Abstract
In this study, we fabricated polyvinyl alcohol (PVA)/chitosan (CS) bilayer films by casting and investigated the effects of preparation conditions and CS content (2, 2.5, or 3 wt.%) on the ability of these films to preserve packaged strawberries. The best performance was achieved at a CS loading of 2.5 wt.% (ultrasound time, 25 min); the strain and stress values were 143.15 ± 6.43% and 70.67 ± 0.85 MPa, respectively, oxygen permeability was 0.16 ± 0.08 cm2·m2·day−1·MPa−1, water vapor permeability was 14.93 ± 4.09 g·cm−1·s−1·Pa−1, and the shelf life of fresh strawberries packaged in the PVA/CS 2.5 wt.% bilayer film was determined to be 21 days at 5 ± 2 °C and a relative humidity of 60 ± 5%. Treatment with PVA/CS bilayer films prevented the decrease in the firmness of strawberries during storage (21 days). The evaluated physicochemical parameters (weight loss, decay, firmness, titratable acidity, soluble solid content, ascorbic acid content, and color) indicated that treatment with PVA/CS bilayer films led to better maintenance of the fruit quality. We believe that our study makes a significant contribution to literature because it paves the way to the fabrication of smart packaging materials and facilitates the commercialization of fresh strawberries as an important health food.
Highlights
Strawberries, which are a highly popular non-climacteric summer fruit rich in polyphenols, anthocyanins, vitamins, and amino acids, should be harvested when fully mature to achieve maximum quality [1]
polyvinyl alcohol (PVA) and PVA/CS 3 wt.% dispersions sonicated for 5 min featured viscosities of 3420 ± 35.51 and 10,626.67 ± 35.31 mPa·s, respectively, whereas significantly higher values (2386.67 ± 45.57 and 9440 ± 74.35 mPa·s, respectively) were obtained after 10-min sonication
The above results clearly indicated that the viscosity of PVA/CS dispersions depends on the duration of ultrasonication, which may be ascribed to the effect of acoustic cavitation [22]
Summary
Strawberries, which are a highly popular non-climacteric summer fruit rich in polyphenols, anthocyanins, vitamins, and amino acids, should be harvested when fully mature to achieve maximum quality [1]. The lack of a protective rind makes strawberries highly susceptible to fungal decay, mechanical injury, water loss, and physiological deterioration during storage, thereby leading to a short shelf life [2]. The main pathogen attacking strawberries during storage is Botrytis cinereal, a saprophytic fungus known as gray mold [3]. This fungus predominantly infects strawberries during cultivation and can spread to nearby fruit, while symptoms mainly develop only after harvesting. Strict normative restrictions and the growing concern of consumers regarding fungicide residues limit the use of conventional fungicides, necessitating the search for better preservation alternatives
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