Sensory and bio‐chemical preservation of ricotta cheese using natural products

The objective of this study was to evaluate the antimicrobial activity and to study their preserving effect on quality and sensory parameters on flavoured ricotta cheese of Argentinean oregano essential oils (EOs). Criollo essential oil was the most effective agent controlling foodborne bacteria, with MIC values of 1.90 E‐04 mg mL^?1 for S. aureus and Salmonella sp. Ricotta with Cordobes essential oil exhibited the lowest percentage of lactic acid at the end of the storage (0.246%). After 30 days of storage, ricotta flavoured with Cordobes and Criollo EOs had the lowest total count (5.63 × 10³ and 7.80 × 10³ cfu g^?1, respectively). The Pearson's correlation analyses (P ≤ 0.05) showed that sour flavour was negatively related to cheese and casein flavours (r = ?0.46 and ?0.52, respectively). The inclusion of oregano EOs into ricotta cheese improves quality parameters but affects its sensory attributes.     

Antifungal activity of natural and enzymatically-modified flavonoids isolated from citrus species

The antifungal activity of isolated flavonoids from Citrus species, such as naringin, hesperidin and neohesperidin, and enzymatically-modified derivatives of these compounds, was studied on four fungi often found as food contaminants: Aspergillus parasiticus, Aspergillus flavus, Fusarium semitectum and Penicillium expansum. Although all the flavonoids showed antifungal activity, the intensity of this activity depended on the type of fungus and compound used. The hesperetin glucoside laurate strongly inhibited the mycelial growth of P. expansum, while prunin decanoate was the most inhibiting flavonoid for A. flavus, A. parasiticus, and F. semitectum.     

Water vapor absorption and permeability of films based on chitosan and sodium caseinate

The objective of this work was to characterize the moisture sorption and water vapor permeation behavior of edible films made from sodium caseinate and chitosan for future applications as protective layers on foods. Glycerol was used as a plasticizer, and the films were obtained by a casting/solvent‐evaporation method. The moisture sorption kinetics and water vapor permeability (WVP) were investigated. The effect of the addition of glycerol on the WVP characteristics of the films was determined at 25°C with a relative humidity (RH) gradient of 0–64.5% (internal to external). Experimental data were fitted with an exponential function with two fitting parameters. WVP increased with increasing glycerol content in both films, chitosan samples being much more permeable than caseinate ones at any glycerol content. WVPs of sodium caseinate, chitosan, and chitosan/caseinate films with 28 wt % glycerol were also determined for two RH gradients, 0 to 64.5% and 100 to 64.5%, higher WVPs being measured at higher RHs. The moisture sorption kinetics of caseinate films prepared with various glycerol contents were determined by the placement of the films in environments conditioned at 20°C and 75% RH. Peleg's equation and Fick's second law were used to predict the moisture sorption behavior over the entire time period. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Morphology of rubber‐modified vinyl ester resins cured at different temperatures

The morphologies of styrene (St) crosslinked divinylester resins (DVER) modified with elastomers were analyzed. The primary focus of this study was on the effect of the molecular weight of the resins, the reactivity of the elastomeric modifiers, and the temperature of curing. All of these variables have a strong influence on both the miscibility and the viscosity of the system, affecting the phase‐separation process that takes place in the unreacted and the reacting mixture. The selected liquid rubbers were carboxyl‐terminated poly(butadiene‐co‐acrylonitrile) (CTBN), a common toughening agent for epoxy resins, and an almost unreactive rubber with the DVER; and St comonomers and vinyl‐terminated poly(butadiene‐co‐acrylonitrile (VTBN), a reactive rubber. Different morphologies potentially appear in these systems: structures formed by DVER–St nodules surrounded by elastomer and spanning the whole sample; dual cocontinuous micron‐size domains formed by elastomer‐rich or resin‐rich domains; and a continuous DVER–St‐rich phase with included complex nodular domains. These microstructures can be varied by just changing the nature and concentration of the elastomer, the molecular weight of the resin, or the curing temperature. The appearance of these morphologies is discussed as a function of the above variables. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 274–283, 2003     

Bibliometric study on food science and technology: Scientific production in Iberian-American countries (1991-2000)

This study presents a bibliometric analysis of the scientific production in the food science and technology (FST) field for the period 1991-2000, in Iberian-America (IA). Eight selected IA countries contributed 97.6% of the IA production and accounted for a 6.6% of the world production. The most frequent document type is journal article published in English. Retrieved records display characteristical authorship patterns and preferred subject areas. Spain, Brazil, Mexico, Argentina and Portugal determine the IA pattern of sources of publication. The fifty top ranked journals, 80% of which were indexed by the SCIE, encompass two-thirds of the IA production. This revised version was published online in August 2006 with corrections to the Cover Date.     

Tungstophosphoric and Molybdophosphoric Acids Supported on Zirconia as Esterification Catalysts

The preparation and characterization of supported acid catalysts, based on tungstophosphoric (TPA) or molybdophosphoric (MPA) acids using ZrO₂ as support, are presented. ZrO₂ was prepared from zirconium oxychloride aqueous solutions by adding ammonium hydroxide solution. Two different techniques were used to obtain the catalysts, equilibrium adsorption and incipient wetness impregnation. The catalyst characterization allowed us to determine the species present on the carrier surface and their acidic properties. The catalytic activity for esterification of acetic acid with isoamyl alcohol of the zirconia-supported TPA catalysts was greater than that corresponding to those based on MPA. Moreover, in the preparative conditions used, the incipient wetness impregnation led to heteropolyacids supported on ZrO₂ with better catalytic performance.     

Aging study of linseed oil resin/styrene thermosets and their composites with wood flour

The changes in the properties of new crosslinked polymers based on renewable resources and their derived composites have been monitored as a function of time; this knowledge being necessary to estimate their behavior in final applications. Rigid thermoset polymers prepared by free radical polymerization of resins obtained from linseed oil and styrene and composites reinforced with wood flour were evaluated in different environmental conditions and at different times after their preparation. The action of atmospheric oxygen on the unsaturated groups in fatty acids produces chemical changes in these polymers, which affect the properties of the cured materials. These changes were analyzed using Fourier transform infrared spectroscopy, dynamic mechanical analysis and mechanical testing. An increase in the modulus with time was observed during exposure of the samples to dry conditions, or humid environments (60% relative humidity), with or without UV irradiation. The reaction with oxygen appears to be accelerated when the materials are subjected to UV irradiation, showing a large effect on the glass transition temperature. Copyright © 2007 Society of Chemical Industry     

Naturally suppressed apoptosis prevents follicular atresia and oocyte reserve decline in the adult ovary of Lagostomus maximus (Rodentia, Caviomorpha)

It has been widely accepted that mammalian females are born with a non-renewing, finite pool of oocytes that will be continuously cleared by atresia, with only a small proportion of them reaching ovulation. Apoptosis regulates this mass germ cell death, especially through the balance between pro- and anti-apoptotic proteins encoded by the BCL-2 gene family. The caviomorph rodent Lagostomus maximus, the South American plains viscacha, displays the highest ovulation rate known for a mammal releasing 400-800 eggs per cycle. We tested the hypothesis that in L. maximus massive polyovulation is a consequence of reduced apoptosis resulting in suppressed follicular atresia. We found that anti-apoptotic BCL-2 gene is markedly expressed in all kind of follicles from primordial to fully mature antral stages in the adult ovary of L. maximus. On the other hand, pro-apoptotic BAX gene showed weak signals or was undetectable by immunohistochemical examination. Western blot against both proteins confirmed immunohistochemical results. Screening for DNA fragmentation by TUNEL assay was conspicuously negative in ovaries from both pregnant and non-pregnant females. In addition, alpha-oestrogen receptor also showed an enhanced expression from primordial stage to fully mature antral follicles. Our results show that natural preferential expression of BCL-2 and restricted BAX expression greatly suppresses apoptosis in the ovary of L. maximus. This prevents the decline of the oocyte reserve by abolishing follicular atresia and enables the highest ovulation rate known for a mammal, 400-800 or more eggs per cycle.     

Composition and potential contribution of iron, calcium and zinc of bread and pasta made with wheat and amaranth flours

Amaranth, a traditional american crop that is nowadays given renewed importance, has good food potential value. The minerals contributed by the grain are quantitatively important. However, as the flour is obtained by total grinding of the grain, this process leads to the presence of anti-nutritional components, such as fitates, and therefore, the evaluation of the actual availability of the minerals of nutritional interest becomes necessary. The process of bread fermentation, plus the addition of fitases and enhancers of mineral availability such as citric and ascorbic acid, might improve mineral bioavailability. The objective of this work was to assess protein, ash, lipids and total dietary fiber content and evaluate the concentration and dialyzability of Fe, Zn and Ca (as mineral bioavailability indicator) in bread and pasta 100% wheat, and bread and pasta obtained by replacing 20% wheat flour (WF) with whole amaranth flour (WAF). Ascorbic acid (AA), citric acid (CA) and fitase were used as mineral bioavailability enhancers. The potential contribution of each mineral (PC) was calculated as each mineral concentration times its dialyzability. In 80:20 bread an increase of total dietary fiber and minerals, compared to 100% wheat products was observed. A maximum FePC in 80:20 bread was obtained with CA and fitase (0.55mg%). In pasta, the maximum effect was observed with CA (0.07 mg%). The CaPC was maximum in 80:20 pasta with CA (16.72 mg%). The greatest ZnPC was found in 80:20 bread with CA and fitase (0.40 mg%). The introduction of the WAF in fermented baked products with addition of CA and fitase allows to obtain nutritional advantages.