*5.2.4 Coatings*

Highly perishable fruits such as berries and tropical fruits are appropriate products to protect with coatings because they are expensive and exhibit a short storage life (**Figure 4**). Coatings can act as moisture and gas semi-permeable barriers, resulting in control of microbial growth, preservation of color and texture [64]. Strawberries, as a typical soft fruit, have a high physiological postharvest activity. As a consequence, they have short ripening and senescence periods that make marketing of this high-quality fruit a challenge.

#### **Figure 4.**

*Fruits treated with coatings have prolonged shelf life: (a) untreated fruits have 10 days of shelf life with improper color development; and (b) shelf life of fruits treated with coatings on 16th day and (c) with coatings on 21st day.*

**31**

[73–75].

*Fruit Physiology and Postharvest Management of Strawberry*

immersed in these solutions and kept for 4 days at 20 ± 1°C.

Chitosan, a high molecular weight cationic polysaccharide, theoretically should

be an ideal preservative coating material for strawberries. It has been shown to inhibit growth of several fungi [65], to induce chitinase, a defense enzyme. Due to its ability to form semi-permeable film [66], chitosan coating can be expected to modify the internal atmosphere as well as decrease the transpiration losses. Therefore a delay in ripening and control of decay by means of chitosan coating could result. Romanazzi et al. [67] found that the commercial chitosan formulation was as effective in the control of gray mold and Rhizopus rot of strawberries

Chitosan-based edible coatings used to extend the shelf-life and enhance the nutritional value of strawberries at either 2°C or 88% relative humidity (RH) for 3 weeks or −23°C up to 6 months which resulted in reduced drip loss and helped to maintain textural quality of frozen strawberries after thawing. In addition, chitosanbased coatings containing calcium or Vitamin E significantly increased the content of these nutrients in both fresh and frozen fruits [68]. There was significant reduction in severity of decay and shelf-life extension on immersing strawberries stored at either 5 or 10°C in chitosan solutions of 0.5, 1.0 and 1.5 g/100 mL for 5 min at 20°C as compared to untreated [69]. Chitosan sprays (2, 4 and 6 g/l) significantly reduced

post-harvest fungal rot and maintained the keeping quality of the fruit [70].

Edible coatings can be made from food materials such as cellulose derivatives, proteins, starch, and other polysaccharides (regarded as GRAS). Starch is the most usually used agricultural raw material for biodegradable films [71]. The filmforming capacity of starches was due to presence of Amylose. Plasticizer, another important component of edible films is required to overcome film brittleness and improve extensibility and flexibility of the films. They reduce intermolecular forces and increase the movements of polymer chains. Plasticizer must be compatible with the film-forming polymer; hydrophilic compounds such as polyols (glycerol, sorbitol, polyethylene glycols) and lactic acid are frequently used in hydrophilic film formulations [72]. The effect of plasticizer on water vapor and gas permeabilities is controversial, depending on matrix, plasticizer type, and environmental conditions

Starch-based coatings can be applied to extend storage life of strawberries (*Fragaria ananassa*) stored at 0°C and 84.8% relative humidity. Coatings made with starches with the higher amylose content decreased WVP and weight losses and retained fruit firmness for longer periods [76]. The coating of strawberries with cassava starch + chitosan provided the best results, with less than 6% of loss in fruit mass, lower counts of yeast and psychrophilic microorganisms and the best appear-

*Aloe vera* (AV), a novel edible coating was used for fruit storage [78, 79] which has antifungal activity against several pathogenic fungi including *Botrytis cinerea* [80]. AV coatings modify the internal gas atmosphere, reduce moisture loss, softening, respiration rates, delay oxidative browning and reduce microorganism proliferation in fruits [79, 81–83]. *Aloe vera* + Ascorbic acid treatments in strawberries delayed weight loss; reduced total aerobic mesophilic, yeasts, and molds populations; and had higher SSC, vitamin C concentrations, and titratable acidity [84].

*DOI: http://dx.doi.org/10.5772/intechopen.84205*

*5.2.4.1 Chitosan*

*5.2.4.2 Starch based coatings*

ance according to the sensory analysis [77].

*5.2.4.3 Botanical coatings*

#### *5.2.4.1 Chitosan*

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

can aid to delay softening and mold growth and decrease the occurrence of physiological disorders [58]. Common techniques like dipping and vacuum or pressure infiltrations are used to increase cell wall Ca content of fruit tissue after harvest. The firming effect can be explained by the crosslinks formation between the carboxyl groups of polyuronide chains found in the middle lamella of the cell wall; Ca also increases cell turgor pressure [59, 60] and stabilizes the cell membrane [61]. Calcium dips have been employed to improve firmness and extend the postharvest shelf-life of a wide range of fruit and vegetables. In strawberries, CaCl2 dips in combination with heat treatment or modified atmosphere storage and refrigeration increase calcium content and fruit firmness and delay postharvest decay [62, 63]. Calcium dips were effective in decreasing surface damage and delaying both fungal decay and loss of firmness in strawberries, compared to untreated fruit [64].

Highly perishable fruits such as berries and tropical fruits are appropriate products to protect with coatings because they are expensive and exhibit a short storage life (**Figure 4**). Coatings can act as moisture and gas semi-permeable barriers, resulting in control of microbial growth, preservation of color and texture [64]. Strawberries, as a typical soft fruit, have a high physiological postharvest activity. As a consequence, they have short ripening and senescence periods that make

marketing of this high-quality fruit a challenge.

*Fruits treated with coatings have prolonged shelf life: (a) untreated fruits have 10 days of shelf life with improper color development; and (b) shelf life of fruits treated with coatings on 16th day and (c) with coatings* 

**30**

**Figure 4.**

*5.2.4 Coatings*

*on 21st day.*

Chitosan, a high molecular weight cationic polysaccharide, theoretically should be an ideal preservative coating material for strawberries. It has been shown to inhibit growth of several fungi [65], to induce chitinase, a defense enzyme. Due to its ability to form semi-permeable film [66], chitosan coating can be expected to modify the internal atmosphere as well as decrease the transpiration losses. Therefore a delay in ripening and control of decay by means of chitosan coating could result. Romanazzi et al. [67] found that the commercial chitosan formulation was as effective in the control of gray mold and Rhizopus rot of strawberries immersed in these solutions and kept for 4 days at 20 ± 1°C.

Chitosan-based edible coatings used to extend the shelf-life and enhance the nutritional value of strawberries at either 2°C or 88% relative humidity (RH) for 3 weeks or −23°C up to 6 months which resulted in reduced drip loss and helped to maintain textural quality of frozen strawberries after thawing. In addition, chitosanbased coatings containing calcium or Vitamin E significantly increased the content of these nutrients in both fresh and frozen fruits [68]. There was significant reduction in severity of decay and shelf-life extension on immersing strawberries stored at either 5 or 10°C in chitosan solutions of 0.5, 1.0 and 1.5 g/100 mL for 5 min at 20°C as compared to untreated [69]. Chitosan sprays (2, 4 and 6 g/l) significantly reduced post-harvest fungal rot and maintained the keeping quality of the fruit [70].

#### *5.2.4.2 Starch based coatings*

Edible coatings can be made from food materials such as cellulose derivatives, proteins, starch, and other polysaccharides (regarded as GRAS). Starch is the most usually used agricultural raw material for biodegradable films [71]. The filmforming capacity of starches was due to presence of Amylose. Plasticizer, another important component of edible films is required to overcome film brittleness and improve extensibility and flexibility of the films. They reduce intermolecular forces and increase the movements of polymer chains. Plasticizer must be compatible with the film-forming polymer; hydrophilic compounds such as polyols (glycerol, sorbitol, polyethylene glycols) and lactic acid are frequently used in hydrophilic film formulations [72]. The effect of plasticizer on water vapor and gas permeabilities is controversial, depending on matrix, plasticizer type, and environmental conditions [73–75].

Starch-based coatings can be applied to extend storage life of strawberries (*Fragaria ananassa*) stored at 0°C and 84.8% relative humidity. Coatings made with starches with the higher amylose content decreased WVP and weight losses and retained fruit firmness for longer periods [76]. The coating of strawberries with cassava starch + chitosan provided the best results, with less than 6% of loss in fruit mass, lower counts of yeast and psychrophilic microorganisms and the best appearance according to the sensory analysis [77].

#### *5.2.4.3 Botanical coatings*

*Aloe vera* (AV), a novel edible coating was used for fruit storage [78, 79] which has antifungal activity against several pathogenic fungi including *Botrytis cinerea* [80]. AV coatings modify the internal gas atmosphere, reduce moisture loss, softening, respiration rates, delay oxidative browning and reduce microorganism proliferation in fruits [79, 81–83]. *Aloe vera* + Ascorbic acid treatments in strawberries delayed weight loss; reduced total aerobic mesophilic, yeasts, and molds populations; and had higher SSC, vitamin C concentrations, and titratable acidity [84].

Cactus mucilage is one of the edible coating which is used for increasing shelf life of strawberries [85]. Mucilages are generally hetero-polysaccharides obtained from plant stems [86]. They may find applications in cosmetics, food, pharmaceutical and other industries. The complex polysaccharide is a part of dietary fiber and has the capacity to absorb more amounts of water by dissolving and dispersing itself and forming gelatinous or viscous colloids [87]. Cactus mucilage as a coating is its low cost.

### **5.3 Storage**

## *5.3.1 Modified-atmosphere packaging (MAP)*

Modified-atmosphere packaging (MAP) of fruit and vegetables is becoming a popular method of extending shelf life [88]. Strawberries fumigated with acetic acid at 5.4 mg/L followed by modified atmosphere packing were found to be free of decay compared to 89% rotted for the control fruit stored for 14 days at 5°C [89].

#### *5.3.2 Controlled atmosphere storage*

The use of a carbon dioxide enriched atmosphere is an extensively used postharvest practice to manage and control fungal decay in freshly harvested fruits and vegetable products. Numerous studies have revealed that controlled atmosphere storage of different cultivated strawberry varieties may enhance their shelf life by slowing down both fungal decay and senescence. These effects are linked with the reduction of respiration and ethylene production rates [51, 90, 91]. Exposure of fruits to high levels of CO2 during cold storage showed enhancement of firmness [92, 93] and resistant to decay [51]. However, combinations of high CO2 and low O2 atmospheres improve most strawberry quality traits, increase in generation of off-flavor compounds like ethanol and ethyl acetate, producing an adverse sensory effect [94]. The atmosphere of high CO2 and high O2 do not ease these off-flavor problems and show to persuade a synergistic effect that even increases the assembly of fermentative metabolites [94, 95]. Allan and Hadwiger [96] studied that 10% CO2/11% O2 combination had efficiently prolonged the shelf life of wild strawberries by maintaining the quality parameters within acceptable values, through inhibiting the development of *Botrytis cinerea*, without significantly modifying consumer acceptance.

#### **5.4 Packaging and transport**

In order to avoid deterioration during storage, strawberries need to be well packed immediately after harvest. Cold-chain system is regularly used to conserve the quality and flavor for a prolonged period.

#### *5.4.1 Cold-chain system*

Precooled strawberries are stored at a low temperature in a cold store, or transported for marketing in a refrigerated van. This system enables the fruits to remain fresh until they reach the consumers. In a well-organized cold-chain system, cold air should be well dispersed within the boxes used for packaging. Furthermore, boxes should not lose their shape even if they become moist. Each box should hold the correct amount of fruit, and be of an appropriate size to reduce the cost of distribution.

#### *5.4.2 Packaging films*

Packaging of fruits with polymeric films is often used to prevent moisture loss, to protect against mechanical damage, and to achieve a better appearance [97].

**33**

**Figure 5.**

*Fruit Physiology and Postharvest Management of Strawberry*

Different types of packaging films include:

Packaging strawberries with plastic films immediately after harvest is only technique to prevent water loss during storage. The water loss may lead to shriveling and a dull appearance of the epidermis having a negative effect on the appearance of the fruit.

Perforated cellophane sheets (CS): these were placed on top of the baskets and

Low density polyethylene bags (PB): these were heat-sealed after introducing

Polyvinyl chloride films (PVC): PVC films has resulted in better fruit weight and firmness retention of fruits of strawberry especially in the last 7 days of storage [98]. The use of Low density polyethylene bags as packing films in strawberry has resulted in the lowest weight losses, conductivity and degree of fruit decay, together

They offer good barrier to oxygen and carbon dioxide transmission but a poor barrier to water vapor under certain conditions of relative humidity (RH) and temperature [97, 100]. These characteristics are favorable for preservation of quality of fruits and vegetables, since they lead to a decline in respiration rate by restricting the exposure to ambient O2 and increasing internal CO2, thus delaying ripening. The poor water vapor barrier allows mobility of water across the film, thus preventing water condensation that can be a possible source of microbial decay in soft fruits

This improved method of packaging consists of an outer box made of corrugated fibreboard (**Figure 5**), having a capacity of 6 kg, and 6 inner boxes made of cardboard, each box have a holding capability of 1 kg fruit. The external box is 54 cm long × 36 cm wide × 9 cm high, and was designed to occupy 96% of the base area.

In order to facilitate the movement of cold air, ventilation holes (**Figure 6**(**a**) and (**b**)) were made on the sides of the box and the internal partitions. Ventilation

*Packaging of strawberries: (a) plastic punnets (b) Corrugated fiber board box.*

*DOI: http://dx.doi.org/10.5772/intechopen.84205*

fixed with elastic bands.

one or more baskets per bag.

*5.4.3 Hydrophilic starch films*

and vegetables [101].

*5.4.5 Ventilation holes*

*5.4.4 Corrugated fiber board boxes*

with the highest firmness values [99].

#### *Fruit Physiology and Postharvest Management of Strawberry DOI: http://dx.doi.org/10.5772/intechopen.84205*

Packaging strawberries with plastic films immediately after harvest is only technique to prevent water loss during storage. The water loss may lead to shriveling and a dull appearance of the epidermis having a negative effect on the appearance of the fruit.

Different types of packaging films include:

Perforated cellophane sheets (CS): these were placed on top of the baskets and fixed with elastic bands.

Low density polyethylene bags (PB): these were heat-sealed after introducing one or more baskets per bag.

Polyvinyl chloride films (PVC): PVC films has resulted in better fruit weight and firmness retention of fruits of strawberry especially in the last 7 days of storage [98].

The use of Low density polyethylene bags as packing films in strawberry has resulted in the lowest weight losses, conductivity and degree of fruit decay, together with the highest firmness values [99].
