Montserrat Pujolà

Determination of equilibrium distribution constants of phenol between surfactant micelles and water using ultrafiltering centrifuge tubes

Abstract Equilibrium distribution constants, K s , of phenol between surfactant micelles and water have been determined by micellar enhanced ultrafiltration (MEUF) using commercial ultrafiltering centrifuge tubes. Three surfactants: sodium dodecyl sulphate (SDS), polyoxyethylene 20 cetyl ether (C16E20) and cetylpiridinium chloride (CPC) were tested with a 10 000 molecular weight cut off (MWCO) membrane. Additionally, membranes of 5000 and 30 000 MWCO were used for CPC. A phenomenological mathematical model has been proposed for the batch MEUF process and checked with the experimental permeate or retentate composition. The model is based on two assumptions: monomeric molecules are not rejected by the membrane and the rejection of micelles is independent of the retentate concentration. The measured micelles rejections for different surfactants and the equivalent molecular weight of the micelles are correlated and they are not significantly affected by the addition of phenol. The estimates of K s for SDS and CPC agree with previously reported values determined by other methods. K s values for CPC, calculated using 5000, 10 000 and 30 000 MWCO membranes, have not been significantly different. K s estimate has allowed to predict the phenol permeate concentration measured in continuous tangential MEUF experiments.

Two-phases model for calcium removal from aqueous solution by polymer enhanced ultrafiltration

Abstract Water softening has been carried out by polymer enhanced ultrafiltration (PEUF). Poly(acrylic acid–maleic anhydride) sodium salt (PAM-Na), a polyelectrolyte containing COO − groups, attracts Ca 2+ and releases Na + ions. When pH is lowered, H + replaces the bound Ca 2+ . Thus, the polyelectrolyte can be regenerated and reused. A model is proposed to explain the observed calcium and sodium rejections at different experimental conditions. The feed solution is considered to be divided into two phases. One phase is occupied by the macro ions and bound counter ions and the other is the remaining solution. The model only needs to determine two equilibrium constants ( K Na,H and K Ca,Na ) which indicate the relative tendencies of Na + versus H + , and Ca 2+ versus Na + to bind the polymer, respectively. K Na,H value was determined by titration and it is pH dependent. K Ca,Na value was calculated from ultrafiltration runs at neutral pH and its value goes well with other ultrafiltration runs when pH is varied.

Characteristics of a common bean landrace (Phaseolus vulgaris L) of great culinary value and selection of a commercial inbred line

The Ganxet bean is a landrace that is greatly appreciated in northeast Spain. For commercial purposes a pure line selection process was undertaken in this landrace. Simultaneously, the Ganxet bean was compared with standard controls for nutritional traits. Seven inbred lines, representative of the variability within the Ganxet germplasm, were studied per se and compared with bean varieties White Kidney, Navy, Faba Asturiana and Tolosa. The Ganxet germplasm was found to contain more protein, less total dietary fibre, more digestible dietary fibre, a higher proportion of seedcoat, more glucose and less starch than the controls. Study of the agronomic, commercial, nutritional and gastronomic aspects of the Ganxet inbred lines showed sufficient variability to allow two inbred lines representative of Ganxet germplasm to be chosen for commercialisation.

Classification of potato cultivars to establish their processing aptitude

BACKGROUND The commercial potato cultivars are diverse not only in their physical characteristics but also in their nutritional compositions and their content of functional compounds (resistant starch, total phenolic content and antioxidant activity), but there is little information about these differences. The aim of this study was to characterise the nutritional value (focusing on carbohydrates and functional compounds) and instrumental parameters of eight potato cultivars consumed in Spain and to determine whether these parameters are useful for classifying the cultivars. RESULTS Significant Pearsons correlations were found due to the common and complex interactions between the constituents of potatoes and their properties (P < 0.05). Principal component analysis revealed the correlations among the physicochemical properties, and the first two principal components explained 56.84% of the variance among the cultivars studied. CONCLUSION The eight cultivars could be classified into three groups: (1) Red Pontiac, Caesar, Kennebec, Agria and Cherie cultivars, (2) Agata and Monalisa cultivars and (3) Spirit cultivar. The results demonstrated that certain nutritional and functional parameters indicated the potential efficacy of different cultivars to satisfy the nutritional needs of consumers, improving the knowledge on the biochemical basis of potato processing to obtain higher-quality products.

Assessing the microstructural and rheological changes induced by food additives on potato puree

The effects of agar, alginate, lecithin and glycerol on the rheological properties of commercial potato puree were investigated and interpreted in terms of starch microstructural changes, and the applicability of the Cox-Merz rule was evaluated. Each additive was applied separately at two concentrations (0.5 and 1%). Microscopic observations revealed more swollen starch aggregations in lecithin and glycerol compared with those of potato puree and agar, consequently affecting the rheological properties of potato puree. All samples exhibited shear thinning non-Newtonian behaviour. Rheological measurements were strongly concentration dependent. At 0.5% concentration, additives exerted decreases in all the rheological properties of potato puree in the order of glycerol>alginate>lecithin>agar, while at 1% concentration, the order changed to glycerol>lecithin>alginate, whereas 1% agar behaved differently, increasing all rheological values. This study also showed that agar and alginate in addition to potato puree could be valuable and advantageous for further technological processes, such as 3D printing.

Effect of the intensity of cooking methods on the nutritional and physical properties of potato tubers

The different intensities of common culinary techniques (boiling, baking and microwaving) produce several changes that reduce the nutritional and physical properties of potatoes. This study evaluated the effect of those cooking methods on the quality of commercial potato tubers (Agata, Kennebec, Caesar and Red Pontiac). The higher weight losses were obtained for baking, but the potato softening depended on the cultivar. Color losses were independent of the intensity of the treatment; however, microwaving promoted a prompt starch gelatinization with respect to the other methods. The resistant starch retention of baking and microwaving was higher than that of boiling, and the maximum retention of bioactive compounds was obtained with the lower core temperature during boiling, as well as higher temperature and shorter baking time and the lower power and longer microwaving time. Principal component analysis revealed significant relationships between the instrumental and functional properties of cooked potatoes.

Viability of the use of polymer-assisted ultrafiltration for continuous water softening

We examined the viability of a continuous metal-removing process using polymer-assisted ultrafiltration. The proposed system has two connected sections at different pH. Each section has an ultrafiltration membrane that filters the aqueous solution and retains the polymer. In the first section, the metal is attached to the polymer. In the second section, the metal is detached. The polymer is recycled, and then recovered, by pumping from the second section into the first section. Preliminary experiments provided sufficient information for simulations of the continuous removal of Ca2+ from water. A poly(acrylic acid–maleic anhydride) sodium salt was selected as the polymer. Ceramic membranes of 5 kDa cut-off were used to filtrate the aqueous solutions. We show that the proposed system continuously removes Ca2+ from water in a satisfactory way.

Characterization of food additive-potato starch complexes by FTIR and X-ray diffraction

Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques were used to study the effect of four food additives, agar, alginate, lecithin and glycerol, at three different concentrations, 0.5, 1 and 1.5%, on the molecular structure of potato puree prepared from commercial potato powder. Vibrational spectra revealed that the amylose-amylopectin skeleton present in the raw potato starch was missing in the potato powder but could be fully recovered upon water addition when the potato puree was prepared. FTIR peaks corresponding to water were clearly present in the potato powder, indicating the important structural role of water molecules in the recovery of the initial molecular conformation. None of the studied puree samples presented a crystalline structure or strong internal order. A comparison of the FTIR and XRD results revealed that the additives exerted some effects, mainly on the long-range order of the starch structure via interacting with and changing -OH and hydrogen bond interactions.