Textural changes and mechanisms in ultra-high-temperature-treated ambient cheese products under different storage...

Ultra-high-temperature-treated cheese products can be stored at ambient temperature for over 6 mo, reducing costs and broadening market reach. However, maintaining texture consistency during storage remains a challenge. This study investigated the textural changes and underlying mechanisms in UHT-treated ambient cheese products stored at 4°C and 25°C for 9 mo. The results revealed that hardness significantly increased over time in both storage conditions, with the 25°C group exhibiting a more pronounced increase. Syneresis initially decreased due to enhanced water-binding capacity from protein hydrolysis and phosphate breakdown but later increased as microstructural rearrangements occurred. The pH values first declined, attributed to acidic byproducts of proteolysis, then rose with phosphate ion formation. Low-field nuclear magnetic resonance analysis showed a shift from free to bound water, correlating with denser protein networks. Analysis via SDS-PAGE confirmed that proteolytic reactions became more extensive with increasing storage temperature and storage time, as shown by a significantly faster rate of protein degradation in ambient cheese products than in refrigerated. Confocal microscopy highlighted structural densification initially, followed by pore formation in later stages. Refrigeration at 4°C slowed deterioration compared with 25°C storage. The findings underscore the combined roles of proteolysis, mineral dynamics, and water redistribution in quality changes, providing insights for optimizing storage conditions of ambient cheese products.