آنالیز انتقال حرارت و جرم طی فرآیند سرخ‌کردن خلال سیب‌زمینی

نوع مقاله : مقاله پژوهشی

نویسندگان

• حسن صباغی
• امان محمد ضیایی فر
• مهدی کاشانی نژاد

گروه علوم و صنایع غذایی، دانشگاه منابع طبیعی گرگان.

https://doi.org/10.22067/ifstrj.v1395i0.52271

چکیده

در این پژوهش، انتقال حرارت و جرم در فرآیند سرخ‌کردن به‌طور جامعی مورد بررسی قرار گرفت. برای این منظور، عملیات سرخ کردن خلال سیب زمینی در یک سرخ‌کن مجهز به سیستم ترموکنترلر با ترموکوپل نوع K، در سه دمای مختلف روغن 145، 160 و °C 175 به مدت60، 120، 180 و 240 ثانیه انجام گرفت. تغییرات دمای مرکزی محصول طی سرخ کردن با استفاده از ترموکوپل نوع T متصل به دستگاه ثبت داده در کامپیوتر ثبت گردید. محتوی رطوبت و روغن نمونه ها نیز در هر زمان و دمای فرآیند اندازه گیری شد. پارامترهای انتقال حرارت و جرم با استفاده از نمودارهای نسبت‌های دمایی و غلظت بدون بُعد و معادلات تجربی با هدف توسعه روشی واقع بینانه در تخمین، برآورد شد. نتایج نشان داد، عدد بایوت انتقال جرم (Bim)، ضریب انتقال جرم و نفوذ موثر رطوبت با افزایش دمای روغن به‌طور معنی‌داری زیاد شد. در مدل های رگرسیونی، با افزایش دمای بستر فرآیند محتوی تعادلی روغن در زمان بی نهایت کاهش یافت و می توان گفت با افزایش دما، جذب روغن کاهش می یابد. از طرفی ارتباط خطی بین ثابت‌های سنتیک کاهش آب و جذب روغن مشاهده شد که تائید کننده تاثیر پیش تیمار خشک کردن جزئی در کاهش ثابت سنتیک جذب روغن نیز است. این تاثیر می تواند به دلیل فشردگی ماتریس ماده غذایی و در نتیجه کاهش نفوذ روغن بعد از خروج از سرخ کن طی سرد شدن باشد. در نهایت، با افزایش دمای فرآیند نیز عدد بایوت انتقال حرارت (Bih)، ضریب انتقال حرارت جابجایی و هدایت حرارتی محصول به‌طور معنی داری کاهش یافت.

کلیدواژه‌ها

• سرخ کردن
• خلال سیب زمینی
• عدد بایوت
• انتقال جرم
• انتقال حرارت

عنوان مقاله [English]

Analysis of heat and mass transfer during frying process of potato strips

نویسندگان [English]

• Hassan Sabbaghi
• Aman Mohammad Ziaiifar
• Mahdi Kashani-Nejad

Department of Food Processing Engineering, Gorgan University of Agricultural Sciences & Natural Resources, Iran.

چکیده [English]

Introduction: Frying phenomena occur during the immersion of the product in oil at a temperature of 150–200 ºC, where a simultaneous heat and mass transfer take place. This is the most popular thermal processes of potato cooking. This fast drying is critical to improve the mechanical and structural properties of the final product. These conditions lead to high heat transfer rates, rapid cooking, browning, texture and flavor development. The fried potato is easier to transport and provides better texture. Researchers have assumed the existence of two regions for fried product, separated by an interface: the core (unfried) and crust (fried) regions. In general, frying process is very complex for two main reasons: i) due to the simultaneous heat and mass transfer between food material and frying oil, ii) due to the progressive deterioration of the oil and structural changes in foods (crust and core regions). The moving boundary problem may be found in many areas of frying research involving heat and/or mass transfer. In this study, heat and mass transfer is entirely investigated during frying of potato strips. The transport phenomena during frying are including: i) Heat convection from the hot oil to the interface via the crust region, ii) Water evaporation at the moving interface at a temperature of 100 ºC, iii) The unsteady state heat conduction in both regions of crust and core, iv) The oil uptake into food. As a result, high temperature and low moisture conditions develop as frying proceeds. Water vapor bubbles escaping from the surface of the food cause considerable turbulence in the oil. Therefore, Heat and mass transfer are dependent on each other during frying process. In fact, heat and mass transfer during frying can be controlled by heat transfer at the product surface. Evaporation rate depends on the temperature difference between oil and boiling point of water. There is little information on modeling, both empirical and phenomenological, for moisture loss and oil uptake during frying. Knowledge of accurate heat and mass transfer parameters is important for modeling processes. Designing of frying processes is possible through the use of mathematical models. The aim of this study is to develop a more completely and realistic approach for determining of heat and mass transfer parameters and their relation to oil temperatures. The main process parameters influencing oil uptake are frying temperature and duration. Heat transfer coefficients for different oil temperatures determined using simple method. Mass transfer of water was assumed to be governed by Fick's law of diffusion. For more details, empirical models were used to describe the mass transport in forms of moisture and oil.

Materials and Methods: The frying operation of potato strips was performed in the fryer that was equipped by thermo controller system with K type thermocouple at three different oil temperature of 145, 160 and 175 ºC for 60, 120, 180 and 240 seconds. The core temperature changes of product recorded on computer during process using T type thermocouple connected to data logger. The moisture and oil content of samples measured for each process time and temperatures. The heat and mass transfer parameters such as kinetic coefficients of moisture (Km) and oil transfer (Ko), mass transfer coefficient (Kc), effective diffusivity (D) and heat transfer coefficient (h) were evaluated with dimensionless temperature and concentration ratio plots and also empirical equations. Relationship of these parameters to the temperature of the oil investigated using the Arrhenius equation. Thermal conductivity of potato strips during frying determined as a function of moisture content using the Anderson and Spell equations.

Results & Discussion: The results showed that mass transfer Biot number (Bim), mass transfer coefficient (Kc) and effective moisture diffusivity (D) increased significantly with increasing in oil temperature. In regression models, the linear correlation between kinetic constant of water loss and oil uptake was observed that is verification on effect of drying pretreatment on reducing oil uptake. In fact, with increasing of oil temperature the kinetic constant of water loss increased and caused increased in kinetic constant of oil uptake. Kinetic models could correctly confirm determination of mass transfer parameters. The heat transfer Biot number (Bih), convective heat transfer coefficient (h) and product thermal conductivity (k) decreased significantly with an increase in process temperature. With increasing in the rate of evaporation, following greater amount of input energy used for water loss. This would reduce the amount of available energy to increase internal energy of product and thus reduce the convective heat transfer coefficient at high temperatures. Frying process caused remove of water from product and increasing of porosity, thus observed gradually fell in thermal conductivity. Although the minimum thermal conductivity at various temperatures are close together, but two equations of Anderson and Spell showed significant difference for values of thermal conductivity and Spell was more close to published papers. High activation energy is achieved for lower moisture content that is normally due to the strong water-substrate interaction.

کلیدواژه‌ها [English]

• Frying
• Potato strip
• Biot number
• Mass transfer
• Heat transfer

مراجع

Ahromrit, A., and Nema, P.K., 2010, Heat and mass transfer in deep-frying of pumpkin, sweet potato and taro. Journal of Food Science and Technology, 47, 632-637.

Alvis, A., Velez, C., Rada-Mendoza, M., Villamiel, M., and Villada H.S., 2009, Heat transfer coefficient during deep-fat frying. Food Control, 20, 321-325.

Andres, A., Arguelles, A., Castello, M.L., and Heredia, A., 2012, Mass transfer and volume changes in French fries during air frying. Journal of Food and Bioprocess Technology, Doi: 10.1007/s11947-012-0861-2.

AOAC, 2000, Official methods of analysis. 17th ed., Association of Official Analytical Chemists. Washington, DC, Unites States.

Baik, O.D., and Mittal, G.S., 2005, Heat and moisture transfer and shrinkage simulation of deep-fat tofu frying, Food Research International, 38, 183-191.

Blumenthal, M.M. and Stier, R.F., 1991, Optimization of deep-fat frying operations, Trends in Food Science and Technology, 2, 144-148.

Budzaki, S. and Seruga, B., 2004, Determination of convective heat transfer coefficient during frying of potato dough. Journal of Food Engineering. Journal of Food Engineering, 66, 307-314.

Costa, R.M., Oliveira, F.A.R., Delaney, O., and Gekas, V., 1999, Analysis of the heat transfer coefficient during potato frying. Journal of Food Engineering, 39, 293-299.

Debnath, S., Bhat, K.K., and Rastogi, N.K., 2003, Effect of pre-drying on kinetics of moisture loss and oil uptake during deep fat frying of chickpea flour-based snack food. Lebensm.-Wiss. U.-Technol, 36, 91-98.

Dincer, I., 1996. Modelling for heat and mass transfer parameters in deep frying of products. Heat and Mass Transfer, 32, 109-113.

Duran, M., Pedreschi, F., Moyano, P., and Troncoso, E., 2007, Oil partition in pre-treated potato slices during frying and cooling. Journal of Food Engineering, 81, 257-265.

Farid, M.M., and Chen X.D., 1998, the analysis of heat and mass transfer during frying of food using a moving boundary solution procedure. Journal of Heat and mass transfer, 34, 69-77.

Farinu, A. and Baik, O.-D., 2008, Convective mass transfer coefficients in finite element simulations of deep fat frying of sweetpotato. Journal of Food Engineering, 89,187-194.

Farinu, A., and Baik, O. D., 2007, Heat transfer coefficients during deep fat frying of sweetpotato: Effects of product size and oil temperature, Food Research International, 40, 989-994.

Farkas, B.E., Sing R.P., and Rumsey T.R., 1996, Modelling heat and mass transfer in immersion frying. I, Model development. Journal of Food Engineering, 29, 211-226.

Gupta, P., Shivhare, U.S. and Bawa, A.S., 2000, Studies on frying kinetics and quality of French fries. Drying Technology, 18, 311-321.

Kita, A., Lisińska, G., and Gołubowska, G., 2007, The effects of oils and frying temperatures on the texture and fat content of potato crisps. Food Chemistry, 102, 1-5.

Krokida, M.K., Oreopoulou, V., and Maroulis, Z.B., 2000, Water loss and oil uptake as a function of frying time, Journal of Food Engineering, 44, 39-46.

Krokida, M.K., Oreopoulou, V., Maroulis, Z.B., and Marinos-Kouris, D., 2001, Effects of pre-drying on quality of French fries. Journal of Food Engineering, 49, 347-354.

Loon, W.A.M.V., Visser, J.E., Linssen, J.P.H., Somsen, D.J., Klok, H.J., and Voragen, A.G.J., 2007, Effect of pre-drying and par-frying conditions on the crispness of French fries. European Food Research and Technology. 225, 929-935.

Mohebbi, M., Fathi, M., and Shahidi, F., 2011, Genetic algorithm artificial neural network modeling of moisture and oil content of pretreated fried mushroom. Food and Bioprocess Technology, 4, 603-609.

Moyano, P.C., and Pedreschi, F., 2006, Kinetics of oil uptake during frying of potato slices: Effect of pre-treatments. LWT - Food Science and Technology, 39, 285-291.

Palaniappan, S., and Sizer, C. E., 1997, Aseptic process validated for foods containing particulates. Food Technology, 51, 60-68.

Parkash, S., and Gertz, C., 2004, New theoretical and practical aspects of the frying Process, European Journal of Lipid Science and Technology, 106, 722-727.

Pedreschi, F., Hernandez, P., Figueroa, C., and Moyano, P.C., 2005, modeling water loss during frying of potato slices. International Journal of Food Properties, 8, 289-299.

Razavi, M., and Akbari, R., 2006, Biophysical properties of agricultural and food materials. Ferdosi university of Mashhad publication, pp. 255-256.

Romani, S., Bacchiocca, M., Rocculi, P., and Rosa, M.D., 2008, Effect of frying time on acrylamide content and quality aspects of French fries. European Food Research and Technology, 226, 556-560.

Sabbaghi, H., Ziaiifar, A. M., Sadeghi Mahoonak, A., Kashaninejad, M., and Mirzaei, H., 2015, Evaluation of mathematical models to describe the effect of temperature. Iranian Journal of Biosystems Engineering, 46(2), 135-145.

Sabbaghi, H., Ziaiifar, A .M. Sadeghi Mahoonak, A., kashaninejad, M., and Mirzaei, H., 2014, Estimation of convective heat transfer coefficient as function of the water loss rate during frying process. Iranian Food Science and Technology Research Journal, 1394(11), 473-484. doi:10.22067/ifstrj.v1394i11.29653

Sahin, S., Sastry, S.K., and Bayindirli, L., 1999, the determination of convective heat transfer coefficient during frying, Journal of Food Engineering, 39, 307-311.

Saravacos, G. D. and Maroulis, Z. B., 2001, Transport Properties of Foods. Marcel Dekker, New York.

Singh, R.P., and Heldman, D.R., 2001, Introduction to food engineering, (3rd Ed.). London, UK: Academic Press.

Taler, J., 2014, Superposition method for multidimensional heat conduction problems, Hetnarski, R. B. (Ed.), Encyclopedia of Thermal Stresses, Springer Netherlands, pp. 4708-4718.

Treybal, R.E., 1995, Mass-transfer operations, (3rd Ed.), McGraw Hill Publication. USA.

Troncoso, E., and Pedreschi, F., 2009, Modeling water loss and oil uptake during vacuum frying of pre-treated potato slices. LWT-Food Science and Technology, 42, 1164-1173.

Ufheil, G., and Escher, F., 1996, Dynamics of oil uptake during deep-fat frying of potato slices, Lebensmittel-Wissenschaft and Technologie. 29, 640-644.

Vitrac, O., Dufour, D., Trystram, G. and Raoult-Wack, A.L., 2002, Characterization of heat and mass transfer during deep-fat frying and its effect on cassava chip quality. Journal of Food Engineering, 53, 161-176.

Wang, N., and Brennan, J.G., 1992, Thermal conductivity of potato as a function of moisture content, Journal of Food Engineering, 17, 153-160.

Yildiz, A., Palazoglu, K., and Erdogdu, F., 2007, Determination of heat and mass transfer parameters during frying of potato slices. Journal of Food Engineering, 79, 11-17.

Zheleva, I., and Kamburova, V., 2009, modeling of heating during food processing. Costa, R., and Kristbergsson, K. (Eds.), Predictive modeling and risk assessment, Springer US, pp. 79-99.

Ziaiifar, A.M., Heyd, B., and Courtois, F., 2009, Investigation of effective thermal conductivity kinetics of crust and core regions of potato during deep-fat frying using a modified Lees method. Journal of Food Engineering, 95, 373-378