BLUEBERRY AND BERRIES - MIRACULOUS FRUITS!

Blueberry, or bilberry, is an organoleptic fruit with excellent nutritional and functional aspects, given its high levels of polyphenols compared to most commercialized fruits and vegetables. Blueberries can be found and consumed fresh or in other processed forms, such as juices, yogurts, jellies, jams, among others (Yang et al., 2010; Del Rio et al., 2010).

The blueberry is a wild fruit of the genus Vaccinium and the family Ericaceae (Fernald, 1950) that has attracted much attention due to its positive role in human health and the prevention of certain pathologies. These protective effects have been generally attributed to the wide range of polyphenols present in the fruit, which are responsible for its high free radical scavenging capacity. Blueberries are credited with antioxidant and anti-inflammatory properties (Karlsen et al., 2007; Brownmiller et al., 2008).

Various beneficial properties associated with blueberries have been described, particularly in the treatment and prevention of urinary tract disorders, cardiovascular pathologies, dental caries, gastric ulcers, and cancer (Burger et al., 2000; Stothers, 2002; Arts & Hollman, 2005; Bodet et al., 2008). Anti-proliferative, anti-carcinogenic, antibacterial, and antiviral properties are also described (Nijveldt et al., 2001; Ferguson et al., 2004; Weiss et al., 2005).

Wild fruits such as blueberry (Vaccinium), blackberry (Rubus sp.), blackcurrant (Ribes nigrum) and redcurrant (Ribes uva-crispa), grape (Vitis vinifera), red raspberry (Rubus idaeus) and black raspberry (Rubus occidentalis), strawberry (Fragaria Ananassa), pomegranate (Punica granatum), and mangosteen (Garcinia mangostana) are a particularly rich source of antioxidants (Seeram et al., 2006; Seeram, 2008a; Szajdek & Borowska, 2008). These are known as natural antioxidants, and due to their high concentration and qualitative diversity in red fruits, they are increasingly referred to as natural functional foods (Szajdek & Borowska, 2008).

The blueberry is a wild fruit available in a large number of varieties, descending from species and subspecies of the Ericaceae family and the genus Vaccinium (Fernald, 1950).

Figure 1 schematically illustrates the scientific classification of the Ericaceae family. All indicated species are shrubs that produce blueberries, described in Table 1. The different species are distinguished primarily based on shrub characteristics and in some cases, by berry attributes.

Blueberries and their products are known for their high concentration of total polyphenols (Vinson et al., 2008). More specifically, these are rich in flavonoids, such as anthocyanins, flavonols, and flavan-3-ols or catechins; condensed tannins (proanthocyanidins, PAC) and hydrolyzable tannins (ellagitannins and gallotannins); and phenolic acids (hydroxybenzoic and hydroxycinnamic acids and their derivatives) (Neto, 2007; Ruel & Couillard, 2007).

Anthocyanins are generally found in red, purple, or blue berries. Their concentrations in foods tend to increase as the fruit ripens and in response to certain climatic factors. Anthocyanins consist of an anthocyanidin molecule linked to one or more sugar units. Glycosylation of anthocyanidins occurs preferentially at the C3 position. The main anthocyanins present in blueberries are cyanidin and peonidin galactosides and arabinoses (Robards & Antolovich, 1997; Nijveldt et al., 2001).

Flavonols are found in abundance in fruits derived from the Ericaceae family, such as blueberries, existing mainly in the skin of these fruits (Robards & Antolovich, 1997).

The main types of flavonols are isorhamnetin, kaempferol, myricetin, and quercetin. All are characterized by being free of any substitution at the C3 position, and furthermore, they are famous for their planar structure due to the double bond present in the central aromatic ring. Flavonols are often found in nature as acylated derivatives, involving linkages between aliphatic and aromatic acids and sugar hydroxyls. The predominant glycosylated flavonols in fruits are 3-O monoglucosides and occur in the following order of sugar preference: glucose > galactose > rhamnose > glucuronic acid (Côté et al., 2010).

Flavanols or catechins are important constituents of fruits, and their presence has been reported in blueberries. Catechins share the same molecular structure as flavonols but lack the C4 carbonyl group (Côté et al., 2010).

Through reactions catalyzed by light, heat, and oxygen, flavanols tend to combine with gallic and ellagic acid esters to form compounds such as ellagitannins and gallotannins (Robards & Antolovich, 1997).

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