**3. Impact of fruit phenolic compounds on sensorial characteristics**

Regarding fruit's oral sensory characteristics, there are six oral sensory attributes of fruit: sourness, sweetness, bitterness, spiciness, aroma, and astringency. For many people, the oral sensory properties of fruit have a great impact on their choice, acceptability, and consump‐ tion. Phenolic compounds, apart from possessing valuable biological properties, impart a high sensory activity to foods [61]. They are closely associated with the sensory and nutri‐ tional quality of fresh and processed plant foods and may affect positively or negatively the sensory characteristics of food with impacts on color, flavor, and astringency. This impact becomes important for consumer's acceptance, so that health‐promoting products can be palatable and largely consumed [2]. Fruit preservation also influences the quantity and quality of fruits' phenolic content. For instances, during thawing of fruits, oxidation of phenolic compounds takes place and is negatively correlated with the acceptance level of fruits [62]. However, in a study comparing different pretreating processes of strawberries, samples with the highest phenolic content were also the most pleasant ones [63]. Specific structures are described to be related to polyphenols' sensory properties, namely color per‐ ception. Color, in fruits, is derived from natural pigments that change through plant rip‐ ening. Chlorophylls (green), carotenoids (yellow, orange, and red), anthocyanins (red and blue), flavonoids (yellow), and betalains (red) are the primary pigments responsible for fruit color [64]. Also, water‐soluble brown‐, gray‐, and black‐colored pigments may occur due to enzymatic and non‐enzymatic browning reactions [65]. Many polyphenol pigments in plants are reactive anthocyanins, yellow flavanols, and flavones [66]. Anthocyanins can be used in food industry to color food. The six anthocyanins that can be found in the following red/dark‐colored fruits are cyanidin (cherries, blackcurrants, raspberries, and elderberries), delphinidin (blackcurrants and blueberries), malvidin (grapes), pelargonidin (strawberries and radishes), peonidin (cranberries), and petunidin (blueberries)—**Figure 2**. Due to their water solubility, anthocyanins are applicable for dyeing low pH systems. Increasing pH leads to a lesser color intensity and a bluer tone appears at pH higher than 4.5, giving its bluish color to blackcurrant. Proanthocyanidins react with anthocyanins to form new red pigments [68]. Loss or stabilization of color and increases in the range of available hues are resulted by the conversion of anthocyanins to other compounds during food processing [2]. The color of fruits is a sensory attribute that can really change consumers' fruit acceptance. It is considered the most important product‐intrinsic sensory cue leading the sensory expecta‐ tions that the consumer holds concerning the foods that they may consume [69] and, accord‐ ing to Piqueras‐Fizman et al. [70], humans' experience of taste/flavor is determined by the expectations that they often generate prior to tasting. Consumers inspect fruits, visually, before deciding on whether or not to buy them. People associate certain colors with certain flavors. For instances, red/dark fruit coloring also appears to be a particularly good inducer of sweetness [71].

Genotype, Environment and Management Practices on Red/Dark-Colored Fruits Phenolic Composition... http://dx.doi.org/10.5772/66881 267

**Figure 2.** Anthocyanins in red/dark‐colored fruits. Adapted from Just the Berries [67].

the two most predominant anthocyanins in many cases [58]. Blueberries also contain varying amounts of other polyphenols, and chlorogenic acid is particularly high as compared with other food sources [59]. It is accompanied by small amounts of quercetin glycosides [60].

Regarding fruit's oral sensory characteristics, there are six oral sensory attributes of fruit: sourness, sweetness, bitterness, spiciness, aroma, and astringency. For many people, the oral sensory properties of fruit have a great impact on their choice, acceptability, and consump‐ tion. Phenolic compounds, apart from possessing valuable biological properties, impart a high sensory activity to foods [61]. They are closely associated with the sensory and nutri‐ tional quality of fresh and processed plant foods and may affect positively or negatively the sensory characteristics of food with impacts on color, flavor, and astringency. This impact becomes important for consumer's acceptance, so that health‐promoting products can be palatable and largely consumed [2]. Fruit preservation also influences the quantity and quality of fruits' phenolic content. For instances, during thawing of fruits, oxidation of phenolic compounds takes place and is negatively correlated with the acceptance level of fruits [62]. However, in a study comparing different pretreating processes of strawberries, samples with the highest phenolic content were also the most pleasant ones [63]. Specific structures are described to be related to polyphenols' sensory properties, namely color per‐ ception. Color, in fruits, is derived from natural pigments that change through plant rip‐ ening. Chlorophylls (green), carotenoids (yellow, orange, and red), anthocyanins (red and blue), flavonoids (yellow), and betalains (red) are the primary pigments responsible for fruit color [64]. Also, water‐soluble brown‐, gray‐, and black‐colored pigments may occur due to enzymatic and non‐enzymatic browning reactions [65]. Many polyphenol pigments in plants are reactive anthocyanins, yellow flavanols, and flavones [66]. Anthocyanins can be used in food industry to color food. The six anthocyanins that can be found in the following red/dark‐colored fruits are cyanidin (cherries, blackcurrants, raspberries, and elderberries), delphinidin (blackcurrants and blueberries), malvidin (grapes), pelargonidin (strawberries and radishes), peonidin (cranberries), and petunidin (blueberries)—**Figure 2**. Due to their water solubility, anthocyanins are applicable for dyeing low pH systems. Increasing pH leads to a lesser color intensity and a bluer tone appears at pH higher than 4.5, giving its bluish color to blackcurrant. Proanthocyanidins react with anthocyanins to form new red pigments [68]. Loss or stabilization of color and increases in the range of available hues are resulted by the conversion of anthocyanins to other compounds during food processing [2]. The color of fruits is a sensory attribute that can really change consumers' fruit acceptance. It is considered the most important product‐intrinsic sensory cue leading the sensory expecta‐ tions that the consumer holds concerning the foods that they may consume [69] and, accord‐ ing to Piqueras‐Fizman et al. [70], humans' experience of taste/flavor is determined by the expectations that they often generate prior to tasting. Consumers inspect fruits, visually, before deciding on whether or not to buy them. People associate certain colors with certain flavors. For instances, red/dark fruit coloring also appears to be a particularly good inducer

**3. Impact of fruit phenolic compounds on sensorial characteristics**

266 Phenolic Compounds - Natural Sources, Importance and Applications

of sweetness [71].

Gavrilova et al. [72] studied the phenolic profile of four blueberry varieties (*V. corymbosum* L., cv. Toro, Legacy, Duke, and Bluecrop) and two varieties (Rosenthal and Rovada) of red currants (*Ribes rubrum* L.) and black currants (*R. nigrum* L.) cultivated in Macedonia. They found that anthocyanins comprised the highest content of total phenolic compounds in cur‐ rants (>85%), namely in the dark (black) currents, and lower and variety dependent in blue‐ berries (35–74%). Hydroxycinnamic acid derivatives comprised 23–56% of total phenolics in blueberries and 1–6% in currants (**Table 2**). Besides bitterness, astringency, and color, some volatile polyphenols are strong odorants [66]. However, in dark‐colored fruits, phenolic com‐ pounds present an almost insignificant role in fruit flavor profile. In raspberry fruit (*Rubus idaeus* L.), phenolic compounds only represent 1% of the total flavor compounds (**Figure 3**), whose concentration varies between "trace amount" and 0.3 mg/kg [73]. Nevertheless, in wild berries, several volatile phenolic compounds were identified by Honkanen et al. [73], such as 2‐methoxy‐4‐vinylphenol, 2‐methoxy‐5‐vinylphenol, 3,4‐dimethoxybenzaldehyde, and 4‐ vinylsyringol, none of which have been reported in cultivated varieties [74]. An important fact stated by Honkanen et al. [73] is that with the exception of ionones, the amounts of individual volatile compounds in wild raspberries were generally three to four times higher than in the cultivated varieties. Moreover, the higher amounts of volatile compounds, in wild raspberry, may have contributed to their characteristic aroma. Also, the increased berry size, hybridiza‐ tion, and/or fertilization lead to worsening in the aroma profile of cultivated raspberries.


**Table 2.** Contents of phenolic compounds in red currants (*Ribes rubrum* L.), black currants (*Ribes nigrum* L.), and blueberries (*Vaccinium corymbosum* L.) determined by HPLC‐DAD and expressed in mg per 100 g fresh weight±SD (n = 3). Adapted from Gavrilova et al. [72].

Plant‐based phenol compounds, flavonoids, isoflavones, terpenes, and glucosinolates are almost bitter and astringent [75]. These substances provide defense against predators by making the plants unpalatable [75]. But also humans reject foods that are perceived to be excessively bitter [76]. Flavonoid phenols have been indicated as the main responsible for the taste of bitterness and the mouth‐fell sensation of astringency in several types of fruits and in beverages [2, 77]. Several works suggested that some polyphenols can be responsible for the bitterness of fruits even if they are present in very low concentrations [78]. The bitterness and astringency of red wines and red/dark‐colored fruits are mainly given by the flavanols. The mechanisms through which bitter taste perception occurs are not well understood; how‐ ever, it is known that these mechanisms involve the activation of distinct human bitter taste receptors [77, 78]. While lower‐molecular‐weight phenolic compounds tend to be likely bitter, higher‐molecular‐weight polymers are perceived as astringent. Astringency or drying/puck‐ ering mouth‐feel detectable throughout the oral cavity is due to a complex reaction between polyphenols and proteins of the mouth and saliva [79]. Interaction between tannins and saliva proteins plays an important role in astringency perception in wine [80]; however, the physi‐ ological and physicochemical mechanisms for this phenomenon are not fully understood and more studies focusing on this subject must be done in wines and fruits.

Genotype, Environment and Management Practices on Red/Dark-Colored Fruits Phenolic Composition... http://dx.doi.org/10.5772/66881 269

stated by Honkanen et al. [73] is that with the exception of ionones, the amounts of individual volatile compounds in wild raspberries were generally three to four times higher than in the cultivated varieties. Moreover, the higher amounts of volatile compounds, in wild raspberry, may have contributed to their characteristic aroma. Also, the increased berry size, hybridiza‐ tion, and/or fertilization lead to worsening in the aroma profile of cultivated raspberries.

**Red currants Black currants Blueberries Compounds (total) Rosenthal Rovada Rosenthal Rovada Toro Legacy Duke Bluecrop**

> 187.69 ± 1.84

> 162.83 ± 2.46

6.95 ± 0.92

11.02 ± 1.23

6.89 ± 0.24 94.60 ± 0.93

56.35 ± 1.04

2.28 ± 0.80

2.85 ± 0.54

33.12 ± 1.78

137.74 ± 1.05

68.55 ± 2.35

5.17 ± 0.03

1.75 ± 0.07

62.27 ± 1.97

113.02 ± 1.28

83.64 ± 3.16

3.41 ± 0.16

25.97 ± 3.21

n.d. 4.52 ± 0.43

120.14 ± 1.02

41.99 ± 0.25

6.08 ± 0.45

67.54 ± 3.03

207.77 ± 1.14

180.44 ± 3.59

7.36 ± 0.57

13.35 ± 0.90

6.62 ± 0.18

**Table 2.** Contents of phenolic compounds in red currants (*Ribes rubrum* L.), black currants (*Ribes nigrum* L.), and blueberries (*Vaccinium corymbosum* L.) determined by HPLC‐DAD and expressed in mg per 100 g fresh

17.97 ± 0.31

14.73 ± 0.29

0.48 ± 0.005

± 0.002

1.16 ± 0.10

Phenolic compounds. 18.05

Anthocyanins 15.93

Flavonols 1.89

Hydroxycinnamic acid

n.d., not detected.

derivatives

± 0.58

268 Phenolic Compounds - Natural Sources, Importance and Applications

± 0.95

± 0.08

0.23 ± 0.002

weight±SD (n = 3). Adapted from Gavrilova et al. [72].

Flavan‐3‐ols n.d. 1.60

Plant‐based phenol compounds, flavonoids, isoflavones, terpenes, and glucosinolates are almost bitter and astringent [75]. These substances provide defense against predators by making the plants unpalatable [75]. But also humans reject foods that are perceived to be excessively bitter [76]. Flavonoid phenols have been indicated as the main responsible for the taste of bitterness and the mouth‐fell sensation of astringency in several types of fruits and in beverages [2, 77]. Several works suggested that some polyphenols can be responsible for the bitterness of fruits even if they are present in very low concentrations [78]. The bitterness and astringency of red wines and red/dark‐colored fruits are mainly given by the flavanols. The mechanisms through which bitter taste perception occurs are not well understood; how‐ ever, it is known that these mechanisms involve the activation of distinct human bitter taste receptors [77, 78]. While lower‐molecular‐weight phenolic compounds tend to be likely bitter, higher‐molecular‐weight polymers are perceived as astringent. Astringency or drying/puck‐ ering mouth‐feel detectable throughout the oral cavity is due to a complex reaction between polyphenols and proteins of the mouth and saliva [79]. Interaction between tannins and saliva proteins plays an important role in astringency perception in wine [80]; however, the physi‐ ological and physicochemical mechanisms for this phenomenon are not fully understood and

more studies focusing on this subject must be done in wines and fruits.

**Figure 3.** Volatile compounds reported in raspberry fruit (*Rubus idaeus* L.) according to chemical class. Adapted from Aprea et al. [74].

Total concentration, mean degree of polymerization [81], subunit composition, and distribu‐ tion [82] are some of the variables related to tannins, highly correlated with the perception of astringency in fruits. Tannins vary in size, from dimers up to oligomers, with more than 30 subunits [83]. Polymer size affects astringency correlating positively with the perception of astringency [84]. Increased galloylation can be responsible for increased "abrasiveness" while trihydroxylation of the B‐ring can decrease it [85]. As referred by He et al. [86], the synthesis of astringent substances controlled by a variety of structural and regulatory genes must be stud‐ ied. Moreover, these authors state that "(…) cloning and functional identification of genes, in the astringency metabolic pathway, and their spatio‐temporal expression patterns as well as tannin biosynthesis‐related transcription factor genes must be considered in future work to finally make it possible to control fruit astringent substances quantitatively (…)"[86].
