Lemongrass-Enhanced Coatings Keep Kinnow Mandarins Fresh and Healthy in the Cold

Mary Jones
29th January, 2024

Lemongrass-Enhanced Coatings Keep Kinnow Mandarins Fresh and Healthy in the Cold

A Kinnow mandarin, focus of the study.

Photo adapted from: SirSadiq / CC BY (Source)
Kinnow mandarins are a popular citrus fruit, but they don’t store well, leading to significant losses after harvest. This is due to natural processes like water loss, decay, and a decline in essential nutrients and flavour. Researchers at Punjab Agricultural University[1] investigated whether a coating made from xanthan gum (XG) and lemongrass essential oil (LG) could help preserve the quality of Kinnow mandarins during storage. The study focused on extending the shelf life of Kinnow mandarins by applying different coatings and then storing the fruit at a cool temperature (5-7°C) with high humidity (90-95%) for 75 days. The researchers compared coated fruits to uncoated ‘control’ fruits. The coatings tested involved varying concentrations of xanthan gum (a common food additive used as a thickening agent) combined with lemongrass essential oil, known for its antimicrobial properties. The results showed that the coated fruits fared significantly better than the control group. They retained more of their initial acidity (titratable acidity or TA), sugar content (soluble solid content or SSC), and vitamin C (ascorbic acid or AsA). They also maintained higher levels of beneficial plant compounds called flavonoids (total flavonoid content or TFC) and had a greater juice content. Importantly, the coated fruits experienced less weight loss and spoilage. The best results were achieved with a coating containing 1.0% xanthan gum and 1.0% lemongrass essential oil. These fruits had the highest levels of TA (0.69%), AsA (203.5 mg/L), and TFC (0.21 mg/g), alongside minimal weight loss (7.57%) and spoilage (3.01%) and a SSC of 11.87%. The coatings also appeared to boost the fruit’s natural defenses. The researchers observed increased activity of enzymes like catalase (CAT), peroxidase (POD), and phenylalanine ammonia-lyase (PAL). These enzymes play a role in protecting the fruit from oxidative stress – a process that can lead to deterioration. Furthermore, coated fruits showed higher total antioxidant activity (TAA), meaning they were better equipped to neutralize harmful free radicals. Microscopic examination (scanning electron microscopy or SEM) revealed that the coating created a smoother surface on the fruit and appeared to close the small pores (stomata) on the skin. This would reduce water loss and potentially limit the entry of decay-causing microorganisms. These findings build upon previous research demonstrating the effectiveness of edible coatings in preserving fruit quality[2][3]. Earlier studies have shown that coatings made from substances like chitosan and alginate create a protective barrier, reducing moisture loss and modifying the atmosphere around the fruit to slow down ripening. The addition of functional compounds like essential oils, as seen in this study, further enhances these protective effects[3]. Indeed, research has shown that combining guar gum and tamarind seed starch coatings can significantly reduce weight loss, decay, and respiration rates in Kinnow fruits, while also preserving their firmness and nutritional content[2]. The current study expands on this knowledge by specifically investigating the combination of xanthan gum and lemongrass essential oil, and demonstrating its effectiveness in maintaining not only the physical quality of Kinnow mandarins but also their nutritional value and antioxidant capacity over an extended storage period. Chitosan-based coatings are also known to modulate oxidative stress within fruit cells[4], and while this study didn’t focus on chitosan, the observed increase in antioxidant enzyme activity suggests a similar protective mechanism may be at play with the xanthan gum and lemongrass oil combination. The research suggests that a 1.0% xanthan gum and 1.0% lemongrass essential oil coating is a promising postharvest treatment for Kinnow mandarins, offering a natural and effective way to extend their shelf life and maintain their quality during cold storage.

FruitsAgricultureBiochem

References

Main Study

1) Xanthan gum coatings augmented with lemongrass oil preserve postharvest quality and antioxidant defence system of Kinnow fruit under low-temperature storage.

Published 26th January, 2024

https://doi.org/10.1016/j.ijbiomac.2024.129776

Related Studies

2) Guar gum and chitosan-based composite edible coating extends the shelf life and preserves the bioactive compounds in stored Kinnow fruits.

https://doi.org/10.1016/j.ijbiomac.2022.10.068

3) Enhancing the functionality of chitosan- and alginate-based active edible coatings/films for the preservation of fruits and vegetables: A review.

https://doi.org/10.1016/j.ijbiomac.2020.07.083

4) Multifunctional Role of Chitosan Edible Coatings on Antioxidant Systems in Fruit Crops: A Review.

https://doi.org/10.3390/ijms22052633


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