Jorge R. Wagner

Effect of calcium salts and surfactant concentration on the stability of water-in-oil (w/o) emulsions prepared with polyglycerol polyricinoleate.

The objective of this work was to obtain water-in-oil (w/o) emulsions with polyglycerol polyricinoleate (PGPR) as emulsifier and to study the effect of the addition of calcium in the dispersed aqueous phase on the stability of these systems. Emulsions were formulated with 0.2, 0.5 and 1.0% w/w PGPR and 10% w/w water containing calcium chloride at varied concentrations or other salts (calcium lactate or carbonate; sodium, magnesium or potassium chloride). The stability of these systems was studied with a vertical scan analyzer during 15 days; coalescence and sedimentation were observed as simultaneous destabilization processes. The increase of PGPR concentration and/or calcium chloride content gave more stable emulsions. The stabilizing effect of calcium salt was attributed to the diminution of the water droplets size, the decrease of the attractive force between water droplets and the increase of the adsorption density of the emulsifier. The viscoelastic parameters of the interfacial film were decreased with increasing calcium and PGPR concentrations. Calcium chloride produced a higher increase of stability than calcium salts with lower dissociation degree. The presence of any assayed salt in the aqueous phase also allowed the stabilization of w/o emulsions with higher water contents.

Migration study of carvacrol as a natural antioxidant in high-density polyethylene for active packaging

The migration behaviour of low molecular weight compounds from food packaging materials is one of the key issues in assessing the possibility of use in such applications. The aim of this work was to study the migration of carvacrol (1% and 2% w/w) when added to high-density polyethylene. All materials were exposed to the food simulants olive oil and distilled water separately at 40°C and 25°C. Three significant variables influencing the migration process were considered: incubation temperatures, the initial concentration of antioxidant, and the type of simulant (oil and aqueous). The amount of carvacrol migrating to olive oil was significantly higher than in water because of the higher solubility of this antioxidant in oil. Experimental results agreed reasonably well with those obtained by the application of a simple model derived from Ficks Second Law. Carvacrol could therefore be used in active packaging formulations as its release from the polymer matrix can be controlled.

Thermal behavior of soy protein fractions depending on their preparation methods, individual interactions, and storage conditions.

Different soy protein isolates (SPI) and whey soy protein (WSP) samples were obtained from fresh and stored soybean flour. Some samples were subjected to a long, cold storage. DSC thermograms of SPI showed the two characteristic endotherms, corresponding to denaturation of β-conglycinin and glycinin. Low value of denaturation enthalpy and high glycinin denaturation temperature were related to a reduction of protein solubility of SPI. DSC thermograms of WSP also showed two characteristic endotherms, corresponding to Kunitz trypsin inhibitor and lectin. The methods and conditions of preparation and storage of WSP samples were factors that modified their thermal behavior. Some SPI-WSP mixtures (1:1) exhibited more complex thermograms and higher denaturation temperatures. Thermograms of SPI-denatured WSP mixtures showed that the thermal stabilization of soybean storage proteins was attributed to protein-protein interactions. The differences in the thermal behavior of single or mixed SPI and WSP could not be explained on the basis of mineral content.

Indigenous filamentous fungi on the surface of Argentinean dry fermented sausages produced in Colonia Caroya (Córdoba)

Some producers of dry fermented sausages use fungal starter cultures with the aim to achieve a desirable surface appearance and avoid the growth of mycotoxigenic fungi. These commercial cultures are mainly composed of Penicillium nalgiovense biotype 6. In contrast, in the case of producers who do not use starters, sausages are spontaneously colonized by the house mycobiota, which generally consists of heterogeneous molds corresponding to different genera and species. In this work, the surface mycobiota of dry fermented sausages produced in Colonia Caroya (Córdoba, Argentina) was determined in both summer and winter seasons. All the sausages sampled had been made without the use of surface fungal starters. In the 57 sausages analyzed in the two winter seasons studied (2010 and 2012), we found a total of 95 isolates of filamentous fungi belonging to six genera (Penicillium, Aspergillus, Mucor, Cladosporium, Scopulariopsis and Eurotium) and ten fungal species, whereas in the 36 sausages analyzed in the two summer seasons studied (2011 and 2012), we found 89 isolates belonging to five genera (Penicillium, Aspergillus, Mucor, Cladosporium and Geotrichum) and ten fungal species. Although 16 different species were found in both winter and summer seasons, only 2 of them predominated completely. P. nalgiovense was found in almost 100% of the sausages analyzed, where biotype 4 was the most frequent. This species gives a whitish gray coloration to the sausages. Considering that the factories sampled do not use fungal starter cultures, this predominance is very interesting since mycotoxin production by this fungus has not been reported. Aspergillus ochraceus was isolated with a frequency of 80-90% in the summer seasons, but in none of the winter samples. The presence of this fungus in sausages produced in the summer was attributed to the high environmental temperatures and the uncontrolled temperature in the ripening rooms during the night. In all cases, A. ochraceus was responsible for the undesirable yellowish gold color of the casing. This fungus thus causes significant economic losses to the producers of Colonia Caroya during the months of high temperatures.

β-Glucan content and hydration properties of filamentous fungi

The aim of this work was to isolate and identify filamentous fungi from several sources to study the dietary fiber and β-glucan content. The fungal hydration properties such as water absorption and water holding capacities were also evaluated. Total dietary fiber of isolates exhibited a noticeable variability from 16 to 53% and the highest values were obtained for the genera Paecilomyces and Penicillium, a fact consistent with a higher content of β-glucans (24 and 17%, respectively), higher than previously reported for Basidiomycetes and yeast. We observed a large decrease (75%) in the water holding capacity when the mycelia were dried. Isolates of filamentous fungi with greater water holding capacity also exhibited greater absorption capacity. Paecilomyces variotii and Penicillium nalgiovense had the best hydration properties. Our results contribute to the search for new unconventional ingredients providing a high protein and β-glucans content. The addition of these dried mycelia could change the hydration properties in the food system.

Acid-Induced Aggregation and Gelation of Sodium Caseinate-Guar Gum Mixtures

The aim of this work was to study the formation of bovine sodium caseinate (NaCAS) acid gels induced by addition of glucono-δ-lactone (GDL) in the presence of guar gum (GG). At low biopolymer’s concentrations, a one-phase system was observed, whereas at higher mixture concentrations two-phase systems were formed. Aggregation (at low NaCAS concentrations) and gelation (at high NaCAS concentrations) processes were analyzed through the use of full and fractional factorial experiment designs, using turbidimetric and rheological techniques. Finally, the gel images were obtained by confocal laser scanning microscopy and the images were analyzed. Results showed that at low NaCAS concentrations, the presence of GG affects the pH at which aggregation begins but was not significant for the time at which aggregation begins. On the other hand, at high NaCAS concentrations, the concentration of GG only affected significantly the elastic character of acid gels. As polysaccharide concentration increases, the gels obtained were weaker and with larger pores. Also, the formation of NaCAS droplet-shaped structures at certain biopolymer ratio was observed. The presence of GG affects both the rate of gelation and phase separation, which, in turn, determine the type of gel microstructure. Phase separation seems to occur prior to protein gelation because the protein gel network is discontinued, hindering the gel compactness and reducing gel strength. In summary, GG modifies NaCAS stabilization (self-association and phase separation) and the viscoelasticity and microstructure of NaCAS acid gels. The control of such processes and properties would allow obtaining mixture gels with different textures.

The formation of non-soluble complexes between polyethyleneimine–anions and their potential use to isolate enzymes

The aqueous solution behavior of polyethyleneimine (a synthetic cationic polymer) in the presence of anions with two or more electrical charges (citrate, phosphate, sulphate, malate, malonate and succinate) was studied by means of turbidimetry and light scattering. Polyethyleneimine forms non-soluble complexes with these anions, which behave as a pseudo-polyampholyte with an isoelectrical pH value dependent on the type of anion. The effect of pH, polymer concentration and ionic strength on the non-soluble complexes formation was examined. The complex precipitation pH range was between 3.5 and 8.0 and also depended on the type of anion. The complex formation was inhibited by the ionic strength in agreement with the electrostatic mechanism of the non-soluble complex formation. Model proteins with isoelectric pH from 1 to 10 were assayed in orden to be precipitated by these complexes. It was found that the non-soluble polyethyleneimine-anion complexes have the property to precipitate macromolecules charged with an opposite electrical charge.

Relación entre la Composición y la Actividad Antitríptica de Sueros de Soja y Tofu y Comportamiento Térmico de sus Proteínas Aisladas

The differences in composition and antitryptic activity of soy whey and tofu whey, in relation to thermal behavior of its proteins, were studied. Soy whey was obtained from an aqueous extract of defatted soybean flour and tofu whey is a liquid industrial residue from the tofu production. Both byproducts contain carbohydrates as main components, proteins, non-protein nitrogen and salts. Tofu whey presented lower values of density, dry extract and proteins, while the antitryptic activity was three times lower than in soy whey. Differential scanning calorimetric studies of soy whey proteins showed the endotherms of lectin and antitryptic factors of Kunitz and Bowman-Birk, while the thermogram corresponding to tofu whey proteins showed only the last factor. The differences between wheys can be explained by the differences in the manufacturing processes.

Acid-Induced Aggregation and Gelation of Bovine Sodium Caseinate-Carboxymethylcellulose Mixtures

Maria Eugenia Hidalgo1, Bibiana D. Riquelme1,2, Estela M. Alvarez1, Jorge R. Wagner3 and Patricia H. Risso1,2,4 1Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario 2Instituto de Fisica Rosario (IFIR), CONICET-UNR, (2000), Rosario, 3Departamento de Ciencia y Tecnologia, 4Facultad de Ciencias Veterinarias,Universidad Nacional de Rosario, Rosario Universidad Nacional de Quilmes, Buenos Aires, Argentina

Impact of Sample Aging on Freeze-Thaw Stability of Oil-in-Water Emulsions Prepared with Soy Protein Isolates

The freeze-thaw stability of oil-in-water emulsions prepared with unheated and heated aqueous dispersions of fresh and stored soy protein isolates was evaluated in the absence and presence of glucose or sorbitol (0.75–15.0% w/w). Sample aging had a negative impact of freeze-thaw stability. The cryoprotectant addition enhanced the freeze-thaw stability, but at low concentrations emulsions prepared with unheated soy protein isolates showed better response to freeze-thawing. Nevertheless, at the highest cryoprotectant concentration, a total stabilization was evidenced for all emulsions. The results of this article indicated that the cryoprotectants act on proteins at interfacial level.