1. Introduction
Around the Senegal river’s valley, the consumption of several forms of Nymphea sp seeds is based on local knowledges that haven been highlighted [1]. It appears that local populations use the seeds of both N. micrantha and N. lotus as substitute for cereals during lean seasons. On the other hand, nutritional analyses reveal low levels of protein (7.90% - 8.24%) and fat (2.32% - 4.29%) and a relatively high content of carbohydrates (74.49 - 77.66) [2]. These averages allowed to consider Nymphea’s seeds similar to cereal. However, despite these considerations, the quality of Nympheas’s seed depends either on amino acid and monosaccharide components or the nature of fatty acids. In fact, few investigations have been made on organic nutrient profiles [3] [4]. According to the role that Nymphea seeds can play in the responses to challenge for food security and food diversification in this region of Senegal, it seems important to know in detail their nutritional quality contribution. Unfortunately, in Senegal, no investigations have yet been carried out to this purpose. Thus, the objective of this work is to complete the nutritional composition and to carry out detailed analyses of these seeds to assess their intrinsic nutritional quality.
2. Material and Methods
2.1. Origin and Pretreatment of Seeds
Mature fruits of Nymphea sp. (N. lotus and N. micrantha) were collected from the streams of the lower valley of the Senegal in three main colection areas where it is well consumed and during the peak production season (Figure 1). Fruits were collected and dried in an oven at 60˚C for 72 hours. Seeds are removed, cleaned and mixed to constitute a representative and homogeneous sample. They were dried in an oven at 103˚C for 2 hours, in accordance with the French standard NF V 03-707 method for moisture determination. Then, they are crushed using a laboratory mill in order to determine the amino acid and sugar profiles under the described conditions [5]. All analyses were repeated in triplicate.
Figure 1. Sample collection’s areas.
2.2. Amino Acids Profile
A sample of 15 mg was hydrolysed in 450 ml of 4 M sulfonic methane acid (Sigma Aldrich, Saint Quentin Fallavier, France) and 50 ml of Norleucine (standard Merck) 25 mmol/ml. The tube was degassed under a flow of nitrogen and then introduced into the device with hydrolysis PIERCE reactive for 120 min at 150˚C. Acid neutralization is done with 450 ml of NaOH 4 N and transferred in a phial gauged and completed by 5 ml of Citrate of sodium (pH 2.2). The homogenous solution was filtered by Sartorius’s filter 0.45 mm. A Biochrom 30+ amino acid analyzer (Serlabo Technologie, Entraigues, France) was used. A standard solution of Sigma Brand Amino Acids containing 18 amino acids (2.5 mmol/ml each except L-cystine 1.25 mmol/ml) was used for comparison (AA-S18, Sigma Aldrich, Saint Quentin Fallavier, France). Internal calibration using a Norleucine standard allowed for precise analysis. The signal was analyzed via EZChrom software and the LOD used was 9ρ moles.
2.3. Sugar Composition
Sugar profile was determined by Dionex DX600 HPLC HPLC equipped with pulsed amperometric detector (Dionex, Sunnyvale, CA) and a CarboPac MA1 column (4 × 250 mm; 7.5 µm, Dionex, Sunnyvale, CA). Extraction solution was 80% ethanol and stationary phase si acolon of CarboPac MA1 (4 × 250 mm; 7.5 μm). The mobile phase was 0.6 to 0.8 N of NaOH solution, with a 0.4 mL/min constituted the mobile phase. Standards markers were obtained from Sigma-Aldrich1 (St. Louis, MO, USA).
2.4. Fatty Acid Profile
Fatty Acid Methyl Ester profile was determined using chromatographic gaz Shimadzu QP2010 (GC-MS), helium as mobile phase, temperatures of 280˚C, one microliter of injected sample, constant pressure of 100 kPa. After separation, a database was used to compare mass spectra, peaks and retention in order to identify fatty acids.
3. Results and Discussion
Table 1 presents the profile of organic matter in seeds of Nymphea sp. The sugar content is represented specifically by glucose (0.67%) and saccharose (7%). The total value of sugar is very low regarding the carbohydrates’s one wich is 76.07 in average [2] while crude fibers value found in such N. lotus, N. pubescens or N. micrantha is 5.08% [3]. It can be deduced from these values that Nymphea seeds are essentially made up of starch i.e. about 63.32%. Fatty acid of Nymphea sp seeds show a predominance of stearic acid and linoleic acid as unsaturated acids (24.86%). In this oil, arachidic and palmitic acids are the only saturated acid found (11.12%) and results are also in accordance with N. lotus [3]. The ratio of unsaturated/saturated acid is 2.23. More amount of unsaturated fatty acid than saturated ones offer a nutritional advantage for the population. In fact, it is recommended to have a minimum ratio UNS/SA of 0.45 or a best value over than 1 [6]. In fact, a good ratio helps to maintain lipid and glycemic metabolic homeostasis [7]. Usually linoleic acid is the predominant fatty acids in the extracted oils samples. In Nymphaea sp seeds consumed in Senegal, this level of linoleic acid is 11.2 g/100g oil which is similar to the results found by Aliyu et al. [3] in N. lotus.
Many fatty acids are not detected such us oleic, linoleic, palmitoleic, myristic, caprylic acids. Previous researches also showed that Myristic acid was absent in Nymphaea lotus seeds oil [4]. Nevertheless, the absence of oleic acid is deplorable because it is a fatty acid that participates in the fight against the development of atherosclerosis and the lowering of cholesterol in the blood [3].
The amino acids profile reveled a low total value (8%) which is very low compare to previous results on N. lotus (73.82%) and N. pubescens seeds (70.70%) [4] and WHO standard references [8]. Then it is no need to calculate quality index protein. This low value of total amino acids highlights that Nymphea sp consumed in Senegal have a poor protein quality and can’t provide sufficient amino acids to population’s diet. Nevertheless, all essential amino acids are present in the seeds.
As it was shouwned by Gueye et al. (1), Nymphea’s seed can be assimilated to cereals, taking into account their energy, protein, lipid and carbohydrate content. Considering the way they are consumed, these seeds are good substitutes for rice and millet couscous, which are very much part of the diets of people in the senegal river’s valley Nymphea seeds also help to diversify the diet. In this respect, a possible domestication is conceivable for a control of the production and its availability to fight against food insecurity.
Table 1. Amino acids, carbohydrates and fatty acid profile of Nymphea’s seeds.
| Amino Acids content(g/100g DM) |
Sugar content(g/100g DM) |
| Ala |
0.56 ± 0.05 |
Glucose |
0.67 ± 0.03 |
| Asp |
1.36 ± 0.14 |
Fructose |
<0.1 |
| Arg |
0.26 ± 0.05 |
Saccharose |
7 ± 0.04 |
| Cys |
0.34 ± 0.01 |
Sorbitol |
0.003 ± 0.00 |
| Try |
0.67 ± 0.03 |
Glycerol |
<0.001 |
| Glu |
1.07 ± 0.33 |
Total |
7.67 ± 0.01 |
| Gly |
0.23 ± 0.04 |
Fatty acid profile (g/100g oil) |
| His |
0.35 ± 0.01 |
Linoleic acid |
11.21 |
| Ile |
0.14 ± 0.12 |
Stearic acid |
13.65 |
| Leu |
0.15 ± 0.01 |
Arachidic acid |
7.6 |
| Lys |
0.34 ± 0.03 |
Palmitic acid |
3.52 |
| Met |
0.27 ± 0.03 |
Caprylic acid |
nd |
| Phe |
0.33 ± 0.05 |
Myristic acid |
nd |
| Pro |
0.02 ± 0.01 |
Palmitoleic acid |
nd |
| Ser |
0.15 ± 0.03 |
Oleic acid |
nd |
| Thr |
0.25 ± 0.02 |
Linolenic acid |
nd |
| Tyr |
1.04 ± 0.05 |
Lauric acid |
nd |
| Val |
0.40 ± 0.03 |
Behenic acid |
nd |
| total |
8.23 ± 0.05 |
|
|
Nd: not found.
4. Conclusion
Nymphea’s seeds consumed do really bring nutriments to population during lean season and might be more promoted. In addition to its energy intake as a cereal, it is a good quality source of fatty acids that can be beneficial to consumers.
Acknowledgements
The authors thank CEA AGRISAN who supported this work through the project “VALONUS”.