Usage of indicator loaded chitosan films for monitoring soft cheese quality during storage

Cheese production has been steadily increasing globally, with over 3,000 different types of cheese being produced. To ensure the safety, quality, and freshness of cheese, advanced packaging methods are necessary. Food spoilage is a natural process that can render food unsuitable for consumption due to changes in sensory characteristics. Microbiological spoilage caused by the proliferation of microorganisms and the release of enzymes or harmful substances, can lead to undesirable changes in food quality and safety. This study aimed to examine the properties of chitosan films loaded with an indicator for packaging soft cheese, evaluate their effectiveness in monitoring cheese quality during storage, compare their findings with physical, chemical, and microbiological parameters, determine suitable storage conditions, and explore potential commercial applications. In this study, samples of fresh cow's milk were collected in an appropriate amount from local farms for the purpose of producing the cheese used in the study, and about 80 pieces of processed cheese were used for the purpose of conducting tests on them. The physical and mechanical properties of the chitosan membrane were investigated in order to characterize the films. Chitosan films were cast by using different volumes of chitosan solution (20mL, 25mL, 30mL and 35mL). The average thickness of the chitosan membrane was determined as 0.08 mm. This value was the average of six readings that were measured by the device, which were 0.076, 0.075, 0.091, 0.081, 0.082, and the 0.078 mm. The value of permeability was determined as 36% and the mechanical properties of the chitosan membrane assay were important in the evaluation because they indicate the strength and durability of this membrane. According to the Tensile strength property and the Elongation ratio of the chitosan membrane. It appeared at 34.1 MPa and 0.192 (εb), respectively. The results showed that the pH values of uncoated cheese (T1) and coated cheese (T2) during the first day of storage were at 6.40 and 6.70, respectively, and ten days of storage appeared at 4.20 and 6.20, respectively. The pH value at 20 and 30 days was not measured for uncoated cheese because the cheese samples were spoiled. In contrast, the pH for the corresponding days (20 and 30 days) for coated cheese was measured as 5.92 and 4.50, respectively. Peroxide value results for the samples were the uncoated cheese T1 and coated cheese T2, on the first day of storage, the POV results were not significantly different and were found to be 0.63 mEq/kg for each of the cheeses. On the other hand, after ten days of storage, a huge increase in the POV of the uncoated cheese was observed. The POV of uncoated cheese was found to be 13.48 mEq/kg, and this value indicated that the product was inappropriate for human consumption. As for the coated cheese samples, acceptable POV levels were maintained even after 30 days of storage. For ten days of storage, the POV was 0.85 mEq/kg, and it was 0.91 mEq/kg in 20 days and 1.27 mEq/kg in 30 days. Storing the sample caused an increase in the TBA within 10 days, and it was found to be 3.28 µM/g for uncoated cheese. This value for uncoated cheese indicates spoilage and unfitness for human consumption. As for the coated cheese samples, normal levels of TBA were maintained even after 30 days of storage, where they were 0.35 µM/g in 10 days, 1.25 µM/g in 20 days, and 1.70 µM/g in 30 days. The cheese samples storage periods at zero and 10 days for treatment T1 were increased significantly (p<0.05) in the total bacterial counts and appeared at 2.4 and 9.1 log cfu/g, respectively, while the total counts of the treatment T2 at storage time zero, 10, 20 and 30 become at 2.4, 3.2, 5.2 and 5.4 log cfu/g respectively. The total counts of lactic acid bacteria were significantly decreased in the treatment of cheese samples, and they appeared in T1 at time zero and 10 days at 5.3 and 4.1 log cfu/g, respectively. In addition, the total LAB counts appeared in a time 0, 10, 20, and 30 days at 5.1, 3.4, 2.5, and 0.0 log cfu/g, respectively. The Staphylococcus aureus and the E. coli isolates of contaminated bacteria for cheese samples and other isolates from gram-positive and gram-negative isolates were diagnosed by following the diagnostic system in the VITEK-2 Compact device, which includes 64 biochemical tests. The test kit was incubated at 37 °C for 4 to 6 hours, and after comparison with the device reader, bacterial species were identified as gram-positive as Staphylococcus saprophyticus, Staphylococcus warneri, while from gram-negative isolates such as E. coli, Klebsiella oxytoca, Acetobacter spp., and P. aeruginosa. In conclusion, the use of chitosan film in food packaging has shown promising results in terms of physical and mechanical properties, as well as its ability to preserve the quality of cheese for an extended period. It exhibits transparency, flexibility, tensile strength, and high activity against microorganisms that cause food poisoning. Further research should explore its use in different types of foods and the development of indicators to detect spoilage and contamination in other food products.