Effect of Chitosan- and Alginate-Based Coatings Enriched with Cinnamon Essential Oil Microcapsules to Improve the Postharvest Quality of Mangoes

Abstract

During this study, fresh mangoes were packed into multilayer coatings made from chitosan containing cinnamon essential oil microcapsules and alginate solutions that were alternately deposited on the mango surfaces by electrostatic interaction. We then compared the physical and chemical indexes to examine the changes in the mangoes during 14 d of storage. The results showed that the microcapsules prepared in the experiment were of uniform size, with the sustained release of essential oil exceeding 168 h. Compared with uncoated mangoes, the mangoes coated with the coatings could effectively inhibit the decrease of the titratable acid, soluble solids, and vitamin C contents; slow down the increase of the weight loss and pH; delay the appearance of mango respiration peaks; and preserve the firmness at storage conditions of 25 °C and 50% RH. Our findings revealed that mangoes without treatment showed losses in their edible and commercial value after 14 days in storage, and the mangoes coated with five layers still retained food and commercial value. Cross-sectional scanning electron microscopy images of the coatings showed that they had distinct layers and were of good uniformity and tight binding, and they also had good adhesion to the mango surface. These findings provide important insights into the use of coatings for the packaging of fruits during storage, which is essential for promoting the application of coatings for packaging preservation without big cost and expensive equipment.

Application of Pullulan and Chitosan Multilayer Coatings in Fresh Papayas

“…However, the respiratory peaks of multilayer coated papayas were both delayed until the 6th day, and the increase in respiration rate was suppressed compared with control fruits (P < 0.05). This indicates that the multilayer coating created a modified atmosphere with high CO 2 and low O 2 in the papaya, which reduced the respiratory rate, as shown in other work with mangoes [21]. Moreover, the antibacterial properties of the chitosan coating could have a role in the inhibition of the activity of respiratory enzymes and delayed respiration, as shown in previous work with nectarine fruits [45].…”

“…Compared with papayas coated with a single-layer, the SSC of papayas coated with two-layer, four-layer, and six-layer increased slower (P < 0.05). The multilayer coatings formed an effective barrier to O 2 in papaya, slowing down respiration and metabolic activity, and therefore retarded fruit ripening, as shown in other work with mangoes [21]. In fact, the change in SSC in the four-layer coated fruit group was minimal.…”

“…Pullulan and chitosan can form stable coatings on the papaya surface through hydrogen bonding and the coatings become denser as the layers increase; therefore, the barrier performance is better. Unfortunately, prolonged exposure of papaya to acidic chitosan solution may damage cell walls of the epidermis and lead to water loss of papaya, as shown in previous work with mango fruits [21]. In this work, the weight loss of the four-layer coated papayas was the smallest.…”

“…Moreover, the chitosan coating may also inhibited the activity of these enzymes [36]. As shown in Figure 1b, we also observed that the papayas coated with a six-layer coating were less firm than those coated with a four-layer coating, which may be due to the increased deposition time resulting in an adverse effect of the acidic chitosan solution to papaya epidermal cells [21]. In conclusion, the four-layer coating showed a positive effect in delaying fruit softening.…”

“…Furthermore, multilayer coatings can effectively maintain the color, freshness, and firmness of fruit, thereby prolonging the postharvest life [20]. Yin et al [21] deposited three-, five-, and seven-layer coatings based on chitosan solution containing cinnamon essential oil microcapsules and alginate solution on mango surface. The mangos were stored at 25 • C, 50% relative humidity (RH).…”