row do not differ by Tukey test (p ≤ 0.05).
GYD-3-G = cyanidin-3-glucoside; GAE = gallic acid equivalent; ACY = total GYD-3-G = cyanidin-3-glucoside; GAE = gallic acid equivalent; ACY = total
anthocyanins; TPC = total phenolic compounds. anthocyanins; TPC = total phenolic compounds.
Tannins
Tannins
Among the bioactive compounds, tannins are also highlighted, which, like Among the bioactive compounds, tannins are also highlighted, which, like the other phenolic compounds, are derived from the secondary metabolism of the other phenolic compounds, are derived from the secondary metabolism of plants.
plants. They They are are present present in in most most plants plants and and can can vary vary in in concentraticoncentrationon depending on the age and size of the plant part collected, the time or even the depending on the age and size of the plant part collected, the time or even the
collection site. The tannins can be categorized into hydrolyzable, and non- collection site. The tannins can be categorized into hydrolyzable, and non- hydrolyzable or condensed tannins [16, 17].
hydrolyzable or condensed tannins [16, 17].
The hydrolyzable tannins are esters of phenolic acids (gallic, caffeic, The hydrolyzable tannins are esters of phenolic acids (gallic, caffeic, ellagic acids) linked to simple sugars. These compounds have smaller ellagic acids) linked to simple sugars. These compounds have smaller molecular chains than condensed tannins and can be hydrolyzed more easily, molecular chains than condensed tannins and can be hydrolyzed more easily, just b
just by y the action the action of of dilute acids dilute acids [18, [18, 19]. 19]. TypicalTypically, ly, hydrolysable tannins arehydrolysable tannins are classified in gallotannins which produce gallic acid after hydrolysis and classified in gallotannins which produce gallic acid after hydrolysis and ellagitannins which produce ellagic acid [20]. However, unlike other berries ellagitannins which produce ellagic acid [20]. However, unlike other berries such as raspberry, strawberry and blackberries, blueberries do not contain such as raspberry, strawberry and blackberries, blueberries do not contain ellagitannins nor other derivatives of ellagic acid. The ellagic acid content in ellagitannins nor other derivatives of ellagic acid. The ellagic acid content in blueberry
blueberry is lower thais lower than 5 mg.100 gn 5 mg.100 g-1-1 fresh fruit [21] after acid hydrolysis. fresh fruit [21] after acid hydrolysis.
For the determination of hydrolyzable tannins in blueberry, the method For the determination of hydrolyzable tannins in blueberry, the method adapted from Brune et al. [22], which consists of the extraction of tannin with adapted from Brune et al. [22], which consists of the extraction of tannin with methyl alcohol, was used. The methanol extract was then mixed with a methyl alcohol, was used. The methanol extract was then mixed with a reaction solution of ferric ammonium sulfate, consisting of 89% urea buffer: reaction solution of ferric ammonium sulfate, consisting of 89% urea buffer: acetate, 10% arabic gum solution 1% in deionized water and 1% ferric acetate, 10% arabic gum solution 1% in deionized water and 1% ferric ammonium sulfate solution 5% in hydrochloric acid 1 mol.L
ammonium sulfate solution 5% in hydrochloric acid 1 mol.L-1-1. The absorbance. The absorbance was read at 578 nm in a spectrophotometer (Ultrospec 2000). The was read at 578 nm in a spectrophotometer (Ultrospec 2000). The determination of the content of hydrolysable tannins was performed through a determination of the content of hydrolysable tannins was performed through a gallic acid standard curve and results were expressed in mg of gallic acid.100 gallic acid standard curve and results were expressed in mg of gallic acid.100 g
g-1-1 sample. sample.
The non-hydrolyzable or condensed tannins, also known as The non-hydrolyzable or condensed tannins, also known as proanthocy
proanthocyanidins, are compounds formed anidins, are compounds formed by the by the polymerizapolymerization of tion of flavonoidflavonoid units, predominantly catechin and are present in a wide variety of foods, and units, predominantly catechin and are present in a wide variety of foods, and can be divided into two main classes that include procyanidins, mixtures of can be divided into two main classes that include procyanidins, mixtures of oligomers and polymers composed of units of (+) -catechin and/or (-)- oligomers and polymers composed of units of (+) -catechin and/or (-)- epicatechins, and propelargonidins composed exclusively of epiafzelechin epicatechins, and propelargonidins composed exclusively of epiafzelechin units [23]. However, blueberries exclusively have procyanidins, which are units [23]. However, blueberries exclusively have procyanidins, which are considered one of the major phenolic compounds present in the fruit pulp [15, considered one of the major phenolic compounds present in the fruit pulp [15, 19, 21, 24]. These compounds are ranked according to their degree of 19, 21, 24]. These compounds are ranked according to their degree of polymeriz
polymerization (DP) where DP = 1 indicates a monoation (DP) where DP = 1 indicates a monomer, while DP = 2-10 andmer, while DP = 2-10 and DP > 10 refer to oligomers and polymers, respectively [25].
DP > 10 refer to oligomers and polymers, respectively [25].
The monomer units of procyanidins are connected via a C4-C8 or C4-C6 The monomer units of procyanidins are connected via a C4-C8 or C4-C6 (type B) bond, and can coexist with a C2-O-C7 bond or, less frequently, with (type B) bond, and can coexist with a C2-O-C7 bond or, less frequently, with C2-O-C5 bond (type A) [23]. Hwang et al. [26] found 300 mg procyanidin C2-O-C5 bond (type A) [23]. Hwang et al. [26] found 300 mg procyanidin B1.100 g
B1.100 g-1-1 fresh fruit in blueberry extracts, well below the contents found for fresh fruit in blueberry extracts, well below the contents found for black chokeberries (
black chokeberries (
Aronia melanocar Aronia melanocarpapa
) of 2.5 g.100 g) of 2.5 g.100 g-1-1 fresh fruit, which is fresh fruit, which is known for itsProcyanidin content in blueberries of Highbush and Lowbush group Procyanidin content in blueberries of Highbush and Lowbush group varieties are often considered alike, ranging between 33-180 mg.100
varieties are often considered alike, ranging between 33-180 mg.100-1-1 of fresh of fresh fruit for the Highbush group and 57-332 mg.100
fruit for the Highbush group and 57-332 mg.100-1-1 fresh fruit in the Lowbush fresh fruit in the Lowbush group [21, 27]. Flavonol dimers represent the majority of flavonols present in group [21, 27]. Flavonol dimers represent the majority of flavonols present in blueberries, approximately 24%
blueberries, approximately 24% of of flavonols, while flavonols, while hexamers, monomers hexamers, monomers andand heptamers, represent an average percentage of 12.6, 11.2 and 11% respectively heptamers, represent an average percentage of 12.6, 11.2 and 11% respectively [27]. The polymeric procyanidins of Lowbush blueberries were characterized [27]. The polymeric procyanidins of Lowbush blueberries were characterized by Gu
by Gu et al. et al. [25], who [25], who reported that the reported that the degree of degree of polymerizpolymerization ranges ation ranges fromfrom 20-114, with epicatechin representing 100% of the extension units, and 20-114, with epicatechin representing 100% of the extension units, and catechin and epicatechin representing 67% and 33% of the terminal units, catechin and epicatechin representing 67% and 33% of the terminal units, respectively.
respectively.
According to Eskin and Snait [28], a number of proanthocyanidin According to Eskin and Snait [28], a number of proanthocyanidin fractions were separated from blueberry extracts. Of these, only fractions were separated from blueberry extracts. Of these, only proanthocy
proanthocyanidin anidin oligomers oligomers of of high high moleculmolecular ar weight weight exhibitedexhibited antiproliferative and anti-adhesion properties. It was found that two fractions antiproliferative and anti-adhesion properties. It was found that two fractions composed predominantly of four to eight proanthocyanidin oligomers bonded composed predominantly of four to eight proanthocyanidin oligomers bonded with an average degree of polymerization of 3.25 and 5.65 prevented with an average degree of polymerization of 3.25 and 5.65 prevented adherence of the
adherence of the organism responsiborganism responsible for le for urinary tract infections,urinary tract infections,
EscherichiaEscherichia
coli
coli
. However, only the fraction with 5.65 proliferation showed. However, only the fraction with 5.65 proliferation showed antiproliferative activity against human prostate cancer and in cancer cells of antiproliferative activity against human prostate cancer and in cancer cells of mice liver.mice liver.
To perform the determination of tannins, the method adapted from Price et To perform the determination of tannins, the method adapted from Price et al. [29] was used. It consists of the extraction step of tannins with methanol, al. [29] was used. It consists of the extraction step of tannins with methanol, and to the methanolic extract, a solution of 1:1 vanillin 1% in methyl alcohol and to the methanolic extract, a solution of 1:1 vanillin 1% in methyl alcohol and 4% hydrochloric acid in methyl alcohol were added. The reading of and 4% hydrochloric acid in methyl alcohol were added. The reading of absorbance was done at 500 nm. The determination of the content of tannins absorbance was done at 500 nm. The determination of the content of tannins was performed using a catechin standard curve and results were expressed in was performed using a catechin standard curve and results were expressed in mg catechin.100 g
mg catechin.100 g-1-1 sample. sample. The content of
The content of condensedcondensed, hydrolyzable and total tannins , hydrolyzable and total tannins in different partsin different parts of Rabbiteye group blueberry cultivars are shown in Table 2.
of Rabbiteye group blueberry cultivars are shown in Table 2. Among the analyzed cultivars
Among the analyzed cultivars
, “Powderblue” had the highest tannin, “Powderblue” had the highest tannin
content, differing significantly from the others. Tannin content in the whole content, differing significantly from the others. Tannin content in the whole fruit represents 6-22% of the content of phenolic compounds. For all cultivars, fruit represents 6-22% of the content of phenolic compounds. For all cultivars, higher tannin content (condensed, hydrolyzable and total) are present in the higher tannin content (condensed, hydrolyzable and total) are present in the peel,peel, with with the the condensecondensed d tannin content tannin content being 140 being 140 times higher times higher than than the the pulppulp content on average. For total tannins, the average is 120 times higher than the content on average. For total tannins, the average is 120 times higher than the content present in the peel. For hydrolysable tannins, this average is around 12 content present in the peel. For hydrolysable tannins, this average is around 12 times higher than the content of tannins in the peel, when compared to the times higher than the content of tannins in the peel, when compared to the tannin content in the pulp. Only the pulp of the fruits showed no significant tannin content in the pulp. Only the pulp of the fruits showed no significant
differences in tannin content (condensed, hydrolyzable and total), between differences in tannin content (condensed, hydrolyzable and total), between different cultivars.
different cultivars.
The condensed tannin content found in this study are similar to the
The condensed tannin content found in this study are similar to the contentcontent found by Yi et al. [30], who worked with the Powderblue and Briteblue found by Yi et al. [30], who worked with the Powderblue and Briteblue cultivars. These authors found condensed tannin contents of 86.9 and 87.9 mg cultivars. These authors found condensed tannin contents of 86.9 and 87.9 mg CAE 100 g
CAE 100 g-1-1 respectively for these cultivars. respectively for these cultivars.
The blueberry cultivars showed an average condensed tannin content 90 The blueberry cultivars showed an average condensed tannin content 90 times the hydrolysable tannin content. Sensorially this is a positive factor times the hydrolysable tannin content. Sensorially this is a positive factor because the
because the condensecondensed tannins hd tannins have a lowave a lower compleer complexing capacitxing capacity with proty with proteinseins than hydrolysable tannins, resulting in lower astringency.
than hydrolysable tannins, resulting in lower astringency.
Table 2. Content of
Table 2. Content of condensed, hydrolyzacondensed, hydrolyzable and total ble and total tannins in tannins in peel,peel, pulp and whole f
pulp and whole fruit of blueberry cultivarsruit of blueberry cultivars
Cultivar
Cultivar Parts of Parts of the the fruitfruit Peel
Peel Pulp Pulp Whole Whole fruitfruit Condensed tannins (mg CAE 100 g
Condensed tannins (mg CAE 100 g-1-1)) Woodard Woodard 623.94 623.94 aAaA1/1/ 2.97 2.97 aC aC 85.57 85.57 bBbB Powderblue Powderblue 523.38 523.38 bA bA 3.02 3.02 aC aC 194.37 194.37 aBaB Bluebelle Bluebelle 182.10 182.10 eA eA 4.92 4.92 aC aC 70.71 70.71 bBbB Briteblue Briteblue 432.75 432.75 cA cA 4.29 4.29 aC aC 71.62 71.62 bBbB Climax Climax 262.16 262.16 dA dA 0.93 0.93 aB aB 37.53 37.53 bBbB Delite Delite 329.50 329.50 dA dA 7.44 7.44 aB aB 44.69 44.69 bBbB Hydrolyzable tannins (mg GAE 100 g
Hydrolyzable tannins (mg GAE 100 g-1-1))
Woodard
Woodard 6.16 6.16 aA aA 0.30 0.30 aC aC 1.47 1.47 abBabB Powderblue 0.99
Powderblue 0.99 dA dA 0.12 0.12 aA aA 0.92 0.92 abAabA Bluebelle
Bluebelle 0.50 0.50 dA dA 0.10 0.10 aA aA 0.45 0.45 bAbA Briteblue
Briteblue 3.80 3.80 bA bA 0.30 0.30 aB aB 1.19 1.19 abBabB Climax
Climax 2.40 2.40 cA cA 0.26 0.26 aB aB 1.60 1.60 aAaA Delite
Delite 3.04 3.04 bbcA cA 0.20 0.20 aC aC 1.12 1.12 abBabB Total tannins (mg 100 g Total tannins (mg 100 g-1-1)) Woodard Woodard 630.10 630.10 aA aA 3.27 3.27 aC aC 87.05 87.05 bBbB Powderblue Powderblue 524.37 524.37 bA bA 3.13 3.13 aC aC 195.30 195.30 aBaB Bluebelle Bluebelle 182.60 182.60 eA eA 5.02 5.02 aC aC 71.16 71.16 bBbB Briteblue Briteblue 436.55 436.55 cA cA 4.59 4.59 aC aC 72.82 72.82 bBbB Climax Climax 264.56 264.56 dA dA 1.20 1.20 aB aB 39.12 39.12 bBbB Delite Delite 332.54 332.54 dA dA 7.64 7.64 aB aB 45.80 45.80 bBbB 1/
1/ Means followed by the same lower case letter in the column and upper case in the Means followed by the same lower case letter in the column and upper case in the
row do not differ by Tukey test (p ≤ 0.05).
row do not differ by Tukey test (p ≤ 0.05).
CAE = catechin equivalent; GAE = gallic acid equivalent. CAE = catechin equivalent; GAE = gallic acid equivalent.
Carotenoids
Carotenoids
Another group of bioactive compounds in blueberries are the carotenoids. Another group of bioactive compounds in blueberries are the carotenoids. These compounds have non-polar nature due to their tetraterpenic structure, These compounds have non-polar nature due to their tetraterpenic structure, which may contain terminal cyclic groups or not have any cyclization. One of which may contain terminal cyclic groups or not have any cyclization. One of its distinct characteristics is the extensive system of conjugated double bonds, its distinct characteristics is the extensive system of conjugated double bonds, which act as light absorption chromophores, thus being responsible for the which act as light absorption chromophores, thus being responsible for the colors yellow, orange and red that these compounds confer to many foods [31, colors yellow, orange and red that these compounds confer to many foods [31, 32, 33].
32, 33].
In the present study the carotenoids were extracted with cold acetone and In the present study the carotenoids were extracted with cold acetone and partitioned
partitioned with with petroleum petroleum ether ether according according to to Rodriguez-Rodriguez-Amaya Amaya [32]. [32]. TheThe absorbance reading of the ether extract was performed in an Ultrospec 2000 absorbance reading of the ether extract was performed in an Ultrospec 2000 UV/Visible (Pharmacia Biotech) spectrophotometer at a wavelength of 450 UV/Visible (Pharmacia Biotech) spectrophotometer at a wavelength of 450 nm. The total carotenoid was based on molar extinction
nm. The total carotenoid was based on molar extinction
coefficient of the βcoefficient of the β
-- carotene, 2500, and molecular weight of 536.9. The carotenoid content was carotene, 2500, and molecular weight of 536.9. The carotenoid content was expressed in mg ofexpressed in mg of
ββ
-caroteno.100 g-caroteno.100 g-1-1 of fresh-fruit. From the carotenoid of fresh-fruit. From the carotenoid evaluation of blueberry, considering its peel, pulp and whole fruit (Table 3), it evaluation of blueberry, considering its peel, pulp and whole fruit (Table 3), it can be observed that there was no significant difference between the content of can be observed that there was no significant difference between the content of the pulp and the whole fruit of the analyzed cultivars; however, the carotenoid the pulp and the whole fruit of the analyzed cultivars; however, the carotenoid content in the peel in both cultivars showed significant difference, with content in the peel in both cultivars showed significant difference, with“Briteblue” cultivar having the highest content (28.38 µg of β
“Briteblue” cultivar having the highest content (28.38 µg of β
-carotene.g-carotene.g-1-1))and “Delite” cultivar which presented the lower content of these compounds
and “Delite” cultivar which presented the lower content of these compounds
(3.8 µg of β
(3.8 µg of β
-caroteno.g-caroteno.g-1-1). The high content of carotenoids in the peel of the). The high content of carotenoids in the peel of the fruit has been documented in several studies with caja, mandarin and melon fruit has been documented in several studies with caja, mandarin and melon [32], since in the same manner as phenolics, carotenoids have phytoprotective [32], since in the same manner as phenolics, carotenoids have phytoprotective action.action.
For the carotenoid content present in blueberry, it is observed that this For the carotenoid content present in blueberry, it is observed that this fruit contains a small amount of this pigment (0.16-
fruit contains a small amount of this pigment (0.16-
0.66 µg of β0.66 µg of β
-carotene g-carotene g-1-1),), which supports data shown by Jacques et al. [8] who on analyzing various which supports data shown by Jacques et al. [8] who on analyzing various fruits, they found that the blueberry was the one with the lowest content of fruits, they found that the blueberry was the one with the lowest content of carotenoidscarotenoids
(1.4 µg of β(1.4 µg of β
-carotene g-carotene g-1-1 fresh fruit). According to Lima et al. fresh fruit). According to Lima et al. [34],[34], fruits whose main compounds belong to the class of anthocyanins, the fruits whose main compounds belong to the class of anthocyanins, the carotenoid content reduces during ripening, consequently, fruits likecarotenoid content reduces during ripening, consequently, fruits like blueberry,blueberry, have small amounts of carotenoids. However, in the peel of cultivars such as have small amounts of carotenoids. However, in the peel of cultivars such as Briteblue and Bluebelle, existing contents are considerable and can be Briteblue and Bluebelle, existing contents are considerable and can be compared with the con
compared with the con
tent found in fruits such as butia (28 µg of βtent found in fruits such as butia (28 µg of β
-carotene g-carotene g-- 11
fresh fruit) and loquat (24 µg of βfresh fruit) and loquat (24 µg of β
- carotene g- carotene g-1-1 fresh Fruit) [8], in which the fresh Fruit) [8], in which the carotenoids were found as the major pigments.Table 3. Carotenoid content in peel, pulp and whole fruit of Table 3. Carotenoid content in peel, pulp and whole fruit of
blueberry cultivars blueberry cultivars
Cultivar
Cultivar Parts Parts of of the the fruitfruit Peel
Peel Pulp Pulp Whole Whole fruitfruit Total carotenoids
Total carotenoids
(µg de β(µg de β
-caroteno.g-caroteno.g-1-1)) Woodard Woodard 6.25 6.25 cAcA1/1/ 0.55 0.55 aB aB 0.66 0.66 aBaB Powderblue Powderblue 7.57 7.57 cA cA 0.47 0.47 aB aB 0.55 0.55 aBaB Bluebelle Bluebelle 14.71 14.71 bA bA 0.41 0.41 aB aB 0.60 0.60 aBaB Briteblue Briteblue 28.38 28.38 aA aA 0.46 0.46 aB aB 0.34 0.34 aBaB Climax Climax 6.47 6.47 cA cA 0.65 0.65 aB aB 0.16 0.16 aBaB Delite Delite 3.80 3.80 dA dA 0.30 0.30 aB aB 0.30 0.30 aBaB 1/1/ Means followed by the same lower case letter in the column and upper case in the Means followed by the same lower case letter in the column and upper case in the
row do not differ by Tukey test (p ≤ 0.05).
row do not differ by Tukey test (p ≤ 0.05).
C
C
OLOROLORColor is a primary indicator of food quality, because it has great Color is a primary indicator of food quality, because it has great importance in evaluating the degree of maturity and freshness of fruits, the importance in evaluating the degree of maturity and freshness of fruits, the storage conditions, postharvest handling and transportation. Therefore, color is storage conditions, postharvest handling and transportation. Therefore, color is characterized as a decisive factor utilized at the time of choice and acceptance characterized as a decisive factor utilized at the time of choice and acceptance of a product, especially blueberry which has as its remarkable characteristic of a product, especially blueberry which has as its remarkable characteristic blue color.
blue color.
Since color is a parameter used to describe quality, its determination is Since color is a parameter used to describe quality, its determination is useful to correlate with the concentration of the pigments present in the fruit.