Two different pre-treatments were applied to grapes prior to drying in a mixed mode solar dryer. Grapes were blanched in water and in a 0.1% sunflower oil water emulsion, both at 99oC and for approximately 15 seconds. Several models were tested to fit the experimental data of drying curves but the normalized Newton model gave the best fit results. Samples blanched in hot water or in the 0.1% edible oil emulsion had faster drying rates than untreated samples. Contrary to what was expected, pre-treating with the 0.1% edible oil emulsion did not increase the drying rate to a higher extent than blanching. Pre-treatments did not give a noteworthy difference in the total drying time. However, they had an important role in accelerating initial drying rates, thus preventing moulds and bacterial growth and consequently increasing farmers’ income.
References
1.
AGUILERA JM, OPPERMANN K, SANCHEZ F. Kinetics of Browning of Sultana Grapes. Journal of Food Science. 1987;52(4):990–3.
2.
Aoac. Official methods of analysis. 2000;17.
3.
Araújo F, Pascoal M, Candeias M, Dias J, Carvalho B, Machado B. 1994;
4.
314 Uvas para passas -estudo da sua produção. :315.
5.
Bala B, Woods J. Simulation of 319 the indirect natural-convection solar drying 320 of rough rice. Solar Energy. 1994;(3):259–66.
6.
Bala BK, Woods JL. Simulation of the indirect natural convection solar drying of rough rice. Solar Energy. 1994;53(3):259–66.
7.
Bennamoun L, Belhamri A. Design and simulation of a solar dryer for agriculture products. Journal of Food Engineering. 2003;59(2–3):259–66.
8.
Bizot H. Using the ’GAB’model to con-328 struct sorption isotherms. 1983;
9.
Escher B, Hallstrom H, Meffert. :43–54.
10.
Box G, Hunter W, Hunter J. Statistics for experimenters an in-335 troduction to design, data analysis and 336 model building john wiley and sons. New. 1978;334.
11.
Doymaz I. Sun drying of figs: an experimental study. Journal of Food Engineering. 2005;71(4):403–7.
12.
Fuller R. Solar drying of horticul-343 tural produce: present practice and future 344 prospects. Postharvest News and Informa-345 tion. 1993;(3).
13.
Grncarevic M, Radler F. A review of 347 the surface lipids of grapes and their im-348 portance in the drying process. American 349 Journal of Enology and Viticulture. 1971;(2):80–6.
14.
Lahsasni S, Kouhila M, Mahrouz M, Jaouhari J. Drying kinetics of. 2004;
15.
Riva M, Peri C. Kinetics of sun and 394 air drying of different varieties of seedless 395 grapes. Journal Of Food Technology. 1986;(2):396–199.
16.
397 Saravacos G, Marousis S, Raouzeos G. Effect of ethyl oleate on the rate 399 of air-drying of foods. Journal of Food En-400 gineering. 1988;(4):263–70.
17.
El-Sebaii AA, Aboul-Enein S, Ramadan MRI, El-Gohary HG. Empirical correlations for drying kinetics of some fruits and vegetables. Energy. 2002;27(9):845–59.
18.
Striegler R, Berg G, Morris J. Raisin production and processing 409. 1996;
19.
Hui. :235–63.
20.
Togrul I, Pehlivan D. Modelling 415 of thin layer drying kinetics of some fruits 416 under open-air sun drying process. Jour-417 nal of Food Engineering. 2004;(3):413–25.
21.
Toğrul İT, Pehlivan D. Modelling of thin layer drying kinetics of some fruits under open-air sun drying process. Journal of Food Engineering. 2004;65(3):413–25.
22.
Vazquez G, Chenlo F, Moreira R, Carballo L. Desorption isotherms of muscatel and aledo grapes, and the influence of pretreatments on muscatel isotherms. Journal of Food Engineering. 1999;39(4):409–14.
23.
Whiting J. Harvesting and drying of 427 grapes. 1992;
24.
25.
Williamson G, Carughi A. Polyphe-431 nol content and health benefits of raisins. 2010;
26.
Williamson G, Carughi A. Polyphenol content and health benefits of raisins. Nutrition Research. 2010;30(8):511–9.
27.
Williamson G, Carughi A. Polyphenol content and health benefits of raisins. Nutrition Research. 2010;30(8):511–9.
28.
Yaldiz O, Ertekin C, Uzun HI. Mathematical modeling of thin layer solar drying of sultana grapes. Energy. 2001;26(5):457–65.
The statements, opinions and data contained in the journal are solely those of the individual authors and contributors and not of the publisher and the editor(s). We stay neutral with regard to jurisdictional claims in published maps and institutional affiliations.