**6. Edible coatings and films**

*Modern Fruit Industry*

10<sup>−</sup><sup>5</sup>

(@8 μmol L<sup>−</sup><sup>1</sup>

**4. Oxalic acid**

**3. Methyl jasmonate (MeJA)**

Jasmonic acid (JA) and its methyl ester (methyl jasmonate (MeJA)) are types of endogenous phytohormones that have distinct and potentially useful properties which affect plant growth and development in response to environmental stresses. Methyl jasmonate (MeJA) was discovered in *Jasminum grandiflorum* flower extracts in 1962 as a sweet-smelling compound [75]. It has inhibitory effect on ethylene biosynthesis and delayed ripening of peaches [15]. Application of jasmonate has been found effective to protect from chilling injury in many fruits crops, such as peach (@ 0.1 mmol L<sup>−</sup><sup>1</sup>

 M) [18]. It has been discovered that exogenous treatment with MeJA enhances antioxidant capacity of different harvested fruits and horticultural crops [17, 76]. Applied MeJA also controls the postharvest diseases and decay of fruits. It was observed that application of 10 μmol/L, MeJA effectively reduced anthracnose in loquats [19] and inhibited rot caused by *Botrytis cinerea* in strawberries when treated with 1 μmol L<sup>−</sup><sup>1</sup>

[20] It has good potential to enhance the postharvest life of Sabrosa strawberry fruit

on fruits of Fuji apple had higher soluble solid content, titratable acidity and delayed fruit firmness loss. Boonyaritthongchai and Supapvanich [23] observed in pineapple that treatment of fruits with 1 mM MeJA inhibits ethylene production, weight loss, internal browning and enhances total phenol which produces during cold storage.

) [21]. Aglar and Ozturk [22] found that application of 2240 mg L<sup>−</sup><sup>1</sup>

Oxalic acid (OA) is an organic compound which is chemically C2H2O4. It naturally occurs in some fruits such as carambola, bilimbi, ripe papaya and kiwifruit. Oxalic acid has main role in regulating the physiology of many processes and various biochemical pathways inside the plants. It helps to increase the photosynthetic ability of plants, thereby cause increase in total soluble solids, sugars and titratable acidity. Oxalic acid reduces the production of polygalacturonase (PG) and pectin methyl esterase (PME), which are responsible for cell wall degradation, so that the treated fruit maintains the firmness in plum [77]. Zheng et al. [24] found that postharvest application of oxalic acid (@30 mM) could be a promising method to extend the storage shelf-life and suppress quality deterioration of mango fruit. It was observed in ber cv. Gola that fruit treated with 10 mM oxalic acid found to be best in maintaining enzymatic activity of phenylalanine ammonia lyase (PAL), malondialdehyde (MDA) and superoxide dismutase (SOD), their minimum values were observed with this treatment [25]. Li et al. [26], observed in mature green tomatoes that postharvest application of OA increased accumulation of lycopene during the postharvest ripening which may be due to upregulation of the expression of genes that codified for enzymes involved in carotenoid biosynthesis. Huang et al. [27] reported that dipping of banana in 20 mM oxalic acid for 10 min followed by storage at room temperature, reduced the deterioration and enhances their storability of fruits.

Salicylic acid (SA) or ortho-hydroxybenzoic acid is a pervasive, natural simple phenolic compound, which is frequently disseminated in plants and involved in the regulation many catabolic activities in fruits and vegetables. It is considered as a safe chemical compound for postharvest application. It has been used to improve postharvest quality such as delay ripening and retention of firmness in guava

pomegranate (@ 0.01 mM) [17], and "Smooth Cayenne" pineapple (@10<sup>−</sup><sup>3</sup>

) [16],

and

.

MeJA

, 10<sup>−</sup><sup>4</sup>

**30**

**5. Salicylic acid**

Edible coatings are the application of commercial food grade waxes or films to product surface natural glossiness in addition to or as a replacement for natural defensive waxy coatings. These provide a barrier for moisture, oxygen and solute movement for the food and extend the shelf life by decreased respiration and ethylene, there are many commercial formulations are available in market which widely applied on the surface of fruits and vegetables. Among them Citrashine, chitosan, SemperFresh, shellac wax, carboxymethyl cellulose, guar gum, lasoda gel, *Aloe vera* gel, bee wax, etc. are common. However, plant based surface coatings and extracts are more popular than those of chemically synthesized. Use of essential oils, leaf extracts and exudations also established their strong market. These can be applied directly on the produce surface due to its edible properties, biodegradability and also healthy distinct from chemical nonedible coating which leave residual effect on the product. They have antimicrobial properties and also act as barrier. It has many positive affect on fruits such as delayed ripening in pomegranate fruits [41], inhibits ethylene production and delays softening process in plum [36], retaining firmness in papaya and [34], reduces weight loss in blueberries [35], inhibits pathogenic spoilage in kiwi fruit slices [39], in fresh cut persimmon [37], in fresh cut orange [38] and in strawberry [40]. Hosseini et al. [42] observed that coating of banana fruits with putrescine and chitosan increases in phenolic compound and antioxidant activity at the end of the storage period and it was also suggest that 1% chitosan coating is effective in enhancing postharvest quality and shelf-life of banana. It was reported that treatment of mango fruits with 2% beeswax and chitosan reduces physiological weight loss, maintained firmness by reduction in respiration rate and reduces the activities of hydrolysis enzymes [43].

Similar to that of waxes, essential oils could be effective in reducing microbial load during transportation and storage. These plant-based oils, oleoresins, leaf extracts, etc. gained popularity as surface disinfectant on fresh fruits. Many researchers have investigated the effect of leaf extracts like custard apple leaf extracts, tea extracts, neem oils, thyme oil, clove oil, ocimum oil, coconut oil, lemon grass oils, *Aloe vera* extracts, and many other herbal formulations on postharvest diseases. They may helpful in reducing many diseases like gray mold of grape, strawberry, blue mold of apple and citrus, anthracnose and stem end rot in mango and citrus, etc. and found to be effective to a certain extent. The application of these oils may increase the activities of certain defense related enzymes thus beneficial in inducing resistance mechanism in fruits. The application of 0.5% black seed oil was found effective in reducing chilling injury and also controlling gray mold disease in pomegranate (Kahramanoğlu et al. [44]). Abd-El-Latif [45] reported that application of eucalyptus, thyme and lemon grass oil (at a concentration of 0.6 and 0.8%) was found effective in reducing the incidence of gray and blue molds in apple fruits. It was observed that coating of mandarin fruits with pure coconut oil (100%) enhance their shelf life, quality and also delayed the mold appearance (Nasrin et al. [46]).

Recently, a new approach of edible coating "layer by layer coating (LBL)" is getting attention which is an electrostatic deposition technique. It is worked by combining the chitosan with other polysaccharides, like carboxymethyl cellulose (CMC). The aim of LBL was effective control the properties and functionality of material by depositing oppositely charged polyelectrolytes [47]. LBL edible coating including the five nanolayers of pectin and chitosan exhibited better quality in terms of weight loss, total soluble solids and titratable acidity in Tommy Atkins' mangoes [48]. Arnon et al. [49] reported in many citrus fruits (mandarins, "Navel" oranges, and "Star Ruby" grapefruit) that bilayer coating with CMC/chitosan slightly maintained fruit firmness. It was reported in strawberry that coating based on chitosan and carboxymethyl cellulose (CMC), (1%) found effective to prevents the loss of firmness and aroma volatiles and it also reduces the primary (involved in carbohydrate, amino acids and fatty acids metabolism) and secondary metabolites (involved in carotenoid, terpenoid, phenylpropanoid and flavonoid metabolism [47].
