As other components and characteristics, fat has a role in determining physical, functional and rheological properties of Mozzarella cheese. Its content in the final product depends on the type of milk used (e.g., in buffalo milk Mozzarella fat content is about 52% on dry matter, while in cow milk Mozzarella cheese is at least 45%) and, eventually, the homogenization of milk to produce either full fat or reduced fat Mozzarella cheese.

In addition to standardizing fat content in milk for more reproducible processes, homogenization of milk allows to obtain Mozzarella cheese at different levels of fat. It also leads to the formation of new fat/water interface, which contains mainly caseins and provides improved stability against free oil formation in cheese. Fat globule size and its dispersion in the casein matrix influences meltability and fat leakage in the final product.

Thus, the fat content of Mozzarella cheese is set by adjusting the casein-to-fat ratio in milk.

At an increased fat content, softness and meltability of Mozzarella cheese improves, while its shreddability tends to be impaired. Also, moisture influences softness and shreddability, following the same pattern of fat. Reducing the fat content leads to a reduction in physical and flavour quality: as an example, low fat mozzarella cheese often tends to toughness and a rubbery aspect.

Generally, Mozzarella cheese made from cow or buffalo milk standardised 3-6% fat shows satisfactory quality. However, lower fat content result in harder texture and in a loss of milky and nutty flavour.

The use of exopolysaccharide (EPS) producing lactic acid bacteria as starter cultures for the improvement of rheological properties of low-fat mozzarella cheese has been widely studied. EPS cultures release these polysaccharides around the bacterial cells, creating a sort of bacterial coats that, due the hydrophilic nature of EPS, helps retain moisture and prevents the fusion of the protein matrix that occurs during cooking and stretching.

Moreover, as reported by Perry et al. (1998), EPS cultures help improve meltability, which is an essential property in low-fat Mozzarella cheese used as pizza topping. The stabilizing effect of exopolysaccharides could be exploited for the production of low-fat dairy products in general (e.g., yoghurt) since they somehow replace fat in relevant functional and rheological properties.

In Mozzarella cheese making process, stretching is a step that strongly depends on moisture content and casein-to-fat ratio in the curd. High fat content influences the stretching temperature, which will increase. Stretching can be defined as a process that transforms a non-oriented matrix, consisting of proteins and fat globules, into a fibrous and highly oriented structure. In this structure, it is interesting how fat, in emulsion, is organized between casein fibres, thus preventing the coalescence of protein fibers.

Another key aspect of stretching is that, during this step, solids are exchanged between the curd and hot stretching water, namely fat and other soluble components, that are lost from the curd. Component losses are to be minimised: in this context, different stretching machines have been developed. One of them is the steam stretching machine, which allows the recovery of the fat recover the fat lost by incorporating the resulting whey in the finished product. Moreover, by implementing mechanical stretching, it is possible to standardise moisture and salt content and minimize cross contamination.

As a concluding remark, to produce Mozzarella cheese with a fat content that satisfies all the physical and sensory properties suitable for the product intended for a specific use (fresh mozzarella, pizza topping, ingredient for different food preparations), we have to consider how fat will affect the final product and how some steps of the process could help avoid fat losses, especially when we plan to introduce low-fat Mozzarella cheese among our product portfolio.

References

Ah, J., & Tagalpallewar, G. P., 2017. Functional properties of Mozzarella cheese for its end use application. Journal of food science and technology, 54(12), 3766–3778. https://doi.org/10.1007/s13197-017-2886-z

Addeo F., 1998. Formaggi da latte di bufala. Aspetti microbiologici e tecnologici. L’allevamento bufalino in Italia. Ieri oggi e domani, «I Georgofili. Quaderni», 1998-IV, Giornata di Studio, Firenze, 30 aprile 1998

Perry, McMahon, Oberg, 1998. Manufacture of Low Fat Mozzarella Cheese Using Exopolysaccharide-Producing Starter Culture. 1998 J Dairy Sci 81:563–566

https://www.journalofdairyscience.org/article/S0022-0302(98)75608-5/pdf

Germano Mucchetti, Erasmo Neviani, 2006. Microbiologia e tecnologia lattiero-casearia. Qualità e sicurezza. Tecniche nuove