ABSTRACT
The yacon roots are rich in fructooligosaccharides (FOS) and highly perishable. Drying is crucial for food quality and extending shelf life. However, preserving thermosensitive compounds, such as FOS, poses a challenge in conventional drying methods. In this regard, microwave drying and ethanol pretreatment (ET) have emerged as promising solutions for maintaining nutrients and reducing drying time (DT). The objective of this study was to assess how ET and sample temperature affect quality and process parameters during intermittent microwave drying of yacon. Drying at 52°C treated with ethanol was the one that stood out for presenting the highest fructan retention (64.1%), low DT, lower energy consumption (EC) (364.00 ± 5.03 kWh kg water-1), higher retention of antioxidant capacity (73.9%) and total phenolic content (77.5%), and slight variation in color parameters. Therefore, microwave drying with a controlled temperature of yacon pretreated with ethanol effectively reduces DT and EC by maintaining quality parameters.
Subject(s)
Antioxidants , Desiccation , Ethanol , Microwaves , Ethanol/chemistry , Desiccation/methods , Antioxidants/chemistry , Phenols/analysis , Plant Roots/chemistry , Oligosaccharides/chemistry , Temperature , Fructans/chemistry , Fructans/analysis , Food Handling/methods , Food Preservation/methodsABSTRACT
This work studied three emerging approaches to improve the convective drying (50 °C, 0.8 m/s) of celery. Celery slices of 2 mm thick were pretreated for 5 min using ultrasound (32 W/L, 40 kHz), vacuum (75 kPa vacuum pressure) and ethanol (99.8% v/v, as drying accelerator) applied individually or in combination. To evaluate individual effects of ultrasound and vacuum, the treatments were also performed with distilled water or air medium, respectively. Moreover, the cavitational level was characterized in each condition. Drying kinetics was evaluated tending into account the drying time required by each treatment and the Page's model parameters. In addition, microstructural effects and shrinkage were evaluated. As results, ethanol combined with ultrasound significantly improved drying kinetics reducing drying time by around 38%. However, vacuum pretreatment did not affect drying kinetics even in combination with ethanol and/or ultrasound. Microstructural evaluation did not evidence cell disruption, suggesting changes in intercellular spaces, pores and/or cell wall permeability. The use of ethanol and vacuum showed a greater effect on shrinkage after pretreatment and after drying, respectively. In conclusion, at the studied conditions, the drying acceleration by vacuum and ultrasound is lower compared to the effect produced using ethanol.
Subject(s)
Apium , Desiccation , Ethanol , Vacuum , VegetablesABSTRACT
In this study, a mathematical formalism that takes into account the surfactant effect on the drainage of the interfacial film between two drops is considered. The effects of thermal perturbations and van der Waals forces are neglected. In the mathematical formalism the Navier-Stokes equations within the lubrication approximation are coupled to a diffusion-convection equation leading to an evolution equation for the interfacial film. This last equation is solved by using the numerical method of lines coupled with an implicit Runge-Kutta method for the integration with respect to time. As a result of the inclusion of interfacial tension gradients a non oscillating dimple arises, even beginning with an initial condition corresponding to a plane interfacial film.
En este estudio se desarrolla un formalismo matemático que toma en consideración el papel del surfactante en el drenaje de la película interfacial entre dos gotas. No se consideran los efectos de perturbaciones térmicas y fuerzas de van der Waals. En el formalismo matemático se acoplan las ecuaciones de Navier-Stokes (dentro de la aproximación de lubricación) con la ecuación de difusión-convección, lo cual conduce a una ecuación de evolución para la película interfacial. Esta última ecuación es resuelta utilizando el método numérico de líneas junto con un método implícito de Runge-Kutta para la integración con respecto al tiempo. Como resultado de la inclusión de los gradientes de tensión interfacial surge una depresión superficial (dimple) no oscilatoria, inclusive comenzando con una condición inicial correspondiente a una película interfacial plana.
Neste estudo se considera um formalismo matemático que toma em consideração o efeito surfactante na drenagem da película interfacial entre duas gotas. Não se consideram os efeitos de perturbações térmicas e forças de van der Waals. No formalismo matemático as equações de Navier-Stokes dentro da aproximação de lubrificação se acoplam a uma equação de difusão-convecção, o qual leva a uma equação de evolução para a película interfacial. Esta última equação é resolvida utilizando o método numérico de linhas junto com um método implícito de Runge-Kutta para a integração relativa ao tempo. Como resultado da inclusão de gradientes de tensão interfacial surge uma depresão superficial (dimple) não oscilatoria, inclusive começando com uma condição inicial correspondente a uma película interfacial plana.