1 African Journal of Food Science Research ISSN 2375-0723 Vol. 2 (11), pp. 149-154, December, 2014. Available online at www.internationalscholarsjournals.org © International Scholars Journals Full Length Research Paper Prediction of drying model and determination of effects of drying temperature on Mucilage and Vitamin-C contents of Fluted Jute (Corchorus capsularis) Leaves Famurewa J. A. V and Akinmuyisitan F A Department of Food Science and Technology, Federal University of Technology, Akure. Accepted 9 December, 2014 This study investigated the suitable drying model and the effects of different drying temperatures on the mucilage property of fluted jute leaves (Corchorus capsularis , . A cabinet dryer was employed to dry a well cleaned leaves in a thin layer, differently at air temperatures of 40, 50, 60 and 70 ℃ respectively. Five thin layer-drying models (Lewis, Page, Modified page, Henderson and Pabis, and Logarithmic) were fitted to the experimental moisture ratio data. The dried samples were analyzed for mucilage and vitamin C contents. Drying of Corchorus leaves prominently occurred in falling rate period. Among the mathematical models investigated, the Logarithmic model satisfactorily described the drying behaviour of Corchorus leaves with highest R 2 and lowest RMSE , MBE, and χ 2 at 40, 50, 60 and 70 0 C respectively. Viscosity was at its highest at 70 0 C and lowest values at 40 ℃ while Vitamin C was highest at 50 0 C and lowest at 40 ℃. Based on the result of this study, drying temperature of 50 ℃ and Logarithmic model were recommended for drying of Corchorus for better retention of vitamin C, though 70 0 C retained higher quantity of mucilage, but not significantly different to that of 50 0 C. Key words: Fluted jute leaves, mucilage, Vitamin C, modelling, drying. INTRODUCTION Green leafy vegetables constitute an indispensable constituent of human diet. In Africa, they are consumed as cooked complements to the major staples, like cassava, cocoyam, guinea corn, maize, millet, rice and plantains. Many of these leaf vegetables are common in all parts of Nigeria, but some are restricted in their natural distribution because of climatic factors. Corchorus spp. is a member of the family Tilaceae, common names include: Long fluted jute, Jew’s marrow, African Sorrel, Bush Okra. Local names include: ‘ewedu’, ‘lalo’, ‘krin krin’. Two main types are common, one with finely serrate leaves, called ‘ Amugbadu’ and the other is shorter with coarsely serrated short leaves called Oniyanya’ *Corresponding author. E-mail: jav_murewa@yahoo.com Oniyanya’ (Oguntona, 1998). It is cultivated as a vegetable and has the advantage of tolerance to many soil conditions. Among any communities, the leaves are valued as a cooked vegetable because of its high proportion of mucilage. The renewed interest in non-orthodox medicine in the World has dramatically increased the demand for plant- based medicine in global market (Natesh 2000). According to Chen and Saad (1981), Corchorus species contain important bioactive compounds such as cardiac glycosides, stropanthidin, b-sitosterol, terpenoid-corosin, flavone glycoside, urasolic acid, vitamin C, b-carotene, mucilage, and others which are potential ingredients for developing plant-based drugs. The leaves are rich in protein, b-carotene, iron, calcium, vitamin B, and vitamin C. They also contain oxydase and chlorogenic acid. According to Awogbemi and Ogunleye (2009), the folic acid content is substantially higher than that of other folacin-rich vegetables. 2 Famurewa and Akinmuyisitan 149 Table 1.Results for Vitamin C and Viscosity Contents of Dried Corchorus leaves. Treatment ℃ Vitamin C (mg/100g) Viscosity (Pascal/ses) 40 359.4 d 2.692 50 1078.75 a 2.693 60 890.03 b 2.694 70 531.25 c 2.969 Values are means of three replicates; values in a column denoted by different letters differ significantly at p <0.05. Drying is one of the oldest methods known for the preservation of agricultural products such as fruits and vegetables, and is the most common in food engineering unit operations. Drying of agricultural products enhances their storage life, minimizes losses during storage, and save shipping and transportation costs (Doymaz 2005). According to Gogus (1994) and Sokhansanj and Jayas (2006), when carried out correctly, the nutritional quality, colour, flavour and texture of rehydrated foods are slightly less than fresh foods. However, if drying is carried out incorrectly there is a greater loss of nutritional and eating qualities and possibly even food poisoning. Drying kinetics of food is a complex phenomenon and requires dependable models to predict drying behaviour (Akpınar and Bicer, 2003). There are several studies describing the drying behaviour of various fruits, vegetables and medicinal plants such as onions (Singh and Sodhi, 2000), garlic cloves (Sharma and Prasad 2001), black tea (Panchariya et al., 2002), grapes (El-Ghetany. 2006), apple (Kaya et al., 2007), Mint leaves, (Kadam et.al 2011b), tomato slices (Abano et al., 2011) and other various vegetables (Awogbemi and Ogunleye, 2009) The objectives of this study therefore are to investigate the effect of drying temperatures on the viscosity of Corchorus capsularis and to predict the mathematical drying models, at four different temperatures, that best describe the drying phenomenon of ‘ewedu’. MATERIALS AND METHODS Materials A cabinet dryer was used. Other materials used include a Digital Weighing balance (accuracy of ± 0.01g), and a bowl. Methods Drying Experiment The Corchorus leaves used for this experiment were all sourced from a farm located at Alaba Layout, South Gate of the Federal University of Technology, Akure. The leaves were separated from the stem and placed in a stainless steel tray. Fifty (50) grams of the leaves were spread in thin layer inside a cabinet dryer. Drying was performed at four different temperatures, 40 ⁰C, 50 ⁰C, 60 ⁰C and 70 ⁰C. Drying continued until two successive constant weights were obtained. Modeling of drying curves For this study, five (5) mathematical models were reported to predict drying conditions; other models showed a very wide variation. These models and their equations are Lewis,. Henderson and Pabis, Page, Modified Page and Logarithmic. Sigma plot Software (Windows Version, 10.0, Synstat Software Inc) was used for the modeling of equations, and the generation of the R 2 Values. Windows Excel (Microsoft Office Suite, Microsoft Inc.) was used in the Calculation of the Root Mean square error (RMSE), Mean Bias error (MBE) and χ 2 values and plotting of the drying curves and the model validation curves for each temperature. Vitamin C and Viscosity Determination Both Vitamin C (Ascorbic acid) and Viscosity (mucilage) were carried out using a method described by AOAC (1990). RESULTS AND DISCUSSION Effect of Drying Temperature on Viscosity and Vitamin C of Corchorus The result in Table (1) showed the effect of drying temperature on the vitamin C content and the viscosity of the leaves. The sample dried at 50 ℃ has the highest value of 1078 mg/100 g, while the sample dried at 40 ℃ had the lowest value at 359 mg/100 g. According to (Ihenkoronye and Ngoddy 1985), vitamin C is heat labile; the low value may be due to the elongated drying period as compared to other samples. This result also agreed with the one reported by Famurewa (2011), when effect 3 150 Afr. J. Food Sci. Res. Figure 1. Drying Curves of Corchorus at different temperatures. Table 2. Values of Model constants for Corchorus dried at 70℃. Model Model Constants R 2 RMSE MBE χ2 Lewis b=0.0344 0.8906 0.107177 -0.04486 0.014359 Page n=0.1592, b=0.8468 0.9988 0.107177 -0.04486 0.074767 Modified Page n=0.1592, b=0.3519 0.9988 0.107176611 -0.04486 0.01914471 Henderson and Pabis a=0.9725, b=0.0332 0.8920 0.107176611 -0.04486 0.01914471 Logarithmic c=0.1737, a=0.8263, b=0.0828 1.0000 0.107176611 -0.04486 0.028717065 of drying on worowo (Senecio biafrae) was investigated. For the Viscosity, the sample dried at 70 ℃ had the highest value, while the sample dried at 40 ℃ s still had the lowest values. Observed Drying Rate during Drying of Corchorus leaves The drying times needed to reach equilibrium moisture content were 420, 390, 160, and 120 min respectively for 40℃, 50℃, 60℃ and 70℃. The results showed that as the temperature was increasing successively by a difference of 10 ℃, drying time was also decreasing. The drying curves showed that the constant rate period was absent; and drying took place in the falling rate period and the moisture loss was faster at the beginning than towards the end of the drying period (Figure 1). These observations are in good agreement with the reports of Sharma and Prassad (2001), Demir et al., (2004) and Premi et al., (2010). Mathematical Models for Fitting of the Drying Curves Moisture ratio drying data for Corchorus were fitted into five mathematical models (Lewis, Page, Modified page, Henderson and Pabis, and Logarithmic). The co-efficient of correlation and statistical analyses for the samples are listed in Tables 2, 3, 4, and 5. In all the models, R 2 values were greater than 0.90 except the Henderson and Pabis model indicating, the fitness of the models in predicting the data and drying behaviour. Results show that the highest value for R 2, , and lowest value for χ 2 , MBE and RMSE were obtained using the Logarithmic Model. This model can therefore be considered as to represent the drying behaviour of Corchorus leaf The results obtained are similar to those reported by Kadam et al., (2011a) for 4 Famurewa and Akinmuyisitan 151 Table 3. Values of Model constants for Corchorus leaf dried at 60℃. Model Model Constants R 2 RMSE MBE χ2 Lewis b=0.0192 0.9163 0.082938 -0.0254 0.008025 Page n=0.5178, b=0.1442 0.9821 0.038389 -0.00226 0.002063 Modified Page n=0.5178, b=0.0237 0.9821 0.038389 -0.00226 0.002063 Henderson and Pabis a=0.9516, b=0.0181 0.9204 0.038389 -0.00226 0.009158904 Logarithmic c=0.1565, a=0.8470, b=0.0340 0.9981 0.012446285 1.42857E- 05 0.000271093 Table 4. Values of Model constants for Corchorus leaf dried at 50℃. Model Model Constants R 2 RMSE MBE χ2 Lewis b= 0.0092 0.8628 0.088378 0.02447 0.102258 Page n= 0.5712, b= 0.0739 0.9672 0.043194 -0.00409 0.110779 Modified Page n= 0.5712, b= 0.0105 0.9672 0.043194 -0.00409 0.110779 Henderson and Pabis a= 0.8862, b= 0.0079 0.8836 0.081406463 -0.024021429 0.110779025 Logarithmic c= 0.1620, a= 0.8423, b= 0.0168 0.9963 0.014506624 -3.96508E-18 0.120849845 Table 5. Values of Model constants for Corchorus leaf dried at 40℃. Model Model Constants R 2 RMSE MBE χ2 Lewis b= 0.0080 0.8712 0.083912 -0.01865 0.007544 Page n= 0.5872, b= 0.0627 0.9763 0.036 -0.00355 0.008124 Modified Page n= 0.5872, b= 0.0089 0.9763 0.036 -0.00355 0.008124 Henderson and Pabis a= 0.8766, b= 0.0067 0.8977 0.074780465 -0.01938 0.008124497 Logarithmic c= 0.1664, a= 0.8307, b= 0.0145 0.9989 0.007607146 6.66667E-06 0.008801538 Figure 2. Validation Curve for various models at 40℃. 0 0.2 0.4 0.6 0.8 1 1.2 0 100 200 300 400 500 M o is tu re R at o , ( P d ) Drying time( min Validation Curve at 40⁰C for the Models. exp lewis page m.page H and P Logarithnic 5 152 Afr. J. Food Sci. Res. Figure 3. Validation Curve for various models at 50℃. Figure 4. Validation Curve for various models at 60℃. Figure 5. Validation Curve for various models at 70℃. 0 0.5 1 1.5 0 200 400 600 M o is tu re R at io , ( M R ,( p re d ) Drying Time, (min) Validation Curve at 50⁰C for the Models exp lewis page m. page H and P Logarithmic 0 0.5 1 1.5 0 100 200 M o is tu re R at io , M R (p re d ) Drying time, (min) Validation Curve at 60⁰C for the Models exp lewis page m. page H and P Logarithmic 0 0.5 1 1.5 0 50 100 150M o is tu re R at io , M R ( P re d ) Drying Time(min) Validation Curve at 70⁰C for the Models exp lewis page m. page H and P 6 Famurewa and Akinmuyisitan 153 basil leaves, Kadam et al., (2011b) for mint leaves, Togrul and Pehlivan, (2002) for apricots; Erenturk et al., (2004) for rosehip and Goyal et al.,(2007) for plum. The mathematical models were subjected to validation, by plotting both the experimented and predicted Moisture ratio values against the drying time. (Figures 2-5). The Figures showed that Logarithmic Model established by mathematical model gave the best fit between experimental and predicted moisture ratios for the four levels of drying temperatures. CONCLUSION Corchorus leaves were dried at 40, 50, 60 and 70°C temperature, the drying rate decreased continuously throughout the drying period. Constant rate period was absent and the drying process of the leaves took place in falling rate period. Drying time decreased considerably with increased temperature. Logarithmic model was the best among the selected models for describing the drying behaviour of Corchorus leaves. The sample dried at 50 ℃ showed the highest retention of vitamin C, while the sample dried at 70 ℃ showed the highest retention of viscosity though not significant to that at 50 0 C. 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