Freezing as a solution to preserve the quality of dairy products: the case of milk, curds and cheese

When thinking of the freezing process in dairy, products consumed in frozen state, such as ice creams come to mind. However, freezing is also considered a viable solutions for many other dairy products, due to increasing interest to reduce food waste and to create more robust supply chains. Freezing is a solution to production seasonality, or to extend the market reach for high-value products with otherwise short shelf life. This review focuses on the physical and chemical changes occurring during freezing of milk, curds and cheeses, critical to maintaining quality of the final product. However, freezing is energy consuming, and therefore the process needs to be optimized to maintain product's quality and reduce its environmental footprint. Furthermore, the processing steps leading to the freezing stage may require some changes compared to traditional, fresh products. Unwanted reactions occur at low water activity, and during modifications such as ice crystals growth and recrystallization. These events cause major physical destabilizations of the proteins due to cryoconcentration, including modification of the colloidal-soluble equilibrium. The presence of residual proteases and lipases also cause important modifications to the texture and flavor of the frozen dairy product.

Water status and dynamics of high-moisture Mozzarella cheese as affected by frozen and refrigerated storage

High-moisture Mozzarella is one of the most exported cheeses worldwide, but affected by short shelf-life. Freezing can help to reduce waste, but its effect on quality needs to be considered. In this study, the physico-chemical changes of Mozzarella occurring during frozen storage and subsequent refrigerated storage (after thawing) were evaluated. Frozen cheeses stored at -18 °C between 1 and 4 months showed microstructural damage and different physical, textural, sensory properties. With NMR relaxometry it was possible to observe freeze-related dehydration of caseins, by measuring the changes in water relaxation times within the matrix. These modifications were confirmed by microstructural observations that showed the formation of larger serum channels in samples subjected to freezing, compared with fresh cheeses. Sensory evaluation showed skin peeling off in frozen samples. By observing the changes at various length scales it was therefore possible to identify the critical points affecting HM Mozzarella cheese quality during frozen storage.

Packaging optimisation to prolong the shelf life of fiordilatte cheese

In this work, an active coating and modified atmosphere packaging (MAP) were investigated to prolong the shelf life of Fiordilatte packaged in traditional brine. First, the screening of MAP was performed in order to select the best gas composition. Then, the combined effect of MAP and coating was investigated. Finally, the coating was loaded with potassium sorbate and its effects under MAP conditions were also assessed. Results highlighted that MAP was able to control growth of the main spoilage microbial group (Pseudomonas spp.); however, the solubilisation of carbon dioxide into the brine compromised Fiordilatte texture. Therefore, the presence of the active coating avoided the damage of gas solubilisation and promoted a shelf life prolongation by about 157%.