PaPer Ital. J. Food Sci., vol. 27 - 2015 513 - Keywords: bush okra, common okra, mineral content, recommended dietary allowance, sticky sauce - ADEQUACY OF MINERAL CONTENTS OF RAW AND PLAIN STICKY SAUCE OF COMMON AND BUSH OKRA MOYIB OLUWASAYO KEHINDE*1, OLADAPO FRANCIS OLUMIDE1, MOYIB FOLAKE RAMAT2 and 1BANjOKO OLUWAKEMI O. 1 Department of Chemical Sciences, Tai Solarin University of Education, PMB 2118, Ijebu-Ode, Nigeria 2 Department of Agricultural Sciences, Tai Solarin University of Education, PMB 2118, Ijebu-Ode, Nigeria *Corresponding author: Tel. +234 8188 464 072, email: kmoyib@hotmail.com, moyibok@tasued.edu.ng AbstrAct In Nigeria, common okra (Abelmoschus esculentus L.) and bush okra (Corchorus olitorius L.) are popular mucilage vegetables used as sticky sauce for easy consumption of starchy staples. both raw vegetables and sticky sauce of common as well as bush okra were estimated for their potential in the provision of daily dietary allowance of important minerals. Modified methods of the Association of Official Analytical chemists (AOAc) were used to estimate the assessed miner- als. the results showed that the raw and sticky sauce of assessed common and bush okra con- tained appreciable levels and essential minerals, but are not adequate to meet recommended di- etary allowance, except for Fe and cu. comparatively, the two species of okra varied significant- ly in their mineral content of the raw and plain sauce. there was also a negative effect of cooking on the mineral contents, which reduced significantly to an average of 30% on a dry weight basis. therefore, the two vegetables, either as a fresh or sticky sauce, require additional sources of P, K, Na, Mg, ca, Mn, and Zn to meet recommended dietary allowance. Furthermore, dried mucilage sauce, though, could be an appreciable post harvest management and storage but not without a loss of about one-third mineral content in the process. However, the sauce of common okra and bush okra are good sources for any of the assessed mineral restricted diets. mailto:kmoyib@hotmail.com 514 Ital. J. Food Sci., vol. 27 - 2015 INtrODUctION Vegetables are nutritious foods that provide sufficient amount of nutrients needed for nor- mal body functions, maintenance and reproduc- tion. Also, their intake in different combination is essential for the maintenance of healthy life and normal body function (rUMEZA et al., 2006). Vegetables have a lot of health benefits, which include reduced cancers, diabetes and cardio- vascular diseases (cOX et al., 2000). Leafy vege- tables are major sources of nutrients in rural ar- eas where they contribute substantially to pro- tein, mineral, vitamins, fiber and other nutri- ents which are usually in short supply in daily diets. besides their use as food, they also add flavor, variety, taste, color and aesthetic appeal to what would otherwise be a monotonous diet (MEPbA et al., 2002). thousands of leafy vegetables abound in Ni- geria and are used primarily as food and med- icine. these vegetables are diverse in species from different families and orders, and many of which have specific regional or local area of domestication (FAFUNsO and bAssIr, 1987; ME- PbA et al., 2007). However, they have crossed regional or local barriers through migration and exchange of goods. Presently, they are be- ing cultivated throughout the country but are concentrated in their domesticated regions or localities. As a consequence, they bear differ- ent local names from one region or locality to the other in order of increasing distance. For example, bush okra in the southern part of Ni- geria, is known as “ewedu” in Lagos and Ogun state, whereas, it is called, “ooyo” in Osun and Oyo state. Leafy vegetables are seasonal and in abundance shortly after the rainy seasons but become scarce during the dry season. they are sold in many Nigerian markets to meet dai- ly demand as an important complement of sta- ple dishes (FAFUNsO and bAssIr, 1987; MEPbA et al., 2007). two of the abundant vegetables in Nigeria are common okra (Abelmoschus esculentus) and bush okra (Corchorus olitorius); common okra is popularly grown at every nooks and crannies of Nigeria while bush okra is concen- trated in southwest Nigeria. common okra and bush okra are largely cultivated by both men and women for domestic and commercial pur- poses. common okra, Abelmoschus esculen- tus (L.) Moench (synonyms, Hibiscus esculen- tus L.), belongs to the family of Malvaceae, and is known as lady’s finger in English. It was be- lieved to have originated in south-East Asia and have spread widely in tropical, subtropical and warm temperate regions, but is particular- ly popular in West Africa (HAMON and sLOtEN, 1995). On the other hand, bush Okra (Corcho- rus olitorius L.) belongs to the family of tiliace- ae, its English name is Jew’s mallow. Genetic diversity points to Africa as its first centre of or- igin (sINGH, 1976). At present, Corchorus olito- rius has widely spread all over the tropics and probably occurs in all countries of tropical Af- rica (EDMONDs, 1990). It is a leading leaf veg- etable in many African countries such as côte d’Ivoire, benin, cameroon, and Nigeria (scHIP- PErs, 2000). common and bush okra are mucilaginous veg- etable, both the fruit and leaves of these popu- lar vegetables are used as food in Nigeria. their young immature fruits are important vegeta- ble, consumed cooked or fried. In Nigeria, they are usually boiled in water to make slimy sticky soups and sauces. the young leaves of common okra are commonly used as spinach and some- times as cattle feed (bUrKILL, 1997) while that of bush okra are more valued as cooked slimy sticky sauce, compared to common okra fruit. In Nigeria, sticky sauces from these two vegeta- bles are found suitable for easy consumption of starchy balls made from cassava, yam or millet (AKOrODA, 1988). the very small fruits of com- mon okra can fetch a higher price, being of prime quality while Jew’s mallow is a high quality leafy vegetable in market value, consumers’ prefer- ence and nutritional value. the two vegetables are grown under rain fed conditions, the imma- ture fruits of common okra and fresh leaves of bush okra can be conserved by drying, whole or chopped, or by pickling and sell as dried ground for the preparation of this slimy sauce during the dry season. common and bush okra mucilage is suit- able for medical and industrial applications. common okra mucilage has been used as a plasma replacement or a blood volume ex- pander and its leaves are sometimes used as basis for poultices, as an emollient and to treat dysuria. Okra mucilage is added as size to glaze paper and is also used in confection- ery. roasted common okra seeds are used in some areas as a substitute for coffee. tests conducted in china suggest that an alcohol extract of Abelmoschus leaves can eliminate oxygen free radicals, alleviate renal tubu- lar-interstitial diseases, improve renal func- tion and reduce proteinuria (tOMODA et al., 1980). On the other hand, Jute mallow has been the most widely used packaging fibre for more than 100 years because of its strength and durability, low production costs, ease of manufacturing and availability in large and uniform quantities. In Kenya, the root scrap- ings of Jew’s mallow are used to treat tooth- ache; in congo, the root decoction is a ton- ic and leafy twigs is used against heart trou- bles; in tanzania, an infusion of the leaves is taken against constipation; while in Nigeria, the seeds are used as a purgative and febri- fuge (EDMONDs, 1990; bUrKILL, 2000). Fresh common okra can be transported quite easily in bulk and kept for a few days without much loss of quality. However, Jew’s mallow Ital. J. Food Sci., vol. 27 - 2015 515 leaves cannot be kept long. Mostly, the prod- uct is sold on the harvest day, and it is con- stantly kept wet. If cooled to 20°c it can be kept for about 1 week, in cold storage for sev- eral weeks. If the leaves are dried and pound- ed to powder, the product can be stored for at least half a year (AKOrODA, 1988). since, both vegetables are prepared as a sticky slim sauce by boiling in water and common okra is consid- ered more stable in quality, then it is assumed that a lesser proportion of its nutrients would be lost through the boiling process when com- pared to Jew’s jute. therefore, the present study was designed to estimate the mineral content of raw and sticky sauce of common and bush okra for recommended daily dietary intake and to compare mineral nutrient loss during prep- aration of common okra and bush okra sauce. the study will enhance knowledge on boiled and dried mucilage as a means of post harvest handling and storage for maintaining mineral constituents. MAtErIALs AND MEtHODs Samples collection and preparation Indigenous fresh green moderate size of com- mon okra fruits and leafy bush okra samples were purchased from three retailers, as three replicates, in three major markets at Ijebu-Ode (New market, Oke-Aje and Ita-Ale). the sam- ples were transported in properly labeled pol- ythene bags to the chemistry Laboratory, tai solarin University of Education, Ijagun, Ije- bu-Ode, Ogun state Nigeria. twenty grams of wholesome samples were handpicked from each of the common okra and bush okra sam- ples, destalked, rinsed thrice in deionized wa- ter, drained, chopped into smaller pieces, and divided into two portions. Preparation of raw vegetables the first portions were air dried in an air-cir- culating oven at 65°c for 5hrs for bush okra samples while common okra was dried for 10 hrs. the dried samples were ground in a sam- ple attrition mill (model no. ED-5), sieved into 4mm particle sizes, kept at 4°c and labeled as r (raw) samples. Preparation of plain sticky sauce samples the second portions were further chopped into smaller pieces and boiled for 5 min to slim sticky sauce as usually prepared as complement to stew for consumption of starchy staples in the southwest of Nigeria but without salt and then air dried at 55°c until constant weight was as- sumed, ground and sieved into 4mm particle siz- es and labeled s (sauce) samples. Assay methods All chemical Analyses were carried out in triplicates using modified methods of the Asso- ciation of Official Analytical chemists (AOAc, 2005). A gram of 4mm particle size of common and bush okra samples were combust at 500°c for 5 hrs in a cool muffle furnace and left over- night to cool to room temperature, the residue was weighed as ash content and kept at 4°c for mineral analysis. Elemental analysis A half-gram ash of each sample was, subse- quently, digested in 2.5 mL selenium/H 2 sO 4 mixture (3.5 g se/1L H 2 sO 4 ) at 200°c. the resi- due was re-suspended in selenium/H 2 sO 4 mix- ture; Na, Mg, ca, and K were determined using Jenway Digital Flame Photometer (PFP7 model), phosphorous by the Vanodo-molybdate method, while Fe, Mn, cu, and Zn were determined us- ing buck scientific Atomic Absorption spectro- photometer (bUcK 210VGP model). Statistical analysis Estimation of precision was measured us- ing the statistical analysis system software package [19]. Detection of variation between vegetables, raw and cooked, and purchased markets for minerals were based on Analy- sis of variance (ANOVA) using General Line- ar model (GLM) and useful relationships be- tween minerals were estimated using Pearson correlation analysis, in the same sAs soft- ware package. rEsULts Mineral levels in raw and sticky sauce of common okra and bush okra samples of Nigerian common okra and bush okra by different retailers were obtained from three different major local markets in Ijebu- Ode and were assessed for nine macro and mi- cro minerals in both raw and sticky sauce. the precision measures the nine assessed miner- als, across all samples of raw and sticky sauce of common and bush okra as estimated in sAs provided in table 1. In overall samples, the de- creasing order of abundance of minerals were as follows: K>Na>ca>P>Fe>Mg>Zn>Mn>cu, with the following mean values on a dry weight basis, 376.03±25.37 mg/100g, 250.2±8.58 mg/100g, 176.73±19.88 mg/100g, 82.11±7.47 mg/100g, 4.23±0.44 mg/100g, 2.91±0.33 mg/100g, 2.39±0.26 mg/100g, 0.88±0.12 mg/100g and 0.75±0.08 mg/100g, respectively. the results indicate the abundance of macro minerals over micro minerals but with a fall in Mg. On a clos- 516 Ital. J. Food Sci., vol. 27 - 2015 er observation made from the visualized bar graphs, levels of minerals were higher in both raw and sticky sauce of bush okra than com- mon okra except cu for raw, Mn and Fe for cooked. Levels of all the minerals in the two vegetables were reduced upon boiling (Fig. 1). based on simple calculations of the estimates obtained in sAs, common okra lost more of Na, K, Mg, and cu on cooking than bush okra while the latter lost more of P, ca and Mn than the former but both lost almost the same amount of Fe and Zn. the minimum estimated loss in common okra on cooking and drying was 8.12% for ca and the maximum was 50.49% for Fe with a mean loss of 30.91% while for bush okra, the loss ranged from 4.78% for Na to 58.10% for Mn with a mean loss of 30.63%. the differ- ence in the overall loss in minerals from the two vegetables could be considered small and in- significant. therefore, one third of the miner- als are lost in the cooking and drying process when packaged as a post harvest handling or table 1 - Descriptive statistics between the raw and boiled common okra and bush okra in Ijebu-Ode. Variable Mean SD SE± CV Range Minimum Maximum N mg/100g Raw-common Okra Sodium 258.77 2.5 1.02 0.97 7 255.1 262.1 9 Potassium 351.32 2.4 0.98 0.68 6.5 347.9 354.4 9 Calcium 95.42 2.28 0.93 2.39 5.7 92.4 98.1 9 Phosphorus 60.32 2.3 0.94 3.82 5.9 57.2 63.1 9 Iron 4.24 0.99 0.4 23.25 2.21 3.1 5.31 9 Zinc 2.67 0.99 0.4 36.93 2.23 1.52 3.75 9 Magnesium 2.48 0.72 0.3 29.12 1.62 1.74 3.36 9 Manganese 0.87 0.5 0.2 57.4 1.08 0.42 1.5 9 Copper 1.05 0.21 0.08 19.76 0.48 0.78 1.26 9 Sauce-common Okra Sodium 223.17 2.32 0.95 1.04 6 220 226 9 Potassium 235.17 2.79 1.14 1.19 8 231 239 9 Calcium 87.67 2.25 0.92 2.57 5.2 84.9 90.1 9 Phosphorus 47.94 2.32 0.95 4.85 6.05 44.75 50.8 9 Iron 2.1 0.99 0.4 46.96 2.23 0.95 3.18 9 Zinc 1.56 0.99 0.4 63.08 2.28 0.39 2.67 9 Magnesium 1.32 0.72 0.3 54.64 1.62 0.58 2.2 9 Manganese 0.63 0.5 0.2 79.17 1.1 0.17 1.27 9 Copper 0.67 0.21 0.08 31.11 0.47 0.4 0.87 9 Raw-bush okra Sodium 278.17 2.79 1.14 1 8 274 282 9 Potassium 487.52 2.4 0.98 0.49 6.5 484.1 490.6 9 Calcium 289.62 2.33 0.95 0.8 6.1 286.4 292.5 9 Phosphorus 127.27 2.25 0.92 1.77 5.2 124.5 129.7 9 Iron 7 1 0.41 14.21 2.46 5.74 8.2 9 Zinc 3.39 0.99 0.4 29.13 2.31 2.2 4.51 9 Magnesium 4.99 0.72 0.3 14.48 1.62 4.25 5.87 9 Manganese 1.43 0.5 0.2 35.12 1.11 0.96 2.07 9 Copper 0.7 0.19 0.09 27.27 0.48 0.38 0.86 9 Sauce-bush okra Sodium 264.87 2.46 1 0.93 6.8 261.3 268.1 9 Potassium 457.57 2.61 1.06 0.57 7.4 453.7 461.1 9 Calcium 234.92 2.58 1.05 1.1 7.3 231.1 238.4 9 Phosphorus 96.94 2.32 0.95 2.4 6.05 93.75 99.8 9 Iron 3.55 0.99 0.4 27.77 2.23 2.4 4.63 9 Zinc 1.98 0.99 0.4 49.75 2.3 0.8 3.1 9 Magnesium 2.8 0.72 0.3 25.84 1.63 2.05 3.68 9 Manganese 0.6 0.5 0.2 83.83 1.11 0.13 1.24 9 Copper 0.46 0.21 0.08 44.88 0.46 0.2 0.66 9 SD, standard deviation; SE, standard error; CV, coefficient of variation. Ital. J. Food Sci., vol. 27 - 2015 517 Fig. 1 - trends of minerals levels in raw and sauce of common and bush okra on dry weight basis. raw_Al, raw common okra; sauce_Al, common okra sauce; raw_co, raw bush okra; sauce_co, bush okra sauce. Fig. 2 - Proportion of mineral loss by common okra and bush okra upon cooking at 100°c for 5 min Okro, common okra; Ol- itorius, bush okra. management for later use as slimy sauce. the trend in mineral loss per vegetable in cooking is provided in Fig. 2. Interaction of vegetable type, purchased market and cooking on mineral content Analysis of variance (ANOVA) based on Gen- eral Linear Model (GLM) in the same sAs pack- age, in overall, showed a very large variation in all the assessed minerals (P<0.0005) but less variation was observed for cu (P<0.005) and Zn (P< 0.05) while Mn was not signifi- cantly varied. the variations observed in the nutrients were highly contributed by the dif- ferences in the vegetable type and raw/cook- ing (processing). However, only raw/cooking contributes to the variation observed in Zn. Manganese, though, not generally significant but was significantly varied between raw or cooked vegetable. therefore, there was a sig- nificant difference between common okra and bush okra for Na, P, K, ca, Mg, Fe, and cu but no significance difference was observed be- tween the two vegetables for Zn and Mn. the results also showed that cooking has a signif- icantly negative effect on the levels of all the minerals assessed, that is, the levels of min- erals reduced on cooking. Effect of market was also tested for only the three micro min- erals; Zn, Mn and cu were significantly var- ied while the rest were not. Duncan multi- ple grouping provides a visual variation of the nutrients between the vegetables, raw/boiled, and markets, based on the significant differ- ence between their means, by assigning them into groups using letters A, b and c. A de- tailed ANOVA measures and Duncan group- ing were also given in table 2. 518 Ital. J. Food Sci., vol. 27 - 2015 Relationship among minerals Pearson correlation analysis was used to iden- tify useful associations among the nutrients. the matrix generated (table 3) revealed that Na was strongly significantly correlated with all the oth- er macro minerals (P<0.0005) and Fe but slight- ly with Zn and Mn. therefore, as the level of Na increases, the level of all P, ca, K, Mg, Fe, Zn and Mn also increases and vice-versa. Potassi- um and calcium were independently correlat- ed with all the macro minerals and Fe but both were insignificant with the rest of micro miner- als. therefore, as levels of K and ca increases, level of other macro minerals and Fe increas- es. A strong positive relationship was observed among Fe, Zn and Mg (P<0.005). Manganese on the other hand was correlated with only Na and P while cu had no relationship with any of the minerals. the correlation matrix also showed that the levels of the minerals were higher in bush okra than common okra except cu that was inversely correlated while Zn and Mn were insignificant. In addition, the levels of minerals were observed to be inversely correlated with cooking except that of P, K and ca. therefore, table 2 - Effect of species type, cooking and purchased market on mineral levels based on GLM-ANOVA. Model Species Raw/Sauce Market Mean CV SS R2 Pr>F Pr>F SS Pr>F SS Pr>F SS Macro-mineral mg/100g Na 256.24 2.58 9187.47 0.91 *** *** 5599.81 *** 3586.81 ns 101.3 K 382.89 6.20 224919 0.95 *** *** 192890 **** 32017 ns 101.3 P 83.12 6.5 22901 0.97 *** *** 20168 *** 2734 ns 101.3 Ca 176.9 7.83 180737 0.98 *** *** 174882 *** 5850 ns 101.3 Mg 2.9 26.78 40.70 0.77 *** *** 23.32 *** 16.88 ns 10.45 Micro-minerals Fe 4.22 24.39 73.62 0.77 *** ** 26.65 *** 46.96 ns 19.41 Cu 0.70 30.27 1.04 0.53 ** ** 0.55 * 0.50 ** 0.85 Mn 0.88 59.64 2.12 0.27 ns ns 0.40 * 1.71 *** 5.02 Zn 2.4 41.22 11.4 0.37 * ns 1.94 ** 9.45 *** 19.41 Duncan Grouping Na K Ca P Mg Mn Fe Zn Cu By Species CommonOkra B B B B B A B A A bush okra A A A A A A A A B By Process Raw A A A A A A A A A Sauce B B B B B B B B B ns, not significant; *, P<0.05; **, P<0.005; ***, P<0.0005, SS, sum of square. Means with the same letter are not significantly different. table 3 - correlation Matrix among the minerals based on Pearson model. Veg_c is degree of common consumption (okra