EFFECT OF DRYING METHODS ON TOTAL CAROTENOIDS CONTENT RETENTION IN PRO- VITAMIN A HIGH QUALITY CASSAVA FLOUR

EFFECT OF DRYING METHODS ON TOTAL CAROTENOIDS CONTENT RETENTION IN PRO- VITAMIN A HIGH QUALITY CASSAVA FLOUR * 1 Onyenwoke, C. A., 2 Ojo, C.C.., 3 Omodamiro, R.M.., 3 Egesi, C.N. and 1 Simonyan, K. J. 1 Department of Agricultural and Bioresources Engineering, Michael Okpara University of Agriculture, Umudike. PMB 7267, Umuahia, Abia State, Nigeria. 2 Department of Food Science and Technology, Michael Okpara University of Agriculture, Umudike. PMB 7267, Umuahia, Abia State, Nigeria. 3 National Root Crops Research Institute, Umudike, P.M.B. 7006, Umuahia, Abia State Nigeria ABSTRACT The effect of drying methods on the retention of total carotenoids (TC) in pro-vitamin A HQCF was studied, two varieties of yellow-fleshed (UMUCASS 36 and UMUCASS 37) cassava roots were used for the study. The two varieties were prepared by washing, peeling, grating, dewatering, pulverizing, and processed into HQCF using different drying methods (Tray, oven, indirect active solar) while direct sun drying method was used as control. Results showed that while the fresh cassava roots of the two varieties had moisture content of 71% and 82% fresh weight (FW), their TC content was 8.23 μg/g and 8.15μg/g, respectively. Results indicated that the extent of carotenoids retention varied with the methods of drying, the highest retention was observed in tray drying (80% TC content retention) followed by indirect active solar drying (54% TC content retention) and oven drying (46%). The lowest retention was recorded in the sun drying method (20% TC content retention). The Higher Temperature-Short Time (HTST) combination rather than low temperature-longer time resulted in higher retention of TC. The highest TC retention was observed in oven dried sample at 120 C for 1 hour (55.1%) and the lowest TC retention was observed at 60 C for 3 hours (39.75%). Tray dried HQCF sample at 80-95 C for 1 hour showed a retention of 91.65% and 68.75% at 55-70 C for 2 hours. Keywords: Cassava, HQCF, drying, carotenoids, pro- vitamin A. 1. INTRODUCTION Drying is an essential operation in the chemical, agricultural, biotechnology, food, polymer, ceramic, pharmaceutical, pulp and paper, and wood processing industries.drying is a separation process that converts a wet solid, semisolid, or liquid feedstock into a solid product by evaporation of the liquid into a vapour phase with the application of heat. Essential features of the drying process are phase change and production of a solid (Irene and Avi, 2002). Drying methods and processes can be classified into several different ways. It can be classified as batch, where the material is inserted into the drying equipment and drying proceeds for a given period of time, or as continuous, where the material is continuously added to the dryer and dried material continuously removed.drying processes can also be categorised according to the physical conditions used to add heat and remove water vapour *Corresponding Author: Onyenwoke C. A. Email: maigidaaus@yahoo.com Phone No: +2348068089373 Hidden hunger, which iscaused by lack of micronutrients in the diet, afflicts billions of people.also known as micronutrient malnutrition, results from poor quality diets, characterized by a high intake of staple foods, such as rice, cassava, and maize, and low consumption of micronutrient-rich foods, such as fruits and vegetables. Fruits, vegetables, and animal products are rich in micronutrients, but are often not available to the poor. The daily diet of the poor consists mostly of a few inexpensive staple foods, such as cassava, maize and sweet potato which are mostly white in colour and devoid of carotenoids (Fabiana et al., 2013).Provitamin A carotenoids are mainly found in plants, algae, and microorganisms and can be metabolized into vitamin A in humans and animals (Bouis et al., 2011). Plant foods do not contain vitamin A in the form of retinol; instead they contain a precursor, provitamin A carotenoids, that can be converted into vitamin A in the body (Krinsky and Johnson, 2005). Cassava (Manihot esculenta Crantz), also known as manioc, mandioca, tapioca, or yucca, is a staple food in West Africa.Cassava is a very versatile commodity with

numerous uses and by products (Mazyia-Dixon et al., 2007). Biofortification of cassava with the provitamina carotenoid (β-carotene) is a potential mechanism for alleviating vitamin A deficiency. Currently, a huge sum of money is spent on getting supplements for children. If sufficient vitamin A can be obtained from cassava then such money can be diverted to other things. It is important to acknowledge that biofortification is a cheaper and more sustainable strategy to address vitamin A deficiency (IITA, 2009).The new variety have good culinary quality when used to make lafun with it, the variety saves cost in the production of garri, as there is no buying of palm oil to process yellow garri, there will be more access to nutritious food, improve nutritional status, food security and standard of living (Koca et al., 2005).Yellow rootcassava is usually stored in the ground until needed, as it is highly perishable (Bokanga, 2000). Drying of the root is one simple method of cassava preservation; however some methods of drying are more effective than others in terms of retaining β-carotene levels.the stability of carotenoids differs in different foods, even when the same processing and storage conditions are used (Britton, 1992). Thus, optimum conditions for carotenoid retention during processing vary from one food to another. Carotenoids per se have different susceptibilities to degradation (Oliveria et al., 2010).The general objective of this study is to determine the effect of drying methods on the retention of total carotenoids (TC) in pro-vitamin High Quality Cassava Flour (HQCF).The conduct of the study focused on the drying process using different drying equipment, at varying time and temperature. The drying method considered are: Tray drying, Oven drying, Indirect active solar drying and direct sun drying as a control. Evaluation of totalcarotenoids retention in the HQCFbefore andafter drying was also carried out. 2. MATERIALS AND METHODS 2.1 Material and processing of sample Two varieties of fresh yellow root cassava namely: UMUCASS 36 (TMS 01/1368) and UMUCASS 37 (TMS 01/1412) were used for this study. The cassava roots were harvested at 11 months after planting. These are roots with high beta carotene (pro- vitamin A), very suitable for gari, fufu and High Quality Cassava Flour (HQCF). (Egesi, 2011)Moisture content of the samples was determined (dry bases) before and after each study (dry bases) using oven dried method at a temperature of 105 0 Cfor 24hours. Twenty (20) kg each of the two yellow root cassava varieties was used for the production of HQCF. Roots of each variety were peeled, washed and then traditional method of producing HQCF as shown in Figure 1 was carried out. FRESH YELLOW ROOT CASSAVA Peeling Washing Grating Pressing Pulverizing Drying Milling Sieving Packaging (HQCF) Figure 1: Traditional processing of raw yellow root cassava into HQCF. Drying of cassava mash samples was carried out using three different drying methods namely: Oven drying, tray drying, and indirect active solar drying, direct sun drying was used as control.the dried grated cassava was milled into flour using attrition mill. The flour samples were then sieved using a muslin cloth and the resultant product was HQCF. 2.2 Oven drying An oven dryer (Memmert Gmbt, type UNB 500, 8.7A, 2000W Nen temperature 220 C made in Germany) was used to dry the cassava mashsamples at different drying temperature (60 C, 90 C, and 120 C). 2.3 Tray drying (Cabinet) A locally fabricated trapezoidal shaped tray dryer was used to dry the samples. It consists of an electric blower (230v, 50Hz, 650 Watts, 1300 rpm), electric heater (230V 50Hz, 2000Watts, 350/600 C) and four trays that are stacked vertically (Figure 2). It has a length of 188 cm, width 97 cm and height 62 cm while the tray length is 54 cm and width is 38 cm. The body of dryer was made of a thick insulated metal sheet to prevent heat loss, electric heater supplies the required heat. The blower helps in circulation of the heat. The tray dryer has small perforations at one of its ends to allow air flow, while the other end is where the heater and blower are mounted. A

digital thermometer was attached to the tray dryer to check the temperature reading. Figure 2: Tray dryer 2.4 Indirect active solar drying An indirect active solar dryer was used to dry samples. In this system, drying was achieved indirectly by using an air collector that channels hotair into a separate drying chamber. The dryer is made up of four units; drying chamber, pneumatic system, heat storage system, andsolar energy collector. The drying chamber was built with angle iron, transparent corrugated plastic sheet, metal sheet, and black polythene to prevent sun ray interference. The chamber (162 cm by 70 cm) stands vertically with tray sittings (70 cm by 60 cm), door, chimney and a diffuser as shown in Figure 3. The chimney (5 cm by 10 cm) is at the top of the chamber and it facilitates easy exit of the humid air from the chamber. The diffuser was positioned at the lower back of the chamber which provides point of attachment to the pneumatic system. The solar energy storage system is made of angle iron frame, metal sheet, stones and transparent corrugated plastic sheet. It is rectangular in shape (78 cm by 60 cm) and lies perpendicular to the drying chamber, the inside and the stones were painted black, it has two openings, the ambient air inlet and the heated air exit. The pneumatic system consists of a centrifugal blower made of sheet metal with two openings, the inlet and outlet air spaces. The blower sucks heated air from the solar energy storage system and spreads it to the drying samples in the drying chamber. 2.5 Direct sun drying Figure 3: Indirect active solar dryer The samples were sun dried as a control for the research, the varieties were put into different trays and kept under the sun. 2.6 Analysis of total carotenoids content The HarvestPlus procedure for carotene analysis was used to determine the total carotenoids content of the fresh cassava roots, reduced mash, and HQCF. Total Carotenoid Content (TCC) was calculated using equation 1 Total Carotenoid content (μg g) = A volume (ml) 10 df A 1% (1) 1cm sample weight (g) Where A = Absorbance volume =Total volume of extract (ml) A 1% 1cm = Absorption coefficient of β carotene in P. E. (2592) df = Dilution factor P.E = Petroleum Ether 2.7 Data collection and statistical analysis

Data from the evaluation were collected and statistically analyzed using GenStat Discovery Edition 3 package to obtain the Analysis of Variance (ANOVA). Complete Randomised Design (CRD) in Factorial Design and Least Significant Difference (LSD) were used to establish if there were significant differences among the samples and drying methods. 3.0 RESULTS AND DISCUSSION 3.1 Moisture content The average moisture content levels of the fresh root, mashed sample, and High Quality Cassava Flour (HQCF) are given in Table 1.The initial moisture content of the two varieties (UMUCASS 36 and UMUCASS 37) was 71% and 82% fresh weight (FW), respectively. The moisture content of the grated mashed samples was 38.25 % - 48.23 % dry basis (db) and TC retained was 24.86-38.66 %.Omodamiroet al., (2012) in their study on production of fufu from yellow cassava roots recorded 21.55-33.87 % TC retentionfor grated cassava mash. The difference in TC retention may be as a result of processing time and initial TC content of fresh roots.total carotenoid (TC) retention reduces as the moisture content reduces.this was as a result of increasing the surface area of the cassava by grating, pressing, and drying, which exposes the carotenoids in the samples to degradation.the Sample moisture content of HQCF produced was within the range of 12% - 14.4% db. 3.2 Effect of drying methods on total carotenoid retention in HQCF The effect of different drying methods on High Quality Cassava Flour (HQCF) samples is presented in Table 2. Table 3 present the ANOVA for treatments.the average percentage retention of total carotenoids using different dryingmethods is presented in Figure 4. Tray drying (Cabinet) showed the highest percentage retention of total carotenoids (80 %), followed by indirect active solar drying (54 %), then oven drying (46 %) and sun drying (20 %). Analysis of variance was used to determine the significant interaction among independent variables. The results of analysis of variance using Completely Randomized Design (CRD) in factorial experiment indicates that there is a statistically high significant effect among treatment means at 1% level of probability (Tray drying, indirect solar drying, oven drying and drying under sun). Interaction between drying methods and varieties are significantly different. Fisher s Least significant difference (FSLDα0.01) was further used to detect the treatment mean difference. There was a great difference in treatment means between tray drying and oven drying (2.45µg/g), while indirect solar drying and sun drying had 2.45 µg/g as their difference mean value. Table 1: Moisture content ofumucass 36 and UMUCASS 37 samples (%) UMUCASS 36 UMUCASS 37 TCC Retention (%) Fresh root 71.00 82.56 71.18-80.94 Grated mashed 38.25 48.23 64.65 68.54 HQCF 12.04 14.40 46.08 54.10 Table 2: Effect of drying methods on total carotenoids content µg/g

TCC Retention % EFFECT OF DRYING METHODS ON TOTAL CAROTENOIDS CONTENT RETENTION IN PRO- VITAMIN A HIGH QUALITY CASSAVA FLOUR. Drying methods UMUCASS 36 UMUCASS 37 Mean Oven 3.67 ab 4.06 ca 3.32 db Sun 1.57 bd 1.59 ce 1.44 ca Indirect active solar 4.60 cd 4.32 de 3.89 ab Tray 6.16 da 6.85 ac 5.77 ba loss ofcarotenoids. The drastic reduction of carotenoids in thisprocess may be due to the detrimental effect of the sunlight on the stability of carotenoid pigment. Similar results were reported by Iglesias et al. (1997) when studying the stability of carotene in response to different processing methods,their average total TC was 27% (range: 10-55%) in sun-dried flour and 55% (range: 17-99%) in oven-dried flour.chavez et al.(2007) evaluated the effect of different drying methods on the trueretention of β-carotene in light-yellow cassava roots.the highest β- carotene retention was obtained by oven-drying (72%), followed by shade-drying (59%), and sun-drying (38%) which was not too different from what was obtained in this study. Means with different superscript in each column are significantly different (p<0.01) from one another Drying methods Tray drying Indirect solar drying Oven drying Sun drying Figure 4: Total carotenoid retention in HQCF with different drying methods There were losses during the drying processes (Figure. 4. Tray drying HQCF had lowest detrimental effect on the TC retention (< 20 %) followed by the indirect active solar drying (< 47 %), oven drying (< 55 %) and sun-drying (< 80 %). Sun drying of cassava mash leads to maximum Table 3: ANOVA for treatments Varieties*drying process Source of variation d.f. s.s. m.s. v.r. F pr. 3.3 Effect of temperature on total carotenoids content Tables 4 and 5 show the effect of temperature on the total carotenoid retention in HQCF. Figure 5 represent the percentage retention of total carotenoid in HQCF. Table 4shows that the highest TC retention (54.9 %) was observed at 120 C for 1 hour and the lowest TC (36.6 %) retention was observed at 60 C for 3 hours in oven dried HQCF. Table 5 shows that the highest TC retention (93.3 %) was observed at 80 C -95 C for 1 hour and the lowest TC (58.9 %) retention was observed at 55 C-70 C for 2 hours in tray dried HQCF. Drying at High Temperature Short Time (HTST) tends to retain more TC content than drying at low temperature long time (holder process) as shown in Figure 5.There was significant difference (P < 0.01) in the tray temperature time as HTLT tends to have less detrimental effect in terms of TC retention than lower temperature longer time (Figure 5). The higher temperature-short time combination rather than low temperature-longer time resulted in higher pvac retention in sweet potato (Bengtsson et al.; 2008, Bechoff et al., 2009) and maize (Burt et al., 2010), which was not different with cassava in this study. Varieties 1 89351 89351 23.66 <.001 Dry process 3 1685108 561703 148.76 <.001 Varieties*dryproess 3 116404 38801 10.28 0.005 Residual 30 113293 3776 Total 37 4027210

TCC Retention % EFFECT OF DRYING METHODS ON TOTAL CAROTENOIDS CONTENT RETENTION IN PRO- VITAMIN A HIGH QUALITY CASSAVA FLOUR. Table 4: Total carotenoids content of oven dried HQCF Temperature UMUCASS 36 (µg/g) UMUCASS 37 (µg/g) 60 C for 3hrs 3.11±0.67 3.85±0.40 90 C for 2hrs 3.21±0.39 3.87±0.67 120 C for 1hr 4.70±0.12 4.47±0.85 mean±sd high significant difference (P < 0.01) between the varieties. Carotenoids are destroyed by heat, light, and oxygen or a combination of all three, increasing the surface area of a cassava by grating, pressing and drying exposes carotenoids in the food to degradation. Consequently, it is notsurprising that processing of plant foods is often associated withdecreases in the amount of carotenoids in the consumed product, the longer the processing time, the more effect it causes on the carotenoids content. According to Azevedo-Meleiro and Rodriguez-Amaya (2004), retention is significantly improved by reducing the processing time, lowering the temperature, and shortening the time lag between peeling, cutting, or puréeing and processing. Rapid processing at high temperature is a good alternative. Analyses of variance were used to determine the significant interaction among independent variables. The results of the analysis of variance using Completely Randomized Design (CRD) in factorial experiment indicates that there is a statistically high significant effect among treatment means at P < 0.01level of significant (Tray drying at temperature range between 55 C - 70 C for 2 hrs and 80 C-95 C for 1 hr) and (Oven drying at 60 C for 3hrs, 90 C for 2hrs and 120 C for 1hr). Interaction between temperature and varieties are highly significantly different at P < 0.01level as shown in Table 6 and 7. Fisher s Least significant difference (FSLDα0.01) was further used to detect the treatment mean difference. There was a great difference in treatment means between tray dying temperature at HTST and LTLT. There was also Temperature( C)/ Time (hr) UMUCASS 36A UMUCASS 37A Figure 5: Total carotenoid retention in tray dried HQCF at different temperature Table 5: Total carotenoids content of tray (cabinet) dried HQCF. Temperature UMUCASS 36 (µg/g) UMUCASS 37 (µg/g) UMUCASS 37 (µg/g) 55 C-70 C for 2 hrs 4.85±3.32 6.10±2.16 6.10±2.16 80 C 95 C for 1 hr 7.46±0.44 7.60±5.10 7.60±5.10 mean±sd Table 6: Oven temperature* varieties

Source of variation d.f. s.s. m.s. v.r. F pr. VRT 3 86967.621 28989.207 15810.49 <.001 OV_TEMP_TIME 2 4457.881 2228.941 1215.65 <.001 VRT.OV_TEMP_TIME 6 16470.568 2745.095 1497.15 <.001 Residual 11 20.169 1.834 Total 23 107920.047 Table 7: Tray temp* varieties Source of variation d.f. s.s. m.s. v.r. F pr. VRT 3 33792.81 11264.27 1079.94 <.001 TD_TEMP 1 106153.92 106153.92 10177.31 <.001 VRT.TD_TEMP 3 75851.64 25283.88 2424.05 <.001 Residual 7 73.01 10.43 Total 15 215930.79 *** Least significant differences of means (1% level) *** 4. CONCLUSION Overall, tray-drying (80%) was not as damaging to the carotenoid content in HQCF as drying with oven (46%), indirect solar drying (54%) and drying under the sun (20.0%). Indirect solar drying is far better than sun drying in terms of carotenoid retention and it may be a better option for drying cassava in the rural environment where oven drying is not available. Temperature had a great effect on the stability of TC in processed pro vitamin A cassava (HQCF). Drying at High Temperature Short Time (HTST) retained more TCC on average, than Low Temperature long Time (LTLT) as was observed during tray drying at temperature range between 80 C- 95 C for 1hour and 55 C-70 C for 2hours and also during oven drying at temperature 60 C for 3hours, 90 C for 2hours and 120 C for 1hour. The processing time should be minimized, since rapid processing at high temperature goes a long way in improving total carotenoids retention. REFERENCES [1] Azevedo-Meleiro C.H. and Rodriguez-Amaya D. B. (2004). Carotenoids of endive and New Zealandspinach as affected by maturity, season and minimal processing.j Food Comp Anal. 21(3) 68-75. [2] Bechoff, A., Dufour, D. and Dhuique-Mayer, C. (2009). Effect of hot air, solar and sun drying treatments on provitamin A retention in orange-fleshed sweet potato. Journal of Food Engineering.92 (2):164-171. [3] Bengtsson, A., Namutebib, A. and Almingera, M. L. (2008). Effects of various traditional processing methods on the all-trans-β-carotene content of orange-fleshed sweet potato. Journal of Food Composition and Analysis. 21(2):134-143. [4] Bokanga, M. (2000). Cassava: Post-harvest operations. Information Network on Post-Harvest Operations. 1-26. FAO Cassava post-harvest pdf.http/;www.fao.org/fileadmn/userupload/info/docs/post-harvest compendium/ [5] Bouis, H.E., Hotz C., McClafferty, B., Meenakshi J. V. and Pfeiffer W. H. (2011). Biofortification: A new tool to reduce micronutrient malnutrition. Food Nutr Bull, 32(1 Suppl):S31-40. [6] Britton, G. (1992). Carotenoids. In: Hendry, G.F. (Ed.), Natural Foods Colorants. G.F.Blackie, New York, pp. 141 148. [7] Burt, A. J., Grainger, C. M., Young J. C., Shelp, B. J. and Lee E. A. (2010). Impact of postharvest handling on carotenoid concentration and composition in highcarotenoid maize (Zea mays L.) kernels. JAgric Food Chem. 58(14):8286-92.

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Onyenwoke et al., 2015