Impact of pulsed light treatments on antioxidant characteristics and quality attributes of fresh-cut apples

The effects of pulsed light (PL) treatments combined with a quality-stabilizing dip on the quality and antioxidant attributes of fresh-cut 'Golden delicious' apples was studied. Apple wedges were dipped into a solution of 1% w/v N-acetylcysteine and 0.5% w/v CaCl2 and flashed with broad-spectrum light with an overall radiant exposure of 4, 8,12 and 16 J.cm(-2). General microbial counts, colour, firmness, phenolic compounds and vitamin C contents were evaluated over 15 days at 5 degrees C. More pronounced reductions of the naturally-occurring microbiota were observed as the applied PL-dose increased. The quality-stabilizing pre-treatment effectively prevented browning phenomena on the cut-tissue surface. In addition, browning and oxidation were not promoted in PL flashed samples. Indeed, the initial contents in phenolic compounds and vitamin C were even better maintained than in untreated samples. Treatments of 8 and 16 J cm(-2) were most effective for maintaining the quality and antioxidant characteristics. Industrial relevance: Pulsed light technology is an emerging technique with good prospects for the decontamination of foods and food contact surfaces. Application of pulse light treatments for increasing safety and extending microbial shelf life of fresh-cut produce seems feasible. However, their effects on the quality and antioxidant characteristics of fruit need to be evaluated for successfully applying the technology at an industrial level. (C) 2015 Elsevier Ltd. All rights reserved.This work was supported by the Generalitat de Catalunya (2014 SGR 1000) and the Ministerio de Economía y Competitividad of the Spanish Government (AGL 2010-21572 and AGL2013-44851-R). O. Martín-Belloso thanks ICREA Academia Award. K. Avalos Llano thanks CONICET and Universidad Nacional del Nordeste (Argentina) for the postdoctoral grant and financial support

Conservación de mosto de uva con pulsos eléctricos de alta intensidad de campo

S’ha realitzat l’estudi de l’efecte del processat de suc de raïm amb polsos elèctrics d’alta intensitat de camp (PEAIC) amb la intenció d’aconseguir la seva conservació. Els seus efectes s’han mesurat en diferents propietats característiques del suc de raïm com el contingut en sòlids solubles, pH, acidesa, conductivitat elèctrica, activitat microbiològica i enzimàtica, alguns compostos bioactius com el contingut en polifenols o vitamina C i capacitat antioxidant. Els valors obtinguts s’han comparat amb els obtinguts del tractament conservant de referència actual, el processat tèrmic. També s’ha determinat l’evolució de components específics durant el procés de vinificació des de l’obtenció del suc de raïm fins a l’envelliment del vi. L’estudi s’ha dut a terme en 4 fases en les que s’ha determinat que els PEAIC redueixen el contingut microbià del suc de raïm, tant l’inoculat com el natural, i l’activitat enzimàtica oxidativa. Així mateix, s’ha constatat que es possible optimitzar el procés tenint en compte les característiques de l’equipament i el medi. La comparació dels resultats de les variables estudiades amb aquesta tecnologia i amb tractament tèrmic a permès evidenciar que els efectes dels PEAIC són menys dràstics, fet que permet la seva utilització en l’elaboració de suc de raïm i vi sense que afecti negativament al procés o a l’envelliment del producte. La principal conclusió de l’estudi amb les dades obtingudes de tres varietats habitualment utilitzades a Catalunya és que el processat amb PEAIC és una eina de conservació del suc de raïm viable des del punt de vista tecnològic. L’adquisició de dades d’altres varietats i temporades fora de gran utilitat per ampliar aquesta conclusió.Se ha realizado el estudio del efecto del procesado de zumo de uva con pulsos eléctricos de alta intensidad de campo (PEAIC) para su conservación. Los efectos se han medido en distintas propiedades características del zumo de uva como el grado brix, pH, acidez, conductividad eléctrica, actividad microbiológica y enzimática, algunos compuestos activos biológicamente como el contenido en polifenoles o vitamina C y la capacidad antioxidante. Los valores obtenidos se han comparado con los del tratamiento conservante de referencia, es decir, el tratamiento térmico. También se ha determinado la evolución de compuestos específicos durante el procesado desde el zumo de uva hasta el envejecimiento del vino. El estudio se ha realizado en 4 fases en las que se ha observado que los PEAIC reducen claramente la micro flora del zumo de uva, tanto la inoculada como la natural, así como la actividad enzimática oxidante. Se ha confirmado, además, que es posible optimizar esta reducción teniendo en cuenta las características del equipo de procesado y el medio. La comparación de resultados de las variables estudiadas tras el procesado PEAIC con el tratamiento térmico ha permitido constatar que los efectos de los PEAIC son menos drásticos lo que permitiría su uso como tratamiento en la elaboración del zumo y vino sin que afecte negativamente al proceso de vinificación o a su envejecimiento. La principal conclusión del estudio con los datos de tres variedades habitualmente utilizadas en Cataluña es que el procesado mediante PEAIC para la conservación de zumo de uva es técnicamente viable. La obtención de nuevos datos de otras variedades y distintas vendimias seria útil para poder generalizar esta conclusión.The effect of pulsed electric fields as a preservation method on grape juice was studied. Its effects were measured on typical grape juice properties such as brix degrees, pH, acidity, electrical conductivity, microbial and enzymatic activities, and some bioactive compounds like vitamin C and polyphenol contents or antioxidant activity. The obtained values were compared with the current preservative reference technology, which is the heat processing. It was also analysed the effect of PEF on the evolution of specific compounds throughout the wine making process from juice to ageing. The study was carried out in 4 phases. It was observed a clear reduction of the microbial populations of both, inoculated and natural flora, as well as the oxidant enzymatic activities of grape juice. Besides, these effects were optimised taking into account the PEF processing device and the food product. The comparison of both treatments revealed that the PEF treatment yielded milder values of the variables than the thermal treatment. Therefore it could be used in juice and wine making without a negative impact on the quality of the product. The main conclusion inferred from the study is that on three commonly used Catalan varieties PEF processing is a feasible technology to preserve grape juice. New data coming from different varieties and years should broaden this conclusion

Optimization and validation of PEF processing conditions to inactivate oxidative enzymes of grape juice

White grape juice was processed using high intensity pulsed electric fields (PEF). The effect of this preservative technology on polyphenoloxidase (PPO) and peroxidase (POD) as well as on refractometric index, sugar content, pH, acidity and density was studied. In addition, the use of the response surface methodology as a tool to obtain accurate information and provide predictions of enzymatic depletion on real foods was assessed. The studied PEF factors were electric field strength, pulse frequency, pulse width and total treatment time. Inactivation values of 100% for PPO and up to 50% for POD were achieved after different PEF treatments. The activity depletion was strongly dependent on the evaluated factors, mainly PEF treatment time. A predictive equation for each residual activity covering the whole range of experimentation was developed and their results were confirmed against a set of validation experiments. In addition, predictions obtained from the developed response surfaces and exponential kinetic models were comparable. In conclusion, PEF treatments depleted PPO and POD activities of grape juice although it was observed that grape POD was less sensible than PPO to PEF technology. Response surface methodology allows analysing and optimizing the PEF treatments as well as predicting their results with very few experiment

Impact of pulsed light treatments on antioxidant characteristics and quality attributes of fresh-cut apples

The effects of pulsed light (PL) treatments combined with a quality-stabilizing dip on the quality and antioxidant attributes of fresh-cut 'Golden delicious' apples was studied. Apple wedges were dipped into a solution of 1% w/v N-acetylcysteine and 0.5% w/v CaCl2 and flashed with broad-spectrum light with an overall radiant exposure of 4, 8,12 and 16 J.cm(-2). General microbial counts, colour, firmness, phenolic compounds and vitamin C contents were evaluated over 15 days at 5 degrees C. More pronounced reductions of the naturally-occurring microbiota were observed as the applied PL-dose increased. The quality-stabilizing pre-treatment effectively prevented browning phenomena on the cut-tissue surface. In addition, browning and oxidation were not promoted in PL flashed samples. Indeed, the initial contents in phenolic compounds and vitamin C were even better maintained than in untreated samples. Treatments of 8 and 16 J cm(-2) were most effective for maintaining the quality and antioxidant characteristics. Industrial relevance: Pulsed light technology is an emerging technique with good prospects for the decontamination of foods and food contact surfaces. Application of pulse light treatments for increasing safety and extending microbial shelf life of fresh-cut produce seems feasible. However, their effects on the quality and antioxidant characteristics of fruit need to be evaluated for successfully applying the technology at an industrial level. (C) 2015 Elsevier Ltd. All rights reserved

Evaluation of physicochemical parameters of grape juices produced in the Serra Gaúcha

The objective of this study was to compare the physicochemical profile of white and purple grape juices through the analysis of reports from the database of an oenological laboratory located in the Serra Gaúcha. The reports of the years 2012 through May of 2016 containing the parameters alcohol, pH, reducing sugars, relative density, titratable acidity, total soluble solids and volatile acidity were used for the statistical evaluation. There was no statistically significant difference regarding the alcohol content and density of white juices compared to purples in any year. Statistically significant pH values were found in the crops of 2014 and 2015. As for the reducing sugars parameter, it was observed a statistically significant difference in the year of 2014. Titratable acidity was statistically significant in all crops. Statistically significant values of total soluble solids were observed in the harvests of 2014 and 2015. The volatile acidity parameter showed statistical significance in the year 2014. The inherent genetic differences between the varieties of grapes used for each juice and the distinct technological processes used in the production are the factors that explain the results