Cherry tomato goodies

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Hi All,

It seems that cherry tomatoes are healthy and that the storage conditions

matter.

Storing at not refrigerated temperatures for 1-3 weeks may be beneficial.

We have two cherry tomato plants in front of the house, and a larger number of

mostly common variety tomatoes and some plum tomatoes at the house. The cherry

tomatoes are too flavorful not cooked, but the other tomatoes are cooked to

derive

maximal benefits from the lycopene that the tomatoes are noted for. Other

goodies

are also in the tomatoes, some at higher levels than that of lycopene.

As an introduction to the value of vine-ripened cherry tomatoes, here is the

Medline

citation and abstract for the first of two pdf-available papers.

J Agric Food Chem. 2005 Apr 20;53(8):3114-9.

Seasonal variations in the level of plant constituents in greenhouse production

of

cherry tomatoes.

Slimestad R, Verheul MJ.

The content of selected plant constituents was measured in cherry tomatoes

(Lycopersicon esculentumMill. cv. Jennita) during conventional Norwegian tomato

production in a greenhouse from May until October 2004. Samples were collected

according to standard production procedure with orange-yellow colored fruits at

weight in the range of 12.4-19.3 g and size in the range of 28.9-33.0 mm

(diameter).

The content of selected compounds based on 100 g FW were found to vary in the

following range during the season: 7.38-28.38 mg of chalconaringenin, 0.32-0.92

mg

of rutin, 0.24-1.06 mg of chlorogenic acid, 5.60-20.02 mg of ascorbic acid,

1.60-5.54 mg of lycopene, and 0.37-0.55 mg beta-carotene. Only minute amounts of

naringenin together with kaempferol 3-rutinoside and caffeic acid, which

previously

have been reported from tomatoes, were detected. The content of chalconaringenin

to

rutin and that of lycopene to beta-carotene showed a strong correlation during

the

season (p < 0.001). The content of total phenolics and methanol-soluble

antioxidants

also showed a correlation (p < 0.001), and were found in the range 14.6-32.6 mg

of

gallic acid equivalents (GAE)/100 g fresh weight (FW) and 445-737 micromol of

Fe(II)/100 g FW, respectively. Seasonal variation in the level of plant

constituents

is shown to be related to photon flux density and fertilization level.

PMID: 15826067

Now, here is next a not in Medline yet paper that details the levels of and

increases or decreases of the beneficial minor nutrients of cherry tomatoes at

4°C,

12°C and 20°C for 0, 1, 2 and 3 weeks.

Content of Chalconaringenin and Chlorogenic Acid in Cherry Tomatoes Is Strongly

Reduced during Postharvest Ripening

Rune Slimestad and Michèl J. Verheul

http://dx.doi.org/10.1021/jf050737d

Abstract:

The contents of chalconaringenin, chlorogenic acid, rutin, ascorbic acid,

lycopene,

and -carotene were analyzed during postharvest and vine ripening of cherry

tomatoes

(Lycopersicon esculentum Mill.) (cv. Jennita) produced in a greenhouse. A

remarkable

decrease in the content of chalconaringenin took place during postharvest

ripening.

The tomatoes were found to contain 15.26 mg 100 g-1 fresh weight (FW) at harvest

but

held only 0.41 mg after 3 weeks at 20 C in darkness. Chalconaringenin did not

convert into naringenin. The content of chlorogenic acid fell from 0.51 to 0.06

mg

100 g-1 FW at the same conditions. The content of rutin and that of total

phenolics

remained stable during postharvest ripening. The amounts of lycopene as well as

-carotene and ascorbic acid increased during postharvest ripening. No

significant

change in the amount of methanol soluble antioxidants or total soluble solids

was

found during postharvest ripening of the tomato fruits. During vine ripening,

the

total amount of phenolics and that of soluble solids (% Brix) increased. The

content

of phenolics correlated well with the content of methanol soluble antioxidants

(p <

0.001). The amount of ascorbic acid increased from 9.7 mg in green-yellow

tomatoes

to 17.1 mg 100 g-1 FW in red tomatoes. The amount of chalconaringenin decreased

to

8.16 mg 100 g-1 FW, whereas no significant change was observed for chlorogenic

acid

or rutin. Possible causes for the decrease in chalconaringenin are discussed.

Introduction

Tomatoes constitute the predominant source of lycopene in most diets, and this

compound has been associated with a range of health benefits (1, 2). Tomatoes

also

contain lower amounts of other carotenoids such as -carotene, which is known for

its

provitamin A activity (3). Consumption of tomatoes and tomato products has thus

been

considered as a nutritional indicator of good dietary habits and healthy life

styles. The carotenoids in tomatoes are also key precursors for nor-isoprenoid

aroma

compounds such as -ionone and geranylacetone (4).

In addition to the particular interest in lycopene, an awareness of other more

or

less well-known tomato constituents has emerged in recent years. Ascorbic acid

is

important in the protection of the tomato itself against oxidative damage that

might

increase with ripening due to enhanced respiration. This maintains firmness and

improves shelf life of the fruit. During the last two decades, several papers

have

reported on the presence of flavonoids in tomatoes (2). This group of

polyphenols,

which comprises a variety of chemical structures with subtle biological

properties,

is in general important in conferring antioxidative benefits (5). Several

flavonoids

have been identified from different tomato varieties. Most of these structures

belong to the flavonols, and the most predominant compound is quercetin

3-rutinoside

(rutin) (Figure 1). The average amount of rutin and other quercetin compounds

has

been estimated to be 8 mg kg-1 FW relative to quercetin aglycone (6). Some few

papers report on chalconaringenin (Figure 1) as the main flavonoid compound in

fresh

tomatoes (7, 8). Chalconaringenin has recently been found to be the predominant

phenolic compound in cherry tomato (cv. Jennita) (9). This compound is unstable

and

is easily converted to naringenin. It is therefore interesting that several

papers

report on naringenin and in some cases prunin (naringenin 7-glucoside) as main

phenolic constituents in fresh tomatoes (10, 11). Chalconaringenin from tomato

extracts has been found to inhibit histamine release in an in vitro assay. This

may

indicate that such extracts can reduce allergic reactions (12).

Some phenolics (chlorogenic acid and rutin) have been suggested as regulants of

auxin (like indole 3-acetic acid) metabolism (13). The production of

photoprotective

compounds such as flavonols in the skins of tomato fruits may afford protection

against UV-B-induced oxidative damage (14).

Cherry tomatoes are small, tasty tomatoes that on average contain a higher

amount of

lycopene than traditional tomatoes. The taste advantage is primarily connected

to

their high content of soluble solids (sugars) and titrable acidity (1). Some

varieties have also been found to contain high amounts of flavonols, primarily

as

quercetin (15). This observation has been used to develop genetically modified

cherry tomatoes with an extraordinary high level of flavonols because of the

potential health benefits of these compounds (8, 16).

This work is part of a project where the overall aim is to develop a strategy

for a

non-GMO greenhouse grown tomato to achieve a documented minimal level of certain

plant compounds (lycopene, -carotene, ascorbic acid, specific flavonoids, and

chlorogenic acid). Seasonal variations in the level of plant constituents in

greenhouse production of cherry tomatoes, harvested at an orange-yellow stage of

ripening and analyzed immediately after harvest, were described earlier (9). The

present work reports on the variations in content of specific plant compounds

during

postharvest and vine ripening. This information will be used to establish

agronomic

efforts and postharvest management in order to increase or maintain the content

of

specific compounds in the fruits above a certain minimal level.

.... Table 1. Content of Plant Constituents and Physical Properties of Cherry

Tomatoes during Postharvest and Vine Ripening a

...................................................

treatment weight (g) size (mm) °Brix phenolics FRAP ascorbic acid chlorogenic

acid

rutin chalconaringenin trans-lycopene cis-lycopene -carotene

none 17.3±2.6 31.7±1.9 7.6±0.5 21.5±7.5 583±134 13.0±3.7 0.51±0.37 0.56±0.12

15.26±8.33 2.89±1.57 0.05±0.23 0.44±0.08

4°C, 1w 15.7±3.6 30.7±2.0 7.3±0.9 25.2±8.5 813±151 12.6±5.1 0.56±0.22 0.48±0.10

16.50±5.25 2.27±1.82 0.00±0.02 0.44±0.09

4°C, 2w 17.1±2.2 31.9±2.0 7.7±0.6 22.0±2.9 654±92 12.0±4.1 0.51±0.15 0.46±0.09

11.44±2.97 2.83±0.79 0.00±0.10 0.48±0.05

4°C, 3w 15.8±3.2 31.7±2.7 7.7±0.5 22.9±2.8 603±201 20.4±4.0 0.36±0.06 0.51±0.17

9.81±3.02 2.85±0.92 0.02±0.17 0.41±0.06

12°C, 1w 16.4±3.4 31.8±2.4 7.6±0.5 19.8±2.5 640±99 10.7±4.3 0.43±0.09 0.45±0.07

9.03±1.59 3.18±1.38 0.30±0.32 0.57±0.12

12°C, 2w 16.4±3.0 32.1±2.2 7.7±1.0 19.4±4.3 617±118 13.4±3.7 0.23±0.10 0.43±0.12

4.61±0.93 8.01±3.10 1.34±0.39 0.75±0.15

12°C, 3w 15.5±2.6 30.6±1.8 7.7±0.8 20.2±1.6 610±41 19.1±4.5 0.11±0.08 0.48±0.17

3.66±0.82 11.66±3.57 2.01±0.66 0.91±0.26

20°C, 1w 16.0±2.7 30.1±2.3 7.6±0.4 18.1±3.0 681±255 13.3±6.1 0.32±0.09 0.42±0.14

2.26±0.59 9.08±4.50 1.84±1.02 0.57±0.17

20°C, 2w 15.9±3.8 30.6±1.8 7.7±0.8 19.6±4.2 558±227 14.3±3.8 0.10±0.05 0.36±0.10

0.53±0.19 14.52±6.02 2.51±0.58 0.55±0.11

20°C, 3w 16.1±3.4 30.8±2.0 7.1±0.9 20.5±1.1 614±67 18.6±8.8 0.06±0.01 0.36±0.15

0.41±0.22 17.62±3.81 3.09±1.58 0.56±0.12

T NS NS NS ** NS NS *** ** *** *** *** ***

S NS NS NS NS ** *** *** ** *** *** *** ***

T ´ S NS NS NS NS NS NS NS NS NS *** ** ***

II 14.8±2.5 30.0±2.2 6.1±0.9 18.3±4.9 513±105 9.7±2.5 0.53±0.18 0.63±0.16

11.25±5.94

0.08±0.31 0.00±0.01 0.35±0.16

IV 17.3±2.6 31.7±1.9 7.6±0.5 21.5±7.5 583±134 13.0±3.7 0.51±0.37 0.56±0.12

15.26±8.33 2.89±1.57 0.05±0.23 0.44±0.08

VI 14.7±4.4 30.1±3.0 9.3±0.9 25.3±5.9 670±107 17.1±3.7 0.63±0.31 0.68±0.18

8.16±2.21

13.20±2.89 1.06±1.07 0.70±0.10

RS * NS *** * * *** NS NS * *** *** ***

.........................................

a The contents of specific compounds are listed as total amount in mg/100 g

FW±SD,

phenolics are given as mg GAE /100 g FW, and FRAP values are given as ímol

Fe II /100 g FW. For postharvest ripening of fruits harvested at stage IV

(orange-yellow), the storage temperature (T) is given in °C, and the storage

duration (S) is given

in weeks; for vine ripening, ripening stage (RS) is given as stage II

(green-yellow), IV, and VI (red) of seven stages of ripeness. Significance of

differences between

treatments is given: NS, not significant; * P < 0.05; ** P < 0.01; and *** P <

0.001.

.... Results and Discussion

Chalconarengenin was found to be the main phenolic compound found in freshly

picked

cherry tomatoes (cv. Jennita). The average amount of chalconarengenin in fruits

picked on three harvesting dates at standard ripening stage (IV) was found to be

15.26 mg 100 g-1 FW (Table 1). The amount varies during the growing season (9).

The

content of chalconaringenin decreased dramatically during postharvest ripening

to a

minimum of 0.41 mg 100 g-1 FW after 3 weeks of storage at 20 C (Table 1). On

average

for all storage temperatures, the chalconaringenin content decreased with 39,

64,

and 70% after, respectively, 1, 2, and 3 weeks of storage (Figure 2a). The loss

of

chalconaringenin was more pronounced at higher temperature. Storage temperatures

of

4, 12, or 20 C lowered the chalconarengenin content with 18, 62, and 93%,

respectively (Figure 2b). No interaction was found between storage time, storage

temperature, and harvesting date for chalconaringenin. To maintain a high amount

of

chalconarengenin in the fruits, a storage temperature of 4 C for less than 2

weeks

should be used. In vine-ripened cherry tomatoes (stage VI), the content of

chalconaringenin fell from 15.26 to 8.16 mg 100 g-1. Because vine ripening from

standard to red in a greenhouse at 20 C normally endures 2-3 days, the loss in

content is comparable to the decrease found in postharvest-ripened fruits at 20

C.

Only a limited number of reports describe chalconaringenin as the main flavonoid

in

tomatoes. The compound has been found to accumulate in peel tissue. It was also

found that the chalconaringenin production occurred simultaneously with color

formation of the fruit (7, 8). Our observations do not support this

development-dependent approach (Table 1). A reasonable explanation of the

disappearance of chalconaringenin during ripening would be its conversion into

naringenin, which has been reported to be one of the main phenolic compounds

present

in tomatoes (10, 11). However, no evidence was found for this conversion here.

Naringenin was detected only as a minor compound in all of the samples, which

was

similar to the level detected during the whole growing season (9). The amount of

chlorogenic acid was far below that of chalconaringenin (Table 1). The two

compounds

showed, however, a similar metabolic turnover during postharvest ripening with a

decrease in level as a function of time and temperature (Figure 2).

After 3 weeks of postharvest storage, the content of chlorogenic acid at overall

temperature was found to be 35% as compared to that found in the freshly sampled

cherry tomatoes. The loss was greatest at the highest temperature. During vine

ripening, no significant change in the content of chlorogenic acid was observed.

The

metabolic turnover of chalconaringenin and chlorogenic acid during postharvest

ripening has not been described previously. However, the highest content of

chlorogenic acid has elsewhere been found at early stages of tomato development

followed by a decrease during vine ripening (25).

As compared to the metabolic change that was detected for chalconaringenin and

chlorogenic acid, the total amount of phenolics did not decrease during

postharvest

ripening of the tomatoes (Figure 2). This content was found to be stable with a

mean

value at 21.0 mg GAE 100 g-1. During vine ripening, the amount rose from 18.3 mg

100

g-1 in green fruit to 21.5 and 25.3 mg 100 g-1 in standard ripened and red

fruits,

respectively.

As the amount of total phenolics was found to be relatively constant during

ripening, the imbalance between the phenolic level and the decrease in content

of

chalconaringenin and chlorogenic acid during ripening has to be made up by other

compounds. Rutin has been the far most highlighted flavonoid in tomatoes due to

its

antioxidant properties and bioavailability to humans. No development-dependent

production of rutin in the cherry tomatoes seems to take place from the green to

the

red ripening stages. Rutin has been reported to be the most important flavonoid

in

tomatoes. Favorita, a red cherry tomato, contains 2.15 mg 100-1 g whereas other

varieties are reported to contain from 0.13 to 2.22 mg 100-1 g of total

flavonols

(26). The chemical constituents in tomatoes are often reported with limited

information about the growth conditions of the plant. However, most of the

tomato

production in the world takes place in open fields. It is therefore assumed that

the

tomatoes that are subjects of most inspections on chemical composition have been

grown in open fields if no other information has been given. Direct exposure to

sun,

with higher levels of UV-B, might explain the high flavonol content (27).

However,

in the present investigation, the amount of rutin was found to be stable during

ripening, and an overall amount was found to be 0.63 mg 100 g-1 in green through

red

cherry tomatoes during vine ripening. The amount of rutin was too low to explain

the

high amount of phenolics still present after the reduction in content of

chalconaringenin and chlorogenic acid. A previous investigation has also

reported

that during tomato vine ripening chlorogenic acid declined whereas no changes

were

observed in rutin (28). The variation in the total content of phenolics has

previously been evaluated during vine and postharvest ripening of tomato cv.

Moneymaker grown in a greenhouse. The total phenolic content was found to be

higher

in postharvest-ripened samples (about 10-20 mg 100-1 g) than in vine-ripened

fruit

(about 7-11 mg 100-1 g) (29). The present data of the cherry tomatoes gave 20.0

and

25.3 mg GAE 100-1 g in postharvest- and vine-ripened fruits, respectively.

Beside

the higher amount of phenolics in this variety, the effect of ripening is

opposite

of that found in Moneymaker.

Ascorbic acid increased in content during tomato ripening and reached maximum

levels

in red fruits (Table 1). The amounts detected in postharvest- and vine-ripened

red

tomatoes were on the same level. In one of the most popular cherry tomato

cultivars,

Favorita, the amount was found to be 18.3 mg 100-1 g (30). The content of

ascorbic

acid has elsewhere been found to decrease during ripening. This decrease has

been

linked to its antioxidant role when the ripening cells absorb higher amounts of

oxygen, a result of an increase in respiration, which is characteristic of

climacteric fruits (31). However, this pattern of ascorbic acid content is

opposite

to our results for postharvest ripening (Figure 3). One reason for this

divergence

is probably the reduced light exposure in our experiment. Another reason may

perhaps

be found in the level of other compounds within the cell vacuoles due to

interaction

between ascorbic acid and for example flavonoids. It is known that flavonoids

seem

to have vitamin C sparing effects and that this phenomenon can be related to

their

antioxidant properties (32). This seems to fit with the present observations: a

raise in the amount of ascorbic acid at the expense of chalconaringenin and

chlorogenic acid. The stable level of the well-known antioxidant rutin may in

this

context be explained by a higher reduction potential than chalconaringenin and

chlorogenic acid. In general, half-cell reduction potentials of flavonoids are

relatively low (0.23 V < E < 0.75 V at pH 7.0) and are therefore

thermodynamically

able to reduce highly oxidizing free radicals (33). Ascorbic acid has a

half-cell

reduction potential at 0.28 V, whereas that of rutin is 0.6 V. No data has been

found for chalconaringenin nor chlorogenic acid. However, it seems that the

difference in redox potential is just one part of complex pattern with respect

to

vitamin C sparing effects (34). It has been found that chalconaringenin acts as

a

prooxidant by increasing the amount of thiobarbituric acid reactive substances

during incubaction of LDL with Cu2+ (35). The present data show that there is a

correlation between chalconaringenin and FRAP values during postharvest ripening

(p

< 0.05) and vine ripening (p < 0.01). Further inspections have to be made to

interpret these results with respect to redox effects of this compound.

Lycopene was continuously produced in all experiments during tomato ripening,

except

at 4 C, and maximum content of the all-trans isomer (17.62 mg 100-1 g FW) was

detected in postharvest-ripened fruits after 3 weeks at 20 C (Figure 4).

Vine-ripened tomatoes were found to contain 13.20 mg 100-1 g all-trans-lycopene

(Table 1). The total tomato lycopene content may range from 4.3 to 18.1 mg 100-1

g

FW, with the most frequent values between 5.5 and 8.0 mg 100-1 g (36). The

amount of

the single cis-lycopene was strongly correlated with the amount of

all-trans-lycopene (p < 0.001), and a maximum of 3.09 mg 100-1 g was detected

after

3 weeks of postharvest ripening at 20 C. The content of -carotene followed a

somewhat different pattern during fruit ripening as compared to that of

lycopene. A

maximum content of 0.91 mg 100-1 g was detected after 3 weeks of storage at 12

C.

Green-yellow tomatoes contained 0.35 mg 100-1 g, which made up half of what was

found in vine-ripened fruits (0.70 mg 100-1 g) (Table 1). Among the carotenoids,

lycopene has been found to be one of the strongest antioxidants (37). However,

we

did not measure antioxidant capacities for fat soluble compounds as part of this

work.

In fruits stored at various temperatures, it has been observed that, at 20 C,

the

biosynthesis and accumulation of phytoene and lycopene were fast, and those of

-carotene were slow (38). By contrast, at 30 C, the biosynthesis and

accumulation of

lycopene and -carotene were fast and phytoene accumulation was slow. In

conclusion,

the formation of lycopene depends on temperature range and seems to occur

between 12

and 32 C (39). When harvested at the pink-ripe stage and stored for ripening, it

was

found that tomato (cv. Sunny) had an optimum lycopene production in the

temperature

range 16-26 C (40). The present results fit these previous reported data with

respect to lycopene accumulation. It also supports the data found for -carotene

at

20 C. It shows, however, that there are two temperature levels that might

stimulate

the accumulation of -carotene, one close to 12 C and one at 30 C.

The content of soluble solids (% Brix) increased during vine ripening and

reached a

level at 9.3 in vine-ripened tomatoes harvested at stage VI. No increase in Brix

value was detected during postharvest ripening (Table 1), and 7.7 was found to

be

the highest value. These results are in accordance with earlier observations

(41),

indicating a sweeter taste of vine-ripened tomatoes.

The sizes of the tomato fruits used in the experiment were not significantly

different. A slightly higher weight was detected for tomatoes harvested at stage

IV

when compared to those harvested at stage II or VI (Table 1).

Tomatoes in Norwegian greenhouses are normally harvested at an early ripening

stage

(IV, orange-yellow) in order to extend shelf life. During transport and storage,

the

fruits become fully red (ripening stage VI). It is assumed that the tomatoes are

consumed 1-3 weeks after harvest. Much of this time, the tomatoes are kept in

dark

or under reduced light conditions. Storage in the dark resulted in a significant

decrease in contents of chalconaringenin and chlorogenic acid. The decrease

correlated with increased temperature. The decrease is less pronounced for

chalconaringenin during vine ripening, and no decrease in content was detected

for

chlorogenic acid upon vine ripening. The level of rutin has been found to be

more or

less constant during both postharvest and vine ripening. The importance of the

changes in chalconaringenin and chlorogenic acid has to be further studied, as

these

constituents are present in cherry tomatoes at higher values than previously

reported.

The time and temperature conditions during postharvest ripening clearly show

that

cherry tomatoes become ripe with respect to color and lycopene content within 1

week

at 20 C or within 2 weeks at 12 C. Postharvest-ripened tomatoes contain the

amount

of -carotene that is normally reported from ripe tomatoes. Ascorbic acid

increased

upon storage at all temperature levels and also during vine ripening.

Postharvest-ripened tomatoes contain similar levels of carotenoids and ascorbic

acid

that are found in vine-ripened cherry tomatoes. The postharvest regimes gave

lower

sugar contents (measured as % Brix) as compared to vine-ripened cherry tomatoes.

Vine ripening combined with a short storage period at lower temperatures might

therefore be a strategy to increase sweetness and to maintain the content of

plant

constituents at a high level.

Al Pater, PhD; email: old542000@...

____________________________________________________

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