# Effect of Chitin-Glucan Hydrogel Coating on Shelf Life of Kashar Cheese

## TL;DR

This study shows that a hydrogel made from fungal waste can significantly extend the shelf life of Kashar cheese by reducing spoilage.

## Contribution

A sustainable, edible chitin-glucan hydrogel coating is developed from biological waste to prolong cheese shelf life.

## Key findings

- Cheese coated with hydrogel had a shelf life of 555 days, compared to 155 days for uncoated cheese.
- KOH-hydrogel reduced lactic acid bacteria proliferation and improved oxidative stability.
- Hydrogel coatings altered cheese texture properties, increasing hardness and chewiness.

## Abstract

The study investigates the use of chitin-glucan-based hydrogel (hereafter referred to as the hydrogel), obtained from Aspergillus niger mycelia grown on biological waste, to extend the shelf life of fresh Kashar cheese by reducing biochemical and microbiological degradation during storage.

Biological waste, used as a medium for obtaining mycelium from A. niger, was collected weekly for four weeks from a hotel. Chitin-glucan nanofibre was produced from the mycelium using an alkaline method. The nanofibre was then freeze-thawed in an alkaline solvent system to form the hydrogel. To investigate the effect of the hydrogel on the shelf life of fresh Kashar cheese, hydrogel-coated cheese samples were analysed.

Fourier transform infrared spectroscopy (FTIR) analysis confirmed that the hydrogel consisted of chitin-glucan complex, while scanning electron microscope (SEM) images demonstrated its successful application as a surface coating. Coating with the hydrogel significantly increased the pH and mass loss of cheese samples compared to the control (distilled water, p≤0.05). Moisture loss rates were 8, 18 and 14 % for samples treated with water, hydrogel obtained by dissolving chitin-glucan complex in KOH (KOH-hydrogel) and NaOH (NaOH-hydrogel), respectively. Although the hydrogel did not significantly inhibit mould and yeast (p≥0.05), the KOH-hydrogel coating effectively reduced lactic acid bacteria (LAB) proliferation (p≤0.05), which is associated with souring. Additionally, reduced peroxide value (PV) in coated samples (p≤0.05) suggests improvements in oxidative stability. Hydrogel coatings also influenced the texture properties of the cheese: hardness, chewiness, adhesiveness and cohesiveness increased, while resilience and gumminess decreased (p≤0.05). Using zero-order kinetics, the shelf life of cheese was calculated based on peroxide formation, with deterioration defined at 2 mmol O2 per kg of fat. The shelf life of uncoated cheese was estimated at 155 days, whereas it extended significantly to 555 days for cheese coated with either KOH- or NaOH-hydrogel. These results show the capacity of the hydrogels to reduce oxidative spoilage, thereby prolonging the cheese usability.

Study highlights that the hydrogel is sustainable, innovative edible coating with antioxidant properties, offering a promising approach for improving the quality and extending the shelf life of Kashar cheese. Future research could further optimize hydrogel formulations to enhance antimicrobial efficacy and explore their application in other high-moisture food products.