An Analysis of the Published Literature on the Effects of Edible Coatings Formed by Polysaccharides and Essential Oils on Postharvest Microbial Control and Overall Quality of Fruit.

Consumers have shown increased concern about the importance of adopting regular fresh fruit consumption. Because fresh fruit are highly susceptible to postharvest decay, several studies have focused on the development of alternative technologies to extend their market period. The application of polysaccharides in combination with essential oils (EOs) to formulate edible coatings has been considered an innovative strategy to reduce postharvest losses in fruit. However, available studies have used different methodological procedures related to the production and application of these coatings on fruit, which could be potential influential factors on the achievement of the desired effects in coated fruit. This review summarized the studies focusing on the application of edible coatings formed by polysaccharides and EOs to preserve fruit, in addition to examine and discuss possible factors affecting their functionalities. The approach given in this review envisages to contribute to research in edible coatings formed by polysaccharides and EOs and help to their optimized application as a postharvest treatment of fruit. Despite of the different methods selected for use in experimental assays, data of available literature demonstrate that coatings formed by polysaccharides (that is, chitosan-the only polysaccharide used as an antimicrobial, cassava starch, flaxseed gum, gum arabic, hydroxypropylmethylcellulose, locust bean gum, mesquite gum, pectin, pullulan, and sodium alginate) and different EOs (or their individual constituents) are effective to reduce postharvest losses in fruit and generally do not adversely affected their physicochemical and sensory characteristics during storage.

Efficacy of a coating composed of chitosan from Mucor circinelloides and carvacrol to control Aspergillus flavus and the quality of cherry tomato fruits.

Cherry tomato (Lycopersicon esculentum Mill) fruits are susceptible to contamination by Aspergillus flavus, which may cause the development of fruit rot and significant postharvest losses. Currently there are significant drawbacks for the use of synthetic fungicides to control pathogenic fungi in tomato fruits, and it has increased the interest in exploring new alternatives to control the occurrence of fungal infections in these fruits. This study evaluated the efficacy of chitosan (CHI) from Mucor circinelloides in combination with carvacrol (CAR) in inhibiting A. flavus in laboratory media and as a coating on cherry tomato fruits (25°C, 12 days and 12°C, 24 days). During a period of storage, the effect of coatings composed of CHI and CAR on autochthonous microflora, as well as on some quality characteristics of the fruits such as weight loss, color, firmness, soluble solids, and titratable acidity was evaluated. CHI and CAR displayed MIC valuesof 7.5 mg/mL and 10 µL/mL, respectively, against A. flavus. The combined application of CHI (7.5 or 3.75 mg/mL) and CAR (5 or 2.5 µL/mL) strongly inhibited the mycelial growth and spore germination of A. flavus. The coating composed of CHI (3.75 mg/mL) and CAR (2.5 or 1.25 µL/mL) inhibited the growth of A. flavus in artificially contaminated fruits, as well as the native fungal microflora of the fruits stored at room or low temperature. The application of the tested coatings preserved the quality of cherry tomato fruits as measured by some physicochemical attributes. From this, composite coatings containing CHI and CAR offer a promising alternative to control postharvest infection caused by A. flavus or native fungal microflora in fresh cherry tomato fruits without negatively affecting their quality over storage.