Jefferson Luiz Gomes Corrêa

Drying of Pineapple by Microwave-Vacuum with Osmotic Pretreatment

Drying of pineapple by microwave-vacuum (MW-V) with osmotic dehydration (OD) as a pretreatment was studied. Central composite design was used for the independent variables sugar concentration (40, 50, and 60 °Brix), immersion time (0, 3, and 6 hours) and product temperature in the microwave cavity (50, 60, and 70°C). The dependent variables were moisture content, shrinkage, rehydration coefficient, visual quality, color, and texture. The osmotic dehydration pretreatment was also evaluated with respect to weight reduction (WR), water loss (WL), and solid gain (SG). Maximizing moisture loss was the main objective of OD pretreatment for various combinations of sugar concentration and immersion time. OD preserved the color of the samples while drying. In the complete process composed by OD and MW-V, only the influence of temperature of the product on the drying rate was statistically significant (P < 0.05), whereas OD reduced shrinkage and improved rehydration capacity. The best visual quality was obtained when the independent variables were diminished. OD also significantly (P < 0.05) affected the texture of product producing softer, less surface-hardened product compared to untreated ones.

Optimization of osmotic dehydration of yacon slices

ABSTRACT Osmotic dehydration assisted by ultrasound (ODAU) at low temperatures reduces water activity (aw) and maintains nutrients. The influence of solution concentration (SC; 20 to 60° Brix, xylitol and sorbitol) and ultrasound application time (tus, 0 to 40 min) in ODAU of yacon was studied with the aid of a response surface method. The optimum condition with respect to mass transfer parameters, aw, and fructan retention was SC of 60° Brix for both solutions and tus of 2.67 min for xylitol samples and 0 min for sorbitol samples. The application of ultrasound improved dehydration but resulted in depolymerization of fructans.

Influência da secagem do pequi (Caryocar brasiliense Camb.) na qualidade do óleo extraído

Pequi (Caryocar brasiliense Camb) has stood out for being an oleaginous fruit rich in carotenoids. Drying is widely used technique in the oil extraction process using hexane, but the degradation of oil and carotenoids may occur. The objective of this study was to evaluate the influence of different drying methods (sun, air-circulated drier at 40 and 60 °C) and time (4 hours and up to constant weight) on the yield and quality of the oil extracted using hexane using a soxhlet apparatus. When the pequi pulp was dried up to 3% or even lower, more oil yield was obtained (52-59%, dry basis). The total carotenoids contents obtained were higher and the peroxide index was lower for the pulp dried at 40 °C in an air-circulated drier when compared to drying at 60 °C in an air-ventilated drier and to sun drying technique. These results indicate that drying in an air-circulated drier at 40 °C for 19 hours resulted in higher oil yields with less heat degradation.

The Influence of Ethanol on the Convective Drying of Unripe, Ripe, and Overripe Bananas

In this work, the influence of ethanol on convective drying of unripe, ripe, and overripe bananas was investigated. The experiments were performed at 60°C with air velocity at 0.84 m s−1 under the following conditions: normal atmosphere, atmosphere modified with ethanol (0.5% v/v), and ethanol brushed on the surface of the samples. Among the ripeness degree, the unripe was correlated with higher diffusivity, followed by the ripe and the overripe conditions, in this order. With respect to the treatments, the higher diffusivity was obtained with the surface use of ethanol, followed by the modified atmosphere and the normal atmosphere, in this order. Shrinkage and color were also investigated. The longitudinal shrinkage was always greater than the radial shrinkage and there was no influence of ethanol treatment on shrinkage. It was observed that there was higher total color difference (ΔE) for unripe and overripe bananas at normal atmosphere and higher ratio of luminosity ( ) when ethanol was used.

Osmotic Dehydration of Tomato Assisted by Ultrasound: Evaluation of the Liquid Media on Mass Transfer and Product Quality

Abstract The treatment of a food in liquid media involves mass transfer and could aid to preserve some food properties. The assistance of ultrasound (US) could even improve the process. Therefore, the aim of this study was to evaluate US (frequency 25 kHz, powder intensity 8 kW m–3) in tomato treatment in sucrose and NaCl solutions, common osmotic agents. Moreover, for testing the influence of the media, distilled water and maltodextrin solution completed the set of tested liquids. Water loss (WL), solid gain (SG), water activity (aw), color parameters, like the total color difference (ΔE) and microstructure were evaluated. The advantages of NaCl and sucrose solutions were the high WL and SG values besides low aw and ΔE. The alterations in the microstructure of US-treated samples in distilled water or maltodextrin suggested that a product with low solid incorporation and reduced drying time could be obtained in a further drying.

Optimization of Pulsed Vacuum Osmotic Dehydration of Sliced Tomato

The osmotic dehydration (OD) is a treatment that reduces partially the moisture content and the water activity of a food. The use of reduced pressure in the first minutes of an OD is called pulsed vacuum osmotic dehydration (PVOD). In PVOD, the expulsion of occlude gases and the entrance of the solution in the food matrix are induced, with consequently mass transfer improvement. In the present work, the influences of independent variables (temperature (T), pressure of vacuum pulse (PV), sodium chloride concentration [NaCl] and sucrose concentration [suc]) on water loss (WL), solid gain (SG), weight reduction (WR), water activity (aw) and moisture content (U) of tomato slices were studied. The optimum condition obtained had its kinetics tested with three models from the literature. The optimized condition (T 40 °C, PV 56.25 mbar, [NaCl] 7.5 % and [suc] 32.5 %) resulted in the maximum values of WL, and WR (42.2, and 36.1 %, respectively) and minimum SG, aw and U (4.0, 0.948 and 76.5 kg water/100 kg sample, respectively). With respect to the kinetics, the best agreement was obtained with the model that considers variable diffusivity.

Secagem de fatias de abóboras (Cucurbita moschata, L.) por convecção natural e forçada

Besides its low price, Pumpkin (Cucurbita moschata, L.) is an important source of provitamin-A, and when dehydrated it offers different options of utilizations and consumption. Natural and forced convection drying were compared according to the drying degree shrinkage as a function of temperature, and air velocity and product dimensions. The obtained results showed that slices with the volume of 6.25 cm3 in forced convection oven at 50 °C and at the velocity of 5.5 x 10-4 ms-1 resulted in a lower shrinkage products, so these conditions were recommended.

Use of Ultrasound in the Distilled Water Pretreament and Convective Drying of Pineapple

Convective drying is a time-consuming process. Pretreatments in distilled water assisted with ultrasound, or the application of ultrasound during convective drying itself, could improve the mass transfer. In this work, the influence of pretreatment using distilled water (20 or 40 min at 25 °C) assisted with ultrasound (55.5 W L−1, 40 kHz) on convective drying kinetics (40 and 70 °C, 1 m s−1) of pineapple slices (2.0 cm diameter, 0.5 cm thickness) was studied. The drying was carried out with (31 kWm−3; 21.8 kHz) and without ultrasound application being the kinetics simulated using a diffusive model. The results showed that pretreatment, the use of high drying temperatures, and the application of ultrasound during drying accelerated the drying process. The effective diffusivity identified by the model allowed the quantification of the effects of each of the studied variables on the drying rate of pineapple slices.

Sugarcane Bagasse Drying in a Cyclone: Influence of Device Geometry and Operational Parameters

Sugarcane bagasse is becoming more and more commonly used in generating electrical energy, steam, and bioethanol. Drying is important in sugarcane and other types of biomass because it can be used to improve the calorific value and overall energetic use. In this work, sugarcane bagasse was treated by drying in a cyclonic dryer. The influence of the geometry of the device (the conical part of the cyclone) and process parameters (bagasse mass flow rate and temperature) were tested. The modification on the conical part was related to two different angles and with two different inferior outlets (B). Experimental design was carried out for each geometry. The independent variables were the drying agent temperature (35 to 275°C) and the bagasse mass flow rate (0.1 × 10−2 to 2.9 × 10−2 kg s−1). The air flow rate was kept constant at 7.5 × 10−2 kg s−1. The dependent variables were moisture reduction (MR) and average particle residence time (tres) in the cyclonic dryer. For both cyclonic geometries, it was observed that MR was directly proportional to the temperature and inversely proportional to the bagasse mass flow rate. tres was also inversely proportional to the bagasse mass flow rate. Decreasing B tended to increase tres and MR.

Influences of convective and vacuum drying on the quality attributes of osmo-dried pequi (Caryocar brasiliense Camb.) slices

Pequi is a fruit from Brazilian Cerrado. Despite its ascorbic acid and carotenoid contents, consumption of pequi is restricted to its region of origin. The goal of this work was to study drying of pequi slices (convective or vacuum drying at 40°C and 60°C) preceded or not preceded by osmotic pretreatment (sucrose solution concentrations of 40% and 60%). It was found that osmotic dehydration pretreatment substantially decreased the moisture content, duration of the drying process, and the volumetric ratio of the dried product. However, it also promoted leaching of bioactive constituents, such as ascorbic acid and carotenoids. Vacuum and low temperature drying without osmotic pretreatment were preferable because the ascorbic acid and carotenoids were retained, rehydration coefficients were higher and there were minimal volume and color changes.