Impact of genotype on fatty acid profile, oil content and nutritional value of the sweet fruits of Acrocomia aculeata

Abstract Macauba (Acrocomia aculeata) has mainly been evaluated as an oil source focused on biodiesel production. Furthermore, the fruit mesocarp and kernel are edible, and candies, jelly, sweet alcoholic liquor and ice cream are also produced from the mesocarp. Despite its consumption, there is still a lack of information on the nutritional composition of macauba. Selected macauba genotypes producing fruits with a sweet mesocarp were evaluated regarding the fruit characteristics, proximate composition, oil content and fatty acid profile. The mesocarp total sugar (fructose and glucose) content ranged from 4.5 to 9.6 g/100 g, total dietary fiber varied from 6.8 to 9.3 g/100 g, while protein content was up to 2.2 g/100 g (wet basis). There was a significant difference among genotypes for fruit characteristics, pulp oil content (7-29 g/100 g wet basis), and fatty acids from the mesocarp such as C18:1 (36-63%), C18:2 (7-35%) and C18:3 (0.8-7%)(p<0.05), and one of the evaluated genotypes may contribute to daily intake of linoleic and linolenic acids. The carotenes in the mesocarp oil ranged from 30-240 mg/kg. Lauric acid was the main fatty acid in the kernel oil. The differences observed depended on the genetic diversity and point out the nutritional value and different applications for macauba mesocarps.

1 PhD, Researcher at Embrapa Agroindústria de Alimentos, Rio de Janeiro-RJ, Brazil. Email: rosemar.antoniassi@embrapa.br  2 PhD, Researcher at Embrapa Agroindústria de Alimentos, Rio de Janeiro-RJ, Brazil. Email: sidinea.freitas@embrapa.br (ORCID 0000-0002-0398-1268) 3 M.Sc., Analyst at Embrapa Agroindústria de Alimentos, Rio de Janeiro-RJ, Brazil. E-mail: tania.silva@embrapa.br (ORCID 0000-0002-4031-1394);4 PhD, Analyst at Embrapa Agroindústria de Alimentos, Rio de Janeiro-RJ, Brazil. E-mail: manuela.santiago@embrapa.br (ORCID 0000-0003-4459-2258) 5 M.Sc., Analyst at Embrapa Agroindústria de Alimentos, Rio de Janeiro-RJ, Brazil. E-mail: allan.wilhelm@embrapa.br  PhD, Researcher at Embrapa Cerrados, Planaltina-DF, Brazil. Email: nilton.junqueira@embrapa.br (ORCID 0000-0001-9814-7104) Impacto do genótipo no perfil de ácidos graxos, no teor de óleo e no valor nutricional dos frutos doces de Acrocomia aculeata Introduction Acrocomia aculeata (Jacq.) Lodd. ex Mart. (family Arecaceae) is a spiny, single-stemmed palm which grows up to 16m in height, and extends from southern Mexico through Central America and the Antilles to northern Argentina. The largest concentrations are found in Paraguay and in the Brazilian States of Minas Gerais, Goias, Mato Grasso and Mato Grosso do Sul, where massive stands are mostly present in pastures as the dominant tree, but also in pastures with shrub vegetation and in forests (SCARIOT et al., 1995). The fruits are spherical or slightly flattened in the shape of a globular drupe, with a diameter ranging from 2.5 to 5.0 cm. The epicarp breaks easily when mature. The mesocarp is edible, fibrous and mucilaginous, sweet in taste, rich in oil and yellow. The endocarp is strongly adhered to the pulp (mesocarp) and contains a white kernel (LORENZI et al., 2010). Lorenzi and Negrelle (2006) reported several applications and uses for macauba including the trunk as wood, the leaves for animal fodder, the stipe to obtain palm heart and sap used as food and drink, respectively. Fruits are eaten fresh or used for oil extraction. The pulp is used to prepare sweetened alcoholic liquor and ice cream, and the kernel serves as food. Several applications and recipes of Cerrado (Brazilian savannah) fruits including macauca mesocarp and kernel were presented by Almeida (1998).
The potencial of macauba as an oil source has been evaluated focusing on biodiesel production (BERGMANN et al., 2013;COLOMBO et al., 2018;CONCEIÇÃO et al., ,a, b, 2015bFERRARI and AZEVEDO FILHO, 2012;LOPES and STEIDLE NETO, 2011). Therefore the oil content and the fatty acid profile of both the mesocarp and kernel oils and fruit characteristics have been more studied than its nutritional value (CONCEIÇÃO et al., ,a,b, 2015bHIANE et al., 2005;VIANNA et al., 2017). Information related to nutritional composition is scarce, and a large variation has been observed for the protein content of the mesocarp ranging from 1.5 to 6.7% (RAMOS et al., 2008;COIMBRA and JORGE, 2011), while total dietary fiber has been presented for some macauba genotypes without evaluating the sugar content. Regarding the presence of sugars, Mooz et al. (2012) reported 3.99ºBrix for the mesocarp, while Ramos et al. (2008) cited glucose as the main sugar in the macauba mesocarp (9.5g/100g). Additionally, bioactive compounds of the mesocarp such as ascorbic acid were measured, ranging from 14.7 to 15.4 mg/100g (MOOZ et al., 2012;LESCANO et al. 2015), carotenoids (300µg/g) and tocopherols (213 mg/kg) for dried pulp by Coimbra and Jorge (2011), and calcium (67 mg/100g) and zinc (0.7 mg/100g) for wet pulp (TACO, 2011).
The selection of A. aculeata genotypes for oil production was carried out by Embrapa Cerrados (Brazilian Agricultural Research Corporation) by evaluating massive palm stands covering four Brazilian states in the Cerrado region (CONCEIÇÃO et al., 2013a,b, CONCEIÇÃO et al., 2015a. Meanwhile, the communities of these areas reported their traditional knowledge, and according to Junqueira (2020) the first inhabitants of Cerrado region used macauba oil for lighting, and the pulp was consumed at breakfast, although they preferred the sweet fruits with low oil content because the oily fruits may cause diarrhea. The kernel was used to feed domestic animals such as pigs, chicken and cows. The sweet macauba fruits were also consumed by the caninde macaw (Ara glaucogularis, family Psittacidae), and their presence was used for identifying these genotypes.
In this work, three sweet macauba genotypes were selected based on the traditional knowledge of the local population who usually produce candies, ice cream, jelly and other products with the mesocarp of these fruits. A comparison of sweet macauba genotypes was carried out regarding fruit characteristics, proximate composition and the sugars profile of the mesocarp and fatty acid composition of the mesocarp and kernel oils.

Material
The sweet genotypes of Acrocomia aculeata were codified as Mac 1, Mac 2 and Mac 3. The Mac1 genotype was selected from a massive stand of A. aculeata in the city of Formosa, Goias State, Brazil at altitude of 858 m and at the geographic coordinates of 15°54'25.72" S and 47°21'47.75" W. The Mac 2 genotype was found at the geographic coordinates of 15°54'22.86" S and 47°22'40.00" W in the Rural Center Jardim 2, Federal District State, Brazil at altitude of 854 m, and the Mac 3 genotype was selected from a massive stand at altitude of 877 m and at the coordinates of 15°53'51.96" S and 47°24'05.77" W, in the Rural Center Buriti Vermelho, Federal District State, Brazil.
The collection of the ripe fruits was carried out using some nets which were placed around the trunk to catch falling fruits and the collection time was controlled to avoid fruit damage.

Fruit Characteristics
Fruits of three selected genotypes were collected from mature bunches, and kept frozen until analysis. The fruits (4 or 5) and their parts were separated and weighed (wet basis). The epicarp was removed, the mesocarp of each fruit was cut and lyophilized, and the woody *JUNQUEIRA, N.T.V. Personal communication, 2020. endocarp was broken. The kernel of each fruit was then dried in an air oven (60°C for six hours). Oil from the mesocarp and kernels from each fruit was extracted by a Soxhlet apparatus (petroleum ether 30-60°C) for 16 hours. The epicarp, endocarp, kernel, and mesocarp (pulp) contents related to fruit weight were evaluated on a wet basis. The kernel and pulp oil contents were reported as wet (WB) and dry basis (DM). The kernel and pulp oil yields per fruit were calculated as wet basis, and the total oil yield per fruit was the sum of both.
The pulp oil was dissolved in hexane and the carotene content was estimated by spectrophotometric analysis according to Davies (1976). It was possible to measure the carotene content for each fruit for the Mac 1 and Mac 3 samples, however the oil for the Mac 2 sample was sampled from different fruits and the analysis was carried out in duplicate.

Fatty acid composition
The fatty acid profile analyses of the mesocarp and kernel oil samples were analyzed separately for each fruit. The methyl esters were prepared according to Hartman and Lago (1973) and analyzed by gas chromatography on Agilent 7890 equipment equipped with a fused silica capillary column covered with a cyanopropylsiloxane film (60 m x 0.32 mm x 0.25 μm) and the temperature was programmed as follows: initial temperature of 100ºC for three min; from 100 to 150ºC with an increase of 50ºC/ min; from 150 to 180ºC with an increase of 1ºC/min; 180 to 200ºC with an increase of 25ºC/min, and at the final temperature of 200ºC for 10 min. The sample (1μL of a 2% w/v) was injected into an injector heated to 250°C and operated in split mode (1:50). A flame ionization detector kept at 280ºC was used for signal collection. Identification was performed by comparing the retention times to NU-CHEK Prep, Inc. (Elysian, MN) standards and quantification was performed by internal normalization. The iodine and saponification indexes were calculated based on the fatty acid composition.

Proximate composition and sugar analysis
The pulp was removed from 10 fruits and homogenized, and the analysis was conducted in duplicate. The proximate analyses were performed according to AOAC Official methods (AOAC, 2005). The moisture was measured until constant weight in an oven at 105ºC, the ash content was conducted by calcination at 550ºC, the oil content was carried out by acid hydrolysis followed by ethyl ether and petroleum ether extraction, and total dietary fiber was determined by the enzymatic-gravimetric method (AOAC 991.43). The protein content was calculated based on nitrogen content determined by the Kjeldahl method and using the factor of 5.75 as reported for vegetable products by Brazilian nutritional labeling regulation (BRASIL, 2003).
The glucose, fructose and sucrose concentrations in the wet pulp were determined by high-performance liquid chromatography (HPLC) with a refractive index detector. The sugars were extracted with ultrapure water and acetonitrile in an ultrasonic bath for 20 min and the extract was filtered. The HPLC analysis was performed using a column Zorbax TM Carbohydrate (30 cm × 4.6 mm x 5µm), and a flow rate of 1.0 mL.min -1 of a mobile phase of acetonitrile:water (75:25 v/v). The quantification was performed based on external calibration with pure standards.

Statistical analysis
Analysis of variance and Tukey test were performed using Statgraphics (Statgraphics Technologies Inc).

Results and discussion
The fruit characteristics of the three genotypes evaluated are presented in Table 1. There was a significant difference for fruit weight, epicarp and endocarp contents (wet basis -WB), pulp moisture, pulp oil content (dry and wet basis) and pulp oil yield and total oil yield/fruit (WB) (p<0.05). The fruit weight varied from 29 to 38 g (fresh weight), which is consistent with the average result (39 g) reported by Vianna et al. (2017) and in the range of 24 to 58 g observed for 35 genotypes by Conceição et al. (2015b). The fruits showed epicarp and endocarp contents varying from 15 to 24% and 28 to 35% (WB), respectively, and both comprised around half of the fruit weight. The pulp and kernel contents (WB) varied around 41-44% and 6-8%, respectively, and no difference was observed among the genotypes evaluated (p>0.05). Although the pulp moisture (50-63 g/100g) was higher than kernel moisture (19-22 g/100g), the pulp oil content (7-29 g/100g WB or 19-60 g/100 g dry matter-DM) led to the pulp oil yield/fruit ranging from 3 to 12%, showing a higher contribution to the total oil yield/fruit (6-15%)(WB) than the kernel oil yield/fruit. The kernel oil content varied from 33-42 g/100g (DM) or 26-35 g/100g (WB). The Mac 3 genotype had the highest pulp oil content and total oil yield/fruit, while the Mac 2genotype presented the lowest figures among the evaluated genotypes. The parameters studied were in the range of those studied by Conceição et al. (2015b). It is noteworthy to highlight that Mac 3 presented the lowest fruit weight, but showed consistent pulp oil content (DM) with the most promising genotypes for oil source evaluated by Conceição et al. (2015b). The total sweet macauba mesocarp sugars ranged from 4.5 to 9.6 g/100g (WB) ( Table 2). Sucrose was not detected, while the fructose results (2.5 to 5.3 g/100g WB) were higher than glucose (2 to 4.4 g/100g WB). Ramos et al. (2008) reported glucose (9.47 g/100g WB) as the main monosaccharide of macauba mesocarp and fructose was not detected or no separation between these compounds was achieved, while sucrose was detected up to 0.07 g/100g. The lower total sugars content was obtained for the Mac 3 sample which also showed the highest pulp oil content, while the highest total sugar content was observed for the Mac 2 sample, being the genotype with the lowest pulp oil content. Thus, the genetic diversity observed for the macauba genotypes for oil content may also be related to mesocarp composition. Knowledge regarding the sugar content is important when considering the sensory acceptance for possible products obtained from the pulp. The mesocarp showed total dietary fiber (TDF) varying from 6.8 to 9.3g/100 (WB) ( Table 2) or 17-24 g/100g (DM), being similar to the results (17-23 g/100g DM) cited by Coimbra and Jorge (2011), TACO (2011) and Silva et al. (2008), however these authors did not include sugar determination data. In order to perform a comparison, the results should be calculated as dry basis, because the mesocarp moisture was different among genotypes, while the result for intake of the edible portion should be informed as wet basis. No other comparison was possible because the enzymatic gravimetric method for TDF analysis is expensive and time consuming. The Mac 2 and Mac 3 genotypes showed similar results, while Mac 1 presented the highest TDF content (24 g/100g DM).
The protein content of mesocarp varied from 1.7 to 2.2 g/100g (WB) and the results calculated as dry basis (4.3-4.4 g/100g) were similar to the range (3.2-4.2 g/100g DM) reported by Ramos et al. (2008), Silva et al. (2008) and TACO (2011), but lower than the result (6.7 % DM) cited by Coimbra and Jorge (2011). The ash contents (1.8 -2 g/100g WB or 3.9-5.1 g/100g DM) were higher than the results obtained by Ramos et al. (2008), TACO (2011), Coimbra and Jorge (2011) and Silva et al. (2008), ranging from 2.1 to 3.2 g/100g (DM). The Mac 2 and Mac 3 genotypes presented the highest and the lowest ash contents, respectively. The variation in the mesocarp oil content (WB) between Tables 1 and 2 was related to sampling, as Table 1 presents the results for fruits which were evaluated separately, and Table 2 shows the sampling results of 10 fruits followed by homogenization. The results were in the range of pulp oil content obtained by Ramos et al. (2008) and TACO (2011), of 8 and 40 g/100g (WB), respectively. The carbohydrates calculated by difference varied from 10 to 22 g/100g, and were only not consistent with sugar content. Further evaluation of the presence of starch as reported by Ramos et al. (2008) should be evaluated. The caloric value ranging from 162 to 288 kcal/100g is mainly related to the high oil content.
The total dietary fiber (TDF), lipids, protein and ash contents of macauba pulp were higher than around 80 commercial and native fruits evaluated by the Brazilian composition table (TACO, 2011), except for pequi pulp (Caryocar spp.) and tucumã (Astrocaryum spp.) regarding TDF content and the protein content reported for tamarinds (Tamarindus indica).
The sweet macauba genotypes evaluated showed high total dietary fiber, sugars and oil contents presenting distinct patterns which can lead to different applications such as ice cream for samples with high oil content, and alcoholic liquors for samples with low oil content.
The differences in nutritional value observed for the sweet macauba genotypes were attributed to genetic diversity because these fruits were collected at the same ripening stage and these genotypes were grown in similar conditions in the Cerrado region. Ripe fruits detached from the bunches and they were collected using some nets in order to avoid fruit damage.
The genetic diversity related to fruit characteristics, oil content and fatty acid profile was also observed by Conceição et al. (2013aConceição et al. ( , 2013bConceição et al. ( , 2015b for A. aculeata genotypes from Brazil. The impact of the genotypes variation was also observed by Górnaś et al. (2017Górnaś et al. ( , 2018 for fatty acids of kernel oil among plum (Prunus domestica L. and P. cerasifera) and apricot (P. armeniaca) genotypes.
The Mac 2 genotype had a different nutritional composition among the sweet macauba genotypes as well as for other macauba genotypes evaluated in Brazil, presenting the highest linoleic and linolenic acid, total sugars and ash contents, and the lowest oil content for the pulp. Additionally, the Mac 3 genotype showed the highest pulp oil content and the lowest total sugars content, while Mac 1 displayed intermediate total sugars and oil contents and presented the highest TDF content.
The nutritional composition of fruits provides valuable information considering health benefits and possible effects on the sensory characteristics of the products from the macauba mesocarp.

Conclusion
The variation observed among sweet macauba genotypes mainly related to the fatty acids of mesocarp oil, mesocarp oil content and nutritional value was attributed to genetic diversity among genotypes.
The pulp oil of two selected genotypes presented fatty acid profile of high oleic acid and low linoleic and linoleic acid contents, but one genotype showed a distinct fatty acid profile with high linoleic and linolenic acid contents.
The mesocarp showed high total dietary fiber, oil content, protein and ash contents among the highest results observed for commercial and native fruits from Brazil.