Studies on drying of the watermelon seeds or rinds are available, but not on drying of the fruit flesh. Data on the sorption of watermelon fruit (Citrullus Lanatus), which are useful and important when identifying optimal food drying and storage conditions, are also not available. Therefore, the main goal of this study is to investigate the water desorption behavior of watermelon using the dynamic method requiring the automated dynamic vapor sorption (DVS) technique based on a humidity-generating device. The moisture desorption isotherms are determined at three different temperatures (20°C, 30°C and 40°C) over a relative humidity range of 0-80%. In addition, 11 different models are applied to the experimental data in order to select the appropriate desorption curve equation. The models are compared using the correlation coefficient, the coefficient of determination, the standard error, the reduced chi-squared, the mean bias error and the root mean square error; they are predicted by a non-linear regression analysis using the Curve Expert software and MS Excel computer program. The effect of the temperature on the constants of the found equation is also examined. Besides, the desorption isosteric heat of watermelon is determined using the Clausius-Clapeyron relation. Contrary to long times taken in the static method, the results show that 4.5 days are widely sufficient to reach the equilibrium via the DVS device. In addition, the obtained curves are of the type III and the Henderson model best fits the experimental data. In the interval 0.05-0.45 kg water.kg dry matter-1 of equilibrium moisture, the values of the isosteric heat vary from 65.02 to 113.25 kJ mol-1. Finally, the equation giving the isosteric heat of desorption v.s. the equilibrium moisture content is obtained.

This paper reports a study of the physicochemical quality and the drying behavior of regal seedless grapes (RSG), pretreated with a novel solution (Olive oil: 2%, calcium carbonate: 2% and distilled water: 96%), then open sundried and dried in an indirect solar dryer. To show the effect of soaking time and temperature of the solution, two soaking times are carried out (120 and 240 s) at two temperatures (333.15 and 353.15 K). Quality indicat or such as shrinkage, color, rehydration capacity, titratable acidity, power of hydrogen (pH) and polyphenol content are evaluated. The results show that the time required to dry treated RSG varies from 220 to 328h during indirect solar drying (ISD) (during 428 h for untreated samples), and from 164 to 180 h during open sun drying (OSD) (during 290 h for untreated samples). The effective moisture diffusivity of solar-dried RSG ranges from 0.316 to 3.030 mm2 s − 1 and that of open sun-dried regal seedless grape ranges from 0.706 to 5.700 mm2 s − 1 . Pretreatment affects the pH values significantly, whereas the rehydration capacity showes a large difference between the treated and untreated RSG. The solar-dried RSG has more stable color and ISD retains more of their polyphenol content.

The effect of static drying on the physicochemical quality of camel (Camelus dromedarius) meat slices as driedin an oven at 65 ◦C, with the aim of contributing to food safety. During the experiments, meat was cutinto. 8 ± 0.2 cm thick slices, soaked in a saline solution for 30 min, and then dried. Moisture content wasmeasured during the drying phase, and physicochemical parameters, such as protein, ash, sodium, pH, and mineral content, such as calcium (Ca), phosphor (P), magnesium (Mg), potassium (K), zinc (Zn), iron (Fe), copper (Cu) and manganese (Mn), were monitored before and after drying. The colorimetric parametersof the dried samples are also measured. The results show that the physicochemical quality of the dried camelmeat meets the requirements of the Codex Alimentarius Commission. Indeed, the moisture content decreased from 73.94 ± 0.51% to 13.33 ± 0.44%, and the dried food samples were characterized by increases (i) from 19.72 ± 0.30% to 50.97 ± 0.65% in protein content; (ii) from 1.115 ± 0.012% to 4.781 ± 0.047%, in ash content; (iii) from 260 ± 11.7 mg to 1690 ± 32 mg, in the sodium content (for 100 g of dry matter), and (iv) from 5.956 ± 0.087 to 6.203 ± 0.091 in pH value. However, the variation is not significant for all mineral content parameters. Finally, themean values of the colorimetric parameters of brightness (L*), redness (a*), and yellowness (b*) are 37.13 ± 1.64, 22.02 ± 0.72, and 7.73 ± 0.69, respectively (before drying) and they are 25.57 ± 1.56, 9.43 ± 0.78, and 3.74 ± 0.21, respectively (after drying).

Keywords: Camelus dromedarius; camel meat; drying; quality; safety food

 

Drying is still considered to be an efficient and important process used for food preservation. Several drying methods are commonly used, so it would be interesting to compare them. The comparison could focus on the quality of the dried products, which is mainly dependent on changes occurring during processing. In the current contribution, an experimental study of drying camel meat (Camelus dromedarius) by two methods, namely direct sun drying and microwave drying, is performed. The investigation is carried out to determine the adequate better drying technique for camel meat from the region of Ouargla, southeast Algeria. Under pre-treatment in a saline solution during 30 minutes of soaking, the samples used are slices 8 mm thick, 100 mm long and 20 mm wide. They are characterized by the initial water content of 73.38 ± 0.13 %, the protein content of 19.77 ± 0.05 %, an ash content of 1.123 ± 0.009 and a lipid content of 3.72 ± 0.05 %. The sun drying experiments are carried out at an average temperature of 21.55 °C and average relative humidity of 28.57 %. The microwave drying is carried out at a power of 180 and 270 W. At the end of drying, kinetics, rate drying, duration drying, organoleptic properties (color and size) and nutritional values (protein and lipid) are determined in each case. Although drying in the microwave is faster and shorter, the results show that the samples sun dried are better. Indeed, sun drying shows a shrinkage rate of 43.63 ± 0.37 % against 56.75 ± 0.36% at 180 W and 57.65 ± 0.32 % at 270 W for microwave drying, with total color differences of 20.59 ± 0.48 against 24.63 ± 0.73 at 180 W and 23.10 ± 0.70 at 270 W for microwave drying. Protein content increases significantly after sun drying (49.44 ± 0.21) and microwave drying (45.30 ± 0.02 % at 180 W and 40.64 ± 0.01 at 270 W). The results also show lipid preservation of 84.13 % during sun drying and an increase in ash content in both drying processes from 1.123 ± 0.009 to: (i) 4.235 ± 0.015 at 180 W and 4.266 ± 0.037 at 280 W, in microwave drying; (ii) 3.903 ± 0.07 during sun drying.

Keywords: Cameline meat, quality, sun drying, microwave drying, experimentation.

 

 

This paper presents a mathematical modeling of thin layer drying of tomato (Solanum lycopersicum L.). To this end, two different methods are used to dehydrate tomato slices namely the solar drying (in an indirect solar drier), and the forced convective drying (in a convective drier). In the solar drier, the experiments are carried out at a constant air velocity of 1 m s-1and average temperatures of 37.2°C, 39.9°C and 42.5°C. In the convective drier, the experiments are performed with five different temperatures (30°C, 40°C, 50°C, 60°C and 70°C) at a constant air velocity of 1 m s-1. In order to estimate and select the appropriate drying curve equation, fifteen different thin layer mathematical drying models available in the literature are applied to the experimental data. The models are compared using the correlation coefficient (r) and the standard error (s) and are predicted by a non-linear regression analysis using the Curve Expert software. The Midilli-Kucuk model shows a better fit to the experimental drying data according to (r) and (s) for the two drying methods. The effect of the drying temperature on the parameters of this model is also determined. The experimental drying curves show only a falling drying rate period. On average, tomatoes are dried until the moisture content to 0.15 kg water kg-1 dry matter from 14.36 kg water kg-1 dry matter in the solar drying, and to the moisture content of 0.10 kg water kg-1 dry matter from 12.66 kg water kg-1 dry matter in the convective drying.

Keywords: solar drying, convective drying, tomato slices, thin layer, mathematical modeling, curve expert software.

In this work, slices of yellow onions (Allium cape) with a diameter of (6.7 ± 0.05) cm and a thickness of (1 ± 0.05) cm are dehydrated in a drying oven at two temperatures: 40 °C and 90 °C. The average initial mass and water content of the samples are 32.61 g and 92.13%, respectively. The microbial flora in moulds and yeast is also enumerated before and after drying. An experiment plan of two variables, namely drying time and temperature, is followed to optimize the process tests. The moisture content is taken as a response. The interactions between operating variables are shown and a mathematical model is established expressing, thus, the variation of the moisture content of the onion slices as a function of the temperature and the drying time. A correlation of experimental results and calculations is indeed established. The results show that drying duration decreases with increasing temperature and water content of onion slices decreases from 92.13% to 4.5% during 2595 minutes, and from 92.13% to 9.47% during 1245 minutes, at 40 °C and 90 °C, respectively. Also, the experimental results lead to the appropriate choice of the temperature and the drying time in order to reach adequate moisture content. Finally, Oven drying of the yellow onions with determined dimensions eliminates the moulds to desired and encouraging values.

Keywords: Static drying; Oven; Yellow Onion; Experimentation; Microbial Flora; Allium cepa.

This paper presents an experimental study of the shrinkage phenomenon of apple slices during two types of drying, namely: static drying (in an electric regulated oven) and open sun drying (naturally, on one tray) under the meteorological conditions of Ouargla city in the south east of Algeria. In the oven, the experiments are performed with three different temperatures (50, 60 and 70 °C). The effect of the water content loss of the fruit samples on the dimensions (thickness and diameter) and on the volume are considered. During the static and sun drying, the results show that the volume decreases by 80% and 86% of its initial values, respectively. During the static drying, the diameter of each apple slice shrinks by 20% and the thickness by 70 % of the initial values. Not far from these values, the diameter decreases by 25% and the thickness by 76% of the initial values during the open sun drying. In addition, the drying of apple slices shows an anisotropic shrinkage independently of temperature and therefore a unique shrinkage equation is proposed for each of both methods of drying. Finally, the importance of considering the phenomenon of shrinkage of the apple fruit during drying is shown in the Krischer curves.

Keywords: Apple slices, Experimentation, Shrinkage. Static drying, Open sun drying.