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Alternative routes to geranial formation. Geranial ( trans -citral) is formed from geranyl diphosphate and geraniol in lemon basil and other plant species (top route). Analyses of carotenoids and volatiles in tomato mutants and in watermelon varieties indicate that lycopene is degraded in vivo to geranial in these fruits (bottom route). Bold lines on double bonds represent possible cleavage.
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Several lines of evidence indicate that important fruit aroma volatiles are derived from the degradation of carotenoid pigments. One such compound, lycopene, the major pigment in the red varieties of tomato and watermelon, gives rise, to a number of aroma volatiles including geranial, a lemon-scented monoterpene aldehyde. Various tomato and waterme...
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... et al ., 2000), and consequently most of the volatiles present in the wild-type tomato, including norisoprene and monoterpene compounds, are absent in ACS-antisensed fruits (Fig. 1). In contrast, guaiacol and methyl salicylate, which are found in green (unripe) wild-type tomato fruit, are prominent in ‘mature’ ACS-silenced fruits (Fig. 1). The lack of aroma in the transgenic fruit can be explained by the repression of the biosynthetic pathways that lead to the formation of aroma volatiles. It could be however, that the mere lack of carotenoids could partially account for the lack of norisoprene and monoterpene volatiles in ACS-suppressed transgenic tomatoes, if these are indeed enzymatically or non-enzymatically derived from carotenoid degradation in vivo . Striking phenotypic similarity in terms of carotenoid composition has been found in tomato and watermelon varieties. This variation is reflected in the color of the fruit (Tadmor, King, Levi, Davis, & Hirschberg, 2004; Tadmor et al ., submitted). The mesocarp of the wild-type tomato contains high concentrations ( w 85% of total carotenoids) of the acyclic pigment lycopene and lower concentrations ( ! 10%) of the bicyclic b -carotene (Hirschberg, 2001; Lewinsohn et al ., in press; Tadmor, King, Levi, Davis, & Hirschberg, 2004; Tadmor et al ., submitted). Despite the fact that watermelon is botanically distant from tomato, the carotenoid composition (lycopene 95% and b -carotene w 5%) of the typical red watermelons, such as ‘Moon and Stars’ (Fig. 2), resembles that of the wild-type tomato. Tomato near-isogenic lines with defined mutations in the carotenoid pathway (Liu et al ., 2003) differ almost exclusively in their carotenoid composition and hence in their color (Fig. 2). The yellow flesh ( r ) mutation of tomato is caused by a non-functional phytoene synthase ( psy1 ) gene, resulting in the accumulation of very low levels of carotenoids in these yellow-fleshed fruits (Fig. 2; Fray & Grierson, 1993). Watermelon cultivars such as ‘Early Moonbeam’, with canary yellow flesh lack lycopene and accumulate only trace levels of b -carotene, giving a carotenoid composition resembling that of the tomato r mutant (Fig. 2). The tangerine ( tg ) tomato mutant, which carries a dysfunctional carotenoid isomerase gene ( CRTISO ), accumulates the orange pigment prolycopene (tetra- cis -lycopene) and higher levels of tetraterpene precursors, including phytoene, phytofluene z -carotene and neurosporene, than the wild-type tomato (Fig. 2; Isaacson, Ronen, Zamir, & Hirschberg, 2002). Orange watermelons, such as ‘Orangeglo’, have a carotenoid profile resembling that of the tg tomato mutant (Fig. 2). The tomato Delta ( Del ) mutant accumulates high levels of the monocyclic tetraterpene pigment d -carotene ( w 80% of the total carotenoids) (Fig. 2; Ronen, Cohen, Zamir, & Hirschberg, 1999). Thus far, no equivalent to the tomato Del has been found in watermelon. The orange-colored High Beta ( B ) watermelon genotype accumulates high levels of b -carotene in addition to low levels of lycopene (Ronen, Carmel-Goren, Zamir, & Hirschberg, 2000). ‘NY162003’, an experimental orange-fleshed watermelon cultivar (Fig. 2), contains mostly ( O 99%) b -carotene and only traces of lycopene and thus is considered to be equivalent to the tomato B mutant. The intense-red- flesh watermelons, such as ‘Crimson Sweet (Fig. 2), contain only lycopene and are essentially devoid of b -carotene. The aroma constituent citral, which has an agreeable scent, reminiscent of lemons, is, in fact, a mixture of the cis and trans non-cyclic monoterpene aldehyde isomers, neral and geranial, respectively. Citral is a major component of lemon basil ( Ocimum basilicum L., Lamiaceae), lemongrass ( Cymbopogon citratus (DC.) Stapf., Poaceae), and other lemon-scented aromatic plants (Bauer, Garbe, & Surburg, 2001; Burdock, 1995). Citral has also a major impact on the aromas of tomato (Baldwin et al ., 2000) and watermelon (Yajima et al ., 1985), but is present only in fruits that contain high levels of lycopene and its tetraterpene precursors (Lewinsohn et al ., in press). Several lines of evidence, gathered from precursor-feeding experiments and from enzymatic cell-free extracts, indicate that in many plants citral is biosynthesized by the action of geraniol synthase on geranyl diphosphate to give geraniol, which is, in turn, converted into geranial and neral (Fig. 3; Banthorpe, Bucknall, Doonan, Doonan, & Rowan, 1976; Iijima, Gang, Fridman, Lewinsohn, & Pichersky, 2004; Potty & Bruemmer, 1970; Singh- Sangwan, Sangwan, Luthra, & Thakur, 1993). The mechanism by which geraniol synthase generates geraniol is similar to the mode of action other monoterpene synthases, and the gene coding for the former enzyme has been isolated from sweet basil (Iijma et al ., 2004). Specific geraniol dehydrogenases that catalyze the oxidation of geraniol to geranial have been found in citrus fruits, lemon basil and lemongrass leaves (Fig. 3; Iijma et al ., 2004; Potty & Bruemmer, 1970; Sangwan, Singh-Sangwan, & Luthra, 1993; Singh-Sangwan et al ., 1993). Tomato fruit also contains alcohol dehydrogenase activity that readily accepts geraniol as a substrate (Bicsak, Kann, Reiter, & Chase, 1982). Thus, although it is widely accepted that in many plants citral is biosynthesized directly from geranyl diphosphate, it seems that this might not be the case in tomato and watermelon fruit. Rather, in these two types of fruit tissue, the monoterpenes geranial and neral are probably derived from carotenoids (mainly lycopene and its tetraterpene precursors) (Fig. 3). This premise is supported by the absence of citral in r tomatoes and Canary yellow watermelons, which are devoid of lycopene (Lewinsohn et al ., in press). The diversion of the metabolic flow out of carotenoid biosynthesis does not cause an enhancement of geranial levels in either the tomato r mutant or the Canary yellow watermelon in contrast to what would have been expected if geranyl diphosphate were the immediate precursor of geraniol and geranial in these fruits (Fig. 3). This finding therefore suggests that in vivo lycopene serves as a precursor for the formation of geranial and neral in red lycopene-containing tomato and watermelon fruits. It is also likely that neurosporene, prolycopene, and d -carotene will give rise to citral in both tomato and watermelon (Fig. 4). Some years ago, it was shown that volatile profiles of tomato varieties differing in flesh color were closely related to the fruit carotenoid composition (Stevens, 1970), a finding suggesting carotenoid breakdown into aroma volatile molecules. At that time, however, it was not possible to show a conclusive direct and casual relationship between color and aroma due to insufficient knowledge of the carotenoid biosynthetic pathway and the lack of the appropriate genetic material. More recent studies have used advanced genetic material with near isogenic backgrounds to exclude linkage drag and the varietal effects. Studies utilizing tomato near-isogenic lines, differing almost only in their carotenoid compositions, have indicated that marked differences in carotenoid compositions do indeed correlate with differences in the composition of the monoterpene and norisoprenoid volatiles (Lewinsohn et al ., 2005). Wild-type (red) tomatoes containing high concentrations of lycopene and lower concentrations of b -carotene also accumulate non-cyclic volatile norisoprenoids [such as 6-methyl-5- hepten-2-one, farnesyl acetone, ( E , E )-pseudoionone, 2,3- epoxygeranial, 2,6-dimethyl hept-5-1-al, geranyl acetone, and dihydro- apo -farnesal] in addition to geranial and neral and the cyclic norisoprenoid b -ionone (Lewinsohn et al ., 2005; Fig. 4). With the exception of farnesyl acetone, such compounds are for the most part absent in the yellow flesh ( r ) mutant of tomato, while the levels of other non- isoprenoid-derived compounds, such as phenylethyl alcohol, 4-vinylphenol and o -guaiacol, are apparently unaffected by the r mutation. These findings indicate that a functional phytoene synthase is required for the synthesis of many aroma volatiles (including citral) and thus revealed the pleiotropic effects of fruit carotenoid pigmentation genes on terpene aroma volatiles (Lewinsohn et al ., 2005). The tomato tg mutant, which accumulates the orange pigment prolycopene (tetra- cis -lycopene) and higher levels of tetraterpene precursors (including phytoene, phytofluene z -carotene and neurosporene) than the wild-type tomato (Fig. 2), contains similar concentrations of non-cyclic norisoprenes and citral to those in the wild-type red tomato. The levels of 6-methyl-5-hepten-2-one, geranyl acetone, dihydro apo farnesal and farnesyl acetone are up to 3-fold higher in the tg mutant line than in the wild-type red tomato. The tomato Del mutant, which accumulates high levels of d -carotene, also produces a -ionone in addition to citral and the non- cyclic norisoprenes detected in the wild-type and tg tomatoes. The orange-colored B genotype accumulates high levels of b -carotene in addition to lycopene. Dihydroactinodiolide, b -ionone, and b -cyclocitral produced in the B line (Fig. 4) are apparently derived from b -carotene. Interestingly, although geranial is a monoterpene, it is consistently present in tomatoes and watermelons in a pattern that follows that of the non-cyclic norisoprenoid present in the fruit. Although there is a clear difference in flavor and aroma between watermelon and tomato, these two fruits share many of the volatile chemicals that give rise to their unique aromas, particularly the non-cyclic norisoprenoids apparently derived from lycopene. Moreover, the volatile norisoprenes found in various watermelon cultivars with different carotenoid compositions display a striking similarity to the norisoprenoid compositions found in the fruits of the near-isogenic tomato lines. Thus, lycopene, prolycopene, d -carotene and ...
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... volatiles in ACS-suppressed transgenic tomatoes, if these are indeed enzymatically or non-enzymatically derived from carotenoid degradation in vivo . Striking phenotypic similarity in terms of carotenoid composition has been found in tomato and watermelon varieties. This variation is reflected in the color of the fruit (Tadmor, King, Levi, Davis, & Hirschberg, 2004; Tadmor et al ., submitted). The mesocarp of the wild-type tomato contains high concentrations ( w 85% of total carotenoids) of the acyclic pigment lycopene and lower concentrations ( ! 10%) of the bicyclic b -carotene (Hirschberg, 2001; Lewinsohn et al ., in press; Tadmor, King, Levi, Davis, & Hirschberg, 2004; Tadmor et al ., submitted). Despite the fact that watermelon is botanically distant from tomato, the carotenoid composition (lycopene 95% and b -carotene w 5%) of the typical red watermelons, such as ‘Moon and Stars’ (Fig. 2), resembles that of the wild-type tomato. Tomato near-isogenic lines with defined mutations in the carotenoid pathway (Liu et al ., 2003) differ almost exclusively in their carotenoid composition and hence in their color (Fig. 2). The yellow flesh ( r ) mutation of tomato is caused by a non-functional phytoene synthase ( psy1 ) gene, resulting in the accumulation of very low levels of carotenoids in these yellow-fleshed fruits (Fig. 2; Fray & Grierson, 1993). Watermelon cultivars such as ‘Early Moonbeam’, with canary yellow flesh lack lycopene and accumulate only trace levels of b -carotene, giving a carotenoid composition resembling that of the tomato r mutant (Fig. 2). The tangerine ( tg ) tomato mutant, which carries a dysfunctional carotenoid isomerase gene ( CRTISO ), accumulates the orange pigment prolycopene (tetra- cis -lycopene) and higher levels of tetraterpene precursors, including phytoene, phytofluene z -carotene and neurosporene, than the wild-type tomato (Fig. 2; Isaacson, Ronen, Zamir, & Hirschberg, 2002). Orange watermelons, such as ‘Orangeglo’, have a carotenoid profile resembling that of the tg tomato mutant (Fig. 2). The tomato Delta ( Del ) mutant accumulates high levels of the monocyclic tetraterpene pigment d -carotene ( w 80% of the total carotenoids) (Fig. 2; Ronen, Cohen, Zamir, & Hirschberg, 1999). Thus far, no equivalent to the tomato Del has been found in watermelon. The orange-colored High Beta ( B ) watermelon genotype accumulates high levels of b -carotene in addition to low levels of lycopene (Ronen, Carmel-Goren, Zamir, & Hirschberg, 2000). ‘NY162003’, an experimental orange-fleshed watermelon cultivar (Fig. 2), contains mostly ( O 99%) b -carotene and only traces of lycopene and thus is considered to be equivalent to the tomato B mutant. The intense-red- flesh watermelons, such as ‘Crimson Sweet (Fig. 2), contain only lycopene and are essentially devoid of b -carotene. The aroma constituent citral, which has an agreeable scent, reminiscent of lemons, is, in fact, a mixture of the cis and trans non-cyclic monoterpene aldehyde isomers, neral and geranial, respectively. Citral is a major component of lemon basil ( Ocimum basilicum L., Lamiaceae), lemongrass ( Cymbopogon citratus (DC.) Stapf., Poaceae), and other lemon-scented aromatic plants (Bauer, Garbe, & Surburg, 2001; Burdock, 1995). Citral has also a major impact on the aromas of tomato (Baldwin et al ., 2000) and watermelon (Yajima et al ., 1985), but is present only in fruits that contain high levels of lycopene and its tetraterpene precursors (Lewinsohn et al ., in press). Several lines of evidence, gathered from precursor-feeding experiments and from enzymatic cell-free extracts, indicate that in many plants citral is biosynthesized by the action of geraniol synthase on geranyl diphosphate to give geraniol, which is, in turn, converted into geranial and neral (Fig. 3; Banthorpe, Bucknall, Doonan, Doonan, & Rowan, 1976; Iijima, Gang, Fridman, Lewinsohn, & Pichersky, 2004; Potty & Bruemmer, 1970; Singh- Sangwan, Sangwan, Luthra, & Thakur, 1993). The mechanism by which geraniol synthase generates geraniol is similar to the mode of action other monoterpene synthases, and the gene coding for the former enzyme has been isolated from sweet basil (Iijma et al ., 2004). Specific geraniol dehydrogenases that catalyze the oxidation of geraniol to geranial have been found in citrus fruits, lemon basil and lemongrass leaves (Fig. 3; Iijma et al ., 2004; Potty & Bruemmer, 1970; Sangwan, Singh-Sangwan, & Luthra, 1993; Singh-Sangwan et al ., 1993). Tomato fruit also contains alcohol dehydrogenase activity that readily accepts geraniol as a substrate (Bicsak, Kann, Reiter, & Chase, 1982). Thus, although it is widely accepted that in many plants citral is biosynthesized directly from geranyl diphosphate, it seems that this might not be the case in tomato and watermelon fruit. Rather, in these two types of fruit tissue, the monoterpenes geranial and neral are probably derived from carotenoids (mainly lycopene and its tetraterpene precursors) (Fig. 3). This premise is supported by the absence of citral in r tomatoes and Canary yellow watermelons, which are devoid of lycopene (Lewinsohn et al ., in press). The diversion of the metabolic flow out of carotenoid biosynthesis does not cause an enhancement of geranial levels in either the tomato r mutant or the Canary yellow watermelon in contrast to what would have been expected if geranyl diphosphate were the immediate precursor of geraniol and geranial in these fruits (Fig. 3). This finding therefore suggests that in vivo lycopene serves as a precursor for the formation of geranial and neral in red lycopene-containing tomato and watermelon fruits. It is also likely that neurosporene, prolycopene, and d -carotene will give rise to citral in both tomato and watermelon (Fig. 4). Some years ago, it was shown that volatile profiles of tomato varieties differing in flesh color were closely related to the fruit carotenoid composition (Stevens, 1970), a finding suggesting carotenoid breakdown into aroma volatile molecules. At that time, however, it was not possible to show a conclusive direct and casual relationship between color and aroma due to insufficient knowledge of the carotenoid biosynthetic pathway and the lack of the appropriate genetic material. More recent studies have used advanced genetic material with near isogenic backgrounds to exclude linkage drag and the varietal effects. Studies utilizing tomato near-isogenic lines, differing almost only in their carotenoid compositions, have indicated that marked differences in carotenoid compositions do indeed correlate with differences in the composition of the monoterpene and norisoprenoid volatiles (Lewinsohn et al ., 2005). Wild-type (red) tomatoes containing high concentrations of lycopene and lower concentrations of b -carotene also accumulate non-cyclic volatile norisoprenoids [such as 6-methyl-5- hepten-2-one, farnesyl acetone, ( E , E )-pseudoionone, 2,3- epoxygeranial, 2,6-dimethyl hept-5-1-al, geranyl acetone, and dihydro- apo -farnesal] in addition to geranial and neral and the cyclic norisoprenoid b -ionone (Lewinsohn et al ., 2005; Fig. 4). With the exception of farnesyl acetone, such compounds are for the most part absent in the yellow flesh ( r ) mutant of tomato, while the levels of other non- isoprenoid-derived compounds, such as phenylethyl alcohol, 4-vinylphenol and o -guaiacol, are apparently unaffected by the r mutation. These findings indicate that a functional phytoene synthase is required for the synthesis of many aroma volatiles (including citral) and thus revealed the pleiotropic effects of fruit carotenoid pigmentation genes on terpene aroma volatiles (Lewinsohn et al ., 2005). The tomato tg mutant, which accumulates the orange pigment prolycopene (tetra- cis -lycopene) and higher levels of tetraterpene precursors (including phytoene, phytofluene z -carotene and neurosporene) than the wild-type tomato (Fig. 2), contains similar concentrations of non-cyclic norisoprenes and citral to those in the wild-type red tomato. The levels of 6-methyl-5-hepten-2-one, geranyl acetone, dihydro apo farnesal and farnesyl acetone are up to 3-fold higher in the tg mutant line than in the wild-type red tomato. The tomato Del mutant, which accumulates high levels of d -carotene, also produces a -ionone in addition to citral and the non- cyclic norisoprenes detected in the wild-type and tg tomatoes. The orange-colored B genotype accumulates high levels of b -carotene in addition to lycopene. Dihydroactinodiolide, b -ionone, and b -cyclocitral produced in the B line (Fig. 4) are apparently derived from b -carotene. Interestingly, although geranial is a monoterpene, it is consistently present in tomatoes and watermelons in a pattern that follows that of the non-cyclic norisoprenoid present in the fruit. Although there is a clear difference in flavor and aroma between watermelon and tomato, these two fruits share many of the volatile chemicals that give rise to their unique aromas, particularly the non-cyclic norisoprenoids apparently derived from lycopene. Moreover, the volatile norisoprenes found in various watermelon cultivars with different carotenoid compositions display a striking similarity to the norisoprenoid compositions found in the fruits of the near-isogenic tomato lines. Thus, lycopene, prolycopene, d -carotene and neurosporene give rise in vivo to the non-cyclic volatiles, neral and geranial, as well as to 6-methyl-5-hepten-2-one, 2,6- dimethyl hept-5-1-al, 2,3-epoxygeranial, and ( E , E )-pseudoionone (Fig. 4). b -Ionone, b -cyclocitral and dihydroactinodiolide are apparently oxidative breakdown products of b -carotene. d -Carotene appears to gives rise to a -ionone, probably by the cleavage of the 3 ionone ring of d -carotene (Fig. 4). Farnesyl acetone, dihydro- apo -farnesal, geranyl acetone and 6-methyl hept-5-en-3-one are probably derived from phytoene or phytofluene (Fig. 4). Thus, in essence, color and aroma compounds ...
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... Oeller, Wong, Rottmann, & Gantz, 1993). Ethylene is biosynthesized from the amino acid methionine (Yang & Hoffman, 1984), with 1-aminocyclo- propane-1-carboxylic acid (ACC) synthase (ACS) being a key enzyme in ethylene formation. Thus, ACC-synthase antisensed tomatoes produce only minute levels of ethylene and do not ripen normally (Oeller, Wong, Taylor, Pike, & Theologis, 1991). These fruits remain green and never ripen fully as do wild-type tomatoes (Fig. 1). The aroma of these transgenic tomatoes is also affected by the genetic manipulation (Baldwin et al ., 2000), and consequently most of the volatiles present in the wild-type tomato, including norisoprene and monoterpene compounds, are absent in ACS-antisensed fruits (Fig. 1). In contrast, guaiacol and methyl salicylate, which are found in green (unripe) wild-type tomato fruit, are prominent in ‘mature’ ACS-silenced fruits (Fig. 1). The lack of aroma in the transgenic fruit can be explained by the repression of the biosynthetic pathways that lead to the formation of aroma volatiles. It could be however, that the mere lack of carotenoids could partially account for the lack of norisoprene and monoterpene volatiles in ACS-suppressed transgenic tomatoes, if these are indeed enzymatically or non-enzymatically derived from carotenoid degradation in vivo . Striking phenotypic similarity in terms of carotenoid composition has been found in tomato and watermelon varieties. This variation is reflected in the color of the fruit (Tadmor, King, Levi, Davis, & Hirschberg, 2004; Tadmor et al ., submitted). The mesocarp of the wild-type tomato contains high concentrations ( w 85% of total carotenoids) of the acyclic pigment lycopene and lower concentrations ( ! 10%) of the bicyclic b -carotene (Hirschberg, 2001; Lewinsohn et al ., in press; Tadmor, King, Levi, Davis, & Hirschberg, 2004; Tadmor et al ., submitted). Despite the fact that watermelon is botanically distant from tomato, the carotenoid composition (lycopene 95% and b -carotene w 5%) of the typical red watermelons, such as ‘Moon and Stars’ (Fig. 2), resembles that of the wild-type tomato. Tomato near-isogenic lines with defined mutations in the carotenoid pathway (Liu et al ., 2003) differ almost exclusively in their carotenoid composition and hence in their color (Fig. 2). The yellow flesh ( r ) mutation of tomato is caused by a non-functional phytoene synthase ( psy1 ) gene, resulting in the accumulation of very low levels of carotenoids in these yellow-fleshed fruits (Fig. 2; Fray & Grierson, 1993). Watermelon cultivars such as ‘Early Moonbeam’, with canary yellow flesh lack lycopene and accumulate only trace levels of b -carotene, giving a carotenoid composition resembling that of the tomato r mutant (Fig. 2). The tangerine ( tg ) tomato mutant, which carries a dysfunctional carotenoid isomerase gene ( CRTISO ), accumulates the orange pigment prolycopene (tetra- cis -lycopene) and higher levels of tetraterpene precursors, including phytoene, phytofluene z -carotene and neurosporene, than the wild-type tomato (Fig. 2; Isaacson, Ronen, Zamir, & Hirschberg, 2002). Orange watermelons, such as ‘Orangeglo’, have a carotenoid profile resembling that of the tg tomato mutant (Fig. 2). The tomato Delta ( Del ) mutant accumulates high levels of the monocyclic tetraterpene pigment d -carotene ( w 80% of the total carotenoids) (Fig. 2; Ronen, Cohen, Zamir, & Hirschberg, 1999). Thus far, no equivalent to the tomato Del has been found in watermelon. The orange-colored High Beta ( B ) watermelon genotype accumulates high levels of b -carotene in addition to low levels of lycopene (Ronen, Carmel-Goren, Zamir, & Hirschberg, 2000). ‘NY162003’, an experimental orange-fleshed watermelon cultivar (Fig. 2), contains mostly ( O 99%) b -carotene and only traces of lycopene and thus is considered to be equivalent to the tomato B mutant. The intense-red- flesh watermelons, such as ‘Crimson Sweet (Fig. 2), contain only lycopene and are essentially devoid of b -carotene. The aroma constituent citral, which has an agreeable scent, reminiscent of lemons, is, in fact, a mixture of the cis and trans non-cyclic monoterpene aldehyde isomers, neral and geranial, respectively. Citral is a major component of lemon basil ( Ocimum basilicum L., Lamiaceae), lemongrass ( Cymbopogon citratus (DC.) Stapf., Poaceae), and other lemon-scented aromatic plants (Bauer, Garbe, & Surburg, 2001; Burdock, 1995). Citral has also a major impact on the aromas of tomato (Baldwin et al ., 2000) and watermelon (Yajima et al ., 1985), but is present only in fruits that contain high levels of lycopene and its tetraterpene precursors (Lewinsohn et al ., in press). Several lines of evidence, gathered from precursor-feeding experiments and from enzymatic cell-free extracts, indicate that in many plants citral is biosynthesized by the action of geraniol synthase on geranyl diphosphate to give geraniol, which is, in turn, converted into geranial and neral (Fig. 3; Banthorpe, Bucknall, Doonan, Doonan, & Rowan, 1976; Iijima, Gang, Fridman, Lewinsohn, & Pichersky, 2004; Potty & Bruemmer, 1970; Singh- Sangwan, Sangwan, Luthra, & Thakur, 1993). The mechanism by which geraniol synthase generates geraniol is similar to the mode of action other monoterpene synthases, and the gene coding for the former enzyme has been isolated from sweet basil (Iijma et al ., 2004). Specific geraniol dehydrogenases that catalyze the oxidation of geraniol to geranial have been found in citrus fruits, lemon basil and lemongrass leaves (Fig. 3; Iijma et al ., 2004; Potty & Bruemmer, 1970; Sangwan, Singh-Sangwan, & Luthra, 1993; Singh-Sangwan et al ., 1993). Tomato fruit also contains alcohol dehydrogenase activity that readily accepts geraniol as a substrate (Bicsak, Kann, Reiter, & Chase, 1982). Thus, although it is widely accepted that in many plants citral is biosynthesized directly from geranyl diphosphate, it seems that this might not be the case in tomato and watermelon fruit. Rather, in these two types of fruit tissue, the monoterpenes geranial and neral are probably derived from carotenoids (mainly lycopene and its tetraterpene precursors) (Fig. 3). This premise is supported by the absence of citral in r tomatoes and Canary yellow watermelons, which are devoid of lycopene (Lewinsohn et al ., in press). The diversion of the metabolic flow out of carotenoid biosynthesis does not cause an enhancement of geranial levels in either the tomato r mutant or the Canary yellow watermelon in contrast to what would have been expected if geranyl diphosphate were the immediate precursor of geraniol and geranial in these fruits (Fig. 3). This finding therefore suggests that in vivo lycopene serves as a precursor for the formation of geranial and neral in red lycopene-containing tomato and watermelon fruits. It is also likely that neurosporene, prolycopene, and d -carotene will give rise to citral in both tomato and watermelon (Fig. 4). Some years ago, it was shown that volatile profiles of tomato varieties differing in flesh color were closely related to the fruit carotenoid composition (Stevens, 1970), a finding suggesting carotenoid breakdown into aroma volatile molecules. At that time, however, it was not possible to show a conclusive direct and casual relationship between color and aroma due to insufficient knowledge of the carotenoid biosynthetic pathway and the lack of the appropriate genetic material. More recent studies have used advanced genetic material with near isogenic backgrounds to exclude linkage drag and the varietal effects. Studies utilizing tomato near-isogenic lines, differing almost only in their carotenoid compositions, have indicated that marked differences in carotenoid compositions do indeed correlate with differences in the composition of the monoterpene and norisoprenoid volatiles (Lewinsohn et al ., 2005). Wild-type (red) tomatoes containing high concentrations of lycopene and lower concentrations of b -carotene also accumulate non-cyclic volatile norisoprenoids [such as 6-methyl-5- hepten-2-one, farnesyl acetone, ( E , E )-pseudoionone, 2,3- epoxygeranial, 2,6-dimethyl hept-5-1-al, geranyl acetone, and dihydro- apo -farnesal] in addition to geranial and neral and the cyclic norisoprenoid b -ionone (Lewinsohn et al ., 2005; Fig. 4). With the exception of farnesyl acetone, such compounds are for the most part absent in the yellow flesh ( r ) mutant of tomato, while the levels of other non- isoprenoid-derived compounds, such as phenylethyl alcohol, 4-vinylphenol and o -guaiacol, are apparently unaffected by the r mutation. These findings indicate that a functional phytoene synthase is required for the synthesis of many aroma volatiles (including citral) and thus revealed the pleiotropic effects of fruit carotenoid pigmentation genes on terpene aroma volatiles (Lewinsohn et al ., 2005). The tomato tg mutant, which accumulates the orange pigment prolycopene (tetra- cis -lycopene) and higher levels of tetraterpene precursors (including phytoene, phytofluene z -carotene and neurosporene) than the wild-type tomato (Fig. 2), contains similar concentrations of non-cyclic norisoprenes and citral to those in the wild-type red tomato. The levels of 6-methyl-5-hepten-2-one, geranyl acetone, dihydro apo farnesal and farnesyl acetone are up to 3-fold higher in the tg mutant line than in the wild-type red tomato. The tomato Del mutant, which accumulates high levels of d -carotene, also produces a -ionone in addition to citral and the non- cyclic norisoprenes detected in the wild-type and tg tomatoes. The orange-colored B genotype accumulates high levels of b -carotene in addition to lycopene. Dihydroactinodiolide, b -ionone, and b -cyclocitral produced in the B line (Fig. 4) are apparently derived from b -carotene. Interestingly, although geranial is a monoterpene, it is consistently present in tomatoes and watermelons in a pattern that follows that of the non-cyclic ...
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... of the acyclic pigment lycopene and lower concentrations ( ! 10%) of the bicyclic b -carotene (Hirschberg, 2001; Lewinsohn et al ., in press; Tadmor, King, Levi, Davis, & Hirschberg, 2004; Tadmor et al ., submitted). Despite the fact that watermelon is botanically distant from tomato, the carotenoid composition (lycopene 95% and b -carotene w 5%) of the typical red watermelons, such as ‘Moon and Stars’ (Fig. 2), resembles that of the wild-type tomato. Tomato near-isogenic lines with defined mutations in the carotenoid pathway (Liu et al ., 2003) differ almost exclusively in their carotenoid composition and hence in their color (Fig. 2). The yellow flesh ( r ) mutation of tomato is caused by a non-functional phytoene synthase ( psy1 ) gene, resulting in the accumulation of very low levels of carotenoids in these yellow-fleshed fruits (Fig. 2; Fray & Grierson, 1993). Watermelon cultivars such as ‘Early Moonbeam’, with canary yellow flesh lack lycopene and accumulate only trace levels of b -carotene, giving a carotenoid composition resembling that of the tomato r mutant (Fig. 2). The tangerine ( tg ) tomato mutant, which carries a dysfunctional carotenoid isomerase gene ( CRTISO ), accumulates the orange pigment prolycopene (tetra- cis -lycopene) and higher levels of tetraterpene precursors, including phytoene, phytofluene z -carotene and neurosporene, than the wild-type tomato (Fig. 2; Isaacson, Ronen, Zamir, & Hirschberg, 2002). Orange watermelons, such as ‘Orangeglo’, have a carotenoid profile resembling that of the tg tomato mutant (Fig. 2). The tomato Delta ( Del ) mutant accumulates high levels of the monocyclic tetraterpene pigment d -carotene ( w 80% of the total carotenoids) (Fig. 2; Ronen, Cohen, Zamir, & Hirschberg, 1999). Thus far, no equivalent to the tomato Del has been found in watermelon. The orange-colored High Beta ( B ) watermelon genotype accumulates high levels of b -carotene in addition to low levels of lycopene (Ronen, Carmel-Goren, Zamir, & Hirschberg, 2000). ‘NY162003’, an experimental orange-fleshed watermelon cultivar (Fig. 2), contains mostly ( O 99%) b -carotene and only traces of lycopene and thus is considered to be equivalent to the tomato B mutant. The intense-red- flesh watermelons, such as ‘Crimson Sweet (Fig. 2), contain only lycopene and are essentially devoid of b -carotene. The aroma constituent citral, which has an agreeable scent, reminiscent of lemons, is, in fact, a mixture of the cis and trans non-cyclic monoterpene aldehyde isomers, neral and geranial, respectively. Citral is a major component of lemon basil ( Ocimum basilicum L., Lamiaceae), lemongrass ( Cymbopogon citratus (DC.) Stapf., Poaceae), and other lemon-scented aromatic plants (Bauer, Garbe, & Surburg, 2001; Burdock, 1995). Citral has also a major impact on the aromas of tomato (Baldwin et al ., 2000) and watermelon (Yajima et al ., 1985), but is present only in fruits that contain high levels of lycopene and its tetraterpene precursors (Lewinsohn et al ., in press). Several lines of evidence, gathered from precursor-feeding experiments and from enzymatic cell-free extracts, indicate that in many plants citral is biosynthesized by the action of geraniol synthase on geranyl diphosphate to give geraniol, which is, in turn, converted into geranial and neral (Fig. 3; Banthorpe, Bucknall, Doonan, Doonan, & Rowan, 1976; Iijima, Gang, Fridman, Lewinsohn, & Pichersky, 2004; Potty & Bruemmer, 1970; Singh- Sangwan, Sangwan, Luthra, & Thakur, 1993). The mechanism by which geraniol synthase generates geraniol is similar to the mode of action other monoterpene synthases, and the gene coding for the former enzyme has been isolated from sweet basil (Iijma et al ., 2004). Specific geraniol dehydrogenases that catalyze the oxidation of geraniol to geranial have been found in citrus fruits, lemon basil and lemongrass leaves (Fig. 3; Iijma et al ., 2004; Potty & Bruemmer, 1970; Sangwan, Singh-Sangwan, & Luthra, 1993; Singh-Sangwan et al ., 1993). Tomato fruit also contains alcohol dehydrogenase activity that readily accepts geraniol as a substrate (Bicsak, Kann, Reiter, & Chase, 1982). Thus, although it is widely accepted that in many plants citral is biosynthesized directly from geranyl diphosphate, it seems that this might not be the case in tomato and watermelon fruit. Rather, in these two types of fruit tissue, the monoterpenes geranial and neral are probably derived from carotenoids (mainly lycopene and its tetraterpene precursors) (Fig. 3). This premise is supported by the absence of citral in r tomatoes and Canary yellow watermelons, which are devoid of lycopene (Lewinsohn et al ., in press). The diversion of the metabolic flow out of carotenoid biosynthesis does not cause an enhancement of geranial levels in either the tomato r mutant or the Canary yellow watermelon in contrast to what would have been expected if geranyl diphosphate were the immediate precursor of geraniol and geranial in these fruits (Fig. 3). This finding therefore suggests that in vivo lycopene serves as a precursor for the formation of geranial and neral in red lycopene-containing tomato and watermelon fruits. It is also likely that neurosporene, prolycopene, and d -carotene will give rise to citral in both tomato and watermelon (Fig. 4). Some years ago, it was shown that volatile profiles of tomato varieties differing in flesh color were closely related to the fruit carotenoid composition (Stevens, 1970), a finding suggesting carotenoid breakdown into aroma volatile molecules. At that time, however, it was not possible to show a conclusive direct and casual relationship between color and aroma due to insufficient knowledge of the carotenoid biosynthetic pathway and the lack of the appropriate genetic material. More recent studies have used advanced genetic material with near isogenic backgrounds to exclude linkage drag and the varietal effects. Studies utilizing tomato near-isogenic lines, differing almost only in their carotenoid compositions, have indicated that marked differences in carotenoid compositions do indeed correlate with differences in the composition of the monoterpene and norisoprenoid volatiles (Lewinsohn et al ., 2005). Wild-type (red) tomatoes containing high concentrations of lycopene and lower concentrations of b -carotene also accumulate non-cyclic volatile norisoprenoids [such as 6-methyl-5- hepten-2-one, farnesyl acetone, ( E , E )-pseudoionone, 2,3- epoxygeranial, 2,6-dimethyl hept-5-1-al, geranyl acetone, and dihydro- apo -farnesal] in addition to geranial and neral and the cyclic norisoprenoid b -ionone (Lewinsohn et al ., 2005; Fig. 4). With the exception of farnesyl acetone, such compounds are for the most part absent in the yellow flesh ( r ) mutant of tomato, while the levels of other non- isoprenoid-derived compounds, such as phenylethyl alcohol, 4-vinylphenol and o -guaiacol, are apparently unaffected by the r mutation. These findings indicate that a functional phytoene synthase is required for the synthesis of many aroma volatiles (including citral) and thus revealed the pleiotropic effects of fruit carotenoid pigmentation genes on terpene aroma volatiles (Lewinsohn et al ., 2005). The tomato tg mutant, which accumulates the orange pigment prolycopene (tetra- cis -lycopene) and higher levels of tetraterpene precursors (including phytoene, phytofluene z -carotene and neurosporene) than the wild-type tomato (Fig. 2), contains similar concentrations of non-cyclic norisoprenes and citral to those in the wild-type red tomato. The levels of 6-methyl-5-hepten-2-one, geranyl acetone, dihydro apo farnesal and farnesyl acetone are up to 3-fold higher in the tg mutant line than in the wild-type red tomato. The tomato Del mutant, which accumulates high levels of d -carotene, also produces a -ionone in addition to citral and the non- cyclic norisoprenes detected in the wild-type and tg tomatoes. The orange-colored B genotype accumulates high levels of b -carotene in addition to lycopene. Dihydroactinodiolide, b -ionone, and b -cyclocitral produced in the B line (Fig. 4) are apparently derived from b -carotene. Interestingly, although geranial is a monoterpene, it is consistently present in tomatoes and watermelons in a pattern that follows that of the non-cyclic norisoprenoid present in the fruit. Although there is a clear difference in flavor and aroma between watermelon and tomato, these two fruits share many of the volatile chemicals that give rise to their unique aromas, particularly the non-cyclic norisoprenoids apparently derived from lycopene. Moreover, the volatile norisoprenes found in various watermelon cultivars with different carotenoid compositions display a striking similarity to the norisoprenoid compositions found in the fruits of the near-isogenic tomato lines. Thus, lycopene, prolycopene, d -carotene and neurosporene give rise in vivo to the non-cyclic volatiles, neral and geranial, as well as to 6-methyl-5-hepten-2-one, 2,6- dimethyl hept-5-1-al, 2,3-epoxygeranial, and ( E , E )-pseudoionone (Fig. 4). b -Ionone, b -cyclocitral and dihydroactinodiolide are apparently oxidative breakdown products of b -carotene. d -Carotene appears to gives rise to a -ionone, probably by the cleavage of the 3 ionone ring of d -carotene (Fig. 4). Farnesyl acetone, dihydro- apo -farnesal, geranyl acetone and 6-methyl hept-5-en-3-one are probably derived from phytoene or phytofluene (Fig. 4). Thus, in essence, color and aroma compounds are highly associated in tomato and watermelon fruits, and this relationship is probably a function of the degradation of carotenoids into aroma volatiles. The ‘high pigment’ photomorphogenic mutants in tomato are characterized by increased pigmentation in fruits due to up to 1.5-fold elevated levels of lycopene and b -carotene. Two types of such mutants are known: the hp- 2 mutants are due to different mutations in the gene encoding the tomato homologue of the Arabidopsis ...
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... precursors ( Lewinsohn et al., in press). Several lines of evidence, gathered from precursor-feeding experiments and from enzymatic cell-free extracts, indicate that in many plants citral is biosynthesized by the action of geraniol synthase on geranyl diphosphate to give geraniol, which is, in turn, converted into geranial and neral ( Fig. 3; Banthorpe, Bucknall, Doonan, Doonan, & Rowan, 1976;Iijima, Gang, Fridman, Lewinsohn, & Pichersky, 2004;Potty & Bruemmer, 1970;Singh- Sangwan, Sangwan, Luthra, & Thakur, 1993). The mechanism by which geraniol synthase generates geraniol is similar to the mode of action other monoterpene synthases, and the gene coding for the former ...
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... synthase generates geraniol is similar to the mode of action other monoterpene synthases, and the gene coding for the former enzyme has been isolated from sweet basil ( Iijma et al., 2004). Specific geraniol dehydrogenases that catalyze the oxidation of geraniol to geranial have been found in citrus fruits, lemon basil and lemongrass leaves ( Fig. 3; Iijma et al., 2004;Potty & Bruemmer, 1970;Singh-Sangwan et al., 1993). Tomato fruit also contains alcohol dehydrogenase activity that readily accepts geraniol as a substrate (Bicsak, Kann, Reiter, & Chase, 1982). Thus, although it is widely accepted that in many plants citral is biosynthesized directly from geranyl diphosphate, it ...
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... it is widely accepted that in many plants citral is biosynthesized directly from geranyl diphosphate, it seems that this might not be the case in tomato and watermelon fruit. Rather, in these two types of fruit tissue, the monoterpenes geranial and neral are probably derived from carotenoids (mainly lycopene and its tetraterpene precursors) (Fig. 3). This premise is supported by the absence of citral in r tomatoes and Canary yellow watermelons, which are devoid of lycopene ( Lewinsohn et al., in press). The diversion of the metabolic flow out of carotenoid biosynthesis does not cause an enhancement of geranial levels in either the tomato r mutant or the Canary yellow watermelon in ...
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... ( Lewinsohn et al., in press). The diversion of the metabolic flow out of carotenoid biosynthesis does not cause an enhancement of geranial levels in either the tomato r mutant or the Canary yellow watermelon in contrast to what would have been expected if geranyl diphosphate were the immediate precursor of geraniol and geranial in these fruits (Fig. 3). This finding therefore suggests that in vivo lycopene serves as a precursor for the formation of geranial and neral in red lycopene-containing tomato and watermelon fruits. It is also likely that neurosporene, prolycopene, and d-carotene will give rise to citral in both tomato and watermelon (Fig. ...
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The biosynthetic processes leading to many of the isoprenoid volatiles released by tomato fruits are still unknown, though previous reports suggested a clear correlation with the carotenoids contained within the fruit. In this study, we investigated the activity of the tomato (Solanum lycopersicum) carotenoid cleavage dioxygenase (SlCCD1B), which i...
Citations
... In the aroma of fruits, VOCs with specific qualitative and quantitative patterns act independently of each other and co-operate with each other to produce a broad range of aromas and confer different aroma characteristics on different types of fruits [9]. Studies have shown that tomatoes, watermelon, and lemon typically exhibit an 'herbaceous aroma', a unique odor formed by volatile compounds derived from alcohols, aldehydes, and carotenoids [10,11]. Bananas, on the other hand, exhibit an 'ester odor', which is attributed to different volatile esters [12]. ...
Aroma, an important quality characteristic of plant fruits, is produced by volatile organic compounds (VOCs), mainly terpenes, aldehydes, alcohols, esters, ketones, and other secondary metabolites, in plant cells. There are significant differences in the VOC profile of various fruits. The main pathways involved in the synthesis of VOCs are the terpenoid, phenylalanine, and fatty acid biosynthesis pathways, which involve several key enzyme-encoding genes, transcription factors (TFs), and epigenetic factors. This paper reviews the main synthetic pathways of the main volatile components in fruit, summarizes studies on the regulation of aroma formation by key genes and TFs, summarizes the factors affecting the fruit aroma formation, describes relevant studies on the improvement of fruit flavor quality, and finally proposes potential challenges and prospects for future research directions. This study provides a theoretical basis for the further precise control of fruit aroma quality and variety improvement.
... Carotenoid breakdown leads to the release of several VOCs, owing to the high instability of their conjugated double-bound structure. Carotenoids play a key role as photosynthetic pigments that harvest light and prevent photo-oxidative damage [51]. In the later stages of carotenoid degradation, the longer chain intermediates are oxidized, forming short-chain mono-and deoxygenated compounds, such as sulcatone, ionones, dihydroactinidiolide, and β-cyclocitral. ...
Spirulina platensis (SP) has gained popularity over the last few years, owing to its remarkable nutritional properties and high potential across various industrial sectors. In this study, we analyzed the volatile profile of eight SP samples from the same strain subjected to different drying (oven-drying, air-drying, and spray-drying) and storing conditions (“freshly prepared” and after 12 months of storage) using HS-SPME-GC-MS. Principal component analysis (PCA) was used as a multivariate technique to discern similarities and differences among the samples. The main aim was to assess the impact of the drying technique on the aroma profile and storage life of SP samples. Air-drying leads to the less pronounced formation of by-products related to heat treatment, such as Maillard and Strecker degradation compounds, but promotes oxidative and fermentative phenomena, with the formation of organic acids and esters, especially during storage. Thermal treatment, essential for limiting degradation and fermentation during storage and extending shelf life, alters the aroma profile through the formation of volatile compounds, such as Strecker aldehydes and linear aldehydes, from amino acid and lipid degradation. High temperatures in spray-drying favor the formation of pyrazines. The findings underscore the trade-offs inherent in choosing an appropriate drying method, thereby informing decision-making processes in industrial settings aimed at optimizing both product quality and efficiency.
... Geranyllinalol, dihydrokiwifolide, and 3-hydroxy-βdihydrodamalone were found in higher concentrations in the enzyme-treated group, and these compounds are the degradation products of carotenoids. In tobacco, terpenoids and their degradation products play a crucial role in the generation aroma, especially the degradation products of carotenoids (Lewinsohn et al., 2005). These compounds are the main aromatic constituents that have strong fruity, woody, and violet aromas, which enhance the sensory experience of tobacco smoke. ...
To study the relationship between the diversity of the surface microbial community and tobacco flavor, and to improve tobacco quality using microorganisms. The microbial community composition and diversity of 14 samples of flue-cured tobacco from tobacco-producing areas in Yunnan with varying grades were analyzed by high-throughput sequencing. PICRUSt was used for predicting microbial functions. A strain of Bacillus amyloliquefaciens W6-2 with the ability to degrade pectin was screened from the surface of flued-cured tobacco leaves from Yunnan reroasted tobacco leave. The enzyme preparation was prepared through fermentation and then applied for treating flue-cured tobacco. The improvement effect was evaluated by measuring the content of macromolecule and the changes in volatile components, combined with sensory evaluations. The bacterial communities on the surface of flue-cured tobacco exhibited functional diversity, consisting primarily of Variovorax, Pseudomonas, Sphingomonas, Burkholderia, and Bacillus. These bacterial strains played a role in the aging process of flue-cured tobacco leaves by participating in amino acid metabolism and carbohydrate metabolism. These metabolic activity converted complex macromolecules into smaller molecular compounds, ultimately influence the smoking quality and burning characteristics of flue-cured tobacco. The pectinase preparation produced through fermentation using W6-2 has been found to enhance the aroma and sweetness of flue-cured tobacco, leading to improved aroma, reduced impurities, and enhanced smoothness. Additionally, the levels of pectin, cellulose, and hemicellulose decreased, while the levels of water-soluble sugar and reducing sugar increased, and the contents of esters, ketones, and aldehydes increased, and the contents of benzoic acid decreased. The study revealed the correlation between surface microorganisms and volatile components of Yunnan tobacco leaves, and the enzyme produced by the pectin-degrading bacteria W6-2 effectively improved the quality of flue-cured tobacco.
... These substances appear to have a crucial role in creating the unique flavours that distinguish these two varieties of soybean paste. In another study, it was reported that the degradation of carotenoids is the most probable origin of the terpenes isolated in pumpkin purée, which are significant for aroma formation [40]. Understanding the role of sensory active compounds is a very important issue to consider to improve the appreciation of the existing complexities of the chemicals involved in flavour perception. ...
Transitioning to a plant-based diet presents a number of complex ethical, environmental, and health-related considerations. This trend is not only reshaping consumer diets, but also steering the food industry towards the development of new plant-based products. The primary aim of this study was to examine and identify the sensory similarities and differences in soybean spreads consisting of vegetable purées—specifically, beetroot, pumpkin, broccoli, and carrot—with the addition of spices such as marjoram and cumin. The sensory assessment was conducted using the Quantitative Descriptive Analysis (QDA). Twenty-three descriptors were selected and defined following the profiling procedure. The sensory properties of soy-based spreads have been significantly altered by the addition of vegetable purées and spices. Adding vegetable purées reduced the intensity of soybean odour and flavour, lowered fatty notes, and resulted in a less dense texture, while enhancing vegetable odour and flavour. This also improved the moisture content and overall sensory quality of the spreads. Although spices did not notably enhance these sensory attributes, soy-based vegetable spreads remain an attractive option for unique vegetarian finger foods and lunch dishes, catering to diverse consumer preferences. The addition of vegetable purées and spices to spreads creates opportunities for innovative and flavourful plant-based options.
... Culoarea florilor și a fructelor plantelor rezultă în principal din acumularea de pigmenți carotenoizi și flavonoizi [45]. În afară de licopen, fructele de roșii conțin și βcaroten, fitoenă, violaxantină și luteină. ...
... For example, lycopene lowers the incidence of prostate cancer, while b-carotene is a precursor for the synthesis of vitamin A (Bendich 1993). Lycopene is a metabolic intermediate in the xanthophyll biosynthesis pathway, and is stored in the chromoplasts of tomato, watermelon, etc. (Lewinsohn et al. 2005). ...
Significant progress has been made in understanding carotenoid biosynthesis in tomato (Solanum lycopersicum), and most pathway genes have been cloned and characterized. However, isolation and characterization of novel fruit ripening mutants is a continuous and essential process. This study describes the characterization of the Tan406 (Tangerine406) mutant of Solanum lycopersicum. Fruits of Tan406-mutant plants have a unique orange color and accumulate prolycopene instead of lycopene. Genetic analysis revealed that a monogenic recessive mutation affects fruit pigmentation in the mutant, which inhibits the conversion of prolycopene to lycopene. Further, molecular analysis indicates that fruit phenotype is attributed to loss of CRTISO gene function, which encodes a carotenoid isomerase enzyme that converts prolycopene to lycopene. The loss of gene function is due to the deletion of 406 bp from the CRTISO promoter region. Analysis of genome-wide transcriptome expression profiling identified several hundreds of differentially expressed genes in the fruit ripening stages. The results of microarray studies showed a tendency for upregulation of the genes at the mature green stage and downregulation at the fully ripened stage in the mutant. The isolated mutant can be used for the development of varieties having altered nutritional value.
... The treated samples only decrease gradually and at day 16 a higher beta-carotene content of 0.054 mg 100 g -1 was recorded. The extreme loss of beta-carotene at day 20 of storage indicated an inappropriately long storage time (Lewinsohn et al., 2005). Beta-carotene content losses in the tomato fruits after day 20 may have been converted or isomerized into other derivative compounds including flavour and aroma constituents (Lewinsohn et al., 2005) or it was converted back into lycopene (Alba et al., 2000). ...
... The extreme loss of beta-carotene at day 20 of storage indicated an inappropriately long storage time (Lewinsohn et al., 2005). Beta-carotene content losses in the tomato fruits after day 20 may have been converted or isomerized into other derivative compounds including flavour and aroma constituents (Lewinsohn et al., 2005) or it was converted back into lycopene (Alba et al., 2000). Table 8 show a general increase from 0.016 to 0.124 mg 100 g -1 in lycopene content of tomato fruit during storage. ...
... The curative effect of watermelon has been attributed to antioxidant compounds [9]. For instance, citrulline is a source of non-essential amino acids abounded in watermelon peels and has an antioxidant effect that protects against free-radical damage [10]. Due to the high amount of pectin and fiber, the watermelon peel is considered a tremendous prebiotic source [11]. ...
... Then, the tubes were incubated at 37 °C for up to 40 h. During incubation, at each predetermined sampling time (0, 2, 4, 6,8,10,14,16,18,20,22,24,30, and 40 h), one tube was removed from each sample group to determine L. acidophilus and L. plantarum counts and pH measurement. The pH values of the samples were measured at 25 °C with a pH meter (Seven Compact S210, Mettler-Toledo, Zurich, Switzerland) calibrated using pH standards (pH 4.0 and 7.0). ...
Fruit peels have potential as prebiotic sources thanks to their dietary fiber contents. This study aimed to determine the effects of freeze-dried banana (BPP) and watermelon (WPP) peel powders on bile salt resistance, growth kinetics, and survival of Lactobacillus acidophilus and Lactiplantibacillus plantarum. In the presence of 0.5–1% bile salt, L. plantarum counts were 0.52–1.13 log CFU/mL higher in MRS broth added with 5% peel powder than without peel powder. Lactobacillus acidophilus population was 2.47–2.79 log CFU/mL higher in MRS broth added with 5% peel powder than without peel powder in the presence of 0.5% bile salt. Both peel powders did not affect the growth kinetics of L. acidophilus in milk. Conversely, the growth of L. plantarum was promoted in milk supplemented with peel powders and yielded a shorter generation time (P < 0.05). The maximum population density of L. plantarum in milk supplemented with BPP (8.68 log CFU/mL) was higher than in milk without peel powder (7.72 log CFU/mL; P < 0.05). Survival of L. acidophilus improved during storage at 4 °C in milk added with peel powders. The results suggest that BPP and WPP can be functional ingredients in probiotic foods and may be used to improve the growth and survival of probiotic cultures.
... Aroma, an important trait of fruit quality, has received increasing attention in recent years. To date, the aromas of various fresh fruits have been evaluated, including white pear [5], apple [3], watermelon [6], mango [7], melon [8], strawberry [9], peach [10] and tomato [11]. Aroma comprises more than eight classes, including amino acid-derived compounds, phenolic derivatives, esters, terpenoids, alcohols, aldehydes, ketones and Life 2023, 13, 1504 2 of 12 alkenes, of which esters are the most important volatiles of pear fruits [4,12,13]. ...
Aroma is an appreciated fruit property, and volatile flavor plays a key role in determining the perception and acceptability of fruit products by consumers. However, metabolite composition that contributes to the aroma in fruit quality is unclear. In this study, we detected 645 volatile organic compounds of ‘Panguxiang’ pear in total, including esters, alcohols, alkanes, acids, ketones, terpenes and aldehydes. In addition, the levels of sugars, organic acids and amino acids in ‘Panguxiang’ pear were investigated using high-performance liquid chromatography. In the aroma generation, glucose was the dominant sugar, followed by sucrose and fructose. At the development transferred storage stage, organic acids may not participate in aroma biosynthesis. The amino acids that may play potential roles in aroma substance synthesis are tyrosine and glycine. Through metabolomics analysis at different stages of ‘Panguxiang’ pear, we selected 65 key metabolites that were significantly related to glucose, sucrose, fructose, tyrosine and glycine, according to the trends of metabolite concentrations. Finally, we chose eight candidate metabolites (e.g., three esters, two aldehydes, one alcohol, one acid and one ketone) as the representative aroma substances of the ‘Panguxiang’ pear compared to the metabolome of the ‘Korla’ at stage Z5. Data and results from this study can help better understand the variations in aroma quality among pear varieties and assist in developing breeding programs for pear varieties.
... Studies pointed out that many of the important fruit aroma volatiles come from the degradation of carotenoid pigments [10]. Norisoprenoids are compounds with specific flavors produced by the degradation of carotenoids and have a low olfactory threshold. ...
Mango juice (MJ) was co-inoculated with Lactobacillus plantarum + Rhodotorula glutinis or Metschnikowia pulcherrima (LP + RG or LP + MP, respectively) and Lactobacillus casei + Rhodotorula glutinis or Metschnikowia pulcherrima (LC + RG or LC + MP, respectively) to evaluate their effect on the physicochemical characteristics, antioxidant capacity, and aroma compounds of MJ after 72 h of fermentation at 28 °C. Results indicated that among the fermented MJ, that which was fermented with LC + RG yielded the highest content of total acid (15.05 g/L). The pH values of MJ fermented with LC + MP, LC + RG, LP + RG, and LP + MP were 3.36, 3.33, 3.26, and 3.19, respectively, and were lower than that of CK (4.79). The juice fermented with LP + MP culture had the lowest sugar content (73.52 g/L), and those fermented with LP + RG and LP + MP had higher total phenol contents and stronger DPPH radical scavenging activity, ABTS radical scavenging activity, iron-reducing antioxidant capacity, and copper reducing antioxidant capacity than the others. Carotenoids in MJ had varying degrees of degradation after mixed fermentation by using all four combinations. Volatile compounds revealed that the co-fermentation of LP + RG produced increased norisoprenoid aroma compounds. The mixed co-inoculation method is a strategy to contemplate for MJ fermentation, but the modalities of inoculation need further investigation. Success depends on the suitable combination of non-Saccharomyces and lactic acid bacteria and consideration of strain variation.
