Study of Pulsed Light-Induced Damage on Saccharomyces cerevisiae in Apple Juice by Flow Cytometry and Transmission Electron Microscopy

This work analyzed the pulsed light (PL) (0.0-71.6 J/cm2)-induced damage on Saccharomyces cerevisiae KE162 cells in peptone water (pH 3.5 or 5.6) and apple juice (pH 3.5) by applying flow cytometry (FCM) and transmission electronic microscopy. Cells were labeled with fluorescein diacetate (FDA) for detecting membrane integrity and esterase activity and with propidium iodide (PI) for monitoring membrane integrity. S. cerevisiae inactivation curves reached 6-7 log reductions (peptone water systems) and 3.9 log reductions (apple juice) after 60 s (71.6 J/cm2) of PL exposure. FCM revealed the same damage pattern (although at different doses) in all media: at low doses, there was an increase in population in PI+-FDA+ quadrant, while at high doses, most of the population was located at quadrant PI+-FDA-, indicating that PL provoked rupture of the cytoplasm membrane allowing PI to penetrate cells and there was progressive loss of esterase activity. Comparison of conventional culture technique with FCM revealed the occurrence of certain cell subpopulations in peptone water with pH 3.5 which were stressed and lost their ability to grow in agar but still showed metabolic activity. Transmission electron microphotographs of PL-treated cells clearly indicated that various cell structures other than plasma membranes were altered and/or destroyed in a different degree depending on exposure time and type of medium.Fil: Ferrario, Mariana Inés. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Ministerio de Educación, Cultura, Ciencia y Tecnología. Secretaria de Gobierno de Ciencia Tecnología e Innovación Productiva. Agencia Nacional de Promoción Científica y Tecnológica. Fondo Argentino Sectorial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; ArgentinaFil: Guerrero, Sandra N.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Alzamora, Stella Maris. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentin

Relationships between rheological properties, texture and structure of apple (Granny Smith var.) affected by blanching and/or osmotic dehydration

The objective of this work was to evaluate and correlate rheological properties (small-scale dynamic oscil- latory and creep/recovery measurements and large-scale compression force-deformation testing), texture (sensory evaluation by trained panel) and structure (optical and transmission electronic microscopy observations) of apples osmotically dehydrated to water activity (aw) 0.97 with glucose, with or without previous blanching. All apple samples showed a solid behavior (G′ > G′′) dominating the viscoelastic response, but both dynamic moduli were reduced due to processing. The instantaneous elastic compliance (J0) and the retarded compliances (J1 and J2) increased for treated tissues and the steady-state viscosity (ηN) was approximately 15% to 29% of the value of fresh apple. In general, compression parameters decreased for all treated tissues. Changes in structural features were mainly evidenced in heated samples. Partial least squares regres- sion analysis regression models revealed that texture could be well predicted by rheological properties (compression and creep parameters). Juiciness, crispness and sensory hardness were negatively correlated to J0, J1 and J2, and ηN was negatively correlated to sensory fracturability. Some mechanical parameters (fracturability, hardness 2, area 2, modulus of deformability and cohesiveness) were positively related to sensory fracturability, crispness and sensory hardness; and juiciness was negatively correlated to hardness. Compression and creep parameters showed ability to evidence structure differences (rupture of membranes, swelling of cells and degradation of cell walls) and to explain texture of treated apples.Fil: Garcia Loredo, Analia Belen. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Industrias; Argentina;Fil: Guerrero, Sandra N.. Universidad de Buenos Aires. Prog.id Fuentes Altern.de M.primas y Energia(p). Departamento de Industrias; Argentina;Fil: Gómez, Paula Luisina. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Industrias; Argentina;Fil: Alzamora, Stella Maris. Universidad de Buenos Aires. Prog.id Fuentes Altern.de M.primas y Energia(p). Departamento de Industrias; Argentina

Technology, Science, and Culture: A Global Vision

The aim of the Workshop: Technology, Science, and Culture - A Global Vision is to create a discussion forum on research related to the fields of Water Science, Food Science, Intelligent Systems, Molecular Biomedicine, and Creation and Theories of Culture. The workshop is intended to discuss research on current problems, relevant methodologies, and future research streams and to create an environment for the exchange of ideas and collaboration among participants

The use of pulsed light in a hurdle preservation strategy

The growing consumer demand for safe foods with improved quality has stimulated interest in alternative technologies for preservation. Among these technologies, pulsed light (PL) is a rapid, low-energy technique which imposes low thermal damage to a product while inactivating food microorganisms. It is however limited to treatments of very transparent liquid foods or surface treatments for foods and food packages, though it can be combined with other hurdles to increase its effectiveness. This chapter provides an up-to-date summary of published findings on the efficacy of PL technology combined with other traditional and emerging hurdles used in a wide variety of foods. Application challenges and research trends in the near future are also considered. It is concluded that much progress has been achieved in this field in recent years. These achievements paved the way for the future industrial-scale application of PL combined with other technologies in the preservation of foods.Fil: Guerrero, Sandra N.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Alzamora, Stella Maris. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Ferrario, Mariana Inés. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Químicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Químicos; Argentin

Inactivation kinetics of some microorganisms in apple, melon, orange and strawberry juices by high intensity light pulses

The suitability of some models was analyzed to characterize the Pulsed Light (PL) inactivation kinetics for Escherichia coli ATCC 35218, Listeria innocua ATCC 33090, Salmonella Enteritidis MA44 and Saccharomyces cerevisiae KE162 in commercial juices and fresh squeezed juices. A negative relationship was found between the absorbance of juices and PL effectiveness. PL treatment (2.4–71.6 J/cm2 ) was ineffective in natural strawberry and orange juices. In general, inactivation curves exhibited a marked upward concavity, reaching after 60 s-PL treatment to 0.3–6.9 log-reduction cycles. Nonlinear semilogarithmic survival curves were fitted by conceptually different models: the Weibull model, the biphasic model and a modified version of the Coroller model. Biphasic and Weibull models compared to the modified Coroller model allowed a better fit and more accurate estimation of parameters. A multivariate approach to data analysis by principal components (PCA) showed relevant spatial relationships among estimated model parameters, revealing PL treatment efficacy in the different juices.Fil: Ferrario, Mariana Inés. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Ciencia, Tecnología e Innovación Productiva. Agencia Nacional de Promoción Cientifíca y Tecnológica; ArgentinaFil: Alzamora, Stella Maris. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Guerrero, Sandra N.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Mild thermal process combined with vanillin plus citral to help shorten the inactivation time for Listeria innocua in orange juice

The response of Listeria innocua (surrogate for Listeria monocytogenes) to combined treatments involving moderate temperatures (57 to 61 °C) and the addition of different levels of citral (0 to 75 ppm) was assessed to obtain a minimally processed orange juice. The presence of citral notoriously increased the bactericidal effect of mild heating treatment. This effect did not depend on the amount of added citral at all assayed temperatures. In a second stage, combinations of two natural antimicrobials (vanillin and citral) were assessed in order to find the most effective inactivation treatment in orange juice. Vanillin (900-1,100 ppm) and citral (25 ppm) combined with mild heating treatment (52 or 57 °C) were tested against L. innocua in orange juice. The addition of 900 ppm vanillin and 25 ppm citral halved or more the time required to achieve five logarithmic cycles of reduction at both temperatures with respect to thermal treatment without antimicrobial addition. The increase in the maximum growth rate calculated from the modified Gompertz model properly correlated with the increasing vanillin level for a given citral concentration. Complementary information was obtained from successfully fitting a Weibullian model to the nonlinear semilogarithmic survival curves: The addition of vanillin and citral significantly increased the bactericidal effect of mild thermal treatment, changing the distribution of inactivation times and obtaining narrower frequency shapes with lower variance and mode values. The combination of vanillin and citral with mild heating treatment resulted in an innovative alternative to minimize detrimental effects caused by thermal processing of fruit juices. In addition, a consumer panel evaluated them with an acceptable overall pleasantness.Fil: Char, Cielo Dolores. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Guerrero, Sandra N.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alzamora, Stella Maris. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Impact of calcium on viscoelastic properties of fortified apple tissue

The objective of this study was to analyze the linear viscoelastic behavior of calcium impregnated apples by creep and sinusoidal tests and to correlate the changes in rheological parameters with some structure features. The effect of different Ca concentrations of impregnation solutions (0, 0.1 and 0.53%, w/w), system pressure (vacuum or atmospheric) and process time was studied. All samples showed a viscoelastic solid behavior with the storage modulus (G′) dominating the viscoelastic response. Treated apple samples with or without calcium showed a pronounced decrease in G′as compared with fresh tissue. Instantaneous compliance (J0), decay compliances (J1 and J2) and fluidity significantly increased after treatments, while retardation times were approximately constant. Impregnation at high calcium concentrations provoked severe folding of walls and/or a general inner disruption of cells with plasmolysis and membrane breakage in a different way according to the pressure applied and the treatment time, explaining the viscoelastic behavior. Changes in compliances and storage modulus values were significantly lower for apples treated under vacuum than when the treatment was performed at atmospheric pressure, suggesting that vacuum impregnation is an effective methodology to fortify apple tissue avoiding serious damage in viscoelastic properties and presumably in texture.Fil: Salvatori, Daniela Marisol. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Doctorovich, Romina S.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; ArgentinaFil: Alzamora, Stella Maris. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Study of the inactivation of spoilage microorganisms in apple juice by pulsed light and ultrasound

The aim of this study was to evaluate the effect of ultrasound (US) (600W, 20kHz and 95.2μm wave amplitude; 10 or 30min at 20, 30 or 44±1°C) and pulsed light (PL) (Xenon l& 3 pulses/s; 0.1m distance; 2.4J/cm2-71.6J/cm2; initial temperature 2, 30, 44±1°C) on the inactivation of Alicyclobacillus acidoterrestris ATCC 49025 spores and Saccharomyces cerevisiae KE162 inoculated in commercial (pH: 3.5; 12.5°Brix) and natural squeezed (pH: 3.4; 11.8°Brix) apple juices. Inactivation depended on treatment time, temperature, microorganism and matrix. Combination of these technologies led up to 3.0 log cycles of spore reduction in commercial apple juice and 2.0 log cycles in natural juice; while for S.cerevisiae, 6.4 and 5.8 log cycles of reduction were achieved in commercial and natural apple juices, respectively. In natural apple juice, the combination of US+60s PL at the highest temperature build-up (56±1°C) was the most effective treatment for both strains. In commercial apple juice, US did not contribute to further inactivation of spores, but significantly reduced yeast population. Certain combinations of US+PL kept on good microbial stability under refrigerated conditions for 15 days.Fil: Ferrario, Mariana Inés. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Ciencia. Tecnología e Innovación Productiva. Agencia Nacional de Promoción Cientifíca y Tecnológica; ArgentinaFil: Alzamora, Stella Maris. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Guerrero, Sandra N.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Modeling the drying of a deep bed of Ilex paraguariensis in an industrial belt conveyor dryer

The evolution of temperature and moisture content of leaves and twigs of yerba maté on different levels of a through-flow dryer was investigated by modeling heat and mass transfer using the finite difference method. To validate the model, the temperature and moisture profiles were used to estimate chlorophyll losses. Great variations were obtained in moisture, temperature, and chlorophyll content at different levels of the bed. Leaf temperature quickly increased in the former nodes, and it then increased slowly until it reached air temperature. In the twigs, the temperature increase was slow and the air temperature was never reached.Fil: Schmalko, M. E.. Universidad Nacional de Misiones; ArgentinaFil: Peralta, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Alzamora, Stella Maris. Universidad de Buenos Aires; Argentin

Hurdle Technology in Fruit Processing

Conventional preservation technologies such as thermal processing ensure the safety and shelf life of fruit-derived products but can result in the loss of physicochemical and nutritional quality attributes. This review examines innovative hurdle techniques to obtain novel fruit products with fresh-like characteristics. The multifactorial processes were based on emerging preservation factors in combination or combining emerging factors with traditional ones. Selected practical examples of fruit processing using UV light, pulsed light (PL), ultrasound (US), and high hydrostatic pressure (HHP) are presented. Some issues of key importance for the design of combination processes are also addressed.Fil: Gómez, Paula Luisina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Welti Chanes, Jorge. Instituto Tecnologico y de Estudios Superiores de Monterrey; MéxicoFil: Alzamora, Stella Maris. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin