Main Article Content
food quality, microwave drying, mathematical model, drying rate, antioxidant activity
This study analysed the effects of convective (50 and 75 °C), microwave (90 and 160 W) and combined microwave-convective (90 W-50 °C, 90 W-75 °C, 160 W-50 °C and 160 W-75 °C) drying methods on the drying characteristics, colour, total phenolic content and antioxidant activity of sliced green table olives. The shortest drying time was found with the combined microwave-convective 160 W-75 °C method, and it was found that the combined microwave-convective method provided the greatest time savings in comparison to other methods tested. According to the test results, the drying rate of samples increased with increasing convective temperature and microwave power. Based on the statistical tests used for evaluation, the Midilli et al. model was found to be the best model to explain test data for sliced green olives samples under all drying conditions. While the colour values L*, b*, and chroma and hue angle decreased, the colour value a* increased in dried sliced green olive samples. It was found that the 160 W microwave method gave colour values closest to those of fresh samples. Among the different drying treatments, the values to closest those of fresh green olive samples with respect to total phenolic content and antioxidant activity were achieved with the 160 W-75 °C combined microwave-convective drying method.
Akpinar, E.K., 2006. Determination of suitable thin layer drying curve model for some vegetables and fruits. Journal of Food Engineering 73: 75-84.
Al-Duri, B. and McIntyre, S., 1992. Comparison of drying kinetics of foods using a fan-assisted convection oven, a microwave oven a combined microwave/convection oven. Journal of Food Engineering 15: 139-155.
Arslan, D. and Ozcan, M.M., 2010. Study the effect of sun, oven and microwave drying on quality of onion slices. LWT-Food Science and Technology 43: 1121-1127.
Ayensu, A., 1997. Dehydration of food crops using a solar dryer with convective heat flow. Solar Energy 59: 121-126.
Boskou, G., Salta, F.N., Chrysostomou, S., Mylona, A., Chiou, A. and Andrikopoulos, N.K., 2006. Antioxidant capacity and phenolic profile of table olives from Greek market. Food Chemistry 94: 558-564.
Charoenprasert, S. and Mitchell, A., 2012. Factors influencing phenolic compounds in table olives (Olea europaea). Journal of Agricultural and Food Chemistry 60: 7081-7095.
Chayjan, R.A., Parian, J.A. and Esna-Ashari, M., 2011. Modeling of moisture diffusivity, activation energy and specific energy consumption of high moisture corn in a fixed and fluidized bed convective dryer. Spanish Journal of Agricultural Research 9: 28-40.
Clydesdale, F.M., 1998. Color: origin, stability, measurement, and quality. In: Taubm A. and Singh, R.P. (eds.) Food storage stability. ICRC Press, Boca Raton, FL, USA, pp. 175-190.
Contreras, C., Martin-Esparza, M.E., Chiralt, A. and Martinez-Navarrete, N., 2008. Influence of microwave application on convective drying: Effects on drying kinetics, and optical and mechanical properties of apple and strawberry. Journal of Food Engineering 88: 55-64.
Demir, V., Gunhan, T. and Yagcioglu, A.K., 2007. Mathematical modeling of convection drying of green table olives. Biosystems Engineering 98: 47-53.
Devahastin, S. and Niamnuy, C., 2010. Modeling quality changes of fruits and vegetables during drying: a review. International Journal of Food Science and Technology 45: 1755-1767.
Doymaz, I., 2007. Air-drying characteristics of tomatoes. Journal of Food Engineering 78: 1291-1297.
Erbay, B., Üçgül, I., Küçüksayan, S. and Küçüköner, E., 2010. Physical, sensorial, color and rehydration properties of dried green olive slices. Journal of Natural and Applied Sciences 14: 246-250.
E?türk, O. and Soysal, Y., 2010. Drying properties and quality parameters of dill dried with intermittent and continuous microwave-convective air treatments. Journal of Agricultural Sciences 16: 26-36.
Funebo, T. and Ohlsson, T., 1998. Microwave-assisted air dehydration of apple and mushroom. Journal of Food Engineering 3: 353-367.
Garau, M.C., Simal, S., Rossello, C. and Femenia, A., 2007. Effect of air-drying temperature on physico-chemical properties of dietary fibre and antioxidant capacity of orange (Citrus aurantium v. Canoneta) by-products. Food Chemistry 104: 1014-1024.
Giri, S.K. and Prasad, S., 2007. Drying kinetics and rehydration characteristics of microwave-vacuum and convective hot-air dried mushrooms. Journal of Food Engineering 78: 512-521.
Goyal, R.K., Kingsly, A.R.P., Manikantan, M.R. and Ilyas, S.M., 2006. Thin-layer drying kinetics of raw mango slices. Biosystems Engineering 95: 43-49.
Hiranvarachat, B., Devahastin, S. and Chiewchan, N., 2011. Effects of acid pretreatments on some physicochemical properties of carrot undergoing hot air drying. Food and Bioproducts Processing 89: 116-127.
Igual, M., García-Martínez, E., Martín-Esparza, M.E. and Martínez-Navarrete, N., 2012. Effect of processing on the drying kinetics and the functional value of dried apricot. Food Research International 47: 284-290.
nchuen, S., Narkrugsa, W., Pornchaloempong, P., Chanasinchana, P. and Swing, T., 2008. Microwave and hot-air drying of Thai red curry paste. Maejo International Journal of Science and Technology 1: 38-49.
Jing, Y., Jin-Feng, C., Yu-Ying, Z. and Lin-Chun, M., 2010. Effects of drying processes on the antioxidant properties in sweet potatoes. Agricultural Sciences in China 9: 1522-1529.
Kammoun, B.A., Kechaou, N. and Boudhrioua, M.N., 2011. Effect of microwave treatment on physical and functional properties of orange (Citrus sinensis) peel and leaves. Journal of Food Processing and Technology 2: 109-116.
Karaaslan, S.N. and Tuncer, I.K., 2008. Development of a drying model for combined microwave-fan-assisted convection drying of spinach. Biosystems Engineering 100: 44-52.
Karakaya, S., 2004. Bioavailability of phenolic compounds. Critical Reviews in Food Science and Nutrition 44: 453-464.
Kassem, A.S., 1998. Comparative studies on thin layer drying models for wheat. In: Proceedings of the 13th International Congress on Agricultural Engineering, 2-6 February 1998, Rabat, Morocco.
Kastorini, C.M., Milionis, H.J., Goudevenos, J.A. and Panagiotakos, D.B., 2010. Mediterranean diet and coronary heart disease: is obesity a link? – a systematic review. Nutrition, Metabolism and Cardiovascular Diseases 20: 536-551.
Kwok, B.H.L., Hu, C., Durance, T. and Kitts, D.D., 2004. Dehydration techniques affect phytochemical contents and free radical scavenging activities of Saskatoon berries (Amelanchier alnifolia Nutt). Journal of Food Science 69: 122-126.
Lopez, J., Vergara, J., Gonzalez, E., Di Scala, K., Uribe, E., Vega-Galvez, A. and Miranda, M., 2010. Effect of air temperature on drying kinetics, vitamin C, antioxidant activity, total phenolic content, non-enzymatic browning and firmness of blueberries variety O’Neil. Food and Bioprocess Technology 3: 772-777.
Madamba, P.S., Driscoll, R.H. and Buckle, K.A., 1996. The thin-layer drying characteristics of garlic slices. Journal of Food Engineering 29: 75-97.
Marsilio, V., Campestre, C. and Lanza, B., 2001. Phenolic compounds change during California-style ripe olive processing. Food Chemistry 74: 55-60.
Maskan, M., 2000. Microwave/air and microwave finish drying of banana. Journal of Food Engineering 44: 71-78.
Maskan, M., 2001. Kinetics of colour change of kiwifruits during hot air and microwave drying. Journal of Food Engineering 48: 169-175.
McMinn, W.A.M., 2006. Thin-layer modeling of the convective, microwave, microwave-convective and microwave-vacuum drying of lactose powder. Journal of Food Engineering 72: 113-123.
Midilli, A., Kucuk, H. and Yapar, Z., 2002. A new model for single layer drying. Drying Technology 20: 1503-1513.
Minguez-Mosquera, M.I. and Gallardo-Guerrero, L., 1995. Disappearance of chlorophylls and carotenoids during the ripening of the olive. Journal of The Science of Food and Agriculture 69: 1-6.
Miranda, M., Vega-Galvez, A., Lopez, J., Parada, G., Sanders, M., Aranda, M., Uribe, E. and Di Scala, K., 2010. Impact of air-drying temperature on nutritional properties, total phenolic content and antioxidant capacity of quinoa seeds (Chenopodium quinoa Willd.). Industrial Crops and Products 32: 258-263.
Mundada, M., Hathan, B.S. and Maske, S., 2010. Convective dehydration kinetics of osmotically pretreated pomegranate arils. Biosystems Engineering 107: 307-316.
Odjo, S., Malumba, P., Dossou, J., Janas, S. and Béra, F., 2012. Influence of drying and hydrothermal treatment of corn on the denaturation of salt-soluble proteins and color parameters. Journal of Food Engineering 109: 561-570.
Ongen, G., Sargin, S., Tetik, D. and Kose, T., 2005. Hot air drying of green table olives. Food Technology and Biotechnology 43: 181-187.
Özbek, B. and Dadal?, G., 2007. Thin-layer drying characteristics and modelling of mint leaves undergoing microwave treatment. Journal of Food Engineering 83: 541-549.
Reddy, L., 2006. Drying characteristics of Saskatoon berries under microwave and combined microwave-convection heating. MSc Thesis, Department of Agricultural and Bioresource Engineering, University of Saskatchewan, Saskatoon, Canada.
Ruiz-López, I.I., Martínez-Sánchez, C.E., Cobos-Vivaldo, R. and Herman-Lara, E., 2008. Mathematical modeling and simulation of batch drying of foods in fixed beds with airflow reversal. Journal of Food Engineering 89: 310-318.
Ryan, D., Antolovich, M., Prenzler, P., Robards, K. and Lavee, S., 2002. Biotransformations of phenolic compounds in Olea europaea L. Scientia Horticulturae 92: 147-176.
Sakouhi, F., Herchi, W., Sebei, K., Absalon, C., Kallel, H. and Boukhchina, S., 2011. Accumulation of total lipids, fatty acids and triacylglycerols in developing fruits of Olea europaea L. Scientia Horticulturae 132: 7-11.
Sharaf-Eldeen, Y.I., Blaisdell, J.L. and Hamdy, M.Y., 1980. A model for ear corn drying. Transactions of the ASAE 5: 1261-1265.
Sharma, G.P. and Prasad, S., 2004. Effective moisture diffusivity of garlic cloves undergoing microwave-convective drying. Journal of Food Engineering 65: 609-617.
Sharma, G.P., Prasad, S. and Chahar, V.K., 2009. Moisture transport in garlic cloves undergoing microwave-convective drying. Food and Bioproducts Processing 87: 11-16.
Singh, R.P., Chidambara, K.N. and Jayaprakasha, G.K., 2002. Studies on the antioxidant activity of pomegranate peel and seed extracts using in vitro models. Journal of Agricultural and Food Chemistry 50: 81-87.
Soysal, Y., 2004. Microwave drying characteristics of parsley. Biosystems Engineering 89: 167-173.
Sultana, B., Anwar, F., Ashraf, M. and Saari, N., 2012. Effect of drying techniques on the total phenolic contents and antioxidant activity of selected fruits. Journal of Medicinal Plants Research 6: 161-167.
Tello-Ireland, C., Lemus-Mondaca, R., Vega-Gálvez, A., López, J. and Di Scala, K., 2011. Influence of hot-air temperature on drying kinetics, functional properties, colour, phycobiliproteins, antioxidant capacity, texture and agar yield of alga Gracilaria chilensis. LW T-Food Science and Technology 44: 2112-2118.
Therdthai, N. and Zhou, W., 2009. Characterization of microwave vacuum drying and hot air drying of mint leaves (Mentha cordifoliaOpiz ex Fresen). Journal of Food Engineering 91: 482-489.
Turkmen, N., Sari, F. and Velioglu, S., 2005. The effect of cooking methods on total phenolics and antioxidant activity of selected green vegetables. Food Chemistry 93: 713-718.
Vadivambal, R. and Jayas, D.S., 2007. Changes in quality of microwave-treated agricultural products – a review. Biosystems Engineering 98: 1-16.
Wang, C.Y. and Singh, R.P., 1978. A single layer drying equation for rough rice. ASAE Paper no. 78-3001, St. Joseph, MI, USA.
Vega-Gálvez, A., Miranda, M., Díaz, L.P., Lopez, L., Rodriguez, K. and Di Scala, K., 2010. Effective moisture diffusivity determination and mathematical modelling of the drying curves of the olive-waste cake. Bioresource Technology 101: 7265-7270.
Westerman, P.W., White, G.M. and Ross, I.J., 1973. Relative humidity effect on the high temperature drying of shelled corn. Transactions of the ASAE 16: 1136-1139.
Wojdylo, A., Figiel, A. and Oszmianski, J., 2009. Effect of drying methods with the application of vacuum microwaves on the bioactive compounds, color, and antioxidant activity of strawberry fruits. Journal of Agricultural and Food Chemistry 57: 1337-1343.
Yagcioglu, A., Degirmencioglu, A. and Cagatay, F., 1999. Drying characteristics of the laurel leaves under different drying conditions. In: Proceedings of the 7th International Congress on Agricultural Mechanization and Energy, Adana, Turkey, pp. 565-569.
Zanoelo, E.F., Cardozo-Filho, L. and Cardozo-Junior, E.L., 2006. Superheated steam drying of mate leaves and effect of drying conditions on the phenol content. Journal of Food Process Engineering 29: 253-268.
Zhang, M., Tang, J., Mujumdar, A. and Wang, S., 2006. Trends in microwave related drying of fruits and vegetables. Trends in Food Science and Technology 17: 524-534.