Variation of Moisture Content in the Fruits of V. doniana and S. comorensis
The moisture content in S. comorensis fruits is similar to the moisture content in other wild fruits reported by [18] in Baccaurea ramiflora (70.21%). [17] pointed out that the lowest moisture content signifies the highest dry matter content in fruits, therefore high moisture content in S. comorensis reveals lowest dry matter content.
However, moisture content in Vitex doniana was close to that in Polyalthia suberosa (64.76 ± 3.91%) reported by [19]. In this study values were higher compared to those in Vitex doniana, Vitex kiniensis and Vitex fischerii reported by [20] that had the value of 39.42 ± 0.72%, 40.56 ± 0.77% and 37.74 ± 0.76%, respectively, this may be due to differences in climatic condition. The lowest moisture content in V. doniana fruits can favour long shelf life because the growth of microorganisms are not favored [21]. The percentage of moisture content in V. doniana and S. comorensis was lower compared to that in Bridela tomentosa and Carissa spinarum, 78.54 ± 1.02% and 73 ± 1.37% respectively as reported by 19. Also some of the domesticated fruits such as Mangifera indica (82.1%) reported by [22], Passiflora edulis (83.11%) reported by [12] and Citrus sinensis (87.1%) reported by [13] have higher moisture content than wild fruits.
Determining moisture content is important in food quality analysis because moisture affects preservation and resistance to deterioration [21]. The percentage of moisture content affects the physical and chemical properties such as color and taste of fresh food material. Therefore, the amount of moisture content in V. doniana and S. comorensis fruits can help to add amount of water in a body for a healthy skin, digestion and good flow of blood in the body.
Variation of Ash Content in the Fruits of V. doniana and S. comorensis
The total ash contents observed in S. comorensis are similar from that reported by [23] on the edible wild fruits from Malawi that had percent of ash content in a range from 3 to 5%. S. comorensis from coastal forests had higher percent of ash content than that reported by 24 in other Saba species for example Saba senegalensis have very low ash content (2.80%). [25] reported the ash content in S. birrea (4.9%) and V. infausta (3.9%) that correlated with the value observed in this study in S. comorensis. The ash content in S. comorensis were similar to those reported by [26] that ranged from 3 to 7.8% in A. digitata pulp and kernel.
[20] reported an amount of total ash in V. doniana (3.41 ± 0.09%) which is higher than ash content in V. doniana fruits samples reported in this study. These results are not similar to those reported on V. doniana by [23, 27] which were 4.8% and 5.27% respectively. The ash content in V. doniana were also similar to those reported by[ 26] that ranged from 3 to 7.8% in A. digitata pulp and kernel. [25] reported the ash content in S. birrea (4.9%) and V. infausta (3.9%) that correlated with the ash content observed in V. doniana in this study.
Ash content helps to determine the amount and type of minerals in food sample, as well as retard the growth of microorganism [28]. Ash content determination is a part of proximate analysis for nutritional evaluation and for preparation of a food sample for a specific elemental analysis [28]. Minerals are involved in the formation of bones and teeth, essential constituency of body fluids and tissues. This range of ash content shows that S. comorensis and V. doniana can be alternative sources of essential mineral nutrients.
Variation of Protein Content in the Fruits of V. doniana and S. comorensis
Most wild fruits have a good value of protein content [24]. V. doniana results obtained are comparable to that reported by [29] in Maerua pseudopetalosa (19.26–22.06%) and similar from that reported in Sterculia Africana oil (24.90 ± 0.63%) by 30. V. doniana which had 7% of crude protein which is higher compared to that reported by [23] with 2.6%. These values indicate that fruits may not be an excellent source of protein. However, S. comorensis from Tanzania have relatively lower protein content than some fruits but also higher than S. senegalensis (0.53%) reported by [24]. In this study, the protein content of S. comorensis is comparable to that of Mangifera indica (4.01 mg/100g) reported by [22] but higher than Passiflora edulis (0.90 mg/100g) reported by [12] and Citrus sinensis (0.8 mg/100g) reported by [13]. [31] reported Dennettia tripetala fruits to have protein content of 15.3 g/100g which is higher than that of S. comorensis. However, [32] reported a protein content of indigenous fruits of South Africa as 8.2 g/100g. Higher amount of protein in S. comorensis and V. doniana showed significant difference at P < 0.05. These differences in protein content can be ascribed to environmental factors and more likely by extraction procedures where during separation of the pulp and seeds, some small quantity of substituents from seed can still be mixed up. Seeds from different studies reported to have high amount of protein than the fruit pulp. It can therefore be said that while S. comorensis and V. doniana are not very good sources of protein, it is still worthy eating these wild fruits in order to get their other nutritional benefits while complementing proteins from other food sources.
Variation of Crude Fat Content in the Fruits of V. doniana and S. comorensis
The range of fat content in most edible fruits is reportedly less than 0.5 g/100g [24]. Fats help to maintain body temperature and make up all body cells. Apart from other sources of energy such as carbohydrate, fats provide high levels of energy and they are also reservoirs of fat-soluble vitamins. The crude fat content of V. doniana and S. comorensis are presented in Table 2.1 and 2.2. This range of results presented in Table 2.1 and 2.2 is very similar to those reported by [18] in Cucumis melo, Psidium guajava, Carica papaya, Carissa carandas which had 0.0084%, 0.023%, 0.02%, and 1.27% respectively. Other similar results are reported by [33] in Baccaurea sapida (0.73%), Morus alba (0.21%) and Terminalia chebula (3.90%). S. comorensis had the lowest content below the detection limit (0.00 ± 0.01%) and (0.00 ± 0.00%) from Tanga and Pwani. The results are very similar to those reported in Passiflora edulis which had 0.00% by [12].
Vitex doniana from Tanga had higher value of fat content (1.9 ± 0.10%) than those reported by [23] in the same fruits that had 0.7%. 30 reported V. mambossae, A. digitata, Opilia amentacea to have high values of fat contents 2.97 ± 0.29%, 3.88 ± 0.13% and 2.45 ± 0.40% respectively, which are higher than those in V. doniana from Pwani and Tanga having the value of 2.4 ± 0.00% and 1.9 ± 0.10% respectively. It can be noted that S. comorensis have low amounts of fats. Low fat foods are considered healthy because high consumption of fats is linked to health problems such as obesity, cardiovascular diseases, higher blood pressure, stroke, breathing problem and higher cholesterol.
Variation of Total Carbohydrate Content in the Fruits of V. doniana and5S. comorensis
The total carbohydrate in S. comorensis and V. doniana were higher than those of domesticated fruits such as Mangifera indica (0.0 mg/100g) reported by [22] and Citrus sinensis (6.0 mg/100g) reported by [13]. The mean value of 7% and 21% of V. doniana from Tanga and Pwani regions is however lower than 29.57 ± 0.07% reported by [20] for the same fruits collected from Kenya. However, the amount of carbohydrate in this study from S. comorensis were lower than those of S. senegalensis (74.23%) which is of the same genus [24]. S. comorensis and V. doniana from Pwani had higher total carbohydrate of 23.81 ± 0.38% and 23.98 ± 0.20% respectively than those found from Tanga. The amount of cabohydtrate in S. comorensis and V. doniana from Pwani region were higher than those reported by [18] for the exotic fruits Psidium guajava (15.52 g) and Carica papaya (10.93 g).
In this study, total carbohydrate content of V. doniana fruits ranged from 23.78–24.18% for fruit samples from Pwani and 8.32–9.12% for fruit samples from Tanga. The differences may be attributed to different soils or other environmental and climatic factor. Different environmental stresses or favorable conditions may affect the metabolic efficiency of plants in those areas and hence perform differently when it comes to the metabolites they produce 34. The amount of carbohydrate determined indicated that wild fruits can be an important source of dietary energy. The amount of carbohydrate in wild fruits contribute to higher calorific value compared to the exotic fruits. Findings from this study recommend the increase consumption of S. comorensis and V. doniana which may serve as valuable source of energy to human body.