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Fil: Sanchez, Virginia. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Fil: Baeza, Rosa. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Fil: Baeza, Rosa. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industria; Argentina Fil: Chirife, Jorge. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Abstract: Background: Anthocyanins are natural colorants and bioactive compounds widely distributed among vegetables and fruits. Unfortunately, in fruit juices stored at room temperature monomeric anthocyanins easily convert to colourless compounds and subsequently to insoluble brown pigments. OBJECTIVE: The object of present study is to compare the stability of monomeric anthocyanins and colour changes during storage temperature at 38◦13 C of pasteurized cherry juice. METHODS: Colour changes of, pasteurized cherry juice (18.7 ºBrix), concentrate and freeze-dried juice. METHODS: Colour changes of, pasteurized cherry juice (18.7 ºBrix), concentrate (61 ºBrix) and juice freeze-dried with addition of maltodextrin and arabic gum as encapsulating agents, were evaluated by CIELab parameters, a*, b* and, L*. Anthocyanins content was measured by pH-differential method and total phenolics were determined by Folin-Ciocalteu method. The glass transition temperature (Tg) of the freeze-dried matrix was determined. RESULTS: It was found the stability of monomeric anthocyanins and colour retention during storage at 38ºC was significantly superior in the freeze-dried encapsulated juice powder than in liquid cherry juices. CONCLUSIONS: This is attributed to the protective encapsulation of the anthocyanins in the amorphous matrix of maltodex trin/arabic gum of reduced water activity

Fil: Sánchez, Virginia. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Fil: Baeza, Rosa. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Fil: Ciappini, C. Universidad del Centro Educativo Latinoamericano; Argentina Fil: Zamora, María Clara. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Zamora, María Clara. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Fil: Chirife, Jorge. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Abstract: The aim of this work was to compare refractometric index (RI) and Karl Fischer (KF) titration methods for moisture content measurement in honeys. In addition, the effectiveness of two different solvents (methanol (M) and methanol: formamide in the ratio 1:1 (M+F)) was evaluated. Results indicated that RI and KF methods yielded similar results for moisture determination in honeys; mainly, when the solvent M+F was used. This solvent mixture (M+F) also allowed a reduction in titration time which may be a potential advantage for measuring moisture content in honey.

A theoretical model is used to predict the growth of Staphylococcus aureus in a pasteurized meat product kept at ambient temperatures for several hours. For this purpose, the temperature profiles of some cities of Mexico were combined with literature data on the kinetics of S. aureus growth. As shown by theoretical predictions, if the food is kept at ambient temperature, the average daily temperature may not give accurate predictions. Um modelo teórico é utilizado para prever o crescimento de Staphylococcus aureus em um produto à base de carne (pasteurizado) deixado por várias horas à temperatura ambiente. Para isso, perfis de temperatura de algumas cidades do México foram combinados com resultados de literatura sobre a cinética de crescimento de S. aureus. Como demonstrado por previsões teóricas, se o alimento é deixado à temperatura ambiente, a utilização da média diária da temperatura pode não dar previsões exatas.

Fil: Baeza, Rosa. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Fil: Zamora, María Clara. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Fil: Zamora, María Clara. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Mielnicki, Diana. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias. Equipo Interdisciplinario para el Estudio de Procesos Atmosféricos en el Cambio Global; Argentina Fil: Mielnicki, Diana. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Fil: Chirife, Jorge. Pontificia Universidad Católica Argentina. Facultad de Ciencias Agrarias; Argentina Abstract: Non-enzymatic browning predictions in reduced-moisture foods stored over one year at “ambient” temperature, were made using, a) realistic environmental daily (and seasonal) temperature fluctuations, and b) a constant mean temperature. Daily temperature records taken every 6 hours from January 1st to December 31 (1460 temperature data) in four selected cities from Argentina, were used. The predicted amount of browning over one year storage was different depending whether the annual mean temperature (Tam), the monthly mean temperature (Tmm) or the daily temperature fluctuations (Tdf) were used for the predictions. Predicted browning over one year was generally higher when realistic storage conditions (i.e. daily/seasonal temperature fluctuations) rather than mean values (annual or monthly), were used instead.

Se estudió el efecto de diferentes polisacáridos en las propiedades de gelificación y espumadode la β-lg en condiciones de limitada compatibilidad termodinámica (pH > pI). En presencia depolisacáridos no gelificantes (λ-C, XAN y PGA) se observó una disminución en la concentraciónmínima de proteína necesaria para gelificar y una modificación en la dinámica de gelificación (tiempo de gelificación y velocidad de desarrollo del gel). La presencia de polisacáridos afectóprincipalmente la etapa de agregación de la proteína, limitante del proceso de gelificación,obteniéndose en presencia de los PS grandes agregados que permitieron la formación de un gel. Seobservó en general un aumento en la estabilidad térmica de los sistemas mixtos β-lgPS (6%/0,5%)en relación a la β-lg sola. Esto se manifestó en un aumento de las temperaturas de inicio dedesnaturalización y del cambio de entalpía total. Las propiedades de los geles mixtos fueron muydiferentes de acuerdo al polisacárido utilizado. En los geles mixtos β-lg/PGA se observó la mayorvariación en las propiedades micro y macroestructurales con el pH, T, concentración de sólidostotales y relación PS/proteína. Las propiedades de las interfases y espumas en sistemas mixtos estarían controladas por laproteína, debido a su mayor actividad interfacial. El efecto de los polisacáridos en las propiedadesinterfaciales de una proteína es complejo debido a la existencia de por lo menos tres fenómenos: (a) Incompatibilidad entre los biopolímeros (b) fenómenos competitivos o cooperativos (c)interacciones específicas de complejamiento a través de ciertas regiones de la molécula del PS y dela proteína. Al estudiar el efecto de los polisacáridos en monocapas esparcidas de β-lg se observóen general un aumento de la presión superficial y una disminución de la elasticidad y módulodilatacional elástico. El Manucol ester mostró una mayor actividad superficial que los otros PGA (K-0 y K-LVF) dado que produjo el mayor aumento de la presión superficial. En los estudios deadsorción dinámica (tensiómetro de gota) se observó que el Manucol ester debido a su mayoradsorción entre los PGA es el que produce películas con menor estructuración. Esto se observó enlos ensayos dinámicos (G’max más bajo), como en los estudios de monocapas esparcidas donde el Manucol dió los menores valores de módulo dilatacional elástico y de elasticidad. En presencia de la goma xántica los resultados muestran que aún sin penetrar en la interfase,este polisacárido tiene una enorme influencia en la misma, derivada principalmente de un posiblecomplejamiento sobre la proteína en la monocapa y de fenómenos de limitada incompatibilidadtanto en el seno de la solución como en la interfase. Las características reológicas de la películainterfacial tienen una profunda influencia en la estabilidad de las espumas In the present work, the effect of polysaccharides on the properties of β-lg gels and foams wasstudied in conditions of limited thermodynamic compatibility (pH > pI). In the presence of non-gelling polysaccharides (λ-C, XAN and PGA) it was observed a decreasein the critical concentrations for β-lg gelation and a modification in the dynamic of proteingelation (gel time, rate of development of the gel structure). The presence of polysaccharidesgreatly affected the aggregation of β-lg, that constituted the limiting step in the rate of gelationprocess. In the presence of PS large aggregates were formed during heat treatment, that allowedgel formation at low β-lg concentration. In general, the presence of PS increased the thermalstability of B-Ig, as we observed an increase in the onset temperature and enthalpy change of thedenaturation process in the mixed systems. The properties of mixed gels were totally differentaccording to the polysaccharide present in the mixed gel. In the presence of PGA it were observedthe greatest variations in macro and microstructural properties of gels with pH, T, solids contentand PS/β-lg ratio. The properties of β-lg interfaces and foams would be controlled by protein, due to its highestsurface activity. The effect of polysaccharide on β-lg interfacial properties is complex due to theexistence of the following phenomena: (a) incompatibility between biopolymers, (b) cooperative orcompetitive adsorption (c) complexation through specific interactions between polar regions on theprotein and polysaccharide molecules. In the study of spread monolayers, it was observed anincrease in surface pressure and a decrease in elastic dilatational modulus and elasticity. MANshowed the highest increase in surface elasticity, as a consequence of its high surface activity. Inthe dynamic adsorption experiments (drop tensiometer) MAN was the polysaccharide thatproduced the less structurated films in the presence of β-lg due to its higher adsorption at theinterface in comparison with K-0 and K-LVF. This was manifested by low G’max and the lowest G’and elasticity obtained in spread monolayers. The presence of XAN produced a large effect in the film properties, even without presentingsurface activity by itself. This effect would be due to complexation with protein adsorbed at theinterface and limited incompatibility in the bulk solution and in the interface. Rheologicalcharacteristics of the film have a large influence on foam stability. Fil: Baeza, Rosa Isabel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.