Duarte Torres

Comparison of adsorption equilibrium of fructose, glucose and sucrose on potassium gel-type and macroporous sodium ion-exchange resins.

Adsorption equilibrium of fructose, glucose and sucrose was evaluated on sulfonated poly(styrene-co-divinylbenzene) cation-exchange resins. Two types of resins were used: potassium (K+) gel-type and sodium (Na+) macroporous resins. Influence of the cation and effect of the resin structure on adsorption were studied. The adsorption isotherms were determined by the static method in batch mode for mono-component and multi-component sugar mixtures, at 25 and 40 degrees C, in a range of concentrations between 5 and 250 g L(-1). All adsorption isotherms were fitted by a linear model in this range of concentrations. Sugars were adsorbed in both resins by the following order: fructose > glucose > sucrose. Sucrose was more adsorbed in the Na+ macroporous resin, glucose was identically adsorbed, and fructose was more adsorbed in the K+ gel-type resin. Data obtained from the adsorption of multi-component mixtures as compared to the mono-component ones showed a competitive effect on the adsorption at 25 degrees C, and a synergetic effect at 40 degrees C. The temperature increase conducted to a decrease on the adsorption capacity for mono-component sugar mixtures, and to an increase for the multi-component mixtures. Based on the selectivity results, K+ gel-type resin seems to be the best choice for the separation of fructose, glucose and sucrose, at 25 degrees C.

Protein content and amino acids profile of pseudocereals

Quinoa (Chenopodium quinoa), amaranth (Amaranthus caudatus) and buckwheat (Fagopyrum esculentum) represent the main protein source in several diets, although these pseudocereals are not currently present in the FCDB nutrient profile information. The aim of this work is to characterise the AA profile of these pseudocereals and compare them with rice. Total protein content revealed to vary from 16.3g/100g (quinoa Salta) to 13.1g/100g (buckwheat) and lower values were found in rice samples (6.7g/100g). For pseudocereals the most abundant essential AA was leucine. Quinoa-Salta evidences the highest leucine content (1013mg/100g) and the minor methionine content (199mg/100g). Buckwheat was the cereal with the highest phenylalanine content (862mg/100g). Rice (Oryza sativa) presents the lowest content for all AA. Results showed pseudocereals as the best source of AA. EuroFIR guidelines where strictly followed and proved to be a crucial tool to guarantee data interchangeability and comparability.

New improved method for fructooligosaccharides production by Aureobasidium pullulans

Fructooligosaccharides are prebiotics with numerous health benefits within which the improvement of gut microbiota balance can be highlighted, playing a key role in individual health. In this study, an integrated one-stage method for FOS production via sucrose fermentation by Aureobasidium pullulans was developed and optimized using experimental design tools. Optimization of temperature and agitation speed for maximizing the FOS production was performed using response surface methodology. Temperature was found to be the most significant parameter. The optimum fermentation conditions were found to be 32 °C and 385 rpm. Under these conditions, the model predicted a total FOS production yield of 64.7 gFOS/gsucrose. The model was validated at optimal conditions in order to check its adequacy and accuracy and an experimental yield of 64.1 (±0.0) gFOS/gsucrose was obtained. A significant improvement of the total FOS production yields by A. pullulans using a one-stage process was obtained.

Rheological study of the effect of Cassia javanica galactomannans on the heat-set gelation of a whey protein isolate at pH 7

Abstract The effect of Cassia gum galactomannan on the thermal gelation of a whey protein isolate (WPI) at 80 °C has been monitored by rheological dynamic measurements at fixed frequency and the mechanical spectra of the gels have been recorded at 80 °C and after quenching to 20 °C. The mechanical spectra were analysed quantitatively by fitting a Cole–Cole model to the storage and loss compliance versus frequency data. The concentration of WPI was 110 g/l and that of Cassia gum varied from 0 to 11 g/l. At low concentration, the presence of the galactomannan enhanced the aggregation rate and the strength of the protein gel but did not modify intrinsically the gelation process and the structure of the system. At higher galactomannan concentrations, the gels displayed substantially lower moduli values and the shape of the mechanical spectra was modified. This was tentatively interpreted as the consequence of a depletion-induced liquid–liquid phase separation occurring during the course of the aggregation process, responsible for the downturn observed on the loss modulus versus time curves monitored at 80 °C.

Characterization of rat heart alkaline phosphatase isoenzymes and modulation of activity

Alkaline phosphatase (ALP) is important in calcification and its expression seems to be associated with the inflammatory process. We investigated the in vitro acute effects of compounds used for the prevention or treatment of cardiovascular diseases on total ALP activity from male Wistar rat heart homogenate. ALP activity was determined by quantifying, at 410 nm, the p-nitrophenol released from p-nitrophenylphosphate (substrate in Tris buffer, pH 10.4). Using specific inhibitors of ALP activity and the reverse transcription-polymerase chain reaction, we showed that the rat heart had high ALP activity (31.73 +/- 3.43 nmol p-nitrophenol.mg protein-1.min-1): mainly tissue-nonspecific ALP but also tissue-specific intestinal ALP type II. Both ALP isoenzymes presented myocardial localization (striated pattern) by immunofluorescence. ALP was inhibited a) strongly by 0.5 mM levamisole, 2 mM theophylline and 2 mM aspirin (91, 77 and 84%, respectively) and b) less strongly by 2 mM L-phenylalanine, 100 mL polyphenol-rich beverages and 0.5 mM progesterone (24, 21 to 29 and 11%, respectively). beta-estradiol and caffeine (0.5 and 2 mM) had no effect; 0.5 mM simvastatin and 2 mM atenolol activated ALP (32 and 36%, respectively). Propranolol (2 mM) tended to activate ALP activity and corticosterone activated (18%) and inhibited (13%) (0.5 and 2 mM, respectively). We report, for the first time, that the rat heart expresses intestinal ALP type II and has high total ALP activity. ALP activity was inhibited by compounds used in the prevention of cardiovascular pathology. ALP manipulation in vivo may constitute an additional target for intervention in cardiovascular diseases.

Enzymatic Hydrolysis of Whey Protein Concentrates: Peptide HPLC Profiles

Abstract Hydrolysis of whey protein concentrates (WPCs) at different temperatures and pHs, using three enzymes: pepsin, trypsin, and Alcalase®, was monitored during more than 5 hr by reversed phase HPLC/UV, using a column containing a polystyrene‐divinylbenzene copolymer‐based packing, and an elution gradient from 8% to 80% acetonitrile containing 0.1% TFA. Peptides were separated according to their polarity and size, and degradation of α‐lactalbumin (α‐la) and β‐lactoglobulin (β‐lg) was evaluated. The three proteolytic enzymes (pepsin, trypsin, and Alcalase®) employed for hydrolysis of WPCs led to different kinetics of degradation of β‐lg. α‐la degradation after 15 min was almost complete for the three enzymes. The hydrolysis catalysed by each enzyme resulted in different peptide profiles by HPLC/UV. Hydrolysates produced by pepsin (HP) were resolved into three main fractions of high retention times, while tripsin hydrolysates (HT) were resolved into nine major peaks and Alcalase® hydrolysates (HA) were resolved into 12 major peaks, presenting a wide range of polarities and sizes. Although, with different β‐lg hydrolysis extension, chromatographic profiles of the degradation and formation of peptides can be used as a finger print of the type of enzyme used, because peptide profile is not affected either by temperature or pH.

Phenylketonuria: Protein content and amino acids profile of dishes for phenylketonuric patients. The relevance of phenylalanine

Phenylketonuria is an inborn error of metabolism, involving, in most cases, a deficient activity of phenylalanine hydroxylase. Neonatal diagnosis and a prompt special diet (low phenylalanine and natural-protein restricted diets) are essential to the treatment. The lack of data concerning phenylalanine contents of processed foodstuffs is an additional limitation for an already very restrictive diet. Our goals were to quantify protein (Kjeldahl method) and amino acid (18) content (HPLC/fluorescence) in 16 dishes specifically conceived for phenylketonuric patients, and compare the most relevant results with those of several international food composition databases. As might be expected, all the meals contained low protein levels (0.67-3.15 g/100 g) with the highest ones occurring in boiled rice and potatoes. These foods also contained the highest amounts of phenylalanine (158.51 and 62.65 mg/100 g, respectively). In contrast to the other amino acids, it was possible to predict phenylalanine content based on protein alone. Slight deviations were observed when comparing results with the different food composition databases.

EURRECA nutritional planning and dietary assessment software tool: NutPlan

Background/Objectives:‘NutPlan’ is developed within the EURRECA Network of Excellence (EURopean micronutrient RECommendations Aligned (http://www.eurreca.org). It is a user-friendly software programme with multiple functions: individual and group nutrition planning, recipe calculation, creating food labels, diet planning and nutrient intake assessment. This paper describes the newly developed software and its features.Subjects/Methods:‘NutPlan’ contains the following databases: foods, dish recipes, meals, menus, average menus and glossary. These databases enable diet planning and diet analysis by comparing foods, dishes, meals or menus with currently available nutritional recommendations accessible by a link to EURRECA tool Nutri-RecQuest to meet individual/group nutritional needs.The software is upgraded by inserting new items (for example, foods, dishes, meals) and for a connection to other software programmes, thus allowing more advanced calculations to be completed.Conclusion:‘NutPlan’ might be the software of choice for individual and group diet planning. It is aimed particularly at Eastern European and West Balkan countries, which currently lack dietary software. It is envisaged for use by small and medium enterprises in the food industry, as well as by health professionals, researchers and policy makers, and can be recommended for educational purposes. Given its characteristics of being upgraded to include new country-specific food data/database, it can be recognized as an important tool in nutritional capacity development in the Central Eastern European and other regions.

A dynamical model for the fermentative production of fructooligosaccharides

In this paper a detailed mathematical model is presented for the fermentative production of fructo-oligosaccharides with Aspergillus sp. The model accounts for hydrolysis and transfructolization reactions, as well as biomass formation and it contains 27 parameters that were determined from experimental data using a System Biology toolbox with the Simulated Annealing method for curve fitting. Several additional experiments were performed in bioreactors where the time variation of 7 state variables (Sucrose, Glucose, Fructose, 1-Kestose, Nystose, 1-fructosyl nystose and Biomass) was measured. Experimental data were compared with results from simulations using the estimated parameters and it was verified that the model can predict the FOS production profile. The good agreement between simulated and experimental data was verified by calculating the relative percentage deviation modulus, which was lower than 10% for all cases except one. The derived and validated model can be used for process optimization, for example for indicating which fed-batch strategy could be used to improve the production of FOS while minimizing glucose concentration.