Utilizing Xanthan Gum Coatings as Probiotic Bacteria Carriers to Enhance Postharvest Quality and Antioxidants in Fresh-Cut Cantaloupe and Honeydew (Cucumis melo L.) Melons

Abstract

Due to spoilage microflora and browning, minimally processed fresh-cut fruits have a short shelf life, and over the years, studies have shown the potential of using edible coatings to extend the shelf life and improve the safety of fresh-cut fruits. Recently, there has been a rise in research on the incorporation of probiotics in edible coatings due to the bespoke health and biopreservation benefits they impart. Therefore, in this study, lactobacillus strains (Lactiplantibacillus plantarum 75 and Bifidobacterium longum) were incorporated into a xanthan edible coating to enhance color retention, sensory properties, antioxidant retention (ascorbic acid, carotenoids, total phenols), and antioxidant activity (FRAP antioxidant power, ABTS scavenger activity) of fresh-cut cantaloupes and honeydew cucumis melo L. melons during cold storage at 5 C and 85% RH for five days. The edible coating was prepared by mixing 0.5% xanthan gum, 1% glycerol, and 2% citric acid solution with L. plantarum 75 (LAB 75) and Bifidobacterium longum bacteria separately, and the final lab count for each strain was made to be 8.0 log CFU/mL. Stable probiotic coatings with ζ-potential of between -39.7 and -51.4 mV and a PdI of 1 were developed, and the incorporation of the probiotic bacteria into the coating was justified using FTIR analysis. The probiotic coatings showed a typical pseudoplastic behavior, in which the viscosity curves fall as the shear rate increases. Thermal stability analysis showed a continuous and multi-step weight reduction in this work, illustrating how the edible coating components interact. The survival of both Lactobacillus strains was recorded on day 5. Both freshly cut melons coated with xanthan and loaded with Lactobacillus strains retained a sufficient quantity of probiotics at the end of storage, while L. plantarum 75 (7 log CFU/g for cantaloupe and 8 log CFU/g for honeydew) retained the highest viability compared to B. longum (6 log CFU/g for cantaloupe and 7 log CFU/g for honeydew). In comparison to the coated and uncoated control samples, the inclusion of L. plantarum 75 in xanthan coatings significantly retained the color properties, pigments (total chlorophyll and carotenoids), ascorbic acid, total phenols, and antioxidant activity (FRAP, DPPH, and ABTS). The overall acceptability of fresh cuts of cantaloupe and honeydew melons coated with xanthan gum loaded with L. plantarum 75 was higher than that of other treatments. Thus, xanthan gum loaded with L. plantarum 75 coating is most suitable for reducing postharvest losses in fresh cuts of honeydew melons and cantaloupe, which will help preserve antioxidant and bioactive properties. The xanthan gum loaded with L. plantarum 75 coatings exhibited the highest preservation impact; therefore, it can be recommended for the fresh-cut industry.

Keywords: antioxidant properties; bioactive compounds; color properties; edible coating; lactobacillus strains; sensory properties.

Figure 1

Process flowchart of fresh-cut cantaloupe and honeydew (Cucumis melo L.) melons coated with probiotic bacteria.

Figure 2

Rheological properties (viscosity) of xanthan pure xanthan gum, xanthan gum + L. plantarum 75 (xanthan + L75), and xanthan gum + Bifidobacterium longum (xanthan + BF) coating.

Figure 3

The thermal stability of pure xanthan gum, xanthan gum + L. plantarum 75, and xanthan gum + Bifidobacterium longum coating. (A): pure xanthan gum, (B): xanthan gum + L. plantarum 75, and (C): xanthan gum + Bifidobacterium longum coating.

Figure 3

The thermal stability of pure xanthan gum, xanthan gum + L. plantarum 75, and xanthan gum + Bifidobacterium longum coating. (A): pure xanthan gum, (B): xanthan gum + L. plantarum 75, and (C): xanthan gum + Bifidobacterium longum coating.

Figure 4

FTIR of pure xanthan gum, xanthan gum + L. plantarum 75, and xanthan gum + Bifidobacterium longum coating.

Figure 5

Effect of coating on the total viable bacterial, lactic acid bacteria, of coated and uncoated melons, (A): Cantaloupe melons, (B): Honeydew melons. Bars represent means, and error bars represent the standard deviations from the mean. Alphabets on the same-colored bar with different letters are significant (p < 0.05). CU = uncoated cantaloupe, CUD5 = uncoated cantaloupe fresh cuts, CXD5 = xanthan coated cantaloupe fresh cuts, CXL75 = Xanthan-L. plantarum LAB 75 coated cantaloupe fresh cuts and CXB5 = Xanthan-Bifidobacterium longum coated cantaloupe fresh cuts, HU = uncoated honeydew melon fresh cuts, HUD5 = uncoated honeydew melon fresh cuts, HX5 = xanthan coated honeydew melon fresh cuts, HXL75 = Xanthan-L. plantarum LAB 75 coated honeydew melons fresh cuts and HXB5 = Xanthan-Bifidobacterium longum coated honeydew melon fresh cuts.

Figure 6

Effect of coating on the sensory properties of cantaloupe (A) and honeydew (B) melons after 5 days of storage. CU = uncoated cantaloupe at day 1, CUD5 = uncoated cantaloupe stored for 5 days, CXD5 = Xanthan coated cantaloupe stored for 5 days, CXL75 = Xanthan-L. plantarum LAB 75 coated cantaloupe at day 5 and CXB5 = Xanthan-Bifidobacterium longum coated cantaloupe stored for 5 days), HU = uncoated honeydew, HUD5 = uncoated honeydew stored for 5 days, HXD5 = Xanthan coated honeydew stored for 5 days, HXL75 = Xanthan-L. plantarum LAB 75 coated honeydew melons stored for 5 days, and HXB5 = Xanthan-Bifidobacterium longum coated honeydew melon fresh cuts.

Figure 6

Effect of coating on the sensory properties of cantaloupe (A) and honeydew (B) melons after 5 days of storage. CU = uncoated cantaloupe at day 1, CUD5 = uncoated cantaloupe stored for 5 days, CXD5 = Xanthan coated cantaloupe stored for 5 days, CXL75 = Xanthan-L. plantarum LAB 75 coated cantaloupe at day 5 and CXB5 = Xanthan-Bifidobacterium longum coated cantaloupe stored for 5 days), HU = uncoated honeydew, HUD5 = uncoated honeydew stored for 5 days, HXD5 = Xanthan coated honeydew stored for 5 days, HXL75 = Xanthan-L. plantarum LAB 75 coated honeydew melons stored for 5 days, and HXB5 = Xanthan-Bifidobacterium longum coated honeydew melon fresh cuts.

Figure 7

(A) Appearance images of fresh-cut cantaloupe melon covered with different films during five days of storage. (B) Appearance images of fresh-cut honeydew melon covered with different films during five days of storage.

Figure 8

(A). Effect of coating on total carotenoids in cantaloupe melons. Data is presented as means, and error bars are standard deviations from the mean. Bars for each melon cultivar, with different letters, are significantly different at p < 0.05. CU = uncoated cantaloupe at day 1, CUD5 = uncoated cantaloupe stored for 5 days, CXD5 = Xanthan coated cantaloupe stored for 5 days, CXL75 = Xanthan-L. plantarum LAB 75 coated cantaloupe at day 5 and CXB5 = Xanthan-Bifidobacterium longum coated cantaloupe fresh cuts). (B). Effect of coating on total chlorophyll in melons. Data is presented as means, and error bars are standard deviations from the mean. Bars for each melon cultivar, with different letters, are significantly different at p < 0.05. HU = uncoated cantaloupe at day 1, HUD5 = uncoated cantaloupe stored for 5 days, HXD5 = Xanthan-coated cantaloupe stored for 5 days, HXL75 = Xanthan-Lactobacillus plantarum LAB 75 coated cantaloupe at day 5 and HXB5 = Xanthan-Bifidobacterium longum coated honeydew melon fresh cuts).

Figure 8

(A). Effect of coating on total carotenoids in cantaloupe melons. Data is presented as means, and error bars are standard deviations from the mean. Bars for each melon cultivar, with different letters, are significantly different at p < 0.05. CU = uncoated cantaloupe at day 1, CUD5 = uncoated cantaloupe stored for 5 days, CXD5 = Xanthan coated cantaloupe stored for 5 days, CXL75 = Xanthan-L. plantarum LAB 75 coated cantaloupe at day 5 and CXB5 = Xanthan-Bifidobacterium longum coated cantaloupe fresh cuts). (B). Effect of coating on total chlorophyll in melons. Data is presented as means, and error bars are standard deviations from the mean. Bars for each melon cultivar, with different letters, are significantly different at p < 0.05. HU = uncoated cantaloupe at day 1, HUD5 = uncoated cantaloupe stored for 5 days, HXD5 = Xanthan-coated cantaloupe stored for 5 days, HXL75 = Xanthan-Lactobacillus plantarum LAB 75 coated cantaloupe at day 5 and HXB5 = Xanthan-Bifidobacterium longum coated honeydew melon fresh cuts).