Main Article Content

D. I. Onwude
N. Hashim
R. Janius
N.M. Nawi
K. Ebdan


Thin layer drying, color kinetics, color measurement, carotenoid, pumpkin


The color changes kinetics of pumpkin slices during convective hot air drying was investigated at drying temperatures of 50, 60, 70 and 80 °C. The hunter lab L* a* and b* color coordinates were used as assessment indicators. The total color change, chroma value, hue angle and brownness index (BI) of the pumpkin slices where also determined. To determine the most suitable kinetics model for the prediction of the color changes of pumpkin, the zero-order, first-order, and fractional conversion models were fitted to the experimental data, using linear regression analysis. The activation energy of the color change parameters (L*, a*, b* and   ) was estimated and found to be 41.59 kJ/mol, 16.287 kJ/mol, 63.856 kJ/mol and 73.390 kJ/mol respectively. The fresh pumpkin samples contained a mean total carotenoid content of 25? g/g, while the total carotenoid content of samples dried at 50 °C, 60 °C,70 °C and 80 °C were 146? g/g, 56.4? g/g, 37.9? g/g and 102.5? g/g respectively. Further, the results of ANOVA showed there was significant difference between the total carotenoid content of the fresh pumpkin samples and those dried in convective hot air dryer at 5% (p<0.05) significant level. 

Abstract 1172 | PDF Downloads 789


Akanbi, C. T. and Oludemi F. O. 2004. Effect of Processing and Packaging on the Lycopene Content of Tomato Products. International Journal of Food Properties 7(1).

Alam, S., Gupta, K., Khaira, H., and Javed, M. 2013. Quality of dried carrot pomace powder as affected by pretreatments and methods of drying. Agric Eng Int: CIGR Journal, 15(4): 236–243.

Alonge, A. F. and Onwude, D. I. 2013. Estimation of Solar Radiation for Crop Drying in Uyo, Nigeria Using a Mathematical Model. Advanced Materials Research, 824: 420–428.

ASAE. 2005. Moisture Measurement — Unground Grain and Seeds. American Society of Agricultural and Biological Engineers 1988: 2–4.

Avila, I. M. L. B., Silva, C. L. M., Gardner, A. C. and Hunter, D. 1999. Modelling kinetics of thermal degradation of colour in peach puree. Journal of Food Engineering 1999, 39 (2): 161–166

Azizah, A. H., Wee, K. C., Azizah, O. and Azizah, M. 2009. Effect of boiling and stir frying on total phenolics , carotenoids and radical scavenging activity of pumpkin ( Cucurbita moschata ). International Food Research Journal, 16: 45–51.

Bal, L. M., Kar, A., Satya, S. and Naik, S. N. 2011. Kinetics of colour change of bamboo shoot slices during microwave drying. International Journal of Food Science & Technology, 46(4): 827–833.

Bechoff, A., Chijioke, U., Tomlins, K. I., Govinden, P., Ilona, P., Westby, A. and Boy, E. 2015. Carotenoid stability during storage of yellow gari made from biofortified cassava or with palm oil. Journal of Food Composition and Analysis.

Bechoff, A., Westby, A., Menya, G. and Tomlins, K. I. 2011. Effect of Pretreatments for Retaining Total Carotenoids in Dried and Stored Orange-Fleshed-Sweet Potato Chips. Journal of Food Quality, 34(4): 259–267.

Dadali, G., Demirhan, E. and Özbek, B. 2007. Color Change Kinetics of Spinach Undergoing Microwave Drying. Drying Technology, 25(10): 1713–1723.

Dadali, G., Kiliç A.D. and Özbek, B. 2007. Color Change Kinetics of Okra Undergoing Microwave Drying. Drying Technology, 25(5): 925–936.

De carvalho, L. M. J., Gomes, P. B., Godoy, R. L. D. O., Pacheco, S., Do Monte, P. H. F., De Carvalho, J. L. V., … Ramos, S. R. R. 2012. Total carotenoid content, ?-carotene and ?-carotene, of landrace pumpkins (Cucurbita moschata Duch): A preliminary study. Food Research International, 47(2): 337–340.

Demirhan, E. and Özbek, B. 2009. Color Change Kinetics of Microwave-Dried Basil. Drying Technology, 27(1): 156–166.

Demirhan, E. and Özbek, B. 2011. Color Change Kinetics of Celery Leaves Undergoing Microwave Heating. Chemical Engineering Communications, 198(10): 1189–1205.

Djuikwo, V. N. D., Ejoh, R. A., Gouado, I., Mbofung, C. M. and Tanumihardjo, S. A. 2011. Determination of Major Carotenoids in Processed Tropical Leafy Vegetables Indigenous to Africa. Food and Nutrition Sciences, 02(08): 793–802.

Doymaz, I. 2007. The kinetics of forced convective air-drying of pumpkin slices. Journal of Food Engineering, 79: 243–248.

Durante, M., Lenucci, M. S. and Mita, G. 2014. Supercritical carbon dioxide extraction of carotenoids from pumpkin (Cucurbita spp.): a review. International Journal of Molecular Sciences, 15(4): 6725–40.

Guiné, R. P. F., Pinho, S. and Barroca, M. J. 2011. Study of the convective drying of pumpkin (Cucurbita maxima). Food and Bioproducts Processing, 89(4): 422–428.

Hashim, N., Janius, R. Bin, Baranyai, L., Rahman, R. A., Osman, A. and Zude, M. 2011. Kinetic Model for Colour Changes in Bananas During the Appearance of Chilling Injury Symptoms. Food and Bioprocess Technology, 5(8): 2952–2963.

Hashim, N., Onwude, D. and Rahaman, E. 2014. A Preliminary Study?: Kinetic Model of Drying Process of Pumpkins ( Cucurbita Moschata ) in a Convective Hot Air Dryer. Agriculture and Agricultural Science Procedia 2, 2: 345–352.

Hosseinpour, S., Rafiee, S., Mohtasebi, S. S. and Aghbashlo, M. 2013. Application of computer vision technique for on-line monitoring of shrimp color changes during drying. Journal of Food Engineering, 115(1): 99–114.

Johnson E.J. 2002. The role of carotenoids in human health. Nutrition in Clinical Care; 5(2): 47–

Koca, N., Burdurlu, H. S. and Karadeniz, F. 2007. Kinetics of colour changes in dehydrated carrots. Journal of Food Engineering, 78: 449–455.

Kotíková, Z., Lachman, J., Hejtmánková, A. and Hejtmánková, K. 2011. Determination of antioxidant activity and antioxidant content in tomato varieties and evaluation of mutual interactions between antioxidants. LWT - Food Science and Technology, 44(8): 1703–1710.

Krokida, M. K., Karathanos, V. T., Maroulis, Z. B. and Marinos-Kouris, D. 2003. Drying kinetics of some vegetables. Journal of Food Engineering, 59(4): 391–403.

Krokida, M. K., Tsami, E. and Maroulis, Z. B. 2007. Kinetics On Color Changes During Drying Of Some Fruits and Vegetables, Drying Technology, 37–41.

Lau, M. H., Tang, J. and Swanson, B. G. 2000. Kinetics of textural and color changes in green asparagus during thermal treatments, 45: 231–236.

Lee, J. S. and Lim, L. S. 2011. Osmo-dehydration pretreatment for drying of pumpkin slice. International Food Research Journal, 18(4): 1223–1230.

Maria, L., Carvalho, J. De, Azevedo, L. De, Moreira, S., Luiz, J., Carvalho, V. De, … Koblitz, B. 2014. Assessment of carotenoids in pumpkins after different home cooking conditions. Food Science and Technology, 34: 365–370.

Misha, S., Mat, A. S., Ruslan, M. H., Sopian, K. and Salleh, E. 2013. The Effect of Drying Air Temperature and Humidity on the Drying Kinetic of Kenaf Core. Applied Mechanics and Materials, 315: 710–714.

Mohammadi, A., Rafiee, S., Emam-Djomeh, Z. and Keyhani, A. 2008. Kinetic Models for Colour Changes in Kiwifruit Slices During Hot Air Drying. World Journal of Agricultural Sciences, 4(3): 376–383.

Moldovan, C. and Raba, D. 2010. Determination by RP-HPLC of ?-carotene concentration from orange ( Citrus sinensis L . ) fruits peel extracts. Journal of Agroalimentary Processes and Technologies, 16(2): 242–246.

Nawirska, A., Figiel, A., Kucharska, A. Z., Sokó?-??towska, A. and Biesiada, A. 2009. Drying kinetics and quality parameters of pumpkin slices dehydrated using different methods. Journal of Food Engineering, 94(1): 14–20.

Nor, N. M. 2013. Development Of Expanded Snack Foods Containing Pumpkin Flour And Corn Grits Using Extrusion. Massey University, Palmerston North, New Zealand.

Norshazila, S., Irwandi, J., Othman, J. and Zuhanis, Y. 2012. Scheme of obtaining ?-carotene standard from pumpkin ( Cucurbita moschata ) flesh. International Food Research Journal, 19(2): 531–535.

Pathare, P. B., Opara, U. L., and Al-Said, F. A. J. 2012. Colour Measurement and Analysis in Fresh and Processed Foods: A Review. Food and Bioprocess Technology, 6(1): 36–60.

Pesek, C. A. and Warthesen, J. J. 1990. Kinetic model for photoisomerization and concominant photodegradation of b-carotene. Journal of Agricultural and Food Chemistry, 38: 1313–1315.

Prakash, S., Jha, S. and Datta, N. 2004. Performance evaluation of blanched carrots dried by three different driers. Journal of Food Engineering, 62(3): 305–313.

Ravelo-perez, M. L., Hernandez-Borges, J., Rodriguez-Delgado, M. A. and Borges-Miguel, T. 2008. Spectrophotometric Analysis of Lycopene in Tomatoes and Watermelons: A Practical Class. Journal of Chemical Educator (13): 11-13.

Rodriguez, G. A. 2001. Extraction, Isolation, and Purification of Carotenoids. In Current Protocols in Food Analytical Chemistry (p. F2.1). John Wiley & Sons, Inc.

Rodriguez-Amaya, D. B. 2003. Enhancing the carotenoid levels of foods through agriculture and food technology. Food Africa, Internet Forum 31 March - 11 April;

Rodriguez-Amaya, D.B. 2002. Effects of processing and storage on food carotenoids. Sight and Life Newsletter 3: 25-35.

Rodriguez-Amaya, D. B. 2001. A Guide To Carotenoid Analysis In Foods (pp. 41–45). ILSI Press, USA.

Sahabi, D., Shehu, R., Saidu, Y. and Abdullahi, A. 2012. Screening for Total Carotenoids and ?- Carotene in Some Widely Consumed Vegetables in Nigeria. Nigerian Journal of Basic and Applied Sciences, 20 (3): 225-227.

Scott K. J. 2001. Detection and Measurement of Carotenoids by UV/VIS Spectrophotometry. Current Protocols in Food Analytical Chemistry. F2.2.1-F2.2.10., John Wiley & Sons, Inc.

Seo, J. S., Burri, B. J., Quan, Z., and Neidlinger, T. R. 2005. Extraction and chromatography of carotenoids from pumpkin. Journal of Chromatography A, 1073(1-2): 371–375.

Stahl, W. 1992. Human and Clinical Nutrition uptake of Lycopene and Its Geometrical Isomers Is Greater from Heat-Processed than from unprocessed Tomato Juice in Humans1, (March, 1992).

Vega-gálvez, A., Lemus-Mondaca, R., Bilbao-Sáinz, C., Fito, P. and Andrés, A. 2008. Effect of air drying temperature on the quality of rehydrated dried red bell pepper (var. Lamuyo). Journal of Food Engineering, 85(1): 42–50.

Xiao, H.W., Law, C.L., Sun, D.W. and Gao, Z.J. 2014. Color Change Kinetics of American Ginseng (Panax quinquefolium) Slices During Air Impingement Drying. Drying Technology, 32(4): 418–427.

Yun, M. S., Zzaman, W. and Yang, T. A. 2015. Effect of Superheated Steam Treatment on Changes in Moisture Content and Colour Properties of Coconut Slices, International Journal on Advanced Science Engineering Information Technology 5(2): 24–27.