Application of osmotic dehydration and microwave drying to strawberries coated with edible films (original) (raw)
Related papers
Osmotically Dehydrated Microwave-Vacuum Drying of Strawberries
Journal of Food Processing and Preservation, 2008
Strawberries were osmotically dehydrated prior to microwave-vacuum drying. Drying kinetics were presented in terms of the temperature of the product during drying, drying curve and drying time. Thin-layer models of Lewis, Henderson and Pabis, and Page were fitted with the observed data. The root mean square error and the coefficient of determination (r 2) were used to evaluate the fit of the models. The effects on quality of dried strawberries were evaluated for various drying parameters such as: with or without osmotic treatment, input power levels (1 W/g and 1.5 W/g) and power modes (continuous, 45 s on/15 s off, 30 s on/30 s off). The effects were evaluated by a standard factorial (2 ¥ 2 ¥ 3) analysis in triplicate. The quality aspects were studied in terms of water activity, shrinkage, rehydration capacity, texture, color and sensory evaluation. The results showed that the osmotic pretreatment did not help in terms of drying time and energy saving but provided a better quality of dried product. Page's model presented the best fit for the observed data.
Journal of Berry Research, 2021
BACKGROUND: The use of polysaccharide based edible coatings as a barrier against the solute entry of high caloric constituents, such as sucrose, is a suitable strategy to develop pro-healthy osmo-dehydrated products. OBJECTIVE: This work aims to study the effect of a calcium alginate film over the drying kinetics of strawberries during an osmotic dehydration (OD) treatment at 60°Brix, 4 h, 40°C (sucrose). Also, textural parameters were evaluated. METHODS: It was determined the changes in some selected physical properties, such as: moisture, total solid contents, one-dimensional shrinkage and texture, at 30 min steps during OD treatment. Besides, water and solid diffusion coefficients ( D e W and D e TS , respectively) were calculated by using the analytical solution of Fick’s equation. RESULTS: Diffusion coefficients for water and solids showed significant differences due to coating presence as an evidence of the barrier effect. Coated strawberry samples presented several changes af...
Journal of Food Engineering, 2008
The influence of air temperature, microwave application and vacuum impregnation or pulsed vacuum osmotic dehydration, as pre-treatments undertaken prior to convective drying, on the drying kinetics of apple and strawberry has been studied. Furthermore, the effect of the above pre-treatments on the optical and mechanical characteristics of dried samples has also been investigated. Empirical equations (linear and page) were used to assess the effect of these factors on drying kinetics, with a good fit being observed between experimental data and model. The effect of microwave on the decrease in drying time was significantly greater than the effect of increasing the air temperature. A dehydrated product with less colour change and a more rigid and firmer structure was obtained at higher air temperature or when applying microwave. However, the higher temperatures during microwave treatment increased pigment degradation. The increase in the liquid phase volume occurring with pre-treatments prolonged the convective drying time process and also implied greater colour changes in the samples. Nevertheless, they enhance the resistance to deformation and fracture of the dehydrated product.
Current Trends in Drying and Dehydration of Foods
Drying and dehydration techniques have constantly been evolving since ancient time; from sun drying to solar drying, from convective air drying to impingement drying. The heating medium has changed from sunlight to dielectric and electromagnetic radiation, from hot air to jet impingement, from steam to superheated steam etc. Drying essentially is a simultaneous heat and mass transfer process, wherein heating medium or internal heat generation helps in evaporation of free water molecules from the product. Mass transfer rate, during the drying/dehydration process, can be enhanced by different pretreatments, apart from using enhanced temperature, optimum air flow rate in case of convective drying or using high intensity electric field as in case of dielectric and other electromagnetic drying systems however, opting for extreme conditions, product quality may be compromised. To suit the consumer demand for quality product, current technologies are aiming at integrating different pre-treatments like blanching, chemical treatment, physical modification, application of thermal and non-thermal processes, for inactivation of enzymes, reduction in microbial load and structural modification with an aim to enhance mass transfer rate. Enhanced mass transfer rate eventually overcomes the drying cost and deterioration associated with longer drying time. Innovative drying technologies such as refractance window drying, corona air or electrohydrodynamic drying, super-critical CO 2 drying and bio-film drying are trying to address some problems associated with drying. Various hybrid drying technologies that manifest judicious integration of several dehydration techniques such as osmosis, convective, vacuum, microwave, radiofrequency, infrared and ohmic heating and freeze drying with non-thermal processing like high pressure, ultrasound, pulse electric field and irradiation are cost effective, as these methods reduce drying time considerably at the same time maintaining the product quality.
Shrinkage effect on diffusion coefficient during carrot drying
2018
Many studies have been previously carried out on the carrot drying and the undergoing processes. The developed mathematical models provide an opportunity to gain an understanding of this complex process and its dynamics. But they are simplified and based on a number of assumptions, including calculation of diffusion coefficient values. In one of the previous studies, the authors of this study determined that the diffusion coefficient is linearly dependent on the moisture concentration with the assumption that the sample's geometric shape does not change. The aim of this study is to determine the dependence of the diffusion coefficient on the moisture concentration taking into account the change in sample thickness during the drying experiment. The experiments were carried out with carrot slices of three different thicknesses: 5 mm, 10 mm and 15 mm thickness on the film infrared dryer at temperature 40 . During the experiments, measurements of the weight and thickness of the slic...
2017
Model-products are products designed to imitate and understand the heat treatment behavior of real products. This is the case of a sodium alginate gel used to simulate the drying behavior of water-rich fruit products (e.g. tomatoes). The aim of this study was to investigate the effect of the shape of a sodium alginate gel as a model-product of microwave drying. Then, from this shape of the gel, find a semi-empirical model that simulated well its drying kinetics. Thus, a sodium alginate gel was developed in cylindrical and slab shapes, which had almost identical volumes and weights, to assess the influence of product shape on drying kinetics. Experiments were performed in a stereo-mode cavity at 2450 MHz with output microwave powers densities of 1, 1.5, and 2 W / g. A regular weighing of dried product mass was carried out to better appreciate drying behavior. In addition, the temperature at the product core was measured by an optical fiber to observe the evolution of gel temperature....
Microwave/vacuum drying of model fruit gels
Combined microwave (MW)/vacuum drying of fruit materials has a promising potential for high-quality dehydrated products. A better knowledge of the drying kinetics of fruit products could improve the design and operation of ecient dehydration systems.
Microwave Drying of Strawberry Slices and the Determination of the Some Quality Parameters
Strawberry slices (Fragaria x ananassa cv. Camarosa) weighing 100 g (±0.04) with a moisture of 11.74 kg (moisture) kg-1 (dry matter) (92.15% wb) were dried using four different microwave output powers: 1000 W, 750 W, 500 W and 350 W. Drying continued until the slices moisture decreased to 0.16 (±0.02) kg (moisture) kg-1 (dry matter) (13.87% (±0.01) wb). Drying periods lasted 4-13.5 min for microwave drying, depending on the microwave output powers. In this study, measured values of moisture were compared with values of predicted obtained from 21l thin-layer equations; the Alibas Model was found to have the best fit. The optimum drying period, color, ascorbic acid and rehydration ratio content were obtained by 500 W.