Firmness is an important parameter in the quality of fruits and vegetables.
As shown in Figure 2, the initial values for this parameter ranged between 4.94 and 6.10 N.
Firmness remained stable for 7 d and differences were only observed by the end of storage.
By day 15, firmness of uncoated and pectin-EAC coated strawberries decreased however, pectin-EAC treated fruits presented higher firmness values compared to control (3.33 and 1.90 N, respectively).
In contrast, pullulan and chitosan-EAC coated strawberries remained stable (P < 0.05) during 15 d.
At the end of storage period, the firmness of pullulan and chitosan coated fruits were 4.73 and 5.13 N, respectively, indicating that these coatings helped to maintain firmness of the fruit.
The main cause of softening in strawberries is degradation of the middle lamella of the cell wall of cortical parenchyma cells, which occurs due to enzymatic processes, water loss by respiration, and damage to structural tissues caused by molds).
Application of polysaccharide-based coatings provided a mechanical barrier that reduced water loss, delayed microbial growth, slowed metabolism, and reduced fruit softening.
The highest firmness was achieved in chitosan and pullulan-EAC coated strawberries after 15 d, can be attributed to the mechanical strength of the film surrounding the fruit and the prevention of water loss and microbial growt.