256 Journal homepage: www.fia.usv.ro/fiajournal Journal of Faculty of Food Engineering, Ştefan cel Mare University of Suceava, Romania Volume XIV, Issue 3- 2015, pag. 256 - 268 EFFECT OF SUN DRYING ON NUTRITIVE AND ANTIOXIDANT PROPERTIES OF FIVE LEAFY VEGETABLES CONSUMED IN SOUTHERN CÔTE D’IVOIRE *ConstantACHO1, LessoyZOUE1, Niamkey ADOM1, Sébastien NIAMKE1 1Biotechnology Laboratory, Biosciences Faculty, Félix Houphouet-Boigny University, PO Box 582, Abidjan 22, Côte d’Ivoire, conxty977@gmail.com, *Corresponding author Received August24th 2015, accepted September 25th 2015 Abstract: This study aimed to evaluate the effect of sun drying on nutrient and antioxidant properties of five leafy vegetables (Basella alba, Colocasia esculenta, Solanum melongena, Talinum triangulare and Corchorius olitorus) commonly used in Southern Côte d’Ivoire. The result of this study revealed that sun drying increased some nutrient contents by concentration phenomenon after 1, 2 and 3 days at 30-32 °C. Ash, fibres, proteins, lipids and carbohydrates contents varied after 3 days of sun drying as follow: 10.12 ± 0.00 to 25.78 ± 0.00 %, 16.50 ± 0.00 to 29.81 ± 0.01 %, 16.67 ± 0.01 to 23.68 ± 0.00 %, 6.28 ± 0.00 to 14.24 ± 0.00 % and 10.21 ± 0.00 to 37.68 ± 0.00 %. The mineral contents increased with respective values after 3 days of sun drying: calcium (82.86-481.65 mg/100 g), magnesium (81.98-298.46 mg/100 g), phosphorus (63.41-297.69 mg/100 g), potassium (419.81-993.41 mg/100 g), iron (20.05-90.37 mg/100 g), sodium (19.43-150.51 mg/100 g) and zinc (15.76-64.39 mg/100 g). However, anti-nutritional factors such as oxalates varied from 123.01 to 815.97 mg/ 100 g for the same period of drying. Losses of vitamin C and carotenoids were estimated to 85.12-96.42% and 98-100% respectively. Contrary to these losses, the antioxidant activity increased and ranged from 75.92 to 82.30% after 3 days of sun drying. All these results suggest that sun drying technique could contribute efficiently to the nutritional requirements and to the food security of Ivorian population. Keywords:Sun drying, Nutritive value, Antioxidant properties, Leafy vegetables. 1. Introduction Hunger and malnutrition threaten millions of people in sub-Saharan andthe increase in consumption of African leafy vegetables (ALVs) can have a positive effect on nutrition, health and economic well-being of both rural and urban populations [1]. Traditional African Leafy vegetables are eaten by many African families because they are rich in micro nutrients needed by humans for good health, growth and development [2]. These plants occupy an important place among the food crops as they provide adequate amounts of many vitamins and minerals for humans[3]. The ethno-botanical reports offers information on medicinal properties of ALVs like anti- diabetic, anti-histaminic, anti-carcinogenic, hypolipidemic and antibacterial activity [4,5]. However ways of leafy vegetables preparation and preservation may affect significantly the concentration and availability of minerals, vitamins and other essential compounds. Indeed, losses of nutrients from vegetables during drying and cooking have been noted in previous studies[6, 7].Drying is the process of removal of moisture due to simultaneous heat and mass transfer actions. It is the http://www.fia.usv.ro/fiajournal mailto:conxty977@gmail.com Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 257 classical method for food preservation which serves lighter weight for transportation and small space for storage[8].Apart from moisture losses, the changes in organoleptic quality of dried vegetables are: optical properties (colour, appearance), sensory properties (odour, taste, flavour), and structural properties (density, porosity, specific volume, textural properties). Dried vegetables are generally tasty, nutritious, lightweight, easy-to prepare, and easy-to-store and use[9]. In rural areas of Southern Côte d’Ivoire (Ivory Coast) were population are not provided by refrigerator, sun drying is the method used for the preservation of leafy vegetables before their consumption through recipes made of sauces and starchy staples foods[10]. Ethno-botanical studies have stated that most people in Southern Côte d’Ivoire consume indigenous green leafy vegetables such as Basella alba “epinard”, Colocasia esculenta “taro”, Corchorus olitorius “kplala”, Solanum melongena “aubergine” and Talinum triangulare “mamichou” [11, 12, 13]. Earlier reports have highlighted the nutritive potential of these fresh leafy vegetables [14] but there is a lack of scientific data with regards to the effect of sun drying methods on their physicochemical and nutritive characteristics. The aim of this study was to determine the effect of sun drying method on chemical composition of five leafy vegetables consumed in Southern Côte d’Ivoire. 2. Matherials and methods 2.1Materials 2.1.1 Samples collection 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). The 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 National Floristic Center (University Felix Houphouët-Boigny, Abidjan-Côte d’Ivoire). 2.1.2 Samples processing The fresh leafy vegetables were destalked, washed with deionized water and edible portions were separated from the inedible portion. The edible portions were allowed to drain at ambient temperature and separated into two portions of 250 g each. The first portion was spread on black polythene sheet and dried under the sun (35-38°C) for 1, 2 and 3 days during 8 hours per day [15]. The leaves were constantly turned to avert fungal growth. The second 250 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 ground with a laboratory crusher (Culatti,France) equipped with a 10 μm mesh sieve and stored in air-tight containers for further analysis. 2.2 Methods 2.2.1 Nutritive properties 2.2.1.1 Proximate analysis Proximate analysis was performed using official methods [16]. The moisture content was determined by the difference of weight before and after drying the sample (10 g) in an oven (Memmert, Germany) at 105°C until constant weight. Ash fraction was determined by the incineration of dried sample (5 g) in a muffle furnace (Pyrolabo, France) at 550°C for 12 h. The percentage residue Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 258 weight was expressed as ash content. For crude fibres, 2 g of 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 and calorific value were calculated using the following formulas [17]: Carbohydrates: 100 – (% moisture + % proteins + % lipids + % ash + % fibres). Calorific value: (% proteins x 2.44) + (% carbohydrates x 3.57) + (% lipids x 8.37). 2.2.1.2 Mineral analysis Minerals contents were determined by the ICP-MS (inductively coupled argon plasma mass spectrometer) method [18].The dried powdered 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. 2.2.1.3 Anti-nutritional factors determination Oxalates content was performed by using a titration method [19]. One (1) g of dried powdered 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.Phytates contents were determined using the Wade’s reagent colorimetric method [20]. A quantity (1 g) of dried powdered 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. 2.2.2 Antioxidant properties 2.2.2.1 Vitamin C and carotenoids determination Vitamin C contained in analyzed samples was determined by titration [21]. About 10 g of ground fresh 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 were extracted and quantified following a spectrophotometric method [22]. Two (2) g of ground fresh 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 Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 259 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. 2.2.2.2 Polyphenols determination Polyphenols were extracted and determined using Folin–Ciocalteu’s reagent [23]. A quantity (1 g) of dried powdered 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. 2.2.2.3 Antioxidant activity Antioxidant activity assay was carried out using the 2, 2-diphenyl-1-pycrilhydrazyl (DPPH) spectrophotometric method [24]. About 1 mL of 0.3 mM DPPH solution in ethanol was added to 2.5 mL of sample solution (1 g of dried powdered sample mixed in 10 mL of methanol), filtered through Whatman No. 4 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] 2.2.3 Statistical analysis All the analyses were performed in triplicate and data were expressed as mean ± standard deviation (SD). Data were analyzed using EXCELL and STATISTICA 7.1 (StatSoft). Differences between means were evaluated by Duncan’s test. Statistical significant difference was stated at p < 0.05. 3. Results and discussion Nutritive and anti-nutritive properties:The results of moisture, ash, fibre, protein, lipid, carbohydratecontents are presented in Table 1. Table 1: Proximate composition of sun dried leafy vegetables consumed in Southern Côte d’Ivoire Moisture (%) Ash (%) Fibres (%) Proteins (%) Lipids (%) Carbohyd. (%) 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 ± 0.70d 44.53 ± 0.04d 1 day 58.43 ± 1.12b 6.58 ± 0.00c 10.46 ± 0.02c 5.72 ± 0.02c 3.69 ± 0.00c 15.09 ± 0.08c 98.81 ± 0.03c 2 days 19.42 ± 0.70c 13.05 ± 0.00b 23.07 ± 0.01b 13.73 ± 0.02b 7.51 ± 0.00b 23.18 ± 0.05a 179.18 ± 0.04b 3 days 9.79 ± 1.23d 16.13 ± 0.00a 29.81 ± 0.01a 16.67 ± 0.01a 9.26 ± 0.00a 18.28 ± 0.07b 183.60 ± 0.08a 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 ± 0.10d 25.36 ± 0.02d Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 260 Data are represented as mean ± SD (n = 3). Means in the column with no common letter differ significantly (p<0.05) for each leafy vegetable. The moisture contents ranged between 5.55-12.07 % after 3 days. Moisture generally refers to the presence of water, often in trace amounts [25]. High moisture content in vegetables is indicative of freshness as well as easy perishability [26]. Higher moisture content of vegetables also suggests that the vegetable could not be stored for long time without microbial spoilage [27,28]. During drying, warm temperatures cause the moisture to move quickly from the food to the air [29].The low moisture content of the dried vegetables makes them suitable for longer storage period [25]. Ash is defined as the inorganic residue remaining after the water and organic matter [30,31]. In this study, ash content was found to be in the range of 1.34-5.20 % (fresh leaves) and 10.12-25.78 % (dried leaves) after 3 days. These results suggest that the dehydration could retain more minerals which may be benefit for consumers. Indeed, it has been reported that leaves should contain 3 % ash are considered as beneficial human foods [32].The values of 1 day 76.08 ± 2.72b 5.09 ± 0.02c 4.46 ± 0.00c 3.26 ± 0.06c 2.03 ± 0.00c 9.05 ± 0.70c 57.36 ± 0.13c 2 days 31.52 ± 1.37c 15.58 ± 0.01b 16.07 ± 0.00b 12.84 ± 0.03b 8.43 ± 0.00b 15.52 ± 0.50a 157.44 ± 0.06b 3 days 12.07 ± 0.29d 22.36 ± 0.00a 23.83 ± 0.00a 17.24 ± 0.00a 14.24 ± 0.00a 10.21 ± 0.10b 197.79 ± 0.00a 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 ± 0.09c 1 day 17.71 ± 0.65b 17.69 ± 0.00c 12.07 ± 0.00c 14.06 ± 0.01c 2.44 ± 0.00c 36.59 ± 0.05a 185.45 ± 0.02b 2 days 13.01 ± 1.93c 20.29 ± 0.01b 13.59 ± 0.02b 17.27 ± 0.04b 6.38 ± 0.00b 29.42 ± 0.08b 200.64 ± 0.03a 3 days 8.43 ± 0.90d 24.56 ± 0.00a 17.01 ± 0.00a 19.90 ± 0.01a 9.17 ± 0.00a 20.88 ± 0.50c 199.98 ± 0.03a 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 ± 0.01c 26.58 ± 0.01d 1 day 65.77 ± 0.57b 8.47 ± 0.00c 4.98 ± 0.00c 6.01 ± 0.00c 1.75 ± 0.00c 12.98 ± 0.05b 75.79 ± 0.00c 2 days 28.43 ± 1.27c 19.28 ± 0.00b 11.00 ± 0.00b 13.21 ± 0.00b 5.51 ± 0.00b 22.53 ± 0.70a 158.9 ± 0.02b 3 days 9.96 ± 0.30d 25.78 ± 0.00a 16.50 ± 0.00a 18.17 ± 0.00a 7.33 ± 0.00a 22.22 ± 0.02a 185.12 ± 0.00a 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 ± 0.01c 43.60 ± 0.00d 1 day 30.40 ± 4.03b 6.22 ± 0.00c 8.84 ± 0.00c 15.70 ± 0.00c 2.30 ± 0.00c 36.50 ± 0.50b 187.94 ± 0.00c 2 days 14.93 ± 4.82c 8.26 ± 0.00b 13.16 ± 0.00b 20.15 ± 0.00b 4.57 ± 0.00b 38.89 ± 0.50a 226.33 ± 0.00b 3 days 5.55 ± 0.30d 10.12 ± 0.00a 16.64 ± 0.00a 23.68 ± 0.00a 6.28 ± 0.00a 37.68 ± 0.01a 244.95 ± 0.00a Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 261 fibre contents ranged from 4.46 ± 0.00 % to 12.07 ± 0.00 after 1 day and from 16.50 ± 0.00 % to 29.81 ± 0.01 % after 3 days of sun-drying. The higher fibre contents may be advantageous since their consumption could enhance digestion and prevent constipation. High crude fibre in the vegetable according could also help in blood cholesterol attenuation, as well as blood glucose attenuation when consumed [33,34,35]. The protein contents in the five dehydrated samples were in the ranged of 3.26-5.72 %, 12.84-20.15 % and 16.67- 23.68 % after 1, 2 and 3 days respectively. The sun drying method increased protein content of the studied vegetables compared to their controls. The increase in protein was due to loss of moisture during drying processing. Many workers had reported similar phenomenon [36]. It is known that loss of moisture increases nutrient content and extends keeping quality of the food [37]. Protein helps in building and maintaining all tissues in the body, forms an important part of enzymes, fluids and hormones of the body [38]. Plant proteins may be less digestible because of intrinsic differences in the nature and the presence of other factors such as fibre, which may reduce protein digestibility.Nevertheless, dietary studies show the adequacy of plant foods, as sole sources of protein [39]. The lipids contents after 3 days of drying were in the range 6.28-14.24 %. The lipid content of dried leaf samples were also higher than their fresh counter parts but leafy vegetables could not be considered as rich source of fat [40, 41]. The relatively low lipid content of the dried vegetables makes them suitable for people who suffer from heart related diseases [25]. Vegetables in their fresh state have been noted to be poor sources of carbohydrate [40,42,43]. However, after drying, carbohydrate content increased and varied from 10.21 to 37.68 % after 3 days of sun drying. Carbohydrates are the most important food energy provider among the macronutrients, accounting for between 40 and 80 percent of total energy intake [44,45]. The low caloric values obtained in this study could be explained to low proteins, lipids and total carbohydrate contents. The result of anti-nutritional factors (oxalates and phytates) contents of the sun dried leafy vegetables were presented in Fig.1. The values ranged within 123.01-815.97 mg/ 100 g and 0.65-3.60 mg/100 g after 3 days of sun drying for oxalates and phytates, respectively. Contrary to the phytate contents, oxalates content increased with sun drying time compared to their controls. Oxalates and phytates are considered as anti-nutritionnal factors because of their ability to chelate minerals such as calcium, iron, magnesium and zinc [46,47]. Mineral composition: Sun drying method had concentration effect on mineral composition of leafy vegetables consumed in Southern Côte d’Ivoire (Table 2). Levels minerals contents were as follow: calcium (82.86-481.65 mg/100 g), magnesium (81.98-298.46 mg/100 g), phosphorus (63.41-297.69 mg/100 g), potassium (419.81-993.41 mg/100 g), iron (20.05- 90.37 mg/100 g), sodium (19.43-150.51 mg/100 g) and zinc (15.76-64.39 mg/100 g) after 3 days. 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 and contribute substantially for improving human diet [48,49,50]. Iron is known to be an essential part of red blood cells (haemoglobin) and enzymes (cytochromes) and consumption of these leafy vegetablescould reduce considerably the risk of anaemia [51]. To predict the effect of phytates and oxalates on Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 262 nutrients, anti-nutritional factors/minerals ratios were calculated (Table 3). Fig.1. Effect of sun drying on oxalate (A) and phytate (B) contents of leafy vegetables consumed in Southern Côte d’Ivoire The calculated phytates/ calcium, phytates/iron and oxalates/calcium ratios of the studied leafy vegetables were below the critical level of 0.5, 0.4 and 2.5, respectively [44]. This implies that phytates and oxalates contents of the dried leaves would have deleterious effects on human nutrition. Table 2. Mineral composition of sun dried leafy vegetables consumed in Southern Côte d’Ivoire Ca Mg P K Fe Na Zn C. esculenta Raw 103.64 ± 0.01c 61.29 ± 0.00d 139.08 ± 0.02d 402.70 ± 0.06d 25.30 ± 0.00d 6.96 ± 0.00d 6.58 ± 0.00d 1 day 247.21 ± 0.02b 150.70 ± 0.02c 238.91 ± 0.02c 562.68± 0.03c 63.43 ± 0.01c 10.84 ± 0.02c 10.43 ± 0.01c 2 days 302.53 ± 0.02a 156.58 ± 0.01b 274.64 ± 0.01b 577.03 ± 0.02b 67.71 ± 0.01b 18.16 ± 0.01b 10.92 ± 0.00b 3 days 302.13 ± 0.05a 171.21 ± 0.04a 297.69 ± 0.04a 628.14 ± 0.04a 73.98 ± 0.00a 19.43 ± 0.02a 15.76 ± 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 Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 263 1 day 102.47 ± 0.07c 81.83 ± 0.09c 95.74 ± 0.05c 349.64 ± 0.06c 10.26 ± 0.00c 84.95 ± 0.08c 17.46 ± 0.03c 2 days 135.49 ± 0.03b 105.44 ± 0.05b 104.77 ± 0.02b 387.98 ± 0.04b 19.64 ± 0.00b 101.08 ± 0.05b 19.07 ± 0.02b 3 days 175.16 ± 0.00a 107.95 ± 0.00a 136.63 ± 0.40a 419.81 ± 0.00a 20.05 ± 0.00a 135.90 ± 0.01a 27.59 ± 0.00a S. melongena 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 1 day 380.48 ± 0.01c 208.71 ± 0.00c 132.28 ± 0.01c 883.38 ± 0.01c 60.63 ± 0.01c 92.47 ± 0.01c 31.65 ± 0.00c 2 days 423.80 ± 0.07b 269.47 ± 0.02b 168.66 ± 0.04b 893.15 ± 0.04b 66.66 ± 0.00b 103.57 ± 0.05b 45.71 ± 0.00b 3 days 481.65 ± 0.02a 298.46 ± 0.01a 171.56 ± 0.02a 993.41 ± 0.02a 90.37 ± 0.01a 150.51 ± 0.01a 64.39 ± 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 1 day 69.81 ± 0.02c 80.76 ± 0.00c 33.41 ± 0.00c 637.37 ± 0.02c 37.10 ± 0.00c 32.75 ± 0.01c 16.74 ± 0.00c 2 days 70.27 ± 0.03b 84.90 ± 0.03b 48.38 ± 0.00b 656.79 ± 0.04b 42.94 ± 0.01b 38.13 ± 0.02b 23.27 ± 0.01b 3 days 82.86 ± 0.00a 92.22 ± 0.00a 63.41 ± 0.00a 672.83 ± 0.01a 46.93 ± 0.00a 47.39 ± 0.00a 29.51 ± 0.00a 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 1 day 78.96 ± 0.00c 54.45 ± 0.00c 58.38 ± 0.00c 447.80 ± 0.00c 26.03 ± 0.00c 19.07 ± 0.00c 5.59 ± 0.00c 2 days 83.37 ± 0.02b 63.69 ± 0.00b 63.02 ± 1.35b 473.83 ± 0.03b 33.44 ± 0.00b 25.86 ± 0.01b 15.77 ± 0.00b 3 days 86.83 ± 0.01a 81.98 ± 0.00a 72.20 ± 0.00a 549.90 ± 0.01a 42.61 ± 0.00a 37.82 ± 0.00a 30.24 ± 0.00a Data are represented as mean ± SD (n=3). Means in the column with no common letter differ significantly (p<0.05) for each leafy vegetable Table 3. Anti-nutritional factors/mineral ratios of sun dried leafy vegetables consumed in Southern Côte d’Ivoire Phytates/Ca Phytates/Fe Oxalates/Ca C. esculenta Raw 0.04 0.18 0.99 1 day 0.03 0.11 0.99 2 days 0.01 0.05 1.04 3 days 0.01 0.01 1.04 B. alba Raw 0.03 0.26 0.87 1 day 0.02 0.16 0.91 2 days 0.01 0.06 0.91 3 days 0.01 0.02 0.94 Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 264 S. melongena Raw 0.05 0.30 0.12 1 day 0.02 0.13 0.13 2 days 0.01 0.04 0.14 3 days 0.01 0.01 0.16 T. triangulare Raw 0.05 0.29 0.86 1 day 0.02 0.13 0.87 2 days 0.01 0.04 0.91 3 days 0.01 0.03 0.94 C. olitorius Raw 0.11 0.40 2.11 1 day 0.04 0.15 1.79 2 days 0.01 0.05 1.75 3 days 0.01 0.03 1.76 Antioxidant properties: Antioxidantcomponentsare substances that may protect cells from the damage caused by molecules known as free radicals. Most common antioxidants in vegetables and spices are vitamin C, E, phenolic compounds and carotenoids [52]. Vitamin C and carotenoids contents of the studied leafy vegetables are shown in Fig. 2. Fig.2. Effect of sun drying on vitamin C (A) and carotenoids (B) contents of leafy vegetables consumed in Southern Côte d’Ivoire Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 265 Vitamin C losses were estimated to 85.12- 96.42 %, after 1 day of sun drying. This decrease could be explained by the fact that vitamin C is subjected to oxidation by exposure to sunlight [41]. Carotenoids are important precursors of retinol (vitamin A) and they have also been studied for their potential protection against numerous cancers [52,53]. After sun drying processing, carotenoids contentsdecreased in all the analyzed samples. Carotenoid losses were estimated to 97.48- 98 % and 99.07-100 % after 1 day and 3 days of sun drying respectively. The drying techniqueused in this work involved subjecting the vegetables to heat, light and oxygen and all of these factors will accelerate the rate of oxidation of carotenoids[54]. Phenolic coupounds and antioxidant activity of the studied leafy vegetables are shown in Fig.3. Fig.3. Effect of sun drying on polyphenols C (A) and antioxidant activity (B) contents of leafy vegetables consumed in Southern Côte d’Ivoire Phenolic agents are major class of antioxidants that are found in plant foodswith relatively high concentration[55, 56]. The phenolic contents of the samples increased during sun drying. The values were in the range of 35.44-191.01 mg/100 g and 198.53-388.69 mg/100 g at 1 day and 3 days, respectively. Phenolic compounds are secondary metabolites synthesized by plants, both during normal development and in response to stress conditions (infection, wounding, UV radiation and others) [57]. They also have antioxidant properties that enable them to Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefancel Mare University - Suceava Volume XIV, Issue 3 – 2015 Constant ACHO , Lessoy ZOUE, Niamkey ADOM , Sébastien NIAMKE, Effect of sun drying on nutritive and antioxidant properties of five leafy vegetables consumed in southern Côte D’Ivoire, Food and Environment Safety, Volume XIV, Issue 3 – 2015, pag. 256 – 268 266 quench free radicals in the body [58]. Phenolic compounds have potentially beneficial effect on human health by reducing the occurrence of coronary heart disease, age-related-eye diseases and atherogenic processes [59, 60]. Moreover, this increase in phenolic contents caused the increase of antioxidant activity because there is a direct correlation between the concentration of antioxidant compounds and the antioxidant activity [61]. Antioxidant activity ranged from 77.36 ± 0.00 % to 82.30 ± 0.00 % after 3 days of sun drying. This increase could to be advantageous from the consumers because antioxidants prevent many diseases [62]. 4. Conclusion The results of the present study showed that Basella alba, Colocasia esculenta, Solanum melongena, Talinum triangulare and Corchorius olitorus consumed as leafy vegetbles in Southern Côte d’Ivoire are good sources of nutrients. It was also observed that sun-drying was the method used to process leafy vegetables for long term preservation by decreasing moisture. Moreover, this technique resulted in concentration of nutrients content of the vegetables (protein, ash, fat, crude fiber and carbohydrates). 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