Wheat Bran Pretreatment by Room Temperature Ionic Liquid-Water Mixture: Optimization of Process Conditions by PLS-Surface Response Design

International audienceRoom Temperature Ionic Liquids (RTILs) pretreatment are well-recognized to improve the enzymatic production of platform molecules such as sugar monomers from lignocellulosic biomass (LCB). The conditions for implementing this key step requires henceforth optimization to reach a satisfactory compromise between energy saving, required RTIL amount and hydrolysis yields. Wheat bran (WB) and destarched wheat bran (DWB), which constitute relevant sugar-rich feedstocks were selected for this present study. Pretreatments of these two distinct biomasses with various 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc])-water mixtures prior to hydrolysis catalyzed by hemicellulolytic cocktail (Cellic CTec2) were finely investigated. The main operating conditions such as pretreatment temperature (25–150°C), time (40–180 min), WB and DWB loading (2–5% w/v) and concentration of [C2mim][OAc] in water [10–100% (v/v)] were screened through glucose and xylose yields and then optimized through a Partial Least Square (PLS)—Second Order Design. In an innovative way, the PLS results showed that the four factors and their interactions could be well-fitted by a second-order model (p < 0.05). The quadratic PLS models were used to predict optimal pretreatment conditions. Thus, maximum glucose (83%) and xylose (95%) yields were obtained from enzymatic hydrolysis of WB pretreated at 150°C for 40 min with 10% of [C2mim][OAc] in water and 5% of WB loading. For DWB, maximum glucose (100%) and xylose (57%) yields were achieved for pretreatment temperatures of 150°C and 25°C, respectively. The required duration was still 40 min, with 20% of [C2mim][OAc] in water and a 5% DWB loading. Then, Multiple Response Optimization (MRO) performed by Nelder-Mead Simplex Method displayed sugar yields similar to those obtained by individual PLS optimization. This complete statistical study confirmed that the established models were appropriate to predict the sugar yields achieved after different pretreatment conditions from WB and DWB biomasses. Finally, Scanning Electron microscopy (SEM) studies allowed us to establish clearer link between structural changes induced by pretreatment and the best enzymatic performances obtained

A statistical approach for assessing the heterogeneity of Hass avocados subjected to different postharvest abiotic stresses

C. Fuentealba, R. Pedreschi, I. Hernández, and J. Saavedra. 2016. A statistical approach for assessing the heterogeneity of Hass avocados subjected to different postharvest abiotic stresses. Cien. Inv. Agr. 43(3):356-365. Hass avocado (Persea americana Mill.) is marketed worldwide. Due to its complex physiology, a wide variability in postharvest ripening can be observed, i.e., heterogeneity in the number of days to reach edible ripeness. There is a need for a simple and objective method for evaluating the efficacy of postharvest treatments in the reduction of this postharvest ripening heterogeneity given the high demand of import countries for consistent quality and product homogeneity. Therefore, the aim of this study was to compare the appropriateness of different statistical methods used to evaluate this ripening heterogeneity. Bartlett’s, Cochran’s, Levene’s homogeneity of variance tests were applied to different treatments. In addition, a multiple comparisons test of squared residuals (parametric and non-parametric) was applied. The classical statistical approaches (Bartlett’s, Cochran’s and Levene’s tests) showed similar results as the multiple comparisons test of squared residuals only when one treatment and large sample sizes (n=100) were evaluated. All statistical methods were able to detect significant differences in ripening heterogeneity from growers and storage conditions. The multiple comparisons test of squared residuals was the most suitable method for multifactorial experiments and small sample sizes (n=30) compared to the classical approaches, which increased the probability of obtaining false positives or a type I error.C. Fuentealba, R. Pedreschi, I. Hernández y J. Saavedra. 2016. Enfoque estadístico para evaluar la heterogeneidad de paltas Hass, sometidas a diferentes estreses abióticos en postcosecha. Cien. Inv. Agr. 43(3):356-365. La palta Hass (Persea americana Mill.) es mundialmente comercializada y los países importadores demandan productos homogéneos y de calidad consistente. Sin embargo, debido a la compleja fisiología del fruto se observa una amplia variabilidad durante su maduración postcosecha, es decir, heterogeneidad en los días para alcanzar la madurez comercial. Por tal motivo, es necesario evaluar la eficacia de tratamientos postcosecha en la reducción de la heterogeneidad en la maduración a través de un método objetivo y simple. El objetivo de este estudio fue comparar diferentes métodos estadísticos para la evaluación de la heterogeneidad en la maduración. A los diferentes tratamientos se aplicaron pruebas de homogeneidad de varianza como Bartlett, Cochran, Levene. Además, se realizó una comparación múltiple a residuales cuadráticos (paramétricos y no paramétricos). Las pruebas estadísticas clásicas (Bartlett, Cochran y Levene) mostraron resultados similares a la comparación múltiple de residuos cuadráticos sólo cuando el tamaño de muestra es grande (n=100) y se realiza sólo un tratamiento. Todos los métodos estadísticos fueron capaces de detectar diferencias significativas en la heterogeneidad en la maduración entre productores y diferentes condiciones de almacenamiento. La comparación múltiple de residuos cuadráticos fue el método más adecuado para experimentos multifactoriales y de tamaños de muestras más pequeños (n=30) en comparación con las pruebas clásicas, donde éstas últimas conducen a un aumento en la probabilidad de obtener falsos positivos o error tipo I

Influencia de un pretratamiento osmótico sobre la deshidratación por aire caliente de manzana granny smith

In this paper we study the influence of an osmotic pretreatment (DO) at three concentrations (30, 40 and 50 º Brix) on the implementation of a process of dehydration of apple by hot air (SAC) at two temperatures (55 and 60 º C ). It was found that higher concentrations in the osmotic dehydration pretreatment occurred nondimensional moisture curves more pronounced. The drying rate was higher for apples pretreated compared with that of fresh product, distinguishing a short induction phase only in SAC, and in both types of treatment (OD + SAC) a second stage imperceptible speed and a clear third stage of decreasing drying rate I and II. The drying rate was modeled using the equations of Newton and Page. The best goodness of fit was obtained by Page model, follow by Newton and HendersonPabis. The two performed temperatures levels (55 º C y 65 º C) were significative, since the meaningful interaction with osmotic dehydration. The better process condition was DO 50º Brix and SAC 65 º C.En este trabajo se estudió la influencia de un pretratamiento osmótico (DO) a tres concentraciones (30, 40 y 50 º Brix) sobre un proceso de deshidratación de manzana por aire caliente (SAC) a dos temperaturas (55 y 65 º C). Las velocidades de deshidratación fueron mayores para las manzanas pretratadas en comparación al producto fresco, distinguiéndose una corta primera etapa de inducción solo en SAC, en ambos tipos de tratamiento (DO+SAC) una imperceptible segunda etapa de velocidad constante, y una clara tercera etapa de velocidad de deshidratación decreciente I y II. La velocidad de deshidratación se modeló utilizando las ecuaciones de Newton, Page y Henderson -Pabis. De estos modelos el que mejor explica el proceso fue la ecuación de Page, seguida por Newton y Henderson -Pabis. Respecto de la temperatura, los niveles ensayados fueron significativos como factor de proceso al presentar una interacción con los pretratamientos osmóticos. La mejor condición la conformó el pretratamiento osmótico DO 50º Brix con aire caliente SAC 65 º

Effects of wine grape cultivar, application conditions and the winemaking process on the dissipation of six pesticides

Pesticide residue in primary products is an important issue for producers and consumers, even though little information is available on the effect of application conditions on residue persistence and the transfer to primary elaborated products. During the 2012 season, field and laboratory studies were conducted to determine the dissipation of lambda-cyhalothrin, buprofezin, pyrimethanil, tebuconazole, imidacloprid and acetamiprid in Sauvignon blanc and Pinot Noir cultivars and their residue dynamics during the winemaking process. Half-life values (DT50) for each pesticide applied alone and as a tank mix of all pesticides were similar and had averages of 6.4, 14.0, 19.7, 26.0, 14.5 and 13.4 days for lambda-cyhalothrin, buprofezin, pyrimethanil, tebuconazole, imidacloprid and acetamiprid, respectively. The grape cultivar did not affect pesticide DT50. All pesticides were transferred from the raw material (grape) to red and white wines except lambdacyhalothrin. The transfer factors of buprofezin, tebuconazole pyrimethanil, imidacloprid and acetamiprid ranged from 3 to 23% in red wine and 9 to 30% in white wine. Alcoholic fermentation, pressing (through pomace) and malolactic fermentation were the steps in which the greatest residue losses occurred in red wine, whereas pressing (through the grape and stem), alcoholic fermentation and clarification with bentonite had the greatest residue loss in white wine. In both cases, bottled wine showed substantial residue reduction after ten months.La presencia de residuos de plaguicidas en productos agrícolas primarios es un tema muy importante para los productores y consumidores, sin embargo la información existente respecto al efecto de las condiciones de aplicación sobre la persistencia de los residuos y su potencial traspaso a productos elaborados es limitada. Durante la temporada 2012, se desarrollaron estudios de campo y laboratorio destinados a determinar la disipación de lambda-cihalotrina, buprofezin, pirimetanil, tebuconazole, imidacloprid y acetamiprid en uva vinífera Sauvignon blanc y Pinot Noir, y la distribución de sus residuos en el proceso de vinificación. La vida media (TD50) cuando estos plaguicidas cuando fueron aplicados en forma individual, o cuando fueron aplicados en mezcla de tanque, no presentaron diferencias y su promedio fue de 16,4; 14,0; 19,7; 26,0; 14,5 y 13,4 días para lambda-cihalotrina, buprofezin, pirimetanil, tebuconazole, imidacloprid y acetamiprid, respectivamente, sin observarse diferencia en su disipación entre ambos cultivares. Todos los plaguicidas, con excepción de lambda-cihalotrina, fueron traspasados desde la uva al vino, observándose un porcentaje de trasferencia promedio entre un 3 a 23% en el caso del vino tinto, y de un 9 a 30% en el caso del vino blanco. Los pasos que lograron una mayor reducción en la concentración de los residuos de plaguicidas en el vino tinto, fueron la fermentación alcohólica, prensado (a través del orujo) y la fermentación malolactica. En el caso del vino blanco fueron el prensado (a través de la uva y raquis), fermentación alcohólica y clarificación con bentonita. Además, en ambos vinos, el almacenado en botellas por diez meses, mostró un efecto importante en la reducción de los residuos de los plaguicidas

Characteristics of Convective Drying of Pepino Fruit (Solanum muricatum Ait.): Application of Weibull Distribution

The aim of this research was to study the behaviour of the drying kinetics of pepino fruit (Solanum muricatum Ait.) at five temperatures (50, 60, 70, 80 and 90 °C). In addition, desorption isotherms were determined at 20, 40 and 60 °C over a water activity range from 0.10 to 0.90. The Guggenheim, Anderson and de Boer model was suitable to depict the desorption data. A monolayer moisture content from 0.10 to 0.14 g water g−1 d.m. was reported. The equations of Newton, Henderson–Pabis, Modified Page, Wang–Singh, Modified Henderson–Pabis, Logarithmic as well as standardised Weibull were tested for modelling drying kinetics. Besides, Fick’s second law model was used to calculate the water diffusion coefficient which increased with temperature from 2.55 to 7.29× 10−10 m2 s−1, with estimated activation energy of 27.11 kJ mol−1. The goodness of fit of the models was evaluated using sum squared error and chi-square statistical tests. The comparison of the experimental moisture values with respect to the calculated values showed that the standardised Weibull model presented the best goodness of fit, showing that this equation is very accurate for simulating drying kinetics for further optimisation of drying times.Fil: Uribe, Elsa. Universidad de La Serena; ChileFil: Vega Gálvez, Antonio. Universidad de La Serena; ChileFil: Di Scala, Karina Cecilia. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Oyanadel, Romina. Universidad de La Serena; ChileFil: Saavedra Torrico, Jorge. Universidad de La Serena; ChileFil: Miranda, Margarita. Universidad de La Serena; Chil

Rehydration Capacity of Chilean Papaya (Vasconcellea pubescens): Effect of Process Temperature on Kinetic Parameters and Functional Properties

Slabs of Chilean papaya hot air-dried at 60 °C were rehydrated at 20, 40, 60, and 80 °C to study the influence of process temperature on mass transfer kinetics during rehydration. Diffusive and empirical models were selected to simulate the experimental rehydration curves. All models parameters showed dependence with temperature, thus activation energy could be estimated according to an Arrhenius-type equation. Among the applied models, Weibull provided the best fit for each rehydration curve based on the statistical tests RMSE, SSE, and chi-square. According to these results, this model could be used to estimate the rehydration time of Chilean papaya. In addition, rehydration ratio and water-holding capacity were analyzed. Both indices showed a decrease with increasing rehydration temperature indicating modification of the papaya cell structure due to thermal treatment which resulted in a reduction of the rehydration ability, in particular at high rehydration temperatures.Fil: Zura, Liliana. Universidad de la Serena; ChileFil: Uribe, Elsa. Universidad de la Serena; ChileFil: Lemus Mondaca, Roberto. Universidad de la Serena; Chile. Universidad de Santiago de Chile; ChileFil: Saavedra Torrico, Jorge. Pontificia Universidad Catolica de Valparaiso; Chile. Centro Regional de Estudios en Alimentos Saludables; ChileFil: Vega Gálvez, Antonio. Universidad de la Serena; Chile. Universidad de la Serena; ChileFil: Di Scala, Karina Cecilia. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Optimized methodology for the extraction of free and bound phenolic acids from Chilean Cristalino corn (Zea mays L.) accession

The aim of this study was to optimize the extraction of free and bound phenolic acids from Chilean Cristalino corn by response surface methodology based on the total phenolic contents (TPCs) and the 2,2-diphenyl-1-picrylhydrazyl scavenging-linked antioxidant capacity (AC) as response variables. Central Composite 22 + axial points experimental designs were applied. The best extraction conditions for the free and bound phenolic fraction were acetone 69% in water for 63 min and a hydrolysis with 3 M NaOH for 90 min, respectively. Under these conditions, TPCs in free and bound forms were 59.9 ± 0.7 and 172.9 ± 1.1 mg gallic acid equivalents/100 g, respectively. Further, AC found in free and bound fractions was 186 ± 3 and 694.5 ± 3.3 µmol Trolox equivalents/100 g, respectively. The experimental and predicted values of TPC and AC were similar in case of free phenolic fraction indicating that the model was adequate and reproducible. Major phenolic acids were found in the bound fraction and were ferulic and p-coumaric acids

Unveiling the Predisposing Factors for the Development of Branch Canker and Dieback in Avocado: A Case of Study in Chilean Orchards

Chilean avocado orchards have been affected by branch canker and dieback, mainly associated with pathogens species of the family Botryosphaeriaceae. Producers often relate water stress to these phenomena; however, predisposing factors for these diseases in Chilean orchards have not been reported. Therefore, the objective of this study was to identify the main climate, planting, and management variables associated with branch canker and dieback in Chilean avocado orchards. Multivariable statistical analyses (PCA and PLS-DA) were performed to analyze 76 variables possibly associated with the incidence of these diseases during two consecutive growing seasons. Our findings indicated that branch canker and dieback are mainly conditioned by orchard variables such as plant age, canopy volume, trunk diameter, leaf area index, and planting density. Variables associated with aged orchards, such as high age, high canopy volume, and high trunk diameter, appeared to be more associated with high incidence levels than were younger orchards with higher planting densities and high tree vigor levels. In addition, abiotic stresses, such as frost and overirrigation, were associated as secondary factors affecting these diseases&rsquo; development in avocado orchards. Moreover, this study allowed us to determine that branch canker and dieback can develop indistinctly in the different Chilean agroclimatic zones