**4. Climatic conditions**

Environmental conditions seem to have a major influence on flavor compound formation in strawberry. Watson [19] reported that SSC in strawberry was more dependent on environmental conditions during production than on the genetic makeup of the plant. Furthermore, relating growth conditions to flavor data may allow modeling of plant and fruit responses to the environment and provide a powerful tool to growers and retailers to manipulate fruit quality [19].

Below are environmental factors that affect fruit quality in strawberry.

#### **4.1 Light intensity**

Preharvest conditions such as light intensity can affect strawberry fruit quality and phytonutrient content. Light is required for proper leaf and fruit development and can improve the fruit quality, but light above photosynthetic saturation levels, especially intense exposure, can increase the fruit temperature and may result in fruit damage and a loss of quality [30, 40]. On the other hand, insufficient light typically results in smaller strawberry fruits [41]. In strawberry, low light decreases the surface glossiness of the fruit [41] and reduces color development [11, 38].

Ezell et al. [34] concluded that bright sunny weather favored high ascorbic acid content, while cool, wet weather resulted in low values. This confirms an observation by Wang [12] that strawberries grown at higher light intensity had increased levels of ascorbic acid. Even fruits shaded by foliage or ripened on cloudy days had 10% less ascorbic acid than berries exposed to sun [42], while berries shaded by leaves showed little change between cloudy and sunny days. Ezell et al. [34] also reported that everbearing varieties grown during the long, warm days, and intense light of early June averaged 34% more ascorbic acid than did the same varieties in late September. By shading either or both berries and plants, Hansen and Waldo [43] found that unshaded berries contained 13% more ascorbic acid than did the shaded ones and 68% more than when plants and berries were shaded. Unshaded plants produced higher dry matter in fruits at the expense of leaf growth but not fresh weight implying fruits with lower moisture content [44].

Light intensity, affected firmness, TSS, acidity, and anthocyanins [36]. The effect of shading was not significant for phenolics, but the opposite was observed for anthocyanins. Shading of strawberry plants has also been shown to cause significant reduction in the concentration of flavor compounds (hexenal, hexanal, ethyl methyl butyrate, and methyl butyrate) in fruit [19].

Light also influences anthocyanin synthesis and therefore color formation in fruit [45]. It appears that lower light intensity favors the development of albinism in strawberry with Sharma et al. [38] reporting that strawberry plants grown under low light intensities (shade) tend to produce a higher proportion of albino fruit.

Production methods will affect the amount of light to which a crop is exposed. Solar radiation experienced by crops grown in a polythene tunnel with new plastic may be 10% less than an outdoor crop, and a glasshouse could reduce light levels by 30% or more compared to that of an outdoor crop [46].

**5**

shapen fruit are produced [11].

*The Effect of Preharvest Factors on Fruit and Nutritional Quality in Strawberry*

size, phytonutrient concentrations, flavor, and aroma compounds [47].

sugar, acid) were negatively affected by green color [48].

ing in improved plant growth and fruit quality [49].

different colored filters (green, neutral, yellow, blue, to red light). Fruit color (chroma), ascorbic acid, yield per plant, and fruit size improved with increasing exposure to reddish orange color. All fruit quality parameters measured (e.g., color,

In another study using five different mulch colors (red, blue, yellow, green, black, and silver), red mulch gave results similar or better than black mulch. Silver mulch reduced fresh fruit weight, fruit length and leaf area, while red mulch increased it. Silver mulch also reduced pH, ratio of TSS/TA and fruit dry weight, while black much increased the ratio. It is thought that increased light from the red and far-red spectrum reflected from red mulch is absorbed by phytochromes result-

Plant growth and development is largely affected by temperature. Temperature also affects cellular compounds and their structure, which ultimately affects firmness. Lower temperatures during the growing season increased fruit firmness [36], and growing strawberry under different temperatures (day/night) could also affect antioxidant activity and total flavonoid content. High temperature growing conditions (25/30°C) significantly enhanced antioxidant activity, as well as anthocyanin and total phenolic content [12]. Wang et al. [51] also reported that "Kent" strawberries exposed to warmer nights (18–22°C) and warmer days (25°C) had higher antioxidant activity than berries grown under cool day and night temperatures (18/12°C). In a separate study, Moretti et al. [50] found that high temperature conditions significantly increased flavonoid levels and consequently antioxidant capacity. Ascorbic acid content in strawberries is also highly affected by climate conditions and growing area [12]. Moretti et al. [50] showed that higher day and night temperatures have a direct influence on strawberry fruit color with berries ripened under these conditions being redder and darker.

However, Wang et al. [51] showed that in strawberry, fruit temperatures can exceed air temperatures by as much as 8°C on sunny days. High fruit temperatures could inhibit enzymes, such as sucrose synthetase, which acts on sucrose production. Increased fruit

Freezing temperatures on the other hand can be detrimental to strawberries. A radiative freeze typically occurs under clear skies with calm or light wind, and a relatively high subfreezing temperature or dew point (similar to the conditions that often cause frost). Radiative freeze damage of strawberry often results in smaller fruit, and depending upon the developmental stage when damage occurs, mis-

Although the climate change subject is controversial, its potential impact on agriculture continues to be discussed. However, few studies have considered the

temperatures may also induce a higher transpirational flux within the fruit [51].

**4.4 Climate change and elevated levels of carbon dioxide and ozone**

The color of plastic mulches frequently used in raised-bed culture affects fruit quality. The most commonly used plastic mulch color is black [47]. Berries that ripened over red plastic mulch were about 20% larger, had higher sugar to organic acid ratios, and emitted higher concentrations of favorable aroma compounds. It has been said that the ratio of far red (FR) to red (R) light reflected from the red mulch modified gene expression through plant phytochrome and increased fruit

Strawberry (cv. Toyonoka) fruit color was greatly affected by light quality under

*DOI: http://dx.doi.org/10.5772/intechopen.84619*

**4.2 Light quality**

**4.3 Temperature**

*The Effect of Preharvest Factors on Fruit and Nutritional Quality in Strawberry DOI: http://dx.doi.org/10.5772/intechopen.84619*

#### **4.2 Light quality**

*Strawberry - Pre- and Post-Harvest Management Techniques for Higher Fruit Quality*

can yield high-quality fruit at reasonable cost [29].

**4. Climatic conditions**

**4.1 Light intensity**

high plant production efficiency [29]. Wild species like *F. virginiana* spp. glauca and *F. vesca* are good sources of bioactive compounds. *F. virginiana* spp. glauca is also an important genetic source of nutritional quality and other unique traits such as day neutrality, and plant and disease resistance [29]. Breeding for improved nutritional and fruit quality parameters offers the possibility of new commercial varieties that

Environmental conditions seem to have a major influence on flavor compound formation in strawberry. Watson [19] reported that SSC in strawberry was more dependent on environmental conditions during production than on the genetic makeup of the plant. Furthermore, relating growth conditions to flavor data may allow modeling of plant and fruit responses to the environment and provide a

Preharvest conditions such as light intensity can affect strawberry fruit quality and phytonutrient content. Light is required for proper leaf and fruit development and can improve the fruit quality, but light above photosynthetic saturation levels, especially intense exposure, can increase the fruit temperature and may result in fruit damage and a loss of quality [30, 40]. On the other hand, insufficient light typically results in smaller strawberry fruits [41]. In strawberry, low light decreases the surface glossiness of the fruit [41] and reduces color development [11, 38].

Ezell et al. [34] concluded that bright sunny weather favored high ascorbic acid content, while cool, wet weather resulted in low values. This confirms an observation by Wang [12] that strawberries grown at higher light intensity had increased levels of ascorbic acid. Even fruits shaded by foliage or ripened on cloudy days had 10% less ascorbic acid than berries exposed to sun [42], while berries shaded by leaves showed little change between cloudy and sunny days. Ezell et al. [34] also reported that everbearing varieties grown during the long, warm days, and intense light of early June averaged 34% more ascorbic acid than did the same varieties in late September. By shading either or both berries and plants, Hansen and Waldo [43] found that unshaded berries contained 13% more ascorbic acid than did the shaded ones and 68% more than when plants and berries were shaded. Unshaded plants produced higher dry matter in fruits at the expense of leaf growth but not

Light intensity, affected firmness, TSS, acidity, and anthocyanins [36]. The effect of shading was not significant for phenolics, but the opposite was observed for anthocyanins. Shading of strawberry plants has also been shown to cause significant reduction in the concentration of flavor compounds (hexenal, hexanal,

Light also influences anthocyanin synthesis and therefore color formation in fruit [45]. It appears that lower light intensity favors the development of albinism in strawberry with Sharma et al. [38] reporting that strawberry plants grown under low light intensities (shade) tend to produce a higher proportion of albino fruit. Production methods will affect the amount of light to which a crop is exposed. Solar radiation experienced by crops grown in a polythene tunnel with new plastic may be 10% less than an outdoor crop, and a glasshouse could reduce light levels by

powerful tool to growers and retailers to manipulate fruit quality [19]. Below are environmental factors that affect fruit quality in strawberry.

fresh weight implying fruits with lower moisture content [44].

ethyl methyl butyrate, and methyl butyrate) in fruit [19].

30% or more compared to that of an outdoor crop [46].

**4**

The color of plastic mulches frequently used in raised-bed culture affects fruit quality. The most commonly used plastic mulch color is black [47]. Berries that ripened over red plastic mulch were about 20% larger, had higher sugar to organic acid ratios, and emitted higher concentrations of favorable aroma compounds. It has been said that the ratio of far red (FR) to red (R) light reflected from the red mulch modified gene expression through plant phytochrome and increased fruit size, phytonutrient concentrations, flavor, and aroma compounds [47].

Strawberry (cv. Toyonoka) fruit color was greatly affected by light quality under different colored filters (green, neutral, yellow, blue, to red light). Fruit color (chroma), ascorbic acid, yield per plant, and fruit size improved with increasing exposure to reddish orange color. All fruit quality parameters measured (e.g., color, sugar, acid) were negatively affected by green color [48].

In another study using five different mulch colors (red, blue, yellow, green, black, and silver), red mulch gave results similar or better than black mulch. Silver mulch reduced fresh fruit weight, fruit length and leaf area, while red mulch increased it. Silver mulch also reduced pH, ratio of TSS/TA and fruit dry weight, while black much increased the ratio. It is thought that increased light from the red and far-red spectrum reflected from red mulch is absorbed by phytochromes resulting in improved plant growth and fruit quality [49].

#### **4.3 Temperature**

Plant growth and development is largely affected by temperature. Temperature also affects cellular compounds and their structure, which ultimately affects firmness. Lower temperatures during the growing season increased fruit firmness [36], and growing strawberry under different temperatures (day/night) could also affect antioxidant activity and total flavonoid content. High temperature growing conditions (25/30°C) significantly enhanced antioxidant activity, as well as anthocyanin and total phenolic content [12]. Wang et al. [51] also reported that "Kent" strawberries exposed to warmer nights (18–22°C) and warmer days (25°C) had higher antioxidant activity than berries grown under cool day and night temperatures (18/12°C). In a separate study, Moretti et al. [50] found that high temperature conditions significantly increased flavonoid levels and consequently antioxidant capacity. Ascorbic acid content in strawberries is also highly affected by climate conditions and growing area [12]. Moretti et al. [50] showed that higher day and night temperatures have a direct influence on strawberry fruit color with berries ripened under these conditions being redder and darker.

However, Wang et al. [51] showed that in strawberry, fruit temperatures can exceed air temperatures by as much as 8°C on sunny days. High fruit temperatures could inhibit enzymes, such as sucrose synthetase, which acts on sucrose production. Increased fruit temperatures may also induce a higher transpirational flux within the fruit [51].

Freezing temperatures on the other hand can be detrimental to strawberries. A radiative freeze typically occurs under clear skies with calm or light wind, and a relatively high subfreezing temperature or dew point (similar to the conditions that often cause frost). Radiative freeze damage of strawberry often results in smaller fruit, and depending upon the developmental stage when damage occurs, misshapen fruit are produced [11].

#### **4.4 Climate change and elevated levels of carbon dioxide and ozone**

Although the climate change subject is controversial, its potential impact on agriculture continues to be discussed. However, few studies have considered the potential impact of climate change on fruit and vegetable quality after harvest [52]. Temperature increase and the effects of greenhouse gases are among the most important issues associated with climate change. Beside rising temperatures, climate changes are also a consequence of changes in the composition of gaseous constituents in the atmosphere. Carbon dioxide accumulation in the atmosphere has direct effects on postharvest quality [50].

The highest temperature that strawberry fruit mature normally is 35°C. At high temperatures and elevated CO2 levels, carbohydrates, such as starch and soluble sugars are degraded in the respiration process and the proteins and most minerals decrease. The nutritional quality also decreased due to more phenols and ascorbic acid. However, the effect of temperature is more pronounced than the elevated CO2 levels [52].

Elevated CO2 levels in storage slightly increased dehydroascorbic acid and firmness, prevented ascorbic acid reduction, and reduced anthocyanin, flavonoids, antioxidant activity and total phenolic compounds [53]. In contrast, increased CO2 concentrations in the growing atmosphere (300 and 600 μmolmol<sup>−</sup><sup>1</sup> above ambient) resulted in increased anthocyanin and phenolic and ascorbic acid content [54]. Siriphanich [55] also reported increased firmness in strawberry treated with CO2. Cell wall analysis showed lower water-soluble pectin and higher chelating soluble pectin in CO2-treated strawberries. The mechanism of firmness enhancement by CO2 was possibly due to changes in intercellular pH and its solute composition.

The influence of ozone on strawberry depends significantly on cultivar and susceptibility to oxidative stress. The effect of ozone on vitamin C content is variable in the reviewed articles and mostly cultivar dependent. In "Korona" and "Elsanta" tested by Keutgen and Pawelzik [56], ozone caused a decrease in ascorbic acid content, and lowered fruit sweetness. The ozone stress did not influence yield, size, antioxidative capacity, anthocyanins, or phenolic compounds of fruit. In the more sensitive cv. "Elsanta," ozone induced sepal injuries and fruit impairment, and a decrease in glutathione content. In contrast, fruit quality of the less sensitive cv. "Korona" remained almost constant [56].

In cv. "Camarosa," ozone enriched storage (0.35 μL/L) for 3 days, increased vitamin C by three times, and reduced volatile esters 40% compared to control [57]. On the other hand, Moretti et al. [50] reported that strawberries stored in atmospheres with ozone ranging from 0.3 to 0.7 μL/L showed no effect on ascorbic acid levels after 7 days of storage under refrigerated conditions.
