In recent years, the role and beneficial effects of many nutrients from plant sources such as fruits and vegetables have attracted much attention from food scientists as well as the public [1]. Plants are generally considered safe and nutritious and proven to be effective against many human ailments [2]. To this end, several plant parts are being screened for their nutraceutical benefits. One such plant whose fruits are being screened by researchers for food and medicinal activities is Carica papaya. This is important in order to determine the scientific basis for the several-century usage of these fruits as food and as traditional medicine [3]. C. papaya is a fast-growing, tree-like herbaceous plant belonging to the family Caricaceae and is widely grown globally in both tropical and subtropical regions of the world, including Nigeria [4]. The Food and Agricultural Organization (FAO) of the United Nations has reported that Nigeria is one of the largest producers of C. papaya globally [5]. The fruit contains papain, a proteolytic enzyme that is also used in the treatment of trauma, allergies, and spot injuries [6]. Several vitamins, including vitamin A, vitamin C, and vitamin E, are predominantly found in the fruit. These substances are useful in nutrition and also have documented antioxidant activities [7].Nutritionally, the major components of papaya fruit pulp dry matter are carbohydrates. At the early stage of fruit development, glucose is the main sugar, but the sucrose content increases during ripening and can reach up to 80% of the total sugars. The edible portion of the ripe papaya fruit contains both macro- and micro-minerals, and these are Na, K, Ca, Mg, P, Fe, Cu, Zn, and Mn. Carica papaya is a source of carotenoids, vitamin C, thiamine, riboflavin, niacin, vitamin B6, and vitamin K [8]. Ripe papaya is most commonly consumed as fresh fruit, whereas green papaya as a vegetable is usually consumed after cooking or boiling [9]. Papaya, as a tropical fruit, was traditionally used as a therapeutic remedy due to its medicinal properties. The fruit is rich in phytochemicals, especially carotenoids and polyphenols [10]. Papaya is also known to be a thirst quencher by people living in tropical countries [11].

The increase in consumption of papaya pulp necessitates the determination of the potential for utilization in different accessions in human diets. Assessment of nutritional quality in different accessions of C. papaya is essential for breeding procedures [12]. As the ultimate goal of most breeders is to improve the productivity of crops as measured in terms of the yield performance or in value addition, which includes nutritional quality. Plant breeding, in principle, involves the creation and exploitation of the genetic variation for different traits of economic importance [13]. Relationships among traits of economic importance impact the breeding strategies along with selection procedures [14]. Therefore, the aim of this study was to determine the proximate, mineral, and vitamin constituents that are present in collected accessions of C. papaya from some southern states of Nigeria. This will help in the determination of its nutritional values, which may be useful in the pharmaceutical and food industries.

Experimental Sites

Matured fruits of C. papaya were collected from five southern Nigerian states, namely Abia, Imo, Rivers, Enugu, and Anambra. Six (6) accessions were collected per state, making a total of 30 accessions. Seeds were collected from each accession, dried, and later planted. Seeds were collected from each accession, dried, and later planted. After harvest, matured fruits of C. papaya were examined for proximate, vitamin, and mineral compositions in different accessions using standard laboratory methods.

Plant Sample and Preparation

Three mature and ripe C. papaya fruits were collected from each accession during harvest. Each of the plant samples was cut into two to remove the seeds, which were washed with clean water, shade-dried, and ground into fine powder using an electric blender. This was then used for the analysis.

Proximate Analysis of C. Papaya Fruit

The C. papaya fruit was analyzed for proximate composition (moisture, crude protein, crude lipid, crude fiber, and total ash) according to AOAC [15]. Crude protein was determined using a Kjeltec Auto 1030 Analyzer after digestion with concentrated sulfuric acid in a digester. Crude lipid was estimated by extracting in chloroform:methanol (2:1) using a Soxhlet extraction HT6 unit. Crude fiber was determined using a Fibretec System 1020 Hot Extractor, and ash content was determined by igniting at 5500°C in a muffle furnace for 12 hours.

Mineral Analysis of C. Papaya Fruit

The atomic absorption spectrophotometer (AAS) was used for the analyses of the following minerals: Mg, Ca, Zn, Fe, and P, while the flame photometer was used in the analyses of K & Na. Using AAS, 10 g of the sample was placed in a dish and heated with a Bunsen burner in a fume cupboard until there was no smoke emitted. This was transferred to the desiccator in order for it to cool, after which 0.1 m HCl solution was added to the ash. The resulting solution was filtered and diluted. Suitable salts of the metals in question were used to make their standards, lamps were fixed, and the analysis was done. Using the flame photometer, the diluent of the sample was aspirated into the Jenway Digital flame photometer using the filter corresponding to each mineral element. All of these were carried out using the method of analyses described by AOAC [15].

Determination of Vitamins

The amount of vitamin B1, B2, B3, and C in the sample was determined using the method described by AOAC [15]. Vitamin B1 and B3 were determined using the method described by Okwu and Ndu [16], while vitamin B2 was determined using the methods described by Okwu and Josiah [17]. The method described by Oulai et al. [18] was used in the determination of β-carotene.

Statistical Procedures

Data was subjected to analysis of variance as a randomized complete block design using the PROC mixed procedure. The analysis estimated the location and genotype effects as well as their interactions.

Proximate Composition of Harvested C. papaya Fruits

The proximate composition of the fruits of Carica papaya is shown in Table 1. Highly significant differences (P<0.001) were observed for most of the parameters, except moisture content, crude fiber, and crude protein. Moisture content was high and varied in all the accessions. It ranged from 82.00% to 96.00% in RIV6 and RIV2, respectively. The ash content also varied from 0.40% to 0.80%. RIV6 and IM5 had the highest ash content (0.80%), while EN2, EN5, and AB3 had the lowest ash content (0.40%). Crude fiber content of the accessions varied from 6.00% to 9.33%, with AN6 and AB6 having the highest crude fiber content (9.33%), while EN3 has the lowest crude fiber content (6.00%). Moreover, the crude protein content of the accessions varied from 0.43% to 2.53%, with IM1 having the highest crude protein (2.53%), while AB3 had the lowest crude protein at 0.43%. The lipid content ranged from 0.22% to 0.70%. EN5 had the highest lipid content (0.70%), while AN5 had the lowest lipid content (0.22%). The carbohydrate content of the accessions varied between 39.33% and 66.67%. AB2 had the highest carbohydrate content (66.67%), while AB4 had the lowest carbohydrate content (39.33%).

Mineral Composition of Harvested C. papaya Fruits

The mineral composition of the fruits of Carica papaya is shown in Table 2. Highly significant differences (P<0.001) were observed for most of the traits except iron, potassium, and sodium. Calcium content of the accessions varied from 19.67 mg/100 g to 35.00 mg/100 g, with AN3 having the highest at 35.00 mg/100 g, while EN5 had the lowest calcium content at 19.67 mg/100 g. Magnesium content of the accessions varied from 9.33 mg/100 g to 14.33 mg/100 g in RIV4 and IM3, respectively. Iron content of the accession ranged from 2.00 mg/100 g to 4.00 mg/100 g, with EN4 having the highest iron content of 4.00 mg/100 g, while EN3 had the lowest iron content of 2.00 mg/100 g. Moreover, the potassium content of the accession varied from 43.33 mg/100 g to 61.67 mg/100 g, with AB5 and AN2 having the highest potassium content of 43.33 mg/100 g, while RIV1 had the lowest potassium content of 43.33 mg/100 g. Sodium content of the accessions ranged from 21.67 mg/100 g to 31.33 mg/100 g in IM4 and AB5, respectively. B-carotene concentration of the accessions was high and ranged from 5067 mg/100 g to 6567 mg/100 g in IM4 and EN4, respectively. Phosphorus concentration of the accessions ranged from 12.67 mg/100 g to 30.33 mg/100 g in AB4 and AN1, respectively (Table 2).

Vitamin Composition of Harvested C. papaya Fruits

The vitamin composition of the fruits of Carica papaya is shown in Table 3. The result showed that highly significant differences were observed for all the vitamins determined (P < 0.001). The result showed that the vitamin concentrations were low, except for vitamin C, which was moderate and ranged from 33.33 g/100 g to 43.67 mg/100 g among the accessions. Generally, the B vitamins were low. Vitamin B2 appears to be the lowest, while vitamin B1 ranged from 0.23 mg/100 g to 0.40 mg/100 g among the accessions. IM1 and IM2 had the highest vitamin B1 (0.40 mg/100 g), while RIV5, EN3, and EN4 had the lowest vitamin B1 content (0.23 mg/100 g). The vitamin B2 content of the accession varied from 0.02 mg/100 g to 0.06 mg/100 g, with IM6 having the highest vitamin B2 content, while AB3, EN1, EN4, and EN6 had the lowest vitamin B2 content of 0.02 mg/100 g. Vitamin B3 content of the accessions ranged from 0.26 mg/100 g to 0.41 mg/100 g in EN3 and 1M3, respectively. The vitamin C concentration of the accessions was moderately high, with the highest concentration at 43.67 mg/100 g in RIV1, while its lowest concentration was 33.33 mg/100 g in RIV3 (Table 3).

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