124 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 © Global Society of Scientific Research and Researchers http://asrjetsjournal.org/ Impact of Shadow Drying on Nutritive and Antioxidant Properties of Leafy Vegetables Consumed in Southern Côte D’Ivoire Florentin Achoa, Lessoy Zouéb*, Sébastien Niamkéc a,b,cBiotechnology Laboratory, Biosciences Faculty, Felix Houphouet Boigny University, 22 BP 582 Abidjan 22 aEmail: conxty977@gmail.com bEmail: y.lessoy@yahoo.fr cEmail: niamkes@yahoo.fr Abstract The abundance of leafy vegetables during the rainy seasons and poor transport and storage systems lead to their post-harvest losses in dry seasons. Effective preservation and storage of these plants would not only reduce their post-harvest losses but make them available throughout the year. Therefore a study was conducted on shadow drying effect on the nutritive and antioxidant properties of five selected leafy vegetables consumed in Southern Côte d’Ivoire. Experiment was conducted as follow: portions of washed and drained fresh leafy vegetables (500 g) were spread on clean filter paper and kept in a well-ventilated room of the laboratory at 25°C for 5, 10 and 15 days. The results of the proximate composition after 15 days of drying were: moisture (14.16 – 20.51%), ash (8.30 -19.16%), crude fibres (11.43 – 21.27%), proteins (9.13 – 19.05%), lipids (3.29 – 7.97%) and carbohydrates (32.45 – 51.74%). The minerals concentration increased with respective values after 15 days of shadow drying: calcium (78.23-337.26 mg/100g), magnesium (70.41-208.46 mg/100g), phosphorus (50.73- 184.81 mg/100 g), potassium (363.56-776.73 mg/100g), iron (12.14-63.57 mg/100g) and zinc (12.57-33.95 mg/100g). During shadow drying, vitamin C and carotenoids were subjected to losses estimated to 65.52 – 91.07% and 39.66 – 95.23%, respectively. Contrary to these losses, antioxidant activity increased and ranged from 66.10 to 74.33% after 15 days of shadow drying. All these results suggest that the considerable nutrient contents of shade dried leafy vegetables make them good source of food when supplemented with sources of vitamin C and carotenoids in order to meet the nutritional requirements of Ivorian population. ------------------------------------------------------------------------ * Corresponding author. http://asrjetsjournal.org/ American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 125 Keywords: food preservation; leafy vegetables; nutritive composition; shadow drying. 1. Introduction Leafy vegetables are herbaceous plants whose leaves are eaten as supporting food or main dishes and they may be aromatic, bitter or tasteless [1]. The utilization of leafy vegetables is part of Africa cultural heritage and these plants play important roles in the customs, traditions and food culture of the African household. The nutrient content of different types of leafy vegetables varies considerably and they are not major sources of carbohydrates compared to the starchy foods but contain vitamins, essential amino acids, as well as minerals and antioxidants [2]. According to [3], leafy vegetables are the cheapest and most available sources of important proteins, vitamins, minerals and essential amino acids. However, there is seasonal variation in the availability of many of these vegetables. In general leafy vegetables grow abundantly during the rainy season and are most readily available than in the dry season [4]. Due to their high moisture content (70 – 90%), leafy vegetables are perishable and have a short self-life (1-3 days) after harvesting [5]. Indeed, during the wet season, the leaves of these plants which are either cultivated or grow naturally are abundant but without post-harvest preservation, the excess after consumption goes to waste. To avoid post-harvest losses, drying processing has been documented as an appropriate method for preserving leafy vegetables in order to ensure that they are available in other seasons [6]. By definition, food dehydration is the process of removing water from food by circulating hot air through it, which prohibits the growth of enzymes and bacteria [7]. According to [8], drying removes moisture and the food becomes smaller and lighter in weight. Because of increasing consumption rate of dried leafy vegetables during the dry season, there is a need to investigate the effect of different drying methods on the nutritive value of common edible African Leafy Vegetables (ALVs). In rural areas of Southern Côte d’Ivoire (Ivory Coast) were population are not provided by refrigerator, shadow drying is the method often used for the preservation of leafy vegetables before their consumption through recipes made of sauces and starchy staples foods [9]. Five (5) leafy vegetables (Basella alba “epinard”, Colocasia esculenta “taro”, Corchorus olitorius “kplala”, Solanum melongena “aubergine” and Talinum triangulare “mamichou”) mostly consumed in Southern Côte d’Ivoire are subjected to this traditional drying method. Earlier reports have highlighted the nutritive potential of these fresh leafy vegetables [10] and the focus of the present research was to establish the effect of shadow drying method on their nutritive and antioxidant properties. 2. Material and Methods 2.1. Material Leafy vegetables (Basella alba, Colocasia esculenta, Corchorus olitorius, Solanum melongena and Talinum triangulare) were collected fresh and at maturity from cultivated farmlands located at Dabou (latitude: 5°19′14″ North; longitude: 4°22′59″West) (Abidjan District, Côte d’Ivoire). Samples were harvested at the early stage (between one and two weeks of the appearance of the leaves). These plants were previously authenticated by the American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 126 National Floristic Center (University Felix Houphouët-Boigny, Abidjan-Côte d’Ivoire). 2.2. Drying processing The collected leafy vegetables were rinsed with deionized water and the edible portions were separated from the inedible portions. The edible portions were allowed to drain at ambient temperature and separated into two portions of 500 g each. The first portion was spread on clean filter paper and kept in a well-ventilated room of the laboratory at 25°C for 5, 10 and 15 days. Natural current of air was used for shadow drying and the leaves were constantly turned to avert fungal growth [11]. The second 500 g portion of leafy vegetables was not subjected to any form of drying and used as the control (raw). After drying period, the dried leaves were stored in air-tight containers for further analysis. 2.3. Nutritive analysis Proximate analysis was performed using official methods [12]. The moisture content was determined by the difference of weight before and after drying samples (10 g) in an oven (Memmert, Germany) at 105°C until constant weight. Ash fraction was determined by the incineration of dry matter sample (5 g) in a muffle furnace (Pyrolabo, France) at 550°C for 12 h. The percentage residue weight was expressed as ash content. For crude fibres, 2 g of dry matter sample were weighed into separate 500 mL round bottom flasks and 100 mL of 0.25 M sulphuric acid solution was added. The mixture obtained was boiled under reflux for 30 min. Thereafter, 100 mL of 0.3 M sodium hydroxide solution was added and the mixture were boiled again under reflux for 30 min and filtered through Whatman paper. The insoluble residue was then incinerated, and weighed for the determination of crude fibres content. Proteins were determined through the Kjeldhal method and the lipid content was determined by Soxhlet extraction using hexane as solvent. Carbohydrates content and calorific value were calculated and expressed on dry matter basis using the following formulas [13]: Carbohydrates: 100 – (% moisture + % proteins + % lipids + % ash + % fibres) Calorific value: (% proteins x 2.44) + (% carbohydrates x 3.57) + (% lipids x 8.37) Minerals contents were determined by the ICP-MS (inductively coupled argon plasma mass spectrometer) method [14]. The crushed samples (5 g) were burned to ashes in a muffle furnace (Pyrolabo, France). The ashes obtained were dissolved in 10 mL of HCl/HNO3 and transferred into 100 mL flasks and the volume was made up using deionized water. The mineral composition of each sample was determined using an Agilent 7500c argon plasma mass spectrometer. Calibrations were performed using external standards prepared from a 1000 ppm single stock solution made up with 2% nitric acid. The titration method as described by [15] was performed for oxalate determination. One (1) g of crushed sample was weighed into 100 mL conical flask. A quantity of 75 mL of sulphuric acid (3 M) was added and stirred for 1 h with a magnetic stirrer. The mixture was filtered and 25 mL of the filtrate was titrated while hot against KMnO4 solution (0.05 M) to the end point. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 127 Phytates contents were determined using the Wade’s reagent colorimetric method [16]. A quantity (1 g) of crushed sample was mixed with 20 mL of hydrochloric acid (0.65 N) and stirred for 12 h with a magnetic. The mixture was centrifuged at 12000 rpm for 40 min. An aliquot (0.5 mL) of supernatant was added with 3 mL of Wade’s reagent. The reaction mixture was incubated for 15 min and absorbance was measured at 490 nm by using a spectrophotometer (PG Instruments, England). Phytates content was estimated using a calibration curve of sodium phytate (10 mg/mL) as standard. 2.4. Antioxidant properties evaluation Vitamin C contained in analyzed samples was determined by titration using the method described by [17]. About 10 g of crushed leaves were soaked for 10 min in 40 mL metaphosphoric acid-acetic acid (2%, w/v). The mixture was centrifuged at 3000 rpm for 20 min and the supernatant obtained was diluted and adjusted with 50 mL of bi-distilled water. Ten (10) mL of this mixture was titrated to the end point with dichlorophenol- indophenol (DCPIP) 0.5 g/L.Carotenoids content was carried out according to [18]. Two (2) g of crushed leaves were mixed three times with 50 mL of acetone until loss of pigmentation. The mixture obtained was filtered and total carotenoids were extracted with 100 mL of petroleum ether. Absorbance of extracted fraction was then read at 450 nm by using a spectrophotometer (PG Instruments, England). Total carotenoids content was subsequently estimated using a calibration curve of β-carotene (1 mg/mL) as standard. Polyphenols content was determined using the method reported by [19]. A quantity (1 g) of crushed sample was soaked in 10 mL of methanol 70% (w/v) and centrifuged at 1000 rpm for 10 min. An aliquot (1 mL) of supernatant was oxidized with 1 mL of Folin–Ciocalteu’s reagent and neutralized by 1 mL of 20% (w/v) sodium carbonate. The reaction mixture was incubated for 30 min at ambient temperature and absorbance was measured at 745 nm by using a spectrophotometer (PG Instruments, England). The polyphenols content was obtained using a calibration curve of gallic acid (1 mg/mL) as standard.Antioxidant assay was carried out using the 2,2-diphenyl-1-pycrilhydrazyl (DPPH) spectrophotometric method outlined by [20]. About 1 mL of 0.3 mM DPPH solution in ethanol was added to 2.5 mL of sample solution (1 g of crushed sample was mixed in 10 mL of methanol, filtered through filter paper and was allowed to react for 30 min at room temperature. Absorbance values were measured with a spectrophotometer (PG Instruments, England) set at 415 nm. The average absorbance values were converted to percentage antioxidant activity using the following formula: Antioxidant activity (%) = 100 – [(Abs of sample – Abs of blank) x 100/Abs positive control] 3. Results and Discussion 3.1. Nutritive properties Table 1 shows the proximate composition of fresh and shade dried leafy vegetables. Moisture content was significantly (p ˂ 0.05) higher (74.38 – 90.20%) for fresh leafy vegetables than dried ones (14.16 – 20.51%) after 15 days of shadow drying. The high moisture content in the fresh leafy vegetables was expected since it has been reported that leafy vegetables in their fresh state contain basically 85% of water [21]. The maximum American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 128 moisture content varies between leafy vegetables because of structural differences and cultivation conditions [22]. High moisture content in leafy vegetables is indicative of their freshness as well as easy perish-ability [23]. Higher moisture content in leafy vegetables also suggests that they will not store for long time without spoilage since higher water activity could enhance microbial activity and food spoilage [24,25]. The lower moisture content of shade dried leafy vegetables is not surprising since [26] reported that drying involves lowering the amount of water to below 1 – 55% in vegetables. Moisture content of a food is very important for shelf-life and any food prepared from dried leafy vegetables has more keeping quality than the fresh one [27]. Generally, the removal of moisture, according to [28] leads to an increase in concentration of nutrients as indicated after 15 days of shadow drying by the contents of ash, crude fibres, proteins, lipids and carbohydrates (Table-1). The ash contents (8.30 -19.16%) of shadow dried samples were similar to that reported by [29] for tomatoes, okra, pepper and onions subjected to the same preservation treatment. Ash content indicates the mineral content of food substances and shade dried leafy vegetables could be considered as valuable sources of minerals in human nutrition. Crude fiber contents were significantly higher (p < 0.05) for 15 days shade dried leaves (11.43 – 21.27%) than those (1.37– 4.23%) of fresh vegetables. Dietary fiber may be classified into three major groups (cellulose, non- cellulose and lignin) according to structure and properties. Foods containing high amount of dietary fiber are very low in caloric content. Thus, high fiber diets as dried leafy vegetables could be recommended for weight reducing regimes [30]. Dietary fiber in vegetables reduces food transit time in the alimentary canal and the incidence of constipation and other related diseases [31]. Therefore, adequate intake of the studied dried leafy vegetables could be useful for maintaining bulk, motility and increasing intestinal tract which is also necessary for healthy condition. The protein content of 15 days dehydrated leaves was in the range of 9.13 – 19.05 g per 100 g. The protein content of 15 days dehydrated leafy vegetables increased by 3 to 12-fold compared to the fresh samples. The author [32] observed that increase in protein content of dried leafy vegetables compared to fresh ones may occur as a result of loss of moisture which in turn has an influence on dry matter. These results are also in agreement with the studies done by [33] which showed that dried leaves retained good amounts of protein. Thus, shadow dried leafy vegetables could be good and affordable sources of protein for poor community of developing countries in order to fight against protein deficiency. The fat content (3.29 – 7.97%) of 15 days dried leaf samples were also higher than their fresh counter parts (0.48 – 1.47%) but leafy vegetables could not be considered as a rich source of fat, which is in agreement with the fact that green leafy vegetables are “heart friendly food”. As far as carbohydrates are concerned, leafy vegetables are not considered as a good source of carbohydrate but after 15 days of dehydration, the carbohydrate content of the leaves (32.45 – 51.74%) was higher than vegetables such as potato (22.6%) and turnip greens (9.4%) [34]. However, low carbohydrates contents of leafy vegetables show that they could supply little or no energy when consumed except when supplemented with other foods [35]. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 129 Table 1: Proximate composition of shade dried leafy vegetables consumed in Southern Côte d’Ivoire Moisture (%) Ash (%) Fiber (%) Proteins (%) Lipids (%) Carbohydrates (%) Energy (kcal /100g) C. esculenta Raw 82.35 ± 2.83a 2.65 ± 0.00d 4.23 ± 0.01d 1.72 ± 0.00d 1.47 ± 0.00d 7.56 ± 0.07d 44.53 ± 0.04d 5 days 74.45 ± 0.47b 3.42 ± 0.00c 5.45 ± 0.00c 2.30 ± 0.00c 2.05 ± 0.00c 9.31 ± 0.00c 56.06 ± 0.00c 10 days 43.29 ± 0.74c 8.71 ± 0.00b 14.13 ± 0.00b 5.88 ± 0.00b 5.13 ± 0.00b 22.82 ± 0.00b 138.90 ± 0.00b 15 days 15.09 ± 2.69d 14.05 ± 0.01a 21.27 ± 0.00a 9.13 ± 0.01a 7.97 ± 0.00a 32.45 ± 0.00a 204.93 ± 0.01a B. alba Raw 89.82 ± 1.24a 2.01 ± 0.00d 1.67 ± 0.00d 1.00 ± 0.00d 0.69 ± 0.00d 4.78 ± 0.01d 25.36 ± 0.02d 5 days 81.48 ± 1.75b 3.68 ± 0.00c 3.07 ± 0.00c 1.90 ± 0.00c 1.33 ± 0.00c 8.50 ± 0.00c 46.19 ± 0.00c 10 days 58.48 ± 0.52c 8.48 ± 0.00b 6.99 ± 0.00b 4.35 ± 0.00b 3.57 ± 0.00b 18.09 ± 0.00b 105.15 ± 0.00b 15 days 18.06 ± 3.27d 16.90± 0.01a 13.96± 0.00a 9.47± 0.00a 7.93± 0.00a 51.74± 0.01a 209.72± 0.05a S. melongena Raw 74.38 ± 0.72a 5.20 ± 0.01d 3.50 ± 0.00d 3.16 ± 0.00d 0.69 ± 0.00d 13.04 ± 0.02d 71.11 ± 0.09d 5 days 65.47 ± 3.36b 7.23 ± 0.00c 4.87 ± 0.00c 4.35 ± 0 .01c 1.08 ± 0.00c 16.96 ± 0.01c 80.28 ± 0.01c 10 days 24.40 ± 1.40c 16.44 ± 0.00b 11.21 ± 0.00b 10.02 ± 0.00b 2.50 ± 0.00b 35.38 ± 0.00b 171.83 ± 0.00b American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 130 Data are represented as Means ± SD (n = 3). Means in the column with no common letter differ significantly (p<0.05) for each leafy vegetable. Mineral composition of dehydrated leafy vegetables is given in Table 2. There was a significant (p < 0.05) increase in the mineral content during shadow drying. Minerals contents after 15 days of shadow drying were as follow: calcium (78.23-337.26 mg/100g), magnesium (70.41-208.46 mg/100g), phosphorus (50.73-184.81 mg/100 g), potassium (363.56-776.73 mg/100g), iron (12.14-63.57 mg/100g) and zinc (12.57-33.95 mg/100g). All the minerals contents increased manifolds in the dehydrated samples and this fact could be beneficial because micronutrient deficiency also referred as “hidden hunger” is a major problem in the developing countries. With regards to the recommended dietary allowances (RDA) as mg/day/person for minerals, the level of iron and zinc in the samples could cover RDA [36]. 15 days 14.16 ± 1.89d 18.81 ± 0.00a 12.97 ± 0.00a 12.40 ± 0.00a 3.29 ± 0.00a 38.32 ± 0.00a 194.72 ± 0.01a T. triangulare Raw 90.20 ± 0.21a 2.17 ± 0.00d 1.37 ± 0.00d 1.68 ± 0.00d 0.48 ± 0.00d 5.17 ± 0.00d 26.58 ± 0.01d 5 days 80.39 ± 3.80b 3.85 ± 0.00c 2.37 ± 0.00c 2.92 ± 0.00c 0.82 ± 0.00c 6.63 ± 0.00c 37.70 ± 0.02c 10 days 54.91 ± 1.47c 10.73 ± 0.00b 6.74 ± 0.00b 8.03 ± 0.00b 2.40 ± 0.00b 17.16 ± 0.00b 101.01 ± 0.00b 15 days 20.51 ± 3.97d 19.16± 0.01a 12.21 ± 0.00a 14.76± 0.01a 4.37± 0.00a 49.50± 0.01a 249.30± 0.05a C. olitorius Raw 84.28 ± 0.34a 1.34 ± 0.00d 1.80 ± 0.00d 3.32 ± 0.00d 0.51 ± 0.00d 8.73 ± 0.00d 43.60 ± 0.00d 5 days 73.50 ± 0.66b 2.32 ± 0.00c 3.21 ± 0.00c 5.76 ± 0.00c 0.88 ± 0.00c 14.31 ± 0.00c 72.54 ± 0.01c 10 days 23.41 ± 0.11c 6.99 ± 0.00b 9.71 ± 0.00b 16.90 ± 0.00b 2.82 ± 0.00b 40.14 ± 0.00b 208.22 ± 0.00b 15 days 14.83 ± 1.23d 8.30 ± 0.00a 11.43 ± 0.00a 19.05 ± 0.00a 3.33 ± 0.00a 43.03 ± 0.00a 228.01 ± 0.00a American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 131 Iron is known to be an essential part of red blood cells (haemoglobin) and consumption of these leafy vegetables could reduce considerably the risk of anaemia [37]. The drying processing used in this study increased by 2 to 9-fold the contents of oxalates and phytates compared to the contents of fresh leafy vegetables (Figure 1). Oxalates and phytates are considered as anti-nutritional factors which reduce minerals bioavailability. In order to predict adverse effects of phytates and oxalates, anti- nutritional factors/minerals ratios were calculated (Table 3). The calculated phytates/calcium ratios of the dried leafy vegetables were below the critical level of 0.5 [38]. This implies that phytates contents of the dried leaves would not have deleterious effects on calcium bioavailability. Table 2: Mineral composition (mg/100g) of shade dried leafy vegetables consumed in Southern Côte d’Ivoire. Ca Mg P K Fe Na Zn C. esculenta Raw 103.64 ± 0.01d 61.29 ± 0.00d 139.08 ± 0.02d 402.70 ± 0.06d 25.30 ± 0.00d 6.96 ± 0.00d 6.58 ± 0.00d 5 days 134.99 ± 0.01c 80.44 ± 0.01c 142.66 ± 0.02c 420.28 ± 0.00c 33.59 ± 0.00c 7.68 ± 0.00c 8.38 ± 0.00c 10 days 159.53 ± 0.00b 92.55 ± 0.00b 171.94 ± 0.00b 517.99 ± 0.00b 42.02 ± 0.00b 8.69 ± 0.00b 9.80 ± 0.00b 15 days 194.51 ± 0.22a 110.81 ± 0.23a 184.81 ± 0.11a 594.45 ± 0.06a 47.62 ± 0.10a 13.25 ± 0.10a 12.57 ± 0.01a B. alba Raw 76.38 ± 0.00d 76.74 ± 0.00d 39.71 ± 0.00d 275.31 ± 0.02d 7.88 ± 0.00d 56.50 ± 0.07d 6.84 ± 0.00d 5 days 81.63 ± 0.18c 84.85 ± 0.02c 64.84 ± 0.02c 304.08 ± 0.02c 8.79 ± 0.03c 64.41 ± 0.08c 9.04 ± 0.00c 10 days 103.76 ± 0.03b 92.57 ± 0.03b 87.48 ± 0.01b 339.72 ± 0.02b 10.16 ± 0.00b 81.81 ± 0.01b 12.20 ± 0.00b 15 days 122.17± 0.24a 97.62 ± 0.22a 98.77 ± 0.09a 363.56 ± 0.13a 12.14 ± 0.04a 103.13 ± 0.16a 20.70 ± 0.01a S. melongena American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 132 Data are represented as Means ± SD (n = 3). Means in the column with no common letter differ significantly (p<0.05) for each leafy vegetable. Raw 204.07 ± 0.00d 123.46 ± 0.00d 95.93 ± 0.00d 578.01 ± 0.01d 35.73 ± 0.00d 82.78 ± 0.02d 16.58 ± 0.00d 5 days 281.52 ± 0.00c 169.87 ± 0.00c 104.62 ± 0.00c 683.50 ± 0.00c 52.65 ± 0.00c 96.89 ± 0.00c 25.35 ± 0.00c 10 days 326.86 ± 0.01b 204.94 ± 0.00b 120.50 ± 0.01b 728.48 ± 0.02b 60.09 ± 0.00b 99.98 ± 0.00b 29.58 ± 0.00b 15 days 337.26 ± 0.06a 208.46 ± 0.05a 128.82 ± 0.15a 776.73 ± 0.02a 63.57 ± 0.00a 129.23 ± 0.09a 33.95 ± 0.00a T. triangulare Raw 58.93 ± 0.00d 74.08 ± 0.00d 23.47 ± 0.00d 495.21 ± 0.00d 10.02 ± 0.00d 25.50 ± 0.00d 3.53 ± 0.00d 5 days 62.16 ± 0.35c 76.31 ± 0.04c 33.73 ± 0.10c 542.53 ± 0.08c 18.34 ± 0.07c 35.29 ± 0.09c 8.14 ± 0.00c 10 days 62.81 ± 0.10b 82.77 ± 0.01b 41.87 ± 0.06b 601.15 ± 0.03b 27.89 ± 0.02b 40.40 ± 0.04b 12.19 ± 0.00b 15 days 78.23 ± 0.42a 88.07 ± 0.11a 50.73 ± 0.13a 619.00 ± 0.09a 29.34 ± 0.07a 45.60 ± 0.16a 19.99 ± 0.01a C. olitorius Raw 58.00 ± 0.00d 36.86 ± 0.00d 49.80 ± 0.00d 412.26 ± 0.05d 15.34 ± 0.00d 4.36 ± 0.00d 3.88 ± 0.00d 5 days 65.4 7± 0.01c 65.21 ± 0.06c 55.64 ± 0.02c 421.49 ± 0.03c 18.45 ± 0.01c 9.48 ± 0.00c 9.15 ± 0.00c 10 days 74.01 ± 0.00b 68.40 ± 0.00b 60.90 ± 0.00b 443.62 ± 0.00b 21.78 ± 0.00b 18.19 ± 0.00b 11.37 ± 0.00b 15 days 80.84 ± 0.03a 70.41 ± 0.02a 63.74 ± 0.00a 490.00 ± 0.17a 23.09 ± 0.00a 24.26 ± 0.04a 19.65 ± 0.00a American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 133 Table 3: Anti-nutritional factors/mineral ratios of shade dried leafy vegetables consumed in Southern Côte d’Ivoire. Phytate/Ca Phytate/Fe Oxalate/Ca C. esculenta Raw 0.04 0.18 0.99 5 days 0.03 0.12 0.99 10 days 0.02 0.08 0.99 15 days 0.02 0.05 1.07 B. alba Raw 0.03 0.26 0.87 5 days 0.01 0.07 0.89 10 days 0.01 0.04 0.89 15 days 0.00 0.01 0.86 S. melongena Raw 0.05 0.30 0.12 5 days 0.01 0.06 0.13 10 days 0.01 0.04 0.14 15 days 0.01 0.02 0.15 T. triangulare Raw 0.05 0.29 0.86 5 days 0.01 0.03 0.89 10 days 0.00 0.02 0.90 15 days 0.00 0.02 0.94 C. olitorius Raw 0.11 0.40 2.11 5 days 0.03 0.11 1.87 10 days 0.02 0.09 1.83 15 days 0.02 0.07 1.81 3.2. Antioxidant properties Most common antioxidants in leafy vegetables and spices are vitamin C, E, phenolic compounds and carotenoids [39]. The contents of vitamin C and carotenoids in the shade dried leafy vegetables are shown in Figure-2. In all the samples, vitamin C and carotenoids contents were depleted during shadow drying. Indeed, losses of these antioxidants components were 65.52 – 91.07% and 39.66 – 95.23%, respectively after 15 days of shadow drying. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 134 Figure 1: Effect of shadow drying on oxalates (A) and phytates (B) contents of leafy vegetables consumed in Southern Côte d’Ivoire. Vitamin C and carotenoids losses were directly dependent on the method of drying leafy vegetables. Indeed, shadow drying generally leads to lower vitamin C and carotenoids contents due to the oxidation phenomenon [40]. In addition, the registered losses in vitamin C and carotenoids were higher than those (8 – 26%) of pretreated (blanching and sulphiting) and dried leaves. Therefore, this justifies the fact that several authors have applied different pretreatments before solar and sun-drying processes in order to improve the quality and nutritional parameters of dried products [41]. The phenolic contents of the samples increased during shadow drying (Figure-3). The values were in the range of 156.28-340.24 mg/100 g at 15 days of drying. These values were 6 to 12-fold higher than those (13.31 – 51.07 mg/100g) of the fresh ones. Increase in phenolics compounds may be due to the concentration effect of drying on nutrients. Phenolics components are secondary metabolites synthesized by plants both during normal development and in response to stress conditions (infection, wounding, UV radiation and others) [42]. They also have antioxidant properties that enable them to quench free radicals which lead to beneficial effect on human health by reducing the occurrence of coronary heart diseases [43]. Furthermore, increasing in phenolics contents caused the increase of antioxidant activity (Figure-3) because there is a direct correlation between the concentration of antioxidant compounds and the antioxidant activity [44]. Antioxidant activity ranged from 66.10 ± 0.00 % to 74.33 ± 0.00 % after 15 days of shadow drying. Thus, this increase in phenolics contents and antioxidant activity could be explored for nutraceutical recipes confection including shadow dried leaf powder. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 135 Figure 2: Effect of shadow drying on vitamin C (A) and carotenoids (B) contents of leafy vegetables consumed in Southern Côte d’Ivoire Figure 3: Effect of shadow drying on polyphenols contents (A) and antioxidant activity (B) contents of leafy vegetables consumed in Southern Côte d’Ivoire American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 21, No 1, pp 124-139 136 4. Conclusion The results of the present study showed that shadow drying of leafy vegetables consumed in Southern Côte d’Ivoire is an effective method of food preservation and could be used to close the seasonal gaps. This drying processing leads to concentration of nutrients per unit. 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