Abstract: This study was carried out to analyze the analytic chemical composition and minerals content of yellow velvetleaf (Limnocharis flava L. Buchenau) edible parts collected from waterways at Sebauh, Bintulu, Sarawak, Malaysia in early July 2008 using standard method of food analysis. The edible parts of L. flava high in total carbohydrate by difference (14.56±0.14%) and gross calorific value (343.26±9.75 kJ/100 g), but low in moisture (79.34±0.15%), ash (0.79±0.03%) and crude protein content (0.28±0.01%) in dry weight basis. However, the crude fat (1.22±0.01%) and crude fiber content (3.81±0.04%) were within the range of Malaysian leafy vegetables. The high concentration of K (4202.50±292.37 mg/100 g), Ca (770.87±105.26 mg/100 g, Cu (8.31±1.83 mg/100 g), Mg (228.10±15.26 mg/100 g) and Zn (0.66±0.05 mg/100 g) were found in edible parts of L. flava. The concentration of Na (107.72±17.15 mg/100 g) was much higher when compared to the recommended dietary allowances. Thus, the edible parts of L. flava provide good sources of minerals such as potassium, calcium, magnesium and copper. However, nutritive value analyzed should not be the exclusive criteria for judging the consumptive significance of the edible parts. Besides, others factors such as palatability should also be taken into consideration.
INTRODUCTION
Yellow velvetleaf (Limnocharis flava L. Buchenau) was considered as an aquatic weed in paddy fields and also blocking the waterways that fed waters for irrigation. Despite of being undesired value to the agriculture, the floral clusters and its young leaves are locally used as raw and cooked. Local people use available natural resources as sources of food and to improve their socioeconomic (Tawan et al., 2007). About 100 species of the 225 vegetables in South East Asia are weeds or wild plants (Grubben et al., 1994). In Sarawak, 43 species belonging to 29 families of the aquatic plants that are utilized by the indigenous people and 19 species are locally used as the vegetable (Muta Harah et al., 2005). The vegetables are consumed because of their sweet taste, pleasant flavor and as a source of nutrients, vitamins and minerals (Grubben et al., 1994; Pampolona Roger, 2003). However, studies have shown that, the nutritive value of vegetables varies widely according to environmental factors, varietal differences, cultural practices, harvesting stage of plant, methods of storage, processing and preparation (Grubben et al., 1994; Guil-Guerrero et al., 1998; Flyman and Afolayan, 2008).
Yellow velvetleaf (Limnocharis flava L. Buchenau) or yellow bur-head and locally known by various names as paku rawan or jinjir or emparuk (Van den Bergh, 1994; Halimatul Saadiah, 2003; Samy et al., 2005; Muta Harah et al., 2005). It is an emergent plant in rice cultivated areas that may become noxious by over growing the areas (Soerjani et al., 1986; Mashoor, 1988; Karim et al., 2004). Young shoot comprising leaves and petioles and flower cluster (unopened inflorescence) are collected, consumed either raw or cooked (Edwards, 1980; Van den Bergh, 1994; Halimatul Saadiah, 2003; Samy et al., 2005; Muta Harah et al., 2005). In West Java and Thailand, it is commonly cultivated in fertile soil and harvested after 2-3 months before being marketed (Van den Bergh, 1994; Maisuthisakul, 2008). Other than serving as food, the nutritive values of L. flava were assessed with regards to ash, protein, fat, carbohydrate and calorific. In addition, L. flava from Thailand were examined for dietary fibers, elements such as iron, calcium, vitamin C, while phenolic and flavonoid content were also studied in relation to antiradical properties by Maisuthisakul (2008). Nutritive values of L. flava plants in Malaysia conducted by Samy et al. (2005) were limited to composition e.g., protein, carbohydrate, calorific value and lacking in information on mineral contents which is also important as an indicator on nutritive value of L. flava. Thus, the aims of this study was to complement available information provided by Samy et al. (2005) on the composition and to provide insights on the mineral contents of edible parts of L. flava from waterways of a wetland area of Sarawak, Malaysia in early July 2008.
MATERIALS AND METHODS
This study was carried out during the flowering season in early July of 2008 from waterways at Sebauh (N 03° 06’ 34.3", E 113° 16’ 15.2", 17 m above sea level), Bintulu, Sarawak, Malaysia.
Sample collection and preparation: Fresh samples of edible parts of young green shoots (leaves and petioles) and flower clusters of L. flava were collected and kept in an ice chest for transportation to the laboratory. In the laboratory, the samples were cleaned under running water and residual moisture evaporated at room temperature. The moisture content of the samples was determined at 60°C until constant weight was obtained following the method of Abuye (Hassan and Umar, 2006). The dried matter obtained was ground to a fine powder and stored in air tight containers prior to further analysis for ash, crude protein, crude fiber and crude fat (Umar et al., 2007).
Analytic chemical composition analysis: Moisture, ash, crude protein, crude fat, crude fiber and total carbohydrate were determined according to AOAC (1990). Ash content was determined by incinerating at 500°C in muffle furnace for 6 h (method 930.05, AOAC, 1990).
Mineral analysis: The ash formed from the determination of ash analysis was placed in porcelain crucible. Few drops of distilled water were added and followed by 2 mL concentrated hydrochloric acid (HCl). Ten milliliters of 20% HNO3 were added evaporated on the hotplate. The sample was filtered through Whatman filter paper No. 2 into 100 mL volumetric flask (method 922.02, AOAC, 1990). The mineral elements Na, K, Ca, Mg, Cu and Zn concentration were determined by atomic absorbance spectrophotometer (AA800 Perkin-Elmer, Germany) (method 975.03, AOAC, 1990).
The percentage of crude protein content was estimated by multiplying the sample percentage of nitrogen content obtained using 2200 Kjeltec Auto Distillation Foss Tecator, Sweden by a factor 6.25 (method 978.04, AOAC, 1990). The crude fat was extracted using 2055 Soxtec Avanti Manual System, Sweden and quantity of lipid was determined gravimetrically (method 930.09, AOAC, 1990). Crude fiber content was determined by the 2010 Fibertec System Foss Tecator, Sweden with repeated treatment of 1.25% sulphric acid (H2SO4) (w/v), followed by 1.25% potassium hydroxide (KOH) (w/v) and washing by water (method 930.10, AOAC, 1990). Total carbohydrate was calculated by difference from [100- (crude protein+crude fat+ash+crude fiber)] (AOAC, 1990). The gross calorific value in kJ/100 g dry matter was determined by automatic calorimeter (AC-350 Leco, USA) using benzoic acid pellets as a standard weight was obtained following the method of ASTM, (Wang and Littell, 1983).
RESULTS
Edible parts of L. flava comprising young shoots and inflorescences collected from residential waterways have a relatively high moisture content when compared to ash, crude protein, crude fat, crude fiber and total carbohydrate content (Table 1). The mineral composition and concentration in edible parts of L. flava is shown in Table 2. Edible parts of L. flava contain Potassium, Sodium, Calcium, Magnesium, Copper and Zinc in varying concentration with Potassium having the highest concentration. Limnocharis flava has a K/Na ratio approaching 40.
| Table 1: | Composition of edible parts of Limnocharis flava L. Buchenau |
| Each value is means of three replicates±Standard Deviation (SD). *Value expressed as % wet weight | |
| Table 2: | Mineral composition and concentration of edible parts of Limnocharis flava L. Buchenau |
| Each value is means of three replicates±Standard Deviation (SD) | |
DISCUSSION
Analytic chemical analysis of a food is the nutritional composition of that food and it is the estimation of the nutritive value of human food in its chemical form (Alli Smith, 2009). The comparison on analytic chemical composition of L. flava edible parts with others leafy vegetables is shown in Table 3. This results obtained from analytic chemical analysis of L. flava edible parts establishes that this species be ranked as moisture rich plant due to their relatively high moisture content when compared with others component, since this plant is aquatic species. However, the moisture content of edible parts in this study was lower than that reported by Maisuthisakul et al. (2008) (94.7%) and on similar aquatic species, Monochoria vaginalis (88.6%) and Ipomoea aquatica (90.9%), respectively by Samy et al. (2005) and Rukayah (2002). In contrast, the moisture content in I. aquatica from similar environment at Nigeria waterways (Umar et al., 2007) was eight percent lower compared to L. flava. The moisture content was however within the range of 87.8-91.6% reported in some Malaysian leafy vegetables (Rukayah, 2002). The ash content (dry weight basis) of edible parts of L. flava was ten times less compared to both Thailand L. flava (Maisuthisakul et al., 2008) and Nigerian waterways I. aquatica (Umar et al., 2007). Compared to others leafy vegetable irrespective from terrestrial or aquatic environment, L. flava is low in ash (Rukayah, 2002) found in Malaysian leafy vegetables and I. aquatica edible parts grown in Malaysia (Samy et al., 2005).
The plant edible parts analyzed were low in crude protein compared to L. flava reported by Van den Bergh (1994), Samy et al. (2005) and Maisuthisakul et al. (2008) with value ranged of 1.0-11.3%. On the other hand, the protein content in M. vaginalis (1.0%) was 80% much higher than the value in L. flava as reported by Samy et al. (2005). In contrast, the crude protein content obtained in aquatic and terrestrial leafy vegetables (1.1-8.4%) was ten times higher than those in L. flava samples (Rukayah, 2002). The protein content of this plant appear to be low, could be as a result from pre-harvest period as a reported in I. aquatica leaves (Umar et al., 2007). The crude fat in L. flava edible parts observed was seven times lower when compared to the L. flava grown in Thailand reported by Maisuthisakul et al. (2008). This value compares favorably six times higher to aquatic plants such as M. vaginalis and I. aquatica (Rukayah, 2002; Samy et al., 2005) with the values of 0.2%, respectively. However, crude fat content is comparable with those some Malaysian leafy vegetables as reported by Rukayah (2002). In contrast, the crude fat in L. flava plants was lower to I. aquatica from similar environment in Nigeria with the value of 11.0% (Umar et al., 2007). The fiber content of L. flava in this study was very low when compared to the value reported by Maisuthisakul et al. (2008). Limnocharis flava edible parts were high in fiber content compared with Malaysian aquatic leafy vegetables but within the reported values of terrestrial leafy vegetables (Rukayah, 2002). A similar trend was reported on the estimated total carbohydrate with the values 3.6-6.7% in Malaysia aquatic leafy vegetables and 0.6-18.4% found in Malaysia terrestrial leafy vegetable (Rukayah, 2002).
| Table 3: | Composition of yellow velvetleaf (Limnocharis flava L. Buchenau)’s edible parts compared with other leafy vegetables |
| *Values are means of three replicates±SD. -: No data available. aValue expressed as % wet weight. Source: 1Samy et al. (2005), 2Maisuthisakul et al. (2008), 3Umar et al. (2007), 4Hassan and Umar (2006) and 5Rukayah (2002) | |
| Table 4: | Mineral composition of edible parts of yellow velvetleaf (Limnocharis flava (L.) Buchenau)’s edible parts compared with other leafy vegetables |
| *Values are means of six replicates±SD. -: No data available. Source: 1Samy et al. (2005), 2Maisuthisakul et al. (2008), 3Umar et al. (2007), 4Hassan and Umar (2006), and 5Rukayah (2002) | |
The calorific values of most vegetables are low within range 125-209 kJ/100 g (Umar et al., 2007). In edible parts of L. flava substantial (343.26±9.75 kJ/100 g) content was observed which is about nine times higher than 37.99 kJ/100 g as reported by Samy et al. (2005) and other edible aquatic species M. vaginalis (69.96 kJ/100 g) and I. aquatica (121.34 kJ/100 g) consumed by Malaysians (Rukayah, 2002; Samy et al., 2005). This calorific value is much lower than (1430.51 kJ/100 g) reported by Maisuthisakul et al. (2008).
The mineral composition in edible parts of L. flava were compared with other leafy vegetables (Table 4). The mineral concentration in edible parts of L. flava shows that potassium is relatively high when compared with other elements. Fresh vegetables are one of the major dietary sources of potassium (K) (Insel et al., 2002). K content (dry weight basis) in this plant was six times higher than those reported in Malaysian leafy vegetables with the values ranged 78-708 mg/100 g (Rukayah, 2002; Samy et al., 2005). The value was similar to those of I. aquatica grown in Nigeria (5458.33 mg/100 g) as reported by Umar et al. (2007). A similar trend was also observed for sodium (Na) which is slightly lower than Nigerian I. aquatica (135.0 mg/100 g) but much higher when compared with sodium in others leafy vegetables available in Malaysia (13-171 mg/100 g) (Rukayah, 2002). Hassan and Umar (2006) noted K/Na in diet is an important factor in prevention of hypertension and arteriosclerosis, with K depresses and Na enhances blood pressure. The ratio of K/Na (39.61±4.91) in edible parts of L. flava was similar to I. aquatica (40.43) from Nigeria (Umar et al., 2007).
Limnocharis flava has about six times higher in calcium (Ca) content compared to L. flava with the value of 52.6 mg/100 g grown in Thailand (Maisuthisakul et al., 2008); others Malaysian leafy vegetables with the values ranged from 53-88 mg/100 g (Paisooksantivatana, 1994; Rukayah, 2002; Samy et al., 2005). The concentration of this element was also higher, about 100% more than that in Nigerian leafy vegetables as reported by Aletor et al. (2002) with the values of 524-633 mg/100 g and found in I. aquatica (416.70 mg/100 g) by Umar et al. (2007), while lower in concentration compared to those in balsam apple leaves (941 mg/100 g) (Hassan and Umar, 2006). This suggests the edible parts of L. flava provide a good source of Ca. Magnesium (Mg) obtained in L. flava was far greater than those recorded in Malaysian I. aquatica leaves with the value of 37 mg/100 g (Samy et al., 2005). Mg is responsible to the formation of chlorophyll or deep green color in vegetables (Insel et al., 2002).
Copper (Cu) is another trace element, essential in human body where it exists as an integral part of copper proteins ceruplasmin, the enzyme that catalyzes the oxidation of ion iron (Insel et al., 2002). The edible parts of L. flava have high concentration of this element. With respect to Cu, only 0.10 mg/100 g was found in cultivated I. aquatica from Malaysia and 0.36 mg/100 g in Nigerian I. aquatica. Comparatively the Cu content is low in Momordica balsamina (5.44 mg/100 g) (Samy et al., 2005; Hassan and Umar, 2006; Umar et al., 2007). Zinc (Zn) element in L. flava from this study was almost similar to I. aquatica consumed by Malaysians with the value of 0.50 mg/100 g (Samy et al., 2005). However, the Zn concentration in I. aquatica grown in waterways, Nigeria was many time higher. Based on the results obtained from the present study in comparison to other studies of aquatic plants (Hassan and Umar, 2006; Umar et al., 2007) at various geographical locations, L. flava has similar trend in mineral concentration categorically as K>Ca> Mg>Na>Zn.
CONCLUSION
Limnocharis flava is typically collected by the local population and encountered in fresh produce markets. It is consumed raw or as cooked vegetable. The results obtained from this study showed that the edible parts of L. flava is low in moisture and crude protein content but having comparable crude fiber and crude fat content to other Malaysians leafy vegetables. The edible parts of L. flava have sweet taste, pleasant flavor and also provide good sources for the minerals (particularly K, Ca, Mg and Cu). The composition and minerals content is comparable to the well-known leafy vegetables such as I. aquatica, M. vaginalis and Momordica balsamina that are commonly consumed by the people in Asia. The nutritive value analyzed in this present study alone should not be the exclusive criteria for judging the consumptive significance of the plant. Analysis on phosphorus, iron, manganese, anti-nutritional and toxicological can be recommended to evaluate further on the plant nutritive properties. Besides, others factors such as palatability should also be taken into consideration.
ACKNOWLEDGMENTS
The authors wish to acknowledge the Faculty of Agriculture and Food Sciences, University of Putra Malaysia Bintulu Sarawak Campus, Malaysia for technical support and the laboratory facilities provided and the Ministry of Science, Technology and Innovation, Malaysia for the research Grant (04-01-04-SF0864) and Ministry of Higher Education Malaysia for a scholarship award, which made this study possible.