Xanthan gum-based edible coating effectively preserve postharvest quality of 'Gola' guava fruits by regulating physiological and biochemical processes

Abstract

Background: Guava is a fruit prone to rapid spoilage following harvest, attributed to continuous and swift physicochemical transformations, leading to substantial postharvest losses. This study explored the efficacy of xanthan gum (XG) coatings applied at various concentrations (0.25, 0.5, and 0.75%) on guava fruits (Gola cultivar) over a 15-day storage period.

Results: The results indicated that XG coatings, particularly at 0.75%, substantially mitigated moisture loss and decay, presenting an optimal concentration. The coated fruits exhibited a modified total soluble soluble solids, an increased total titratable acidity, and an enhanced sugar-acid ratio, collectively enhancing overall quality. Furthermore, the XG coatings demonstrated the remarkable ability to preserve bioactive compounds, such as total phenolics, flavonoids, and antioxidants, while minimizing the levels of oxidative stress markers, such as electrolyte leakage, malondialdehyde, and H₂O₂. The coatings also influenced cell wall components, maintaining levels of hemicellulose, cellulose, and protopectin while reducing water-soluble pectin. Quantitative analysis of ROS-scavenging enzymes, including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase, revealed significant increases in their activities in the XG-coated fruits compared to those in the control fruits. Specifically, on day 15, the 0.75% XG coating demonstrated the highest SOD and CAT activities while minimizing the reduction in APX activity. Moreover, XG coatings mitigated the activities of fruit-softening enzymes, including pectin methylesterase, polygalacturonase, and cellulase.

Conclusions: This study concludes that XG coatings play a crucial role in preserving postharvest quality of guava fruits by regulating various physiological and biochemical processes. These findings offer valuable insights into the potential application of XG as a natural coating to extend the shelf life and maintain the quality of guava fruits during storage.

Keywords: Antioxidant activities; Cell wall degradation; Guava postharvest; Hemicellulose; Hydrocolloid; Pectin; Polysaccharide coating.

Fig. 1

The impact of xanthan gum (XG)-based coatings on moisture loss (A), decay incidence (B) and visual appearance of harvested guava fruits. Each bar corresponds to the mean ± SE (n = 4). Statistical analysis using Fisher’s LSD revealed significant differences among coating treatments on each sampling day, denoted by different small letters (p ≤ 0.05)

Fig. 2

The impact of xanthan gum (XG)-based coatings on total soluble solids (A), total titratable acidity (B), sugar-acid ratio (C) and ascorbic acid content (D) in harvested guava fruits. Each bar corresponds to the mean ± SE (n = 4). Statistical analysis using Fisher’s LSD revealed significant differences among coating treatments on each sampling day, denoted by different small letters (p ≤ 0.05)

Fig. 3

The impact of xanthan gum (XG)-based coatings on total phenolics (A), flavonoids (B) and antioxidants (C) in harvested guava fruits. Each bar corresponds to the mean ± SE (n = 4). Statistical analysis using Fisher’s LSD revealed significant differences among coating treatments on each sampling day, denoted by different small letters (p ≤ 0.05)

Fig. 4

The impact of xanthan gum (XG)-based coatings on electrolyte leakage (A), malondialdehyde (B) and hydrogen peroxide content (C) in harvested guava fruits. Each bar corresponds to the mean ± SE (n = 4). Statistical analysis using Fisher’s LSD revealed significant differences among coating treatments on each sampling day, denoted by different small letters (p ≤ 0.05)

Fig. 5

The impact of xanthan gum (XG)-based coatings on hemicellulose (A), cellulose (B), water soluble pectin (C), and protopectin in harvested guava fruits. Each bar corresponds to the mean ± SE (n = 4). Statistical analysis using Fisher’s LSD revealed significant differences among coating treatments on each sampling day, denoted by different small letters (p ≤ 0.05)

Fig. 6

The impact of xanthan gum (XG)-based coatings on fruit respiration (A) and ethylene (B) rate in harvested guava fruits. Each bar corresponds to the mean ± SE (n = 4). Statistical analysis using Fisher’s LSD revealed significant differences among coating treatments on each sampling day, denoted by different small letters (p ≤ 0.05)

Fig. 7

The impact of xanthan gum (XG)-based coatings on activities of ROS-scavenging enzymes i.e., SOD (A), POD (B), CAT (C), and APX (D) in harvested guava fruits. Each bar corresponds to the mean ± SE (n = 4). Statistical analysis using Fisher’s LSD revealed significant differences among coating treatments on each sampling day, denoted by different small letters (p ≤ 0.05)

Fig. 8

The impact of xanthan gum (XG)-based coatings on activities of fruit softening enzymes i.e., pectin methylesterase (A), polygalacturonase (B), and cellulase (C) in harvested guava fruits. Each bar corresponds to the mean ± SE (n = 4). Statistical analysis using Fisher’s LSD revealed significant differences among coating treatments on each sampling day, denoted by different small letters (p ≤ 0.05)

Fig. 9

Pearson (n) correlation among different studied parameters of guava fruits. Abbreviations: ML – moisture loss; DI – decay incidence; TSS – total soluble solids; TTA – total titratable acidity; SAR – sugar-acid ratio; VitC – ascorbic acid; Phen – total phenolics; Flav – total flavonoids; Antiox – total antioxidants; EL – electrolyte leakage; MDA – malondialdehyde content; H2O2 – hydrogen peroxide; HS – hemicellulose; Cls – cellulose; WSP – water soluble pectin; PRP – protopectin; Res – respiration; Ety – ethylene; SOD – SOD activity; POD – POD activity; CAT – CAT activity; APX – APX activity; PME – PME activity; PG – PG activity; CS – CS activity; Accept – overall acceptability