Physicochemical characterization of fruits of Campomanesia guazumifolia (Cambess.) O. Berg (Myrtaceae)

Belonging to the family Myrtaceae, ‘sete capotes’ is a plant native to the Atlantic Forest biome. It produces yellow-green fruits between February and May. Although used for consumption by local populations, studies of the fruit are rare. The present work aimed at characterize the fruit in terms of physicochemical properties. We quantified mass, volume, moisture, pulp yield, pH, titratable acidity, soluble solids/titratable acidity, proteins, lipids, total sugars, reducing sugars, ash, macronutrients, micronutrients, pectin, vitamin C and phenolic compounds. Compared with commercial fruits and other native fruit trees, sete capotes is unusual for its pulp yield, vitamin C levels, total phenolic compound content, protein levels, calcium content, potassium levels and iron content. Through the results it is verified of the fruit as a functional food, mainly because of its nutritive content and because of its bioactive compounds. Our data emphasize the importance of study of the constituents of native flora.


Introduction
Brazil has the richest flora in the world, with more than 46 thousand species currently cataloged. Such diversity, in addition to presenting challenges in terms of conservation, presents a vast field for botanical and pharmacological research (Flora, 2017).
The territorial dimensions and ecological diversity of the country is also reflected in fruticulture. Occupying third place in the world in terms of production of commercial fruits, Brazil stands out for her variety of native fruits. (Raseira, Antunes, Trevisan, & Gonçalves, 2004).
Among native Brazilian fruit trees are those belonging to the family Myrtaceae. In general, their fruits potentially provide great nutritional and medicinal value, because of the presence of vitamins, minerals and antioxidant compounds, being consumed in natura or in the form of jellies, sweets and liqueurs (Reynertson, Yang, Jiang, Basile, & Kennelly, 2008).
Campomanesia guazumifolia (Cambess.) O. Berg, popularly known as sete capotes, sete cascas or capoteira belongs to the family Myrtaceae. It is a fruit tree plant found in Brazil from Bahia to Rio Grande do Sul, being found in soaked soils. It is consumed strictly by local populations. Its leaves are used in the production of teas (Lorenzi, 1998). The fruits mature between the months of February to May, a season characterized by low supply of commercial fruits. Even with this wide distribution, studies of the fruit remain scarce.
In light of the importance of studies that consider regional flora and the lack of bibliographical information related to sete capotes, the objective of this work was to characterize its fruits in terms of their physicochemical properties.

Material and methods
These experiments were conducted in the fruticulture and post-harvest laboratory at the Universidade Federal da Fronteira Sul-UFFS, Chapecó campus. The fruits used were collected from sete capotes (C. guazumifolia) located in the municipality of Guatambú, State Santa Catarina.
The fruits were collected in February 2017, at ideal maturation stage, when there was a yellow-green coloration of the skin. After collection, the fruits were selected, cleaned in running water, dried on at 760 nm. The average result of the total phenolic compound content was expressed as gallic acid equivalent (GAE) per gram of sample (mg GAE per 100 g).
Experimental design: The evaluation of mass, volume, moisture, yield, seeds per fruit and SS were performed with 10 replicates, while the other tests were performed in triplicate. The results were expressed through the mean obtained in the tests, followed by their respective standard deviations, and the results were analyzed in Microsoft Excel 2010.

Results and discussion
A mean of 14.32 ± 2.29 g was verified by measuring fruit mass. Mean volume was 12.9 ± 2.28 cm 3 . The pulp yield was 97.39 ± 0.73%. Mean number of seeds per fruit was 10.9 ± 0.87, and mean moisture content was 77.16 ± 1.30%.
As for the number of seeds per fruit, our data were similar to those described for the same species in Santos, Ferreira, and Áquila (2004), in which an average number of 11 seeds per fruit were reported. Nevertheless, these authors reported moisture content in the fruits, after desiccation, of 78%. Thus, it can be stated that in both studies, the values found in these variables were similar.
The pH readings of the juice samples had an average value of 3.38 ± 0.045. In analyses performed with gabiroba (Campomanesia xanthocarpa), guavira and cambuci (Campomanesia phaea) species belonging to the same genus as sete capotes, the average values of pH were, 3.77, 4.50, and 2.9, respectively (Vallilo, Garbelotti, Oliveira, & Lamardo, 2005;Scalon, Oshiro, & Dresch, 2012;Santos et al., 2013). In addition to varying species, the pH in fruits is influenced by environmental factors and degree of maturation, among factors (Scalon et al., 2012). The Brazilian consumer has a preference for in natura consumption of sweet fruits with low acidity. Thus, acidic fruits are commonly employed in prepared foods such as jellies and jams. The fruits of sete capotes have acidity similar to those of other fruits of the same genus referenced here.
Regarding titratable acidity, the average result obtained from the samples evaluated was 1.591 ± 0.16 g of citric acid per 100 mL. When analyzing the TA in other species, it was found that the orange (Citrus sp.), the Myrtaceae most consumed in Brazil, and the guava (Psidium guajava), the most commercially-cultivated fruit, presented TA values of 1.14 and 0.51 g per 100 mL, respectively. In other Myrtaceae, including the uvaia (Eugenia pyriformis), gabiroba and guavira, the values described were 0.46, 1.39 and 0.33 g of citric acid per 100 mL, respectively (Scalon et al., 2012;Krumreich, D'Avila, Freda, Chim, & Chaves, 2016).
According to Instituto Adolfo Lutz (2008), although non-linear, the acid content in citric acid present in fruits varies proportionally according to their vitamin C content. Thus, the high content of citric acid found in sete capotes fruits, compared to the species mentioned, highlights its potential as a source of organic acids.
On determination of soluble solids by refractometry, we recorded values of 13.18 ± 1.10 Brix degrees. The SS/TA ratio was 1.59. This relationship expresses fruit maturation, flavor and texture index, and more specifically, sugar/acid content, defining the characteristic fruit flavor (Instituto Adolfo Lutz, 2008). This is parameter is specific to each species and variety in terms of flavor. In fruits grown on a commercial scale [e.g., orange, apple (Malus domestica), grape (Vitis vinifera), among others] this ratio is used as a standard. However, native species do not present such values, making comparisons difficult. Nevertheless, the higher the ratio, the sweeter the fruit. For a comparison, the pineapple varies between 19 -28 and in citrus the ratio is 0.5 -0.7 (Lessa, Ledo, Amorim, & Oliveira, 2014).
On determination of protein content, we recorded an average value of 1.904 ± 0.006 g per 100 mL of juice. Compare this value to that of other Myrtaceae, such as 1.1% in the gabiroba, 0.46 in the pitanga, 0.44 in the cambuci and 0.50% in the araçá (Psidium cattleianum) (Vallilo et al., 2005;Silva, Cavalcante, Gebrim & Martins, 2008;Santos et al., 2013;Batista et al., 2017). In commercial cultivars, values of 0.3% for apples and 1% for peaches have been reported (Cunha, Durigan, & Mattiuz, 2010). Note that, compared to other fruits, sete capotes stands out in terms of protein content.
Although proteins of plant origin do not present the same biological value as those derived from animals, the consumption of fruits rich in these compounds, especially unconventional fruits, may represent an alternative for those populations with food restrictions (Kinupp & Barros, 2007). Therefore, given its protein content, the consumption of sete capotes can supplement the diet of its consumers.
Lipids are highly energetic molecules, found in high amounts in seeds, mainly oilseeds. However, in fruits and vegetables, lipids are only available in reduced amounts (Santos et al., 2013), explaining the low lipid content found in sete capotes.
Reducing sugar analysis revealed an average value of 2.86 ± 0.01 g per 100 mL of juice. In the study by Santos et al. (2013), the content of reducing sugars found in gabiroba was 6.77%. In the study of Oshiro, Dresh, and Scalon (2013), who studied guavira, the value described was 3.14%. In addition, in analyses performed with fruits of the pitangueira, Oliveira, Figueiredo, and Queiroz (2006) reported content of 3.82, with 13.2 in apple and 2.5% in peach (Cunha et al., 2010).
The content of reducing sugars in fruits is generally higher than that of non-reducing sugars (Oshiro et al., 2013). In terms of nutrition, the varied consumption of fruits represents, among other benefits, an important source of carbohydrates. Substitution of sugars from industrialized foods can be accomplished by consuming fruits. These habits have been highlighted by investigators in the field as important for maintaining a healthy diet.
With our data, we may conclude that the reference values for reducing sugars vary according to the species, even when comparing fruits belonging to the genus Campomanesia. Therefore, despite the lack of concentration of reducing sugars, the consumption of sete capotes may represent an supplement to the diet.
The quantification of total sugars in glucose by phenol-sulfuric method revealed 7.57 ± 0.19 g of sugar per 100 mL of juice. In a similar trial performed with gabiroba, Santos et al. (2013) reported a 7.88% content. In a study carried out by Oshiro et al. (2013), a content of 12.26% was reported. Regarding the chemical characterization of the red arachnid, the values were 6.79% (Santos, Petkowicz, Wosiacki, Nogueira, & Carneiro, 2007). The values were 10.5 in apple and 9.5% in peach (Rizzon, Bernardi, & Miele, 2005).
The difference in total sugar content in terms of glucose compared to that of related species was similar to that found in samples of sete capotes with respect to reducing sugars.
The quantification of ash content is only a complementary datum, since ash content does not necessarily express all the inorganic matter present in the sample. In addition to organic compounds, certain salts can also be volatilized (Instituto Adolofo Lutz, 2008). However, although secondary in terms of characterization, the ash content of sete capotes is a notable physicochemical property.
The quantification of the macro and micronutrients evaluated in sete capotes in this study, as well as the levels observed in fruits of some Myrtaceae, compared to the data obtained in the seven layers, are displayed in Table 1. Compared to the other fruits referenced, sete capotes stands out in terms of its high levels of potassium, calcium and iron.
The consumption of foods rich in minerals is fundamental for their replacement in the human body to ensure complete homeostasis (World Health Organization [WHO], 2003). Fruits and vegetables are known to be primary sources of these compounds. Therefore the inclusion of native fruits in the diet, among them, sete capotes, can potentiate the supplementation of these and other indispensable nutrients in the maintenance of the quality of life of the population.
Present in the cell wall of plant tissues, pectins represent about one third of the dry matter weight in fruits. Due to their gelling properties, they have been used since ancient times in the production of fruit jellies and industrially as thickening and stabilizing agents. It can be observed that sete capotes had an average pectin content similar to some fruits of the same family. According to Torrezan (1998), about 1% of pectin is sufficient to make jellies with a firm appearance, not necessarily in the case of sete capotes.
The evaluation of the vitamin C content in the fruits of sete capotes showed an average of 198.33 ± 12.58 mg of ascorbic acid per 100 mL of juice. In a study carried out by Giacobbo, Zanuzo, Chim, and Fachinello (2008) with araçá, a mean value of 38.85 mg per 100 mL was reported. In similar trials with fruits of the same family, contents of 313.21 mg per 100 mL were described for gabiroba, 234 mg per 100 mL in guavira, and 33 mg per 100 mL in cambucius, while 43 mg per 100 mL were reported for jambolão (Syzygium cumini) and 27 mg per 100 mL for uvaia (Vallilo et al., 2005;Vallilo et al., 2006;Santos et al., 2013). Hummer and Barney (2002) demonstrated a disparity in vitamin C content between different fruits, as in the case of apple having 5.7 mg per 100 g and blackberry (Rubus spp) having 181 mg per 100 g. Similarly, it can be stated that such variation occurs in fruits from the same family, including individuals from the family Myrtaceae.
Since vitamin C is an essential compound for proper homeostasis, participating in several cellular mechanisms, the sete capotes presents itself as a viable alternative in the supply of this and other bioactive compounds.
The quantitative analysis of total phenolic compounds in sete capotes showed an average value of 312.13 ± 3.11 mg of gallic acid equivalents (GAE) per 100 g of fruit.
In a phytochemical study, Stuelp-Campelo, Arruda, Bianchini, and Rosa (2016) verified the presence of phenolic compounds in capoeira stem tissues, however, he did not report the content found.
In a study of optimization for extraction of bioactive compounds in gabiroba, pitanga-do-cerrado (Eugenia punicifolia) and pêra-do-cerrado (Eugenia klostzchiana) phenolic compounds indices of 385, 364, and 271 mg GAE per 100 g, respectively, were reported (Rocha et al., 2011). Alves, Alves, Fernandes, Naves, and Naves (2013) performed extraction in methanol, and reported that fruits of gabirobeira had an average value of 1222 mg GAE per 100 g. In addition, Lima, Castro, Sabino, Limas, and Torres (2016) reported indices of 229 and 511 mg GAE per 100 g for yellow gabiroba (Campomanesia lineatifolia) and myrtle (Blepharocalyx salicifolius), respectively. Infante, Rosalen, Lazarini, Franchin, and Alencar (2016), in tests of fruits from the genus Eugenia, reported levels of 151, 183, 266 and 178 mg GAE per 100 g for araçá-pitanga (Eugenia leitonii), cherrygrove, grumixama (Eugenia brasiliensis) and pessegueiro-do-mato, respectively. The author also emphasized the difference in the contents of these compounds in fruits of the same species when collected in different locations, revealing the influence of environmental factors on the production of these substances.
As in other Myrtaceae fruits, the content of phenolic compounds found with sete capotes enhances the nutritional and functional potential of the fruit.

Conclusion
The physicochemical characterization of sete capotes revealed the potential of this fruit as a nutritious and functional food.
The fruit harvest period (February to May) coincides with the season of low supply of fruits in the national market (Brazil).
The fruit stood out in relation to other Myrtaceae in terms of pulp yield, vitamin C, total phenolic compounds, protein and calcium content, potassium and iron.
The diffusion of knowledge about the constituents of the fruit, in addition to appreciating the diversity of the regional flora, can stimulate interest and can increase its addition in the diet.