**3. Tomato physical properties**

and ascorbic acid amount in tomatoes within their ripening vary greatly; some authors say that tomato ascorbic acid levels increase rapidly throughout ripening [33], while others report

that there were no significant differences [56].

54 Plants for the Future

**Figure 8.** Amount of lycopene in different cultivars at different tomato ripening stages.

**Figure 9.** Amount of β-carotene in different cultivars at different tomato ripening stages.

Studies have shown that amounts of ascorbic acid (Fig. 10) and total sugars (Fig. 11) throughout tomato ripening increased in some investigated cultivars, while in others decreased. In fully ripened tomato fruits, the average amount of ascorbic acid varies from 10 to 20 mg 100 g-1. However, some scientists note that the average amount of ascorbic acid is 25 mg 100 g-1 in fresh tomatoes [57]. According to this study, it was found that ascorbic acid increased rapidly within tomato ripening only in cv. 'Vilina' fruits and the highest amount of ascorbic acid was accumulated in fully ripe tomatoes and reached 20.4 mg 100 g-1. Throughout the ripening period of tomatoes, there were no trends found of ascorbic acid accumulation in other cultivars. The lowest levels of ascorbic (in all ripening stages) were found in cv. 'Milžinai and varied from 3.8 to 4.2 mg 100 g-1. It is possible to make a conclusion that the amount of ascorbic acid mainly depends on tomato genotype and lees influenced by fruit ripening stage. Thus, the

In additional to chemical composition, texture and fruit colour are also very important quality attributes of fruit vegetables. Firmness is related to the susceptibility of fruit to physical damage within harvest and storage. For fresh tomatoes, the two quality attributes—texture and skin colour—are very important to buyers and consumers. Texture is influenced by flesh firmness and skin strength. The degree of fruit firmness has been used as an indication of fruit quality, and firmness may be the final index by which the consumers decide to purchase a given batch of tomatoes [14, 58, 59]. Therefore, fruit firmness and colour are the main elements for external tomato quality evaluation. According to provisions, All marketable tomatoes should have firmness over 1.45 N mm−1, but the means of fruits for home use should be higher 1.28 N mm−1 [60]. Thus, there are two possible minimum limits for tomato fruit firmness considering to market regulations and for home use. Previous investigations have shown that the growing system affected fruit firmness, but only in some tomato cultivars [48].

#### **3.1. Fruit physical properties of organic tomato**

Experimental evidence (Fig. 12) has indicated that higher tomato fruit skin and flesh firmness were found in hybrids grown conventionally [44]. Conventional tomato fruits of hybrid 'Benito' had significant stronger skin (294.3 N cm-2) and flesh (53.8 N cm-2) firmness, meanwhile organic fruits skin firmness reached 273.1 N cm-2 and flesh firmness—41.5 N cm-2. There were no significant differences found in tomato cv. 'Vilina' skin and flesh firmness between organic and conventional fruits, but skin and flesh firmness of organic tomato fruits was slightly stronger. Average data of fruit firmness showed that conventional tomato fruits had stronger skin and flesh compared with organic ones, but difference was not significant.

**Figure 12.** The influence of farming systems on tomato fruit skin and flesh firmness.

People identification of colours is sufficiently complex where sensations like brightness, intensity, lightness, and others modify the perception of the primary colours (red, blue, and yellow) and their combinations, meaning that in many ways colour definition is a matter of subjective interpretation. Colour scale gives measurements of colour in units of approximately visual uniformity across the colour solid. According to the Hunter scale, lightness measured by value *L*\* and varies from 100 for perfect white to 0 for black, approximately as the human eye would appreciate it. Value *a*\* measures greyness when zero, greenness when negative, and redness when positive; value *b*\* measures greyness when zero, blueness when negative, and yellowness when positive. *C* indicates colour pureness, and *h*° indicates colour tone [61].

Colour development in tomato fruits is temperature sensitive with better plastid conversion occurring above 12°C and below 30°C [62]. Scientists found that index *b*\* suffered big changes if tomatoes were ripened to high temperatures (over 30°C) and yellowing took place due to the inhibition of lycopene synthesis and the accumulation of yellow/orange carotenoids. Otherwise, at low temperatures (below 12°C), chlorophyll is not degraded and lycopene accumulation does not start. This could be related to abnormal ripening conditions; changes in the *b*\* values may compensate *a*\* magnitudes, depending on their mathematical relationship, leading to misleading results [14, 63]. According to average data of colour indexes (Table 1), it was established significant increase in tomato fruit colour tone (by 4.78 U) and pureness (by 2.46 U) in conventional tomato, meanwhile organic tomato fruits distinguished with signifi‐ cant higher value of colour index *a*\* (redness) by 4.18 U. There were no significant differences found in colour index *b*\* and chroma (*C*) values between organic and conventional tomato fruits.


**Table 1.** Farming systems influence on colour indexes in tomato fruits

should have firmness over 1.45 N mm−1, but the means of fruits for home use should be higher 1.28 N mm−1 [60]. Thus, there are two possible minimum limits for tomato fruit firmness considering to market regulations and for home use. Previous investigations have shown that

Experimental evidence (Fig. 12) has indicated that higher tomato fruit skin and flesh firmness were found in hybrids grown conventionally [44]. Conventional tomato fruits of hybrid 'Benito' had significant stronger skin (294.3 N cm-2) and flesh (53.8 N cm-2) firmness, meanwhile organic fruits skin firmness reached 273.1 N cm-2 and flesh firmness—41.5 N cm-2. There were no significant differences found in tomato cv. 'Vilina' skin and flesh firmness between organic and conventional fruits, but skin and flesh firmness of organic tomato fruits was slightly stronger. Average data of fruit firmness showed that conventional tomato fruits had stronger

the growing system affected fruit firmness, but only in some tomato cultivars [48].

skin and flesh compared with organic ones, but difference was not significant.

**Figure 12.** The influence of farming systems on tomato fruit skin and flesh firmness.

People identification of colours is sufficiently complex where sensations like brightness, intensity, lightness, and others modify the perception of the primary colours (red, blue, and yellow) and their combinations, meaning that in many ways colour definition is a matter of subjective interpretation. Colour scale gives measurements of colour in units of approximately visual uniformity across the colour solid. According to the Hunter scale, lightness measured by value *L*\* and varies from 100 for perfect white to 0 for black, approximately as the human eye would appreciate it. Value *a*\* measures greyness when zero, greenness when negative, and redness when positive; value *b*\* measures greyness when zero, blueness when negative, and yellowness when positive. *C* indicates colour pureness, and *h*° indicates colour tone [61].

Colour development in tomato fruits is temperature sensitive with better plastid conversion occurring above 12°C and below 30°C [62]. Scientists found that index *b*\* suffered big changes

**3.1. Fruit physical properties of organic tomato**

56 Plants for the Future

#### **3.2. Tomato fruit colour and firmness changes during ripening**

Tomato fruit ripening provides positive and negative features to the final product. Even if ripening provides desired taste, texture and colour, considerable costs, and harvest losses result from negative ripening features. The increase of fruit pathogen susceptibility related with ripening is a main factor to production losses before and after harvest. This change is genetically regulated fruit physiology, and it necessitates use of various fumigants and pesticides in attempts to minimise losses. In addition to being potentially harmful and wasteful of energy and to the environment, such practices represent main costs in agricultural output. Eventually, ripening imparts abundant nutritional and quality parameters upon a very important component of the human diet, fruit [1, 64, 65].

One of the most important parameter of all complex attributes of fruit quality is fruit colours. The complexity of tomato fruit colour is subject of both environmental and genetic regulation due to the presence of a various carotenoid pigment system with appearance conditioned by pigment types and quantity [30].

Tomato fruits are generally consumed at their last ripening stage, which appears when fruit reach the full red colour but before it softening. Thus, it is possible to say that tomato colour is one of the most important external parameter to appreciate ripeness level and postharvest life and is a main contributor in the final consumer's purchase [49, 50, 66].

Thompson and coworkers [67] compared the colour measurements of tomato fruits (meas‐ urements were taken at fruit equatorial) with the homogeneous ones from the same region and reported that the hue (*h*<sup>o</sup> ) of homogeneous tomatoes was a better indicator for lycopene content than fruit surface hue. The earlier colorimetric investigation showed that the ratio between the chromatic coordinates (*a*\*/*b*\*) separated better than the tomato colour index in the fruits of the different varieties as a function of their external colour [49, 60, 68].

The study of tomato fruit colour changes during ripening [69, 70] revealed that colour index *L* has a tendency to decline (Table 2) from 49.5 till 44.7 (after 10 days) in tomato fruits during ripening on vine. The polynomial trendline of fruit ripening time and colour index *L* revealed that the determination coefficient (*R*<sup>2</sup> ) was 0.9504.


**Table 2.** Tomato fruit colour changes during ripening on vine

At the beginning of tomato ripening, colour index *a*\* was negative. Positive value of index *a*\* was detected only on the 6th day of experiment. Hence, colour index *a*\* has a tendency to increase during tomato ripening and that was expressed by a polynomial trendline where the coefficient of determination (*R*<sup>2</sup> ) reached 0.9592. Colour index *b*\* has distinguished on the 6th day when reached 31.9 value, but there were no significant differences between the rest measurements. A significant increase in chroma value (*C*) on the 6th day was established, and it reached 34.0. The comparison of the rest measurements showed that chroma had varied in small range, and there were no big differences. The experiment showed that hue angle has a tendency to decline during tomato fruit ripening on vine from 96.80 to 66.92, and it was expressed by polynomial trendline where the coefficient of determination (*R*<sup>2</sup> ) reached 0.9739. Previous studies showed that tomato fruit lightness (*L*\*), at different ripening stage, varied from 42.3 to 50.7, chroma (C\*)—from 32.5 ('Brooklyn H') to 44.1 ('Benito H'), colour index *b*\* (yellowness)—from 28.8 ('Rutuliai') to 36.5 ('Benito H'), colour index *a*\* (redness)—from 12.9 ('Brooklyn H') to 26.1 ('Tolstoi H'), and hue angle (*h*<sup>o</sup> )—from 49.3 ('Tolstoi H') to 66.6 ('Brooklyn H') [70].

Maturation of tomato fruits continues after their harvest, so they may quickly overripe, which affects fruit quality and reduce their realisation time. The quality of tomato texture is deter‐ mined by tomato skin and flesh firmness and their relationship. Tomato fruit firmness is strongly correlated with fruit quality parameters (colour, shape, appearance, etc.). Fruit firmness is used as a parameter in determining the quality of tomatoes. The hardness of the fruit can be a crucial factor to the consumer choice. The transportability of fruit is very important factor because the stronger fruits are less vulnerable to harvesting, sorting, pack‐ aging, and transporting production [71]. The assessment of data showed that the skin (Fig. 13) and fruit flesh (Fig. 14) firmness value of tomato fruits went down throughout ripening period.

**Figure 13.** Fruit skin firmness of different cultivars at different tomato ripening stages.

is one of the most important external parameter to appreciate ripeness level and postharvest

Thompson and coworkers [67] compared the colour measurements of tomato fruits (meas‐ urements were taken at fruit equatorial) with the homogeneous ones from the same region

content than fruit surface hue. The earlier colorimetric investigation showed that the ratio between the chromatic coordinates (*a*\*/*b*\*) separated better than the tomato colour index in the

The study of tomato fruit colour changes during ripening [69, 70] revealed that colour index *L* has a tendency to decline (Table 2) from 49.5 till 44.7 (after 10 days) in tomato fruits during ripening on vine. The polynomial trendline of fruit ripening time and colour index *L* revealed

) was 0.9504.

**Period (days)** *L a\* b\* C ho*

0 49.65 ±2.11 -3.23 ±4.16 27.54 ±1.06 27.99 ±0.98 96.67 ±4.57 2 49.50 ±2.57 -3.42 ±4.29 27.39 ±1.95 27.87 ±2.02 96.87 ±4.94 4 49.58 ±2.38 -0.87 ±8.88 26.92 ±1.35 28.05 ±2.57 92.75 ±6.99 6 48.12 ±3.66 5.41 ±11.62 31.85 ±2.84 34 ±2.82 81.25 ±5.21 8 45.52 ±3.02 7.43 ±10.26 24.54 ±1.95 27.29 ±2.08 74.53 ±6.42 10 44.68 ±3.52 11.2 ±11.55 24.13 ±1.99 28.61 ±2.20 66.92 ±5.38

At the beginning of tomato ripening, colour index *a*\* was negative. Positive value of index *a*\* was detected only on the 6th day of experiment. Hence, colour index *a*\* has a tendency to increase during tomato ripening and that was expressed by a polynomial trendline where the

day when reached 31.9 value, but there were no significant differences between the rest measurements. A significant increase in chroma value (*C*) on the 6th day was established, and it reached 34.0. The comparison of the rest measurements showed that chroma had varied in small range, and there were no big differences. The experiment showed that hue angle has a tendency to decline during tomato fruit ripening on vine from 96.80 to 66.92, and it was

Previous studies showed that tomato fruit lightness (*L*\*), at different ripening stage, varied from 42.3 to 50.7, chroma (C\*)—from 32.5 ('Brooklyn H') to 44.1 ('Benito H'), colour index *b*\* (yellowness)—from 28.8 ('Rutuliai') to 36.5 ('Benito H'), colour index *a*\* (redness)—from 12.9

Maturation of tomato fruits continues after their harvest, so they may quickly overripe, which affects fruit quality and reduce their realisation time. The quality of tomato texture is deter‐ mined by tomato skin and flesh firmness and their relationship. Tomato fruit firmness is

expressed by polynomial trendline where the coefficient of determination (*R*<sup>2</sup>

) of homogeneous tomatoes was a better indicator for lycopene

) reached 0.9592. Colour index *b*\* has distinguished on the 6th

) reached 0.9739.

)—from 49.3 ('Tolstoi H') to 66.6 ('Brooklyn

life and is a main contributor in the final consumer's purchase [49, 50, 66].

fruits of the different varieties as a function of their external colour [49, 60, 68].

and reported that the hue (*h*<sup>o</sup>

58 Plants for the Future

that the determination coefficient (*R*<sup>2</sup>

**Table 2.** Tomato fruit colour changes during ripening on vine

('Brooklyn H') to 26.1 ('Tolstoi H'), and hue angle (*h*<sup>o</sup>

coefficient of determination (*R*<sup>2</sup>

H') [70].

Fruit skin firmness varied from 109 N cm-2 in fully ripened tomatoes (cv. 'Milžinai') to 303 N cm-2 in green fruits of the cv. 'Aušriai'. Tomato flesh firmness varied from 6.0 N cm-2 (fully ripened cv. 'Vilina') to 68.0 N cm-2 (green tomatoes cv. 'Milžinai'). The comparison of fully ripened tomatoes revealed that fruits of cv. 'Vėža' had the strongest skin and fruits of cv. 'Aušriai' had the strongest flesh. A significant increase of tomato flesh firmness between the III and the IV ripening stages in 'Skariai' fruits was also found.

**Figure 14.** Tomato flesh firmness in different tomato cultivars at different ripening stages.
