Review on nutritional composition of orange‐fleshed sweet potato and its role in management of vitamin A deficiency

Abstract A wide variety of the roots and tubers plays a major role in human diet, animal feed, and industrial raw materials. Sweet potatoes (SPs) play an immense role in human diet and considered as second staple food in developed and underdeveloped countries. Moreover, SP production and management need low inputs compared to the other staple crops. The color of SP flesh varied from white, yellow, purple, and orange. Scientific studies reported the diversity in SP flesh color and connection with nutritional and sensory acceptability. Among all, orange‐fleshed sweet potato (OFSP) has been attracting food technologists and nutritionists due to its high content of carotenoids and pleasant sensory characteristics with color. Researchers reported the encouraging health effects of OFSP intervention into the staple food currently practicing in countries such as Uganda, Mozambique, Kenya, and Nigeria. Scientific reviews on the OFSP nutritional composition and role in vitamin A management (VAM) are hardly available in the published literature. So, this review is conducted to address the detailed nutritional composition (proximate, mineral, carotenoids, vitamins, phenolic acids, and antioxidant properties), role in vitamin A deficiency (VAD) management, and different food products that can be made from OFSP.


| INTRODUC TI ON
Root and tuber crops play a significant role in agriculture and facilitate food security in many developing countries. In the year 2017 worldwide, 494.6 million tons of roots and tubers (including potato) are produced (FAOSTAT, 2019). Roots and tubers are part of diet for majority of the global population, with world average per capita consumption of 19.4 kg/year (2013-2015) and projecting to achieve 21.0 kg/year by 2025 (OCED-FAO, 2016) and also contributing to animal feeds and industrial needs (starch source) (Scott, Rosegrant, & Ringler, 2000). Among the roots and tubers, SP (Ipomoea batatas) is very important after potato on the basis of production and consumption. SP is a dicotyledon associated with Convolvulaceae family and ranks worlds' seventh most important food crop (Ahn et al., 2010); it is a potential energy contributor and considered as fifth essential crop (fresh weight basis) after rice, wheat, maize, and sorghum (Ndolo, Nungo, Kapinga, & Agili, 2007). Currently, SP cultivation was reported in more than 115 nations (FAOSTAT, 2019), and SP was recognized as the secondary staple food and possess significant role in diet of humans in many underdeveloped countries (Van Jaarsveld et al., 2005). In contrast to the other staple food crops, Trancoso-Reyes et al. (2016) defined that SP possess special attributes such as adoptability in wider topography, ability to grow in subsidiary circumstance, good productivity in short durations, | 1921 SATHEESH And WORKnEH and balanced nutritional composition. Sweet potato was reported to have good sensory acceptability due to the eye-pleasing colors and sweet taste. This high sensory acceptability of some SP varieties was suitable in malnutrition management and facilitating food security in underdeveloped nations (Julianti, Rusmarilin, Ridwansyah, & Yusraini, 2017).
Central American countries are considered as the center of SP origin, but recent times they are extensively cultivated in the tropical, in the subtropical zone, and in few temperate locations with divergent agroclimatic conditions (Chandrasekara & Josheph Kumar, 2016). The roots of SP plants are primary storage organs and act as sinks to photosynthetic products, and it resulted in the deposition of different micro (phytochemicals)-and macro (carbohydrates) nutrients (Lemoine et al., 2013). SP was reported to have highest dry matter content due to its sink strength (Rukundo, Shimelis, Laing, & Gahakwa, 2013), and this crop was highly appreciated for the positive agronomic and nutritive characteristics (Abidin, Carey, Mallubhotla, & Sones, 2017).
Sweet potato production was reported to be 112.8 million tons (in 115 countries) in 2017, and China is the leading producer, followed by Nigeria and Tanzania, Indonesia, and Uganda (FAOSTAT, 2019). SP production and consumption in Africa, Asia, South American continents, and Caribbean islands are increased tremendously in recent times (Figures 1 and 2). SP is the most abundantly grown root crops in Africa. International Potato Center (2017) reported that sweet potato is 3rd vital food crop in seven central and eastern African countries, 4th priority crop in six South African nations, and 8th in four West African countries. SP is a key conventional crop, growing traditionally in limited area for domestic consumption purpose. SP is praised as a "poor man's" crop as it characteristically grown and consumed by meager communities especially by women-headed families (Githunguri & Migwa, 2004;Ndolo et al., 2001). SP considered as the food security crop due to its low agriculture input requirements and high yields in wider climatic conditions (Ziska et al., 2009). SP crop is recently changing from a sustainable low-input, low-output crop to a significant cash crop. As a food security crop, it can be harvested at the point of demand as gradually (Tairo et al., 2005), also contributing to a reliable source of food and revenue to pastoral farmers who are frequently susceptible to regular crop damages.
Even though SP is a good source of carbohydrates (20%), the World Health Food Organization (WHFO) has acknowledged as the root crop with "antidiabetic" activity (Anbuselvi, Kumar, Selvakumar, Rao, & Anshumita, 2012). In vivo studies concluded that carbohydrate from SP stabilizes the sugar levels in blood and decreases the resistance to insulin (Mohanraj & Sivasankar, 2014). Hernández Suárez et al. (2016) reported that SP also provides the substantial quantities of selected vitamins (Vit C and PVA), specific minerals (potassium, magnesium, and calcium), and various bioactive compounds (phenolic acids and anthocyanins [ACN]) for consumers.
Researchers reported the clear role of variety difference in physical properties and chemical compositions of SP; for instance, van Jaarsveld, Marais, Harmse, Nestel, and Rodriguez-Amaya (2006) reported that purple-and orange-fleshed cultivars possess higher quantities of ACN and carotenes in comparison with white-fleshed cultivars. In recent time, demand and attention on orange-fleshed sweet potato (OFSP) are raised due to the high concentrations of β-carotene (BC) and non-pro-vitamin A carotenoids (NPVAC). Kurabachew (2015) reported that OFSP has high potential to address VAD by food-based intervention programs in targeted nations (Kurabachew, 2015). OFSP has given credit in recent scientific reports for its role in bakery, snack, and confectionery foods (Chen, Schols, & Voragen, 2003).
There are many scientific studies reported on the nutritional properties of the OFSP in different countries and varieties.
Differences in nutritional contents are noticed among the varieties, and this created ambiguity in researchers. The review on

| OFS P
From a dietary point of view and nutritional perspective, OFSP ranked as number 1 among all vegetables. OFSP tubers are considered as an significant dietary resource of VAC and NPVAC (Mohammad, Ziaul, & Sheikh, 2016). OFSP is appreciated due to the VA contribution and role in VAD eradication in developing countries (Girard et al., 2017;Kurabachew, 2015;Van Jaarsveld et al., 2005). Due to the many positive aspects related to agriculture,  Rumbaoa et al., 2009;Tang, Cai, & Xu, 2015;Teow et al., 2007).

| N UTRITI ONAL COMP OS ITI ON OF OFS P
The OFSP is a good source of the basic nutrients and different vitamins, minerals, polyphenols, antioxidants, and ACN.

| Proximate composition
Orange-fleshed sweet potato is a second staple food crop in many countries of African and Asian continents for most of the population, so the proximate composition is very important to understand the role of this tuber crop in basic nutrition. In this section summarized is the proximate composition of the OFSP reported by different researchers. The proximate analyses of the OFSP from different countries and varieties are depicted in Table 1.
Moisture is the major component in OFSP, which accounts for >62% and <75% (Endrias et al., 2016;Lyimo, Gimbi, & Kihinga, 2010;Nicanuru, Laswai, & Sila, 2015). Other root and tubers also reported similar moisture contents such as potato (79%), cassava (60%), WFSP (77%), and yam (70%) (USDA, 2018). Usually, roots and tubers are consumed in fresh after boiling or minimal processing with traditional practices. Different researchers reported the various drying techniques for OFSP and converted into flour to the moisture content of <11% (Rodrigues et al.., 2016). The low moisture content is very important for OFSP flour to maintain long shelf life. These similar trends were reported in case of staple grains also, and usually at the time of harvesting, cereals possess moisture contents >22% to 25% and dried to 9%-13% for long-term storage (Liu, Chen, Wu, & Peng, 2007). The moisture content of OFSP reported variation in different studies; this may be related to the diversity in variety, agroclimatic conditions, agriculture practices employed, etc.
Ash is an inorganic residue in any food substance, which directly denotes the mineral content. The ash values were reported from the range of 1.17%-4.33% (Mohammad et al., 2016), this broad range is obvious, and it happened due to the varietal and agrogeological differences. Also, processes such as peeling and blanching were followed by drying reported on the ash contents (Endrias et al., 2016).
The ash contents of OFSP are comparable with other roots and tubers.
Proteins are very important nutrients for structural, functional performers of different biomolecules in human body, and they provide the essential amino acids required for metabolism. The protein in the range of 1.91%-5.83% was reported in OFSP (Mohammad et al., 2016). Usually, roots and tuber are the poor source for protein, which is similar in case of the OFSP. The protein contents of the OFSP are in similar to those of potato (2%), cassava (1.4%), WFSP (1.6%), and yam (1.5). In contrast, the protein compositions of OFSP are very low as compared to the staple food grains, such as maize (9.4%), rice (7.1%), wheat (12.6%), and sorghum (11.6%) (USDA, 2018). So, to combat the Protein Energy Malnutrition (PEM), it is very important to consume the protein-rich pulses and animal foods among communities where OFSP is considered as second staple (Neumann, Harris, & Rogers, 2002).
Very low concentration (<1%) of the fat was reported in OFSP; usually, this trend is the property of roots and tubers (Lyimo et al., 2010;Mohammad et al., 2016;Rodrigues et al., 2016). The fat concentration of the OFSP is even little better than other roots and tubers such as potato (0.09%), cassava (0.28%), WFSP (0.05%), and yam (0.17%) (USDA, 2018). Usually, staple crops contain less concentration of the oils and fats; this is true in case of rice (0.66%) and wheat (1.54%). The fat concentrations directly influence the energy density of the food, but people with limited energy to avoid certain disease can consume OFSP (Hu, van Dam, & Liu, 2001).
However, people in underdeveloped countries in Africa are consuming OFSP more so, and supplementation of the oilseeds and highenergy foods is highly recommended to certain vulnerable groups (need high energy) (Butte, 2000).
The high starch (65.41%) concentration was reported in OFSP on fresh weight basis (Rodrigues et al., 2016). This is similar to other staple cereal, roots, and tubers. Starch is one of the very important energy sources for the consumers. So, OFSP can consume as the staple crop because of high concentration of carbohydrates (Jobling, 2004). Energy density is a very important property of the staple crops, for example, 344.52-375.05 kcal/100 g in OFSP (Endrias et al., 2016;Nascimento, Dhiego, Cristina, José, & Maria, 2015). The energy of OFSP is comparable with the cereals such as maize (365.2 kcal/100 g) and rice (365 kcal/100 g); in comparison with the other roots and tubers, the energy composition of the OFSP was reported better.
Due to this property, the OFSP is one of the choices for staple foods (Prentice & Jebb, 2003).
pH and TSS are very important parameters that influence the taste and overall sensory acceptability of foods. The almost neutral pH (6.52) and TSS (acidity) of 1% (Rodrigues et al., 2016) were reported in the OFSP. It denotes the plain flavor of the OFSP, which is suitable for all age groups as a staple food.

| MINER AL COMP OS ITI ON OF THE OFS P
Minerals are the inorganic components, having very specific and important role in metabolism (Soetan, Olaiya, & Oyewole, 2010).
Consumption of optimum concentration of minerals is recommended (Soetan et al., 2010). The mineral compositions of the OFSP from different researchers are tabulated in Table 2.
Calcium plays a major role in muscle function, formation and strengthening of bones, teeth, conducting nerve impulses, blood clotting, and maintaining a normal heartbeat (Zemel, 2009 Okpara, 2009). The Ca content in OFSP was reported as superior to common staple cereals, roots, and tubers. Sorghum (28 mg/100 g), maize (7 mg/100 g), rice (28 mg/100 g), wheat (29 mg/100 g), potato (12 mg/100 g), cassava (6 mg/100 g), WFSP (30 mg/100 g), and yam (17 mg/100 g) are reported to have superior concentration of Ca than common staples (USDA, 2018). In all the common roots and tubers, high concentration of the Ca, high amount of OFSP has to consume, or the food rich in Ca (animal-based food) has to incorporate into the staple diets to achieve RDA of Ca was reported in OFSP.
Magnesium is one of the six important key macrominerals and essential mineral in >300 metabolic functions and possesses role in strong bones, appropriate muscle tasks, optimal blood pressure, and appropriate cardiac tempo (Saris, Mervaala, Karppanen, Khawaja, & Lewenstam, 2000). Sales and Pedrosa (2006) reported the DNA synthesis and stability depend on magnesium. The RDA of Mg to men and women is 420 and 320 mg, respectively. The Mg concentration of 3-37 mg/100 g was reported in OFSP, and this variation was at- which is almost equal to the other roots and tubers such as potato (57 mg/100 g), cassava (27 mg/100 g), WFSP (47 mg/100 g), and yam (55 mg/100 g) (Endrias et al., 2016;Lyimo et al., 2010;Nicanuru et al., 2015). In contrast, staple grains contain high concentration of the phosphorous, maize, rice, and wheat are reported to have 210 mg/100 g, 115 mg/100 g, and 288 mg/100 g of phosphorous, respectively (USDA, 2018). The consumption of whole grains is recommended achieving RDA of phosphorous along with the OFSP.
Potassium along with Na and Ca regulates the fluid balance, maintains normal heart rhythm (Khaw & Barrett-Connor, 1987), and is accountable for nerve signals and muscle functions. Potassium in the range of 138-334 mg/100 g was reported in OFSP (Endrias et al., 2016;Lyimo et al., 2010;Nicanuru et al., 2015), and these amounts are better than rice (115 mg/100 g) and maize (287 mg/100 g), but wheat (363 mg/100 g) contains similar amount of K with OFSP (USDA, 2018). In case of roots and tubers, cassava (271 mg/100 g) contains lesser concentration of potassium than OFSP, but potato (421 mg/100 g) and yam (816 mg/100 g) contain higher amount of K, and among all, yam is rich source of potassium. Children older than 13 years and adults RDA of K are 4,700 mg, but lactating women require 5,100 mg. The roots and tubers are good source of K, and OFSP is moderately providing the RDA of potassium for consumers (Constán-Aguilar et al., 2014).
So, OFSP is a good source for providing the RDA of iron.
Zn plays an important role in body where deficiency symptoms are shown in many ways (Powell, 2000). Antinutritional factors are prime known inhibitor of zinc, which abundantly present in cereals and grains (Janet, 2003). Zinc is required for good immune system function, cell growth, wound healing, and insulin function (Chausmer, 1998). OFSP was reported to be 0.24-0.93 mg/100 g of zinc, but staple food grains such as maize (2.21 mg/100 g), rice (1.09 mg/100 g), and wheat (2.65 mg/100 g) have high concentration of the Zn, whereas potatoes (0.29 mg/100 g), cassava (0.34 mg/100 g), WFSP (0.3 mg/100 g), and yam (0.24 mg/100 g) contain the zinc in the range of OFSP (Endrias et al., 2016;Lyimo et al., 2010;Nicanuru et al., 2015). RDA of Zn varied depends on the age, 14 years old and above need 11 mg/day, and women in age 19 and above need 8 mg/ day (Lutter & Rivera, 2003), whereas pregnant and lactating women need 13 and 14 mg/day, respectively. OFSP provides very small quantities of the Zn, but the bioavailability is more comparative to the cereals and grains because of no or less antinutritional factors (phytate) (Wanasundera & Ravindran, 1994).
Human body acquires sodium from food and drink, and losses through sweat and urine; kidneys play a crucial role in sodiumlevel adjustments (Reynolds, Padfield, & Seckl, 2006). OFSP was reported to be 23-59 mg/100 mg, staples foods such as maize (35 mg/100 mg) contain the Na within the range of OFSP; however, rice (5 mg/100 mg), wheat (2 mg/100 mg), potato (6 mg/100 mg), cassava (14 mg/100 mg), and yam (9 mg/100 mg) contain less concentrations (Endrias et al., 2016;Lyimo et al., 2010;Nicanuru et al., 2015). RDA of sodium is 1,500 mg; less concentrations of the sodium in food source may not have any health problem, because the addition of sodium in form of table salt is a common practice in human food preparation for sake of taste.  are accountable for yellow, orange, and red colors in different plant products (fruits, vegetables, and flowers), distinct aromatic scents, and flavors (Namitha & Negi, 2010).

| β-Cryptoxanthin
Limited studies were reported on concentration of BCX in OFSP as 21.2 (µg/g db) (Kim et al., 2015). So, consumption of OFSP with BCX concentration will contribute to the 0.5 µg of VA by 1 g consumption. So, 100 g of OFSP will provide 50 µg of VA, and it contributes to the VA RDA requirements with BCX, AC, and BC. Some foods such as pumpkin, papaya, oranges, carrots, and yellow corn are rich sources of BCX. The comparable BCX concentrations in agreement with other foods is reported in OFSP (Breithaupt & Bamedi, 2001).
The composition of different carotenoids and their concentrations in OFSP are reported in Table 3.

| Lutein and zeaxanthin
Lutein (β,ε-carotene-3′,-diol) is naturally present with zeaxanthin (β, β-carotene-3,3′-diol) as stereoisomer and available in large quantities in leafy vegetables (Perry, Rasmussen, & Johnson, 2009). Lutein and zeaxanthin are structured with 40 carbon atoms and named as tetraterpenoids, and they are synthesized only in plant kingdom (Shegokar & Mitri, 2012). Lutein and zeaxanthin belong to xanthophyll family and do not possess any VA activity (Abdel-Aal, Akhtar, Zaheer, & Ali, 2013). The yellow colors of these two xanthophylls are connected to their structural properties and responsible for orange to yellow color of different vegetables and animal products (egg yolk, animal fat). The animal retina is exceptional and contains a yellow colored region positioned in its ocular center known as "macula lutea" (Kalariya, Ramana, & vanKuijk, 2012). This yellow color attributed to the accumulation of lutein, zeaxanthin, and meso-zeaxanthin, and they are very important in eye well-being (Kijlstra, Tian, Kelly, & Berendschot, 2012;Nwachukwu, Udenigwe, & Aluko, 2016).
Xanthophylls play a critical role in the defense of skin against sunlight (Stahl & Sies, 2007). Lutein and zeaxanthin protect eye from high-energy blue light, and inhibit and repair the photoinduced oxidative damage (Bian et al., 2012).
Limited reports were available on the concentration of the lutein and zeaxanthin in OFSP. Brown, Edwards, Yang, and Dean (1993) reported the 120-148 (µg/g fw) and 242-2,055 (µg/g fw) of lutein and zeaxanthin respectively, whereas Donado-Pestana et al. (2012) reported 1-4 (µg/g db) and 1-2 (µg/g db) of lutein and zeaxanthin in OFSP, respectively. The orange color of the OFSP is devoted to the presence of this lutein and zeaxanthins. The differences in the reported concentrations of the two reports may be attributed to the variety-related issues. Researchers reported the intensity variations of orange color among the cultivars in different countries, and this was directly linked to the concentration of lutein + zeaxanthin.
However, the lutein + zeaxanthin by Brown et al. (1993) reported high concentration in OFSP, which is comparable with the other leafy vegetables. Vegetables such as baby carrots, peaches, corn, papaya, and oranges possess <1 mg of lutein + zeaxanthin in 100 g of fresh weight (Holden et al., 1999). Ziegler et al. (2015) reported the limited quantity of lutein esters in cereals; in contrast, xanthophylls are rich in fruits and vegetables such as collards, capsicum, yellow corn, and spinach (Sajilata, Singhal, & Kamat, 2008). Consumption of OFSP also provides the required xanthophylls to the consumers.
Recent studies reported that these two xanthophylls possess very important role in different disease management such as skin damages, reduce the chance of pancreatic cancer, reducing the CHD, and increase in overall antioxidant activity (Gordon, 1996;Mares-Perlman, Millen, Ficek, & Hankinson, 2002).

| α, β-Carotenes (AC and BC)
AC and BC are prime bases for VA; they metabolize to retinol in humans. Fruits and vegetables with orange, yellow, and green color are rich source of these two carotenoids (Saini, Nile, & Park, 2015). The VA conversion efficacy of BC is double in comparison with AC, one portion of BC yields two portions of retinol, but AC yields only half portion (Thurnham, 2007). Due to the large concentrations of the BC shares with AC in plant sources, its medicinal values are not well established (Murakoshi et al., 1992).
Variations in polar groups determine the metabolic roles of carotenoids (Britton, 2008).  Ekavali, 2015), lung cancer (Ziegler, 1989), and coronary health and vision problems (Meyers et al., 2013;Sharoni et al., 2012). Shortage of carotenoid consequences with broader medical symptoms related to the eye and vision (Sommer, 2008) weaken innate, adaptive immunity (Stephensen, 2001). Levy et al. (1995) reported that BC is very effective in the suppression of malignant tumor cells.
The OFSP is considered as the good source of the carotenoids, and many researches are recommended to use the OFSP to combat the problems of VAD in developing countries. Stinco,

| Carotenoid isomers in OFSP
Carotenoids naturally exist in different isomers; obviously, the majority of the carotenoids happen in trans-isomers in vegetative source. Nevertheless, rise in cis-isomers attributed to food processing conditions (Schieber & Carle, 2005 Kumar et al., 2015;Parker, 1996).
Carotenoids with seven and more double bonds (conjugated) are identified for good AA (Borsarelli & Mercadante, 2009). Trans-BC is highly sensitive to heat and light and isomerizes to cis-isomers when exposed; for instance, Vásquez-Caicedo, Schilling, Carle, and Neidhart (2007)  13-cis-AC and BC isomers are identified in extended storage durations (Tang & Chen, 2000). Chen and Huang (1998) reported that the reflux heating converts BC to all-trans-BC and 13-cis-BC. Pasteurized and sterilized carrot juice reported the presence of high concentration of 13-cis-BC, while 9-cis-BC was reported in blanched conditions. Moreover, 9-cis-and 13-cis-BC were reported to produce independently from cis bases due to the nonenzymatic actions of all-trans forms (Marx, Stuparic, Schieber, & Carle, 2003). In contrast, heating and exposure to air of cis-BC found no difference in all-trans-isomer (Qiu et al., 2009); however, studies conclude that BC undergoes to the isomerization rather degradation when exposed to adverse condition. Recent studies reported that all-trans forms contain higher biological availability than cis-counterpart, while BC and β-apo-12′-carotenal have the highest bioconversion rate (Castenmiller & West, 1998).

| A SCORB I C ACID
Vitamin C naturally presents in two isomers as ascorbic and dehydroascorbic acid, and they are metabolites in various plants, animals, and fungi (Drouin, Godin, & Page, 2011). The biological activity of ascorbic acid depends on redox state, acting as cofactor for eight human enzymes and different antioxidants (Padayatty & Levine, 2016). Vit. C is known as one of the safest and most effective nutrients, and involves in immune system functions (Padayatty et al., 2003), cardiovascular disease (Simon, 1992), prenatal health problems, eye disease, and skin wrinkling (Vitamin C & Eye Health, 2007).

| ANTHOC YANINS
Anthocyanins are very essential pigments in vascular plants, responsible for glittery orange, pink, red, violet, and blue colors in plants (Glover & Cathie, 2012); they are safe and effortless to apply in aqueous media as natural water-soluble dyes (Wrolstad, 2000). They naturally occur as glycosides, and anthocyanidins are bound with different sugar groups (Kong, Chia, Goh, Chia, & Brouillard, 2003).
Anthocyanin consumption in worldwide reported in high variation depends on the diet composition and eating patterns of the individuals. Studies identified the deviations in the anthocyanin intake in different countries such as the United States (12.5 mg/day) (Wu et al., 2006), the Netherlands (19.8 mg/day), Italy (64.9 mg/day), and Spain (18.4 mg/day) (Zamora-Ros et al., 2013). In case of OFSP, different authors reported the concentration of ACN. Teow et al. (2007) reported 17-38 (µg/g fw), Shih, Kuo, and Chiang (2009) reported 4.0-8.5 (µg/g db), and Tang et al. (2015) reported 2.9 (µCyE/g) anthocyanins in OFSP (Table 3). The variation in the concentrations reported in OFSP by different researchers may be due to the agrogeological conditions. However, the OFSP is not the good source of the anthocyanin compared to the other fruits and vegetables.
In case of fresh weight base, researchers reported 0-27,791 (AU) of total diCQA with mean of 11,020 (AU). The isomers of diCQA, 4,5-diCQA were reported to be 9.2-32.4 (µg/g db) (Padda & Picha, 2008), but Lebot et al. (2016) reported (0-1030) mean of 310 (µg/g fw) (e.g., 3,4 diCQA). Other isomer 3,5-diCQA is reported in dry weight base to be from 56.3 to 300 (µg/g db) as reported by Grace et al. (2014) and Padda and Picha (2008), whereas in wet base weight (0-430) with mean of 170 (µg/g fw), it was reported by Lebot et al. (2016). 3,4-diCQA was reported to be in the range of 1.9-20 (µg/g db) by Grace et al. (2014) and Padda and Picha (2008). Comparative to the other fruits and vegetables, the low concentration of the phenolic acids was reported in OFSP. Researchers reported wide variation in the total phenolic acid concentration in OFSP in different varieties and grown in wider geographical locations. The concentration of individual phenolic acids reported by the different phenolic acids is tabulated in Table 5.
In case of OFSP, free radical scavenging activity (µmol TE/kg fw) was reported to be 493-969 by Oki et al. (2006) samples from Japan, and in case of iron-chelating ability, Rumbaoa et al. (2009) reported 310.7 (mg/mg, fw). In case of DPPH scavenging capacity, TA B L E 6 Some human and animal studied on the orange-fleshed sweet potato (OFSP) in vitamin A-related disease management S. no.

Mozambique/Children
Longitudinal study reported from three deliberately selected districts, two are selected for intervention and one as control. Information was collected on demographic, agricultural, and anthropological issues.
Blood samples were collected from all respondents for biochemical analysis Intervention children reported higher intake of OFSP, reported high VA. Mean serum retinol level increased by 0.100 mM in intervention children, which are not increased in control subjects Low et al. (2007) 2 Uganda/Children and women Study was conducted to know impact of the intensive (IP) and reduced practices (RP) with a control on OFSP and VA intakes among children aged 6−35 months and 3-5 years and women, and IP compared with control on VA status of 3-to 5-year-old children and women with serum retinol <1.05 mM at baseline 9.5% point reduction in prevalence of serum retinol <1.05 mM identified. At follow-up, VA intake from OFSP was correlated with VA status. Use of OFSP increased VA intakes of children and women Hotz, Loechl, Lubowa, et al. (2012) 3 Bangladesh/women Daily consumption of OFSP with or without added fat, on the VA status of Bangladeshi women with low initial VA status was done. Women received one of the following for 6 days/week over 10 weeks.
1. 10 mg RAE/day (WFSP and a corn oil) 2. 600 mg RAE/day (OFSP and a corn oil) 3. Fried OFSP and a corn oil capsule 4. Boiled WFSP and a retinyl palmitate capsule in addition to their home diets. Retinol and BC and VA were assessed before and after the 60 days BC concentrations in plasma found in this study were high in groups consumed OFSP and plasma BC was higher in the consumed fried OFSP compared with boiled OFSP. Initial and final total body VA pool sizes were 0.060-0.047 mmol and 0.091-0.070 mmol. Concluded that, the impact of OFSP on VA status in Bangladeshi women was marginal Jamil et al. (2012) 4 Mozambique/general consumers Reported study on OFSP consumption. The two intervention models were compared: Noodles with OFSP showed quality of moisture and protein and concluded as OFSP is a promising for noodle ingredient Ginting and Yulifianti (2015) Flours (extruded and nonextruded) OFSP flour produced by extruded and nonextrusion. Effect of process on carotenoid contents of raw flours was determined Extrusion reported stabilization of OFSP flours but reported in carotenoids losses due to moisture and screw speed with fixed screw configuration, barrel temperature, and formulation Waramboi, Gidley, and Sopade (2013) Pasta OFSP processed into flour using different processing methods with pretreatment (blanching, steaming, grilling) and produced pasta by extrusion Pretreatments and processing methods had a significant effect on functional properties and the chemical properties of the OFSP. Concluded that OFSP could be used for pasta production with rich BC TA B L E 7 (Continued) total polyphenolic acid and ACN content of different colored SP depend on the environmental factors and application of the fertilizer in agriculture practices. Black, Morris, and Bryce (2003) reported the role of retinol deficiency in night blindness, susceptibility to infections, cognitive development problems and immune system function, susceptibility to respiratory infection, diarrhea, measles, and malaria (Thurnham, McCabe, Northrop-Clewes, & Nestel, 2003). UNICEF (2018)  One of the easiest ways to introduce more VA into the diet is by consuming the carotene-rich plant-based foods like OFSP. This is a good source of carotenoids, and they readily convert into retinol in human body. International Potato Center (2017) reported that supplementation of 100-150 g of the OFSP in human diet can prevent VAD in younger's and also radically diminish maternal mortality. Low et al. (2007) reported that in Mozambique 50 million children <6 year got benefited by consumption of WFSP along with OFSP. OFSP is popularizing to combat VAD in several SSA countries (Kapinga, Byaruhanga, Zschocke, & Tumwegamire, 2009)

, including
South Africa (Faber, Venter, & Benadé, 2002;Laurie & Faber, 2008) through community-dependent food intervention programs. In different strategies, incorporation of OFSP resulted in VA increase in different targeted groups (Haskell et al., 2004;Low et al., 2007). Hortz et al. (2012) reported in their studies that introduction of OFSP in SSA countries such as Uganda and Mozambique is raised in VA intakes among children and women. Jones and de Brauw (2015) reported that biofortified OFSP in Mozambique facilitated the improved child health status and also reported the decrease in incidence and extent of diarrhea in children <5 years. Low et al. (2007) concluded that amplified production and utilization of the OFSP improved the nutritional status of the consumers in African countries, especially in Nigeria (Fetuga et al., 2013). With recent introduction of OFSP in East African countries such as Nigeria, peoples and government and nongovernment agencies concern on growth and utilization (Hagenimana & Low, 2000).
Still more efforts are required from the agriculture and health extension officers to encourage production and utilization of OFSP connecting households with young children in pastoral areas of VAD populations (Low et al., 2007). Prolonged storage of OFSP is usually achieved by drying (sun drying), and during the traditional drying (sun drying) techniques, microbial contamination was reported as the major problem due to the high moisture content of the fresh OFSP. Amajor et al. (2014) reported that OFSP flours can produce by sun drying and milling of the fresh OFSP roots. OFSP flour prepared by milling of dried slices can also utilize as entire flour or as a combined with others. Some of the reported studies on animal or human studies related to the role of OFSP in VAD management are summarized in Table 6.

| PRODUC TS FORM OFS P
Orange-fleshed sweet potato consumed frequently in family meal of different SSA countries by boiling, steaming, roasting, and drying (Low et al., 2007). Traditional sweet potato products are having  Table 7 shows the detailed explanation of different foods prepared by OFSP.

| CON CLUS ION
An eye pleasant color and good flavor make OFSP possesses acceptable by different age groups in many processed forms. The OFSP Finally, it is concluded that OFSP is a good secondary staple food for the developed countries.

ACK N OWLED G M ENTS
Authors are thankful to the Dean, Faculty of Chemical and Food Engineering, Scientific Director, Bahir Dar Institute of Technology, Bahir Dar University, Ethiopia, for their considerable help to complete this review successfully.

CO N FLI C T O F I NTE R E S T
The authors declare no conflict of interest.

E TH I C A L S TATEM ENT
This study does not involve any neither human nor animal testing.