthalpy and entropy, are directly related to the reference temperature and Z-value commonly used for kinetic analysis in food microbiology. An essential feature of the kinetic model is that its parameters, and hence the transition temperature, are treated as stochastic variables. The characteristic line shape of the primary model is the log-normal distribution. The performance of the model was validated, using literature data for enzyme and microbial inactivation over a wide range of temperature and pH.
Assuntos
Termodinâmica , Temperatura Alta , Cinética , Viabilidade Microbiana , Desnaturação Proteica , TemperaturaRESUMO
This study investigated acrylamide and 5-hydroxymethylfurfural (HMF) formation during biscuit baking. Four types of wheat flour with different molar ratios of total fructose and glucose to asparagine were investigated. Nevertheless, the molar ratio in all four biscuit doughs exceeded one after proofing due to enzyme action. Data obtained after baking were used to develop a mechanistic model, based on the asparagine-related pathway, for acrylamide and HMF formation in the four baked biscuit types. Asparagine reacted with fructose to form a Schiff base before decarboxylation to produce acrylamide without Amadori rearrangement product and sugar fragmentation. Fructose contributed considerably to acrylamide formation and to HMF formation via caramelization in all four biscuit types. No clear correlation was found between acrylamide and HMF in baked biscuits, nor between asparagine and the sum of glucose and fructose concentrations in the wheat flour.
Assuntos
Acrilamida/química , Asparagina/química , Farinha/análise , Manipulação de Alimentos , Furaldeído/análogos & derivados , Acrilamida/análise , Frutose/química , Furaldeído/análise , Furaldeído/química , Glucose/química , Temperatura Alta , Cinética , Triticum/químicaRESUMO
Application of mild (non)-thermal processing technologies have received considerable interest as alternative to thermal pasteurisation, because of its shorter holding time and lower temperature aiming for an improved product quality. To understand and develop these alternative technologies, like pulsed electric fields, a proper comparison between the conventional thermal and alternative process is necessary. Up to recent, no suitable models were available to predict the inactivation of micro-organisms by a thermal process at a chosen short holding time, due to non-linearity. The recently developed Gauss-Eyring model with two variables temperature and time has the properties to be a suitable model to apply for short holding times, and was tested for this purpose. Therefore, this study aims to validate if the Gauss-Eyring model can be used to describe non-linear isothermal (a fixed temperature with varying holding time) and isotime (a fixed holding time with varying temperature) thermal inactivation data, and if it is a suitable model to predict the thermal inactivation as a function of temperature for short holding times. Inactivation data of Escherichia coli, Listeria monocytogenes, Lactobacillus plantarum, Salmonella Senftenberg and Saccharomyces cerevisiae in orange juice were collected via isothermal and isotime inactivation kinetics. Survival of the tested micro-organisms was modelled with the Gauss-Eyring model, which contains three parameters σ, Tr and Z. The transition of 'no inactivation' to 'inactivation' (i.e. the 'shoulder' in inactivation curves) can be characterised as the temperature-time (T,t) combination where T=Tr-Z·log10(t), with Tr as the reference temperature defined for 1s treatment, Z as the temperature needed for a 10-fold increase of decrease of the holding time t, and σ as the temperature width of the distribution. The Gauss-Eyring model fitted well to the experimental data, and revealed different sensitivity for the tested micro-organisms. Based on the parameter estimations, survival curves for the desired short holding times were predicted.
Assuntos
Escherichia coli/crescimento & desenvolvimento , Manipulação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Listeria monocytogenes/crescimento & desenvolvimento , Contagem de Colônia Microbiana , Manipulação de Alimentos/instrumentação , Microbiologia de Alimentos , Temperatura Alta , Cinética , Modelos Biológicos , Fatores de TempoRESUMO
This paper discusses the importance of the Maillard reaction for food quality and focuses on flavour compound formation. The most important classes of Maillard flavour compounds are indicated and it is shown where they are formed in the Maillard reaction. Some emphasis is given on the kinetics of formation of flavour compounds. It is concluded that the essential elements for predicting the formation of flavour compounds in the Maillard reaction are now established but much more work needs to be done on specific effects such as the amino acid type, the pH, water content and interactions in the food matrix. It is also concluded that most work is done on free amino acids but hardly anything on peptides and proteins, which could generate peptide- or protein-specific flavour compounds.
Assuntos
Aromatizantes/metabolismo , Reação de Maillard , Aminoácidos/química , Carboidratos/química , Fermentação , Aromatizantes/química , Tecnologia de Alimentos/métodos , Humanos , Cinética , Compostos Orgânicos/química , Compostos Orgânicos/metabolismo , PaladarRESUMO
Pulsed electrical field (PEF) technology offers an alternative to thermal pasteurisation of high-acid fruit juices, by extending the shelf life of food products, while retaining its fresh taste and nutritional value. Substantial research has been performed on the effect of electrical field strength on the inactivation kinetics of spoilage and pathogenic micro-organisms and on the outgrowth of spoilage micro-organisms during shelf life. However, studies on the effect of electrical field strength on the inactivation and outgrowth of surviving populations during shelf life are missing. In this study, we assessed the influence of electrical field strength applied by PEF processing and storage temperature on the outgrowth of surviving yeast and mould populations naturally present in fresh fruit smoothie in time. Therefore, an apple-strawberry-banana smoothie was treated in a continuous-flow PEF system (130L/h), using similar inlet and outlet conditions (preheating temperature 41°C, maximum temperature 58°C) to assure that the amount of energy across the different conditions was kept constant. Smoothies treated with variable electrical field strengths (13.5, 17.0, 20.0 and 24.0kV/cm) were compared to smoothies without treatment for outgrowth of yeasts and moulds. Outgrowth of yeasts and moulds stored at 4°C and 7°C was analysed by plating and visual observation and yeast growth was modelled using the modified logistic growth model (Zwietering model). Results showed that the intensity of the electrical field strength had an influence on the degree of inactivation of yeast cells, resulting in a faster outgrowth over time at lower electrical field strength. Outgrowth of moulds over time was not affected by the intensity of the electrical field strength used. Application of PEF introduces a trade-off between type of spoilage: in untreated smoothie yeasts lead to spoilage after 8days when stored at 4 or 7°C, whereas in PEF treated smoothie yeasts were (partly) inactivated and provided outgrowth opportunities for moulds, which led to spoilage by moulds after 14days (7°C) or 18days (4°C).
Assuntos
Conservação de Alimentos/métodos , Fragaria/microbiologia , Frutas/microbiologia , Malus/microbiologia , Musa/microbiologia , Leveduras/crescimento & desenvolvimento , Eletricidade , Sucos de Frutas e Vegetais/microbiologia , Pasteurização/métodos , TemperaturaRESUMO
To investigate the possible role of glycation in the aging of lens proteins, we used bovine lenses as a model. We studied crystallins isolated from prenatal bovine lenses, calf lenses and lenses from mature animals (up to 20 years old). The experiments show an increase in glycation levels with age in all crystallin fractions. Regarding the lysine content of the different crystallins, gamma-crystallin showed relatively high levels of early glycation products. The results also revealed high levels of early glycation products for the HM material (containing mainly alpha-crystallin). In alpha-crystallin, alpha A-subunits were glycated to a higher extent compared with the alpha B-subunits. There is an age-related increase in advanced glycation products, measured as specific fluorescence (excitation/emission wavelengths 370/440 nm), mainly present in the HM and alpha-crystallin fraction.
Assuntos
Cristalinas/química , Produtos Finais de Glicação Avançada/química , Animais , Bovinos , Técnicas In Vitro , Cristalino/química , Espectrometria de FluorescênciaRESUMO
Glycation is a non-enzymatic modification of proteins by sugars, probably responsible for the initiation of complications in diabetes patients and aging individuals. Our in vitro experiments show an inhibition of sugar attachment in the presence of Diclofenac. The levels of advanced glycation products, measured as specific fluorescent groups, were also lowered due to Diclofenac. These results were compared with inhibition by Aspirin (acetylsalicylic acid), a known inhibitor of the glycation process. The protection by Diclofenac is based on a non-covalent interaction of the drug with serum albumin. There is evidence that Diclofenac specifically blocks at least one of the major glycation sites of human serum albumin.
Assuntos
Diclofenaco/química , Glucofosfatos/química , Albumina Sérica/química , Aspirina/química , Ligação Competitiva , Glucose-6-Fosfato , Humanos , Ligação Proteica , Espectrometria de FluorescênciaRESUMO
From the alignment of 14 EST clones, the cDNA sequence of a novel human small heat shock protein (sHsp), called HspB3, could be deduced. The 3' part of the HspB3 cDNA is 99% identical to that of the previously reported HspL27 cDNA (W.Y. Lam, S.K. Wing Tsui, P.T. Law, S.C. Luk, K.P. Fung, C.Y. Lee, M.M. Waye, Isolation and characterization of a human heart cDNA encoding a new member of the small heat shock protein family-HSPL27, Biochim. Biophys. Acta 1314 (1996) 120-124). We argue that the HspB3 cDNA sequence is a corrected version of the HspL27 cDNA. The HspB3 cDNA is 742 bp long and contains an open reading frame specifying a polypeptide of 150 amino acid residues. Among the six known human sHsps it is evident that HspB3 is the most deviating one, having a unique N-terminal domain and essentially lacking a C-terminal extension. Northern blot analysis shows that in smooth muscle tissue the cDNA hybridizes with mRNA of about 0.9 kb.
Assuntos
Proteínas de Choque Térmico/química , Sequência de Aminoácidos , Etiquetas de Sequências Expressas , Humanos , Dados de Sequência Molecular , Fases de Leitura Aberta/genética , RNA Mensageiro/análise , Alinhamento de SequênciaRESUMO
The major lens protein alpha-crystallin is composed of two related types of subunits, alphaA- and alphaB-crystallin, of which the former is essentially lens-restricted, while the latter also occurs in various other tissues. With regard to their respective chaperone capacities, it has been reported that homomultimeric alphaA-crystallin complexes perform better in preventing thermal aggregation of proteins, while alphaB-crystallin complexes protect more efficiently against reduction-induced aggregation of proteins. Here, we demonstrate that this seeming discrepancy is solved when the reduction assay is performed at increasing temperatures: above 50 degrees C alphaA- performs better than alphaB-crystallin also in this assay. This inversion in protective capacity might relate to the greater resistance of alphaA-crystallin to heat denaturation. Infrared spectroscopy, however, revealed that this is not due to a higher thermostability of alphaA-crystallin's secondary structure. Also the accessible hydrophobic surfaces do not account for the chaperoning differences of alphaA- and alphaB-crystallin, since regardless of the experimental temperature alphaB-crystallin displays a higher hydrophobicity. It is argued that the greater complex stability of alphaA-crystallin, as evident upon urea denaturation, and the higher chaperone capacity of alphaB-crystallin at physiological temperatures reflect the evolutionary compromise to obtain an optimal functioning of heteromeric alpha-crystallin as a lens protein.