1 Acerola

1.1 (Malpighia glabra L.)

Katia Sivieri1

1Department of Food and Nutrition, School of Pharmaceutical Sciences, State University of São Paulo (UNESP). Araraquara- SP, Brazil

Corresponding author: [email protected]

1.2 Agronomic characteristics

1.2.1 Taxonomy

Acerola (Figure 1.1), also known as Antillean cherry, is described in the literature as originating from two species: Malpighia punicifolia and Malpighia glabra. In Puerto Rico, there is a contradiction regarding to the species to which the berry belongs to, since, for many botanists, Malpighia punicifolia and Malpighia glabra are not different species, but different botanical forms of the same species (MENDES et al., 2012).

A) Acelora tree, B) Acerola fruit

Figura 1.1: A) Acelora tree, B) Acerola fruit

Malpighia glabra L. is described as a medium-sized glabrous bush (hairless), 2-3 m high, with dense and scattered branches; opposite leaves with short, oval and elliptic-petiolate petiole; going from 2.5 cm to 7.5 cm (MENDES et al., 2012).

The acerola is native to the Antilles, it is cultivated at a commercial scale in Puerto Rico, Hawaii, Jamaica and Brazil. However, it can be found throughout all the continent. Table 1.1 shows the taxonomic classification of acerola.

Cuadro 1.1: Acerola taxonomic classification
Kingdom Plantae
Filum Malpighiaceae
Class Magnoliopsida
Order Malpighiales
Family Malpighiaceae
Gender Malpighia
Source: Mendes et al., (2012)

1.2.2 Culture condition

The acerola can be propagated either by the use of seeds (sexual propagation), or by cutting and grafting (asexual or vegetative propagation), therefore it is considered a plant of fairly easy propagation (JUNQUEIRA et al., 1997). Seed propagation

Seed propagation is still the most common practice in the establishment of commercial plantations of acerola trees in Brazil. The lumps are selected from well-shaped and nourished plants, extracted from senescent fruits (fully mature) by sifting them under running water or by fermentation. The lumps should be thoroughly washed and allowed to dry in the shade for two days, then they can be immediately sown or stored in a refrigerator for up to four months. To select the ideal lumps, they should be placed in a bucket with clean water, discarding the lumps that float in the surface. Sowing should be performed in furrows with a distance of 10 cm between each other, and a depth of 0.5 to 1.0 cm; in beds with dimensions of 1.0 m in width and 1.5 m in length, containing substrate consisting of soil + organic matter in a ratio of 2:1 (JUNQUEIRA et al., 1997).

Daily watering should be done with watering can, with germination occurring from 20 to 30 days after sowing. The seedlings should then be peeled and placed into bags of 16 X 25 cm (volume of 2 liters) with substrate consisting of soil + organic matter in the proportion of 3:1, mixing 600 g of single superphosphate for every m3 of substrate. When the seedlings reach 25-30 cm high, they should be transplanted to the pits. This type of propagation has caused considerable damages to the producers, due to the great variability of plants and fruits, generating unevenness in the production and quality of the fruits. Another great problem is the low germination rate, which normally varies from 25 to 30%, due to incompatibility in pollination, generating absence or problems in the formation of the embryo (MARINO, 1986). Propagation by cutting

Propagation by cutting is a method that allows obtaining uniform plants; however, it is more difficult to perform and has a higher production cost. It is recommended to use semi-shallow cuttings containing a pair of leaves measuring 15 to 20 cm in length and 3 to 6 cm in diameter. The cuttings should be collected before the flowering period. After the collection, the stake base is placed in 6.000 ppm of Indole-butyric acid (IBA), a hormone solution powder for 15 seconds, then the cuttings are rooted in 72-cell polyethylene trays containing either washed sand or a commercial vermiculite substrate. This step should be performed in a greenhouse with intermittent misting and controlled temperature irrigation system. After 60 days, the rooted cuttings are transferred to bags with dimensions of 16 X 25 cm (volume of 2 liters) containing substrate composed of soil + organic matter in a ratio of 3:1, mixing 600 g of simple superphosphate for every m3 of substrate. The seedlings should be transplanted to the pits when they reach 25-30 cm in height from the lap of the plant, (BATISTA et al., 1989). Propagation by grafting

Another method that can be used is grafting. Using rootstocks obtained from seeds. When the seedlings are about 10 to 12 months old or have a diameter of 0.8 to 1.0 cm, they are grafted with healthy pimples and removed from seedlings with desirable agronomic characteristics. The advantages of grafting include reducing plant size, facilitating crop and harvesting, maintaining the desirable characteristics of the variety used as a matrix, precocity at the beginning of production and uniformity (ALVES, 1992).

1.3 Physical, chemical and physicochemical characteristics of acerola

The fruit of the acerola, is a meaty drupe, varying in shape, size and weight. Inside of it there is the epicarp which is a thin film; the mesocarp which is the pulp and the endocarp which is made of three joined cores with parchment texture, that give the fruit a lobade aspect. Seeds go from 3 to 5 mm long, in an ovoid shape and with two cotyledons (ALMEIDA et al., 2002). The size of the fruit may vary from 1 to 2.5 cm, the diameter from 1 to 4 cm and the weight from 2 to 15 g. The mesocarp or pulp represents 70% to 80% of the total fruit weight (ALMEIDA et al., 2002).

Acerola undergoes changes rapidly after harvesting regarding color, aroma, flavor and texture, with the fruits being round, oval or even conical (GONZAGA NETO & SOARES, 1994).

The acerola can be classified as a climacteric fruit that undergoes a series of alterations during the maturation and senescence processes: a remarkable degradation of chlorophyll, a synthesis of carotenoids and anthocyanins, a decrease in acidity, and loss of vitamin C during these stages. These can occur when the fruit is in the plant or after the harvest, as they can be harvested at the beginning of maturation (when they are green, yellowish green or until they begin to acquire a red pigmentation), when they are focused on the production of vitamin C (ALVES, CHITARRA, 1995). Therefore, the chemical composition, including the distribution of aroma components, depends on the species, environmental conditions and, also, the maturation stage of the fruit. Acerola is a very acidic fruit and, in the same way that occurs with other components of the fruit, the pH also varies with the stage of maturity (VENDRAMINI & TRUGO, 2000).

The content of vitamin C and other characteristics attributed to acerolas, such as color, fruit weight and size, soluble solids content and pH of the juice are influenced by several factors, such as rainfall, temperature, altitude, fertilization, irrigation, and the occurrence of pests and diseases (NOGUEIRA et al., 2002). The physical and chemical characteristics of the acerolas in different maturation stages can be observed in Table 1.2.

Cuadro 1.2: Physicochemical characteristics of the acerolas in different maturation stages.
Composition Immature (green) Intermediate (yellow) Mature (red)
Vitamin C (mg 100 g-1) 2,164.0 1,065.0 1,074.0
Protein (g 100 g-1) 1.2 0.9 0.9
Ash (g 100 g-1) 0.4 0.4 0.4
Humidity (g 100 g-1) 91.0 92.4 92.4
Acidity 18.2 15.6 34.4
pH 3.7 3.6 3.7
Soluble solids (ºBrix) 7.8 7.7 9.2
Carbohydrate (g 100 g-1) 4.4 4.3 4.4
Source: Freitas et al., (2006)

1.3.1 Phytochemicals in acerola fruit

The term phytochemical or phytonutrient refers to the compounds that have been associated with reducing the risk of major chronic diseases. These groups of bioactive compounds include phenolic compounds, carotenoids, alkaloids, nitrogen containing compounds and organosulfur compounds. The area of phytochemicals in the acerola is poorly documented; the most studied so far are the phenolic compounds and carotenoids (DEVA et al., 2012).

The phenolic compounds found in foods originate from one of the main classes of secondary metabolites of plants. They are particularly important for plant metabolism and have also become important to humans because of their health characteristics, particularly related to their antioxidant power. The phenolic compounds found in foods can be categorized into simple phenols, phenolic acids, flavonoids, stilbenes, lignans and tannins (Figure 1.2) (SHAHIDI et al., 2007).

Main phenolic compounds present in acerola fruit. Source  (Deva et al., 2012).

Figura 1.2: Main phenolic compounds present in acerola fruit. Source (Deva et al., 2012).

1.4 Food products

There are few countries that commercially profit from acerola products, Brazil being one of them. Initially, the acerola was introduced in Pernambuco, spreading to the Northeast and other Brazilian regions. Currently, all Brazilian states cultivate acerola, except for the southern region during the winter. Most of the production is destined for exportation as pulp, frozen fruits and whole juice (BLISKA et al., 1995).

The main attraction of acerola fruit is its high content of vitamin C, as discussed previously; however, it is also rich in other nutrients such as carotenoids, thiamine, riboflavin and niacin. In the market, several food products of acerola can be found, being the most common forms of commercialization the acerola in its natural form as well as and frozen pulp and juice, ice cream can be found as well (Figure 1.3). The shelf life of these products, according to manufacturers, varies from 4 to 12 months (YAMASHITA et al., 2003).

The annual production of acerola in Brazil is approximately 150 thousand tons of fruits, produced mainly by the Northeast Region. A considerable part of this production is not used due to the high perishability of the fruits, giving an estimate of 40% post-harvest losses. In the domestic market, the produced acerola is distributed among industry (46%), wholesale (28%), and retail (19%), as well as cooperatives and other associations of producers (7%). During the processing of acerola for the production of pulp or juice, fruit pressing produces a fibrous residue (bagasse), which is often discarded, generating a large volume of organic waste (SOBRINHO, 2014).

Examples of acerola food products in Brazil market

Figura 1.3: Examples of acerola food products in Brazil market

1.4.1 By-product of pulp and acerola juice production

The acerola by-product is an alternative source of dietary fiber, contributing to the prevention of gastrointestinal and cardiovascular diseases (PEREIRA et al., 2003; BRAGA et al., 2010). Usually, the acerola bagasse becomes a problem for industry, because it does not have a specific destination, besides being rich in organic matter, it is also highly polluting. In addition, its treatment for disposal demands high operating costs. In this way, the use of the by-product of acerola contributes to the environment, besides being a strategy for enriching and developing new functional products (MARQUES, 2013).

Table 1.3 shows the values of phenolic compounds and antioxidant capacity of acerola flour (by-product). The total phenolic compounds found were 52.50 mg EAG 100-1. The antioxidant capacity values were 226.86 mmols ET g-1 according to DPPH method and 51 mmol ET g-1 for FRAP. Other authors evaluated the content of the total phenolic compounds present in acerola flour using the ethanoic extraction process. The values found varied between 30.75 mg EAG g-1 and 72.65 mg EAG g-1 (BORGES, 2011; SILVA et al., 2014). Silva et al. (2014) also showed that the by-product of acerola presented higher levels of anthocyanins and flavonoids compared to fruit pulp.

Vasco, Ruales, & Kamal-eldin (2008) evaluated the content of total phenolic compounds of seventeen acerola fruits, using the Folin-Ciocalteu method. The obtained results found between 0.26 - 21.00 mg EAG/g. Thus, the authors suggested classifications according to the total phenolic compounds content, with high concentrations being greater than 10 mg EAG/g; and low concentration amounts being less than 1 mg EAG/g. Thus, the acerola by-products are rich in total phenolic compounds.

The antioxidant capacity of the acerola by-product was evaluated by Pereira et al., 2013 using the DPPH free radical resulting in an average value of 416.44 μg / ml.

The different chemical values of acerola by-products may be associated to the different agricultural practices, soil composition, climatic variations, type of drying, extraction method and solvent used, and different stages of fruit ripening (MORALES-SOTO et al., 2014; PAZ et al., 2015).

Cuadro 1.3: Mean values and standard deviation of total phenolic compounds and antioxidant capacity of acerola powder.
Total phenolic compounds (mg EAG 100-1) Antioxidant capacity (mmols ET g-1)
52.50 ± 1.25 226.86 ± 4.84 51.00 ± 16.91
Source: Sgarbosa (2017)

The acerola powder can be considered a good source of fibers, since it presents in its composition the amount of 56.28 ± 0.19% of total fibers (PEREIRA et al. 2010; SILVA et al., 2014).

1.5 Therapeutic properties of acerola

Several studies report the therapeutic properties of acerola, especially those related to antioxidant activity. Table 1.4 shows some therapeutic effects related to acerola.

Cuadro 1.4: Therapeutic properties of acerola
Properties Reference
Antihyperglycemic Hanamura et al., (2005)
Cytotoxic Motohashi et al., (2004)
Antioxidant activity Mezadri et al., (2008)
Anti-genotoxicity Horta et al., (2016)
Oxidative stress Alvarez-Suarez et al., (2017)
Anti-obesity Leffa et al., (2015)
Anti-inflammatory Dias et al., (2014)

1.6 Conclusions and future perspective

Healthy foods are becoming popular all over the world, especially with the increasing obesity rate worldwide. Major multinational companies and fast-food manufacturers, which were previously focused on practicality, are now experimenting with and introducing products based on natural ingredients that are low in calories but high in nutritional value.

Several companies have diversified fruit juices and created products fortified with vitamins and other supplements. Acerola is rich in bioactive compounds, especially ascorbic acid and polyphenols, and has a number of beneficial effects on health. Therefore, the acerola is expected to be a good candidate for food supplements and functional food manufacturers seeking the development of new products.

1.7 References

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