Graphical abstract
Keywords
Food
Health
Lotus
Medicine
Nutrition
Water lilies
1. Introduction
Food and Agricultural Organization is concerned that the world would not produce enough food to meet the demand for the ever-increasing population expected to be 10 billion by 2050 putting challenge to crop scientists to meet this growing demand (Parihar et al., 2022). Today, many people suffer from hunger and malnutrition despite there can be many potential edible aquatic plants are available in water which can be used as a food. Non-conventional, lesser-known edible aquatic plants are promising to feed the unabated population growth (Das et al., 2021). Edible aquatic plants refer to macroscopic aquatic plants that are found in lakes, ponds, streams, rivers and waterlogged soils (Chai, Ooh, Quah, & Wong, 2015). Aquatic plants are classified as partially or totally submerged, free floating, rooted floating leaf type or emergent plants (Sharma & Singh, 2017).
Globally 3000 plants have been used as food by humans throughout history and at least 150 of those plants have been grown commercially. However, over the centuries there has been a tendency to concentrate on fewer and fewer plants so that today most of the world's people are fed by about 20 crop species. The emergent macrophyte rice species, Oryza sativa, is the only aquatic plant that is the most significant single crop in the world and constitutes a staple food for more than 50% of the world's population (Bin Rahman & Zhang, 2022). The cultivation of aquatic plants is a grossly neglected area and it is timely to consider such neglected edible aquatic plants to determine their potential role in increasing human food supply. More than 40 species of edible freshwater aquatic plants were thought to exist but only around 25% of these species are now being grown for food on a large scale or have the potential to become cultivable in a way that is economically feasible. Cognizant of these facts, edible aquatic plants are alternative food, contains sufficient nutrient for nutritional needs, food supplements, health, and potential drugs (Hernawati et al., 2022). This current review highlights the nutritional, food, anti-oxidant and health importance of the two prominent edible aquatic plants; water lilies and lotus. Water lilies belongs to the family Nymphaeaceae where as sacred lotus belongs to the family Nelumbonaceae. The leaves and flowers of water lilies (Nymphaea) float on the water's surface, however, the leaves and flowers of lotus (Nelumbo) are emergent or rise above the water's surface. The explored water lilies species were Nymphaea lotus, Nymphaea nouchali, Nymphaea pubescens, Nymphaea petersiana, Nymphaea stellata, Nymphaea odorata, Nymphaea alba, Nymphaea rubra, Nymphaea caerulea, Nymphaea micrantha, Nymphaea tetragona, Nymphaea antares, Nyhmphaea hybrid, Nymphaea indica, Nymphaea candida and lotus (Nelumbo nucifera).
2. Importance of water lilies and lotus
Water lilies and lotus are the most fascinating aquatic plants that regulate the ecosystem structure and functions of wetlands. They are receiving great attention from food technologists and nutritionists because of their nutritional value and health benefits. They possess phytochemicals that have great application in food and pharmaceutical industries (Debbarma et al., 2022). Several edible aquatic plants are nutritionally important for human beings, so it is necessary to explore alternative healthy ingredients. The edible aquatic plants are significant to supply nutrients for nutritional needs, food supplements, health and drugs (Hernawati et al., 2022). Edible aquatic plants can be used as food, nutritional, nutraceutical, functional, medicinal, cultural, social, industrial, economical and ecosystem benefits (Haroon, 2022). Water lilies are commonly used for treatment of several diseases in addition to their nutritional value (Nishan, 2020). But because of social and economic developments as well as modernization of lifestyles, and lack of knowledge, edible aquatic plants are mis-used (Butt et al., 2021). Water lilies and lotus produce perennial or annual rhizomes that can be used as food and in traditional medicine to cure a number of life threatening diseases.
2.1. Cultivation of water lilies and lotus
The major reasons for the low utilization of edible aquatic plants are lack of enough information regarding the nutritional value, cultivation, production, harvesting, processing and their food preparation techniques. These plants are neglected by agri-business, researchers, policymakers, investors and development practitioners (Rampa et al., 2020). The cultivable aquatic food crops are lotus, water lily, Euryale and water chestnut (Jana et al., 2019). Water lilies and lotus can grow, develop and produce seed. Naturally, lotus and water lilies grow with seeds in soil and water in paddy field (Rusmayadi & Khairina, 2015). Lotus grows under tropical and sub-tropical climate. The distribution mapping of N.pubescens was reported, it grows best at water depth (35-121 cm), a light penetration depth (23-100 cm), a water pH (6.25-8.37), and a sediment pH (3.33-4.69) (Yuliarti et al., 2022). The cultivation of lotus requires heavy, muddy and soil rich in organic matter. In Vietnam, lotus cultivation gained popularity and emerged as alternative to rice receiving attention from national and international actors (Vo et al., 2021). Lotus and water lilies grow easily in ponds, whiskey barrel or planter. The agronomic practices of lotus cultivation, propagation methods, planting distance, fertilizer application and yield quantity per hectare were reported (Jana, 2019). Lotus plant can propagate through seed/plantlet, planting distance (1 m x 1 m), fertilizer N: P: K (kg/ha) in the ratio of 100:60:40 and yield 1.5 ton per hectare (Jana et al., 2019). As similar to lotus, water lily can grow in ponds, lakes and perennial water bodies in all types of climate. Water lilies can propagate through either corm or seed. The ideal soil for water lily cultivation is soil rich organic matter. The plant need planting space of 1 m x 1 m, an ideal fertilizer rate of N: P: K (60:40:30) for growth and development, yield 25 tons per hectar (Jana, 2019). The study on the productivity of hairy water lily (N. pubescens) in Paharangan, Hambuku and Ampukung districts of Indonesia was reported that the water lily seeds were 0.653 t/ha, 1.057 t/ha and 1.121 t/ha, respectively (Rusmayadi & Khairina, 2015).
2.2. Harvesting and processing of water lilies and lotus
The rhizome of water lilies and lotus can be plucked from muddy or sand of water shore that can be either boiled or raw sliced, dried, grounded and finally combined with other grains to make different value added food products. Seedpods of water lilies and lotus can easily hand picked as the matured seedpods submerge in the water. The poppy seeds of water lilies are harvested from the pods. Inventing new technologies for the production, processing, and marketing of water lilies and lotus is crucial for increasing productivity of these aquatic crops (Jane, 2019).
3. Water lilies and lotus as food
Edible aquatic plants have organs that potentially provide food for humans due to their accumulated food reserves. The most significant of food reserves in edible aquatic plants are seeds, roots and rhizomes (Fig. 1). There are several old literatures that water lilies and sacred lotus are consumed as food. The rhizome of N.lotus is a useful human food in West Africa nations and consumed as either raw or cooked (Irvine, 1952). The seeds, leaves, stems or rhizomes of water lilies and lotus were reported to be consumed in Nigerian (Danhassan et al., 2018), Senegal (Gueye et al., 2020), Bolgatanga people of Ghana (Adanse et al., 2019), Guinea (Watt & Breyer-Brandwijk, 1962), Malawi (Chawanje et al., 2001), Sudan (Ibrahim, 2007), Bangladesh (Khan, 2019), India (Jarapala et al., 2021), Thailand (Singthong & Meesit, 2017), Pakistan (Hujjatullah et al., 1967), as an emergency food during famines in Finland (Airaksinen, 1986), Kenya (Kabuye, 1986) and Ethiopia (Kloos, 1982). In some area of the world, the leaves and flowers were reported to be consumed as cooked vegetables, whereas in some other parts, the seeds were reported to be consumed as a grain or rhizome as starchy tubers. The rhizomes and seeds of N.lotus and N.nouchali were reported to be consumed during food shortage in Kara and Kwego people/lower Omo River valley of Ethiopia (Teklehaymanot & Giday, 2010). The Afar, Kereyu, Jille, and Arsi pastoralists groups throughout the Awash Valley in Ethiopia gathered wild plants during seasonal food shortages to supplements their predominant milk diet (Kloos, 1982). The Afar sought the tubers and seedpods of water lilies (N.caerulea), which they prepare as a porridge with milk, rhizomes of bulrush (Typha sp.) that are gathered after burning the stems, and the sweet roots of the swamp grass gedleboyta (Kloos, 1982). Moreover, around Lake Ziway, Ethiopia, Typha latifola, Arundo donex and Nymphaea lotus were reported to be the edible aquatic plants harvested as food (Merga, 2021). There are other aquatic plants that are used for human food but for the majority there are limited data available. Some of the edible aquatic plants that are consumed during shortage of foods are arundo, typha, cyperus, and echinochloa (personal observation).
Fig. 1. Rhizomes (A), Seed pod (B) and Seed (C) of Nymphaea lotus.
The rhizome of lotus contains carbohydrate and energy to be exploited as staple foods. The energy and carbohydrate content of water lily rhizome can be higher than cultivated potatoes (Sukhija et al., 2016). Lotus rhizome was reported as good source of resistant starch for different food application (Sukhija et al., 2016). Seed and rhizome of water lilies and lotus could be processed in food product formulations and other applications (Bangar et al., 2022). The best way to prepare lotus rhizome is cooking that retain the nutritional composition and antixodant properties (Chen & Tegku Rozaina, 2020). Cooking of lotus rhizome improves its palatability. Chen and Tengku Rozaina (2020) reported that steaming has no effect on crude protein, fat, fiber, carbohydrate, vitamin C, potassium, zinc and copper contents of raw lotus rhizome. Different value added food products can be prepared from roots, rhizome, stems, leaves or seeds with plants or animal products (Table 1). Different parts of water lily like rhizomes, stems, leafs and flowers have great potential for food and non-food application as it contain good amount of starch, dietary fiber, vitamins and minerals (Showkat et al., 2021). Some of the bakery products developed using parts of water lily, fish and cereals are presented below. The flour of water lilies and lotus rhizome or seed can be combined with grain and pulse flour to combat the prevailing malnutrition (Jane, 2019).
Table 1. Different value added food products prepared from different parts of water lilies and lotus.
| Edible aquatic plants | Anatomical parts of plants | Mode of consumption | Properties improved (physicochemical, functional, health benefits) | Bioactivities of the products | Refs. |
|---|---|---|---|---|---|
| Lotus | Roots | Bread sticks | Inclusion of 15% lotus flour to wheat flour in bread stick improved the nutrient, antioxidant, consumer acceptance and texture, | Functional and nutraceuticals bread | Thanushree et al. (2017) |
| Lotus | Roots | Unleavened flatbread | Inclusion of 15% lotus flour to wheat flour in traditional unleavened flatbread improved the consumer acceptance and texture. | Functional and nutraceutical flour | Saeed et al. (2021) |
| Lotus | Rhizome | Bread | Addition of 10% powder of Thai lotus (N.nucifera) rhizome was found to enhance bread quality and consumer acceptability | Functional and health food supplements | Singthong & Meesit (2017) |
| Loots | Roots | Chinese steamed bread | Chinese steamed bread prepared from 30% wheat substitution with lotus root powder improved cohesiveness, springiness and fluffy texture of bread | Hypoglycemic, hypolipidemic and antioxidant stress | Li et al. (2021) |
| Lotus | Roots | Soup, sausage, mayonnaise, salad dressing | Flour of lotus root high protein, high water/ oil absorption, high viscosities, good emulsion, stability, high temperature for gelatinization and pasting | – | Singthong & Meesit (2017) |
| Lotus | Roots | Fat mimetic biscuits | Replacing wheat flour at 15% with lotus root flour improves overall sensory acceptability, bioactive compounds, dietary fibers, and polyphenols | Improves antioxidant properties of biscuits | Saeed et al. (2021) |
| Lotus | Seed | Addition of lotus seed flour (2.5%−10%) increased phenolic content (217 mg/100 g), fibers (0.73 g/100 g) and higher sensory acceptability | Promote functional and health properties of consumer | Shahzad et al. (2021) | |
| Lotus | Seed | Cookies | Incorporating multigrain and lotus seed flour in regular wheat flour increases WAC and OAC, but decreased emulsion activity and foam capacity | – | Dinkar & Mishra (2020) |
| Lotus | Seed | Noodles | 5% substitution of lotus seed flour in wheat noodles was reported to improved higher fiber content (0.83%), ash content (0.9%), and phenolic content (0.019 mg/ GAE/100 mg) than control noodles | Alternative product with health benefits for consumers | Jirukkakul & Sengkhampam (2018) |
| Lotus | Stem | Cookies | Addition of 30% stem of lotus to refined flour improve the sensory acceptability and mouth feel, calcium, iron and total dietary fiber of cookies as compared to refined flour | Decrease micronutrient deficiencies in toddlers. | Khushboo et al. (2020) |
| Lotus | Seed | Patties | Incorporation of 10% fresh stem of lotus into chicken patties was found to enhance fiber in meat products | –Enhance fiber in meat products | (Bharti, Pathak, Goswami, Sharma, & Ojha, 2017) |
| Lotus | Rhizome | Port patties | Incorporation of 1% lotus rhizome root powder into cooked pork patties improved shelflife during storage | The patties had higher antimicrobial and antioxidant activity | Qiu & Chin (2022) |
| Lotus | Roots | Tofu Noodle | Replacement of wheat flour (5% to 10%) improve texture and antioxidant capacity but delayed starch digestion after cooking of tofu | Starchy vegetables of plant-based noodles for diabetic patients | Kim et al. (2021) |
| Lotus | Roots | Chicken nuggets | Addition of 3% N.nucifera roots powered increased pH values, cooking yield, emulsion stability, ash, fiber, moisture, carbohydrate, moisture retention, fat retention and moisture protein ratio. However, the addition reduced protein, fat, and energy values | improved the dietary fibers of meat nuggets | Verma et al. (2022) |
| N. lotus | Seeds | Muffins | Substitution of wheat flour (20% to 75%) with N.lotus seed was superior in protein, fat and fiber contents | – | Adanse et al. (2021) |
| N. lotus | Biscuits | Biscuit prepared from 80% wheat, 12% N. lotus, and 8% coconut flour was preferred most to that of the rest of biscuit samples produced. | Healthful wheat-coconut-nymphaea blend biscuit | ||
| N.pubescens | Seed | Cookies | Addition of 30% Olu seed flour with wheat flour in cookies recipes was acceptable to substitute | – | Nizam & Arampath (2016) |
| N. nouchali | Petal | Tea | Petal extracts of N.nouchali enhances the dietary intake of nutrients and acts as natural food preservative with no toxicity properties | No toxicity in plants, zebrafish embryo, and cell lines. | Dias et al. (2021) |
| Water lily cultivars | Petals | Tea beverages | Tea infusion have 29 volatile compounds | Physiologically and health function | Yin et al. (2015) |