Introduction
Adequate nutrition is critical for pregnant women due to their vulnerability to malnutrition(Reference Nguyen, Nguyen and Gonzalez-Casanova1). It needs targeted efforts to promote the consumption of local nutrient-rich edible plants(Reference Ransom and Elder2). Furthermore, maternal nutrition is important for the quality of their lives and their children(Reference Wani and Jan3). An adequate diet before pregnancy reduces the chance of preterm and other related complications while the problems of under as well as over-nutrition are common in the female population globally(Reference Wani and Jan3,Reference Khan4) .
Despite the agricultural potential in rural areas in different parts of the world, food insecurity and poor-quality diets remain a challenge for women(Reference Maina, Mbugua and Waswa5). Moreover, in rural areas, the local community depends on wild edible plants to satisfy the diversity of their food(Reference Misra, Maikhuri and Kala6). Wild plants play a role in increasing dietary diversity and as a means of income for women in different parts of the world(Reference Namrata, Ghosh and Dwivedi7).
Senegal date palm (Phoenix reclinata) is one of the wild edible plants in rural communities of western Ethiopia. It is a drought-tolerant plant native to tropical Africa, specifically western Senegal that was distributed from Senegal to Ethiopia(Reference Kinnaird8,Reference Thomas9) . Palms are important to humans as a food source and 183 genera of the palm family, of which Phoenix is one of the genera that consists of 14 species(Reference Johnson10). Out of these, reclinata is native to tropical Africa, Comoros, Madagascar and Arabian Peninsula(Reference Hope, Gries and Casagrande11).
The heart of the palm is an extracted product of the palm which can be prepared in different forms and consumed in salads, soups and other dishes(Reference Trabzuni, Ahmed and Abu-Tarboush12). It is an important source of dietary fibre and a good source of vitamins that can be added to any healthy diet(Reference Shimizu, Melo and Dos Santos13). Even though the palm's heart is less utilised than edible palm products, it is a major part of the food industry in contrast to most palm products(Reference Salvi and Katewa14).
The nutritional composition and antioxidant capacities of different parts of various palm species such as fruits, hearts and buds were reported in many studies(Reference Trabzuni, Ahmed and Abu-Tarboush12,Reference Agboola and Adejumo15–Reference Nehdi, Omri and Khalil17) . However, the nutrient composition of the palm heart of Phoenix reclinata is not yet investigated. Moreover, studies on wild edible plants of Ethiopia cover only about 5 % of the country's districts when compared with the wild edible plant wealth of the country(Reference Lulekal, Asfaw and Kelbessa18). As a consequence of poverty, and food insecurity, rural population of Ethiopia especially women are highly exposed to malnutrition (undernutrition)(Reference Saldanha, Buback and White19). Therefore, sustainable harvesting of wild economic species requires strong policy support to maintain nutritional security for local communities of Ethiopia.
Methods and materials
Sampling procedure
The samples of palm hearts were collected randomly by experienced people from their natural habitat in rural areas of Asossa and Sherkole districts, West Ethiopia. The tree was cut down and the bark was removed leaving layers of white fibres around the centre core. Then, sampling as many plants as possible and under calm climatic conditions is recommended(Reference Jones20,Reference Kalra21) . Moreover, samples should be large enough for all intended analyses. In line with this, homogeneous samples of 1000 g are generally sufficient and considered for this study(Reference Pomeranz22). During sampling, samples that had suffered long-term climatic stress, damaged mechanically, infested with disease and contained dead plant tissue were excluded(Reference Jones23).
Sample preparation
The samples were converted into homogeneous material for various nutritional analyses. Drying and grinding are essential operations since the elemental concentration used for interpretation was based on the dry weight of the sample(Reference Isaac and Jones24). Therefore, the collected palm heart was washed using running water and stored under freezing temperature. Then, the sample was frozen-dried, and ground to a fine powder in a mixer grinder to 1 millimetre (mm) particle size, stored in polythene bags and transported to the Ethiopian Health and Nutrition Research Institute(Reference Horwitz, Kamps and Boyer25).
Sample analysis
The proximate composition of the sample for the percentage of moisture content, and macronutrient contents such as crude protein, crude fat, ash contents and crude fibre in the sample was determined using standard methods of the Association of Official Analytical Chemists methods (AOAC, 2000). In line with this, crude fibre was determined using the neutral detergent fibre estimation method in three replicates and the average was considered. But carbohydrate was obtained by calculating the difference (the sum of protein, fat, ash and crude fibre on a dry basis is subtracted from 100)(Reference Adeolu and Enesi26,Reference Belachew, Hadley and Lindstrom27) .
The fat content of the sample was determined using the Soxhlet extraction apparatus (Model Soxtherm Automatic), whereas the ash content was determined by igniting a weighed portion of the dried sample in a muffle furnace (Model Heraeus, Germany) at 550°C and weighing the residue (ash). Finally, the energy content of the sample was calculated using the factors of protein × 4, fat × 9 and digestible carbohydrate × 4(Reference Okeke, Eneobong and Uzuegbunam28).
Total nitrogen (crude protein) was determined using the Kjeldahl method. The sample is digested in sulfuric acid using potassium sulfate and copper sulfate (K2SO4 CuSO4/TiO4) as a catalyst. Nitrogen is converted into ammonia (NH3), then distilled trapped in boric acid, and titrated with hydrochloric acid (HCl). Finally, crude protein was calculated from total nitrogen by multiplying it with 1⋅4007 conversion factor of the total percentage of nitrogen(Reference Sáez-Plaza, Navas and Wybraniec29). The sample was done in three replicates and the average was taken.
The dry-matter determination is used to correct the sample element concentration to an absolute dry-matter basis. Thus, all nutritional analyses were based on dry matter content. The sample was weighted initially and then inserted in an oven-dried at 65°C for 72 h or 3 d. Likewise, weight was also taken after oven drying. The sample determination for the dry matter was done in three replicates, the average was taken, and was reported to the nearest 0⋅1 %(Reference Reuter, Robinson and Peverill30).
The amount of potassium and sodium from the sample was determined by the flame Photometric method. Reagents such as: dilute nitric acid (HNO3) (1:1 with water), deionised water, sodium stock solution (3⋅05 parts per million (ppm)), potassium stock standard (3⋅15 ppm) and dilute solutions of potassium were used. Furthermore, the flame photometer with 3⋅05 ppm of sodium solution which gives 90 absorbance using a sodium filter was calibrated. Likewise, 3⋅15 ppm of potassium solution which gave 100 absorbances using a potassium filter was also calibrated. Finally, values for the zero-concentration standard were corrected. Then, after wet digestion, the sodium or potassium content was measured using flame photometrically(Reference Osborne and Voogt31).
Results
The concentration (g/100 g) of dry matter and carbohydrates for the palm heart of Phoenix reclinata were found to be 92⋅4 and 78⋅2, respectively. Its crude fat content was 2⋅9 g/100 g. The energy content of the sample was 366 kilocalories per gram (kcal/g) sample. The concentration (g/100 g) of the crude fibre and ash content were 1⋅8 and 10⋅3, respectively. Likewise, the concentration of potassium (K+) per mg/100 g of the sample was 1962⋅3 (Table 1).
Proximate nutrient composition of palm heart of Phoenix reclinata, west Ethiopia, 2022
Discussion
The concentration (g/100 g) of carbohydrates for the palm heart of Phoenix reclinata was found to be 78⋅2. This is much higher than the heart of date palm from three Saudi varieties: Sukkari (41⋅5), Solleg (44⋅7) and Naboat Saif (50⋅9)(Reference Trabzuni, Ahmed and Abu-Tarboush12,Reference Roy, Shrivastava and Mandal32) . Its fat content is much higher as compared with Sukkari (1⋅7), Solleg (1⋅8) and Naboat Saif (1⋅6) and also that of okra (7⋅03) and Moringa oleifera leaves (38⋅6)(Reference Trabzuni, Ahmed and Abu-Tarboush12,Reference Roy, Shrivastava and Mandal32,Reference Yaméogo, Bengaly and Savadogo33) . This might be due to environmental factors and soil conditions. This variation may have occurred due to the difference in the climatic conditions of the countries. On the other hand, this result was comparable with the carbohydrate contents of different staple foods of Ethiopia: teff (73), maize (72) and wheat (71)(Reference Baye34). When compared with the World Health Organization (WHO) RDA for carbohydrates, it covers about 78⋅5 % of the total daily RDA for that nutrient which is 130 g. This implies that an intake of palm heart of Phonex reclinata is very crucial in reducing malnutrition specifically in rural communities of developing countries like Ethiopia where there is food insecurity.
The fat content of this wild edible plant was comparable with wild vegetables consumed in Bangladesh and the staple food of Ethiopia: teff (2⋅5), wheat (2⋅0) and rice (2⋅2)(Reference Baye34,Reference Satter, Khan and Jabin35) . This is also adequate for daily diet. But the crude fat content for this sample was lower when compared with other edible plant leaves of Moringa oleifera (17⋅1)(Reference Yaméogo, Bengaly and Savadogo33).
The energy contents of Phoenix reclinata are low as compared with fruits of Phoenix dactylifera L. (389 kcal/g) and all oat varieties of Ethiopia which ranges from 431 to 439 kcal/g. But this is comparable with that of wild vegetables in Bangladesh which ranges from 326 to 371 kcal/g(Reference Agboola and Adejumo15,Reference Satter, Khan and Jabin35,Reference Alemayehu, Forsido and Tola36) . The result was comparable with that of the most common staple food of Ethiopia: teff (357 kcal/100 g flour), maize (375 kcal/100 g), sorghum (370 kcal/100 g), wheat (359 kcal/100 g) and rice (357 kcal/100 g)(Reference Baye34). This indicates that the consumption of palm heart of Phoenix reclinata as a cabbage plays a great role in maintaining the daily energy needs and preventing energy deficiency problems in rural communities of developing countries(Reference Roy, Shrivastava and Mandal32). However, the energy content per 100 g of the sample was much higher than that of okra (31 kcal/g) and potatoes (310 kcal)(Reference Singh, Raigond and Dutt37).
The nutritional composition of Phoenix varies from species to species and also differs from the edible plant parts. Accordingly, the concentration of the crude fibre and ash content of the sample was much lower than others(Reference Agboola and Adejumo15,Reference Roy, Shrivastava and Mandal32,Reference Satter, Khan and Jabin35) . Likewise, this is also lower than that of the staple food of Ethiopia: teff(Reference Baye34). Dietary fibre is important in reducing the formation of free radicals and serves as an important part of a healthy diet(Reference Mandalari, Tomaino and Rich38). In line with this, foods containing considerable amounts of fibre are used in the digestion process (prevents constipation), reduce levels of circulating cholesterol, prevent colon cancer and can also decrease the conversion of starch to simple sugars (prevents diabetics)(Reference Saldanha39–Reference Cust, Skilton and Van Bakel41). Therefore, the consumption of palm heart of Phoenix reclinata as a cabbage plays a very important role in reducing different nutritional-related problems and also alleviation of malnutrition in rural communities of Ethiopia.
The concentration of crude protein in the sample was much lower as compared with others(Reference Satter, Khan and Jabin35). Similarly, as compared with the crude protein content of oat grains cultivated in Ethiopia, that of Phoenix reclinata was much lower(Reference Alemayehu, Forsido and Tola36). Out of the total RDA value of protein needed per day, only 3 % is obtained from the palm heart of Phoenix reclinata. On the other hand, the crude protein content of the sample was higher than that of fruits of Phoenix dactylifera L. and also that of okra and potatoes(Reference Agboola and Adejumo15,Reference Roy, Shrivastava and Mandal32,Reference Raidl42) . There is evidence that indicated that crude protein is used as the enzymatic catalyst which mediates different metabolic process and control cell growth, and differentiation(Reference Gerbens-Leenes and Nonhebel43). This indicates that natural resources have the potential to play a central role in addressing food insecurity in sub-Saharan Africa like Ethiopia. Thus, the utilisation of nutritive wild edible plants could be cost-effective and a sustainable method of preventing nutritional-related health problems, especially for pregnant women(Reference Fungo, Muyonga and Kabahenda44).
The palm heart of Phoenix reclinata contains a high concentration of potassium and sodium as compared with the chemical composition of different cultivators of fruits of date palm(Reference Aspire45,Reference Al Juhaimi, Ghafoor and Özcan46) . Likewise, its potassium content was also higher as compared with those found in okra and eggplant(Reference Roy, Shrivastava and Mandal32,Reference Arivalagan, Bhardwaj and Gangopadhyay47) . These variations could be due to different factors such as a variety of palms, parts of palm used for food, soil type, and fertility, climatic conditions, or stage of plant part taken for sample analysis.
The palm heart of Phoenix reclinata had much nutritional importance for pregnant women in reducing the different nutritional deficiencies as a result of their vulnerability. In line with this, wild edible plants are the backbone of dietary diversity, especially for pregnant women in rural communities of developing countries(Reference Durst and Bayasgalanbat48). This indicated that indigenous plant foods have great potential in preventing both macro and micronutrient deficiency(Reference Deore49). Similarly, women who consume such food sources had higher intakes of calcium (Ca) and iron (Fe) than those who did not(Reference Ghosh-Jerath, Singh and Magsumbol50). Thus, the consumptions of wild edible plants have much nutritional importance for women which covers about 50 % of their total daily energy intake and other micronutrient needs(Reference Okeke, Eneobong and Uzuegbunam28).
Conclusion
The present study revealed that the palm heart of Phoenix reclinata had different nutritional values which are comparable with different staple foods of the country. This prevents different macro and micronutrient deficiencies in pregnant women. Therefore, it has a role in maintaining household food security in rural communities. Promotion and encouragement of its utilisation and detailed scientific studies on its nutritional composition will be needed. Likewise, community awareness of health-promoting components of palm heart of Phoenix reclinata in the daily diet of pregnant women, and policy attention are recommended.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/jns.2022.112.
Acknowledgements
We would like to extend our gratitude and appreciation to all data collectors, Ethiopian Health and Nutrition Research Institute, Jimma University College of Veterinary Science, Regional and Zonal Health Offices of Benishangul Gumuz, West Ethiopia, and the respective administrative organs of all districts.
This study was supported by Mettu University, Mettu, Ethiopia.
E. N. K. investigated the article, performed formal analysis and wrote the original draft. D. T. conceptualised the data, verified the methods, made substantial contributions to funding acquisition, supervised the article, reviewed and edited the article. T. B. conceptualised the data, verified the methods, supervised the article, and reviewed and edited the article.
The authors declare that there is no conflict of interest.
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