Improving quality and functionality of low-fat mozzarella cheese using whey proteins and plant proteins

Abstract

Whey proteins and plant proteins are used in cheese milk as additives and they play a significant role in quality and functionality of cheese. The use of whey protein concentrate (WPC), denatured whey protein (DWP), soy protein hydrolysate and pea protein hydrolysate on the color and browning, texture, meltability, pizza bake performance, stretch property, micro-structure and proteolysis of low-fat Mozzarella cheeses (LFC) made by pre-acidification of milk with organic acids to different pH values were investigated during 28 days of cold storage. Full-fat Mozzarella cheeses (FFC) were manufactured as a control. The results showed that the addition of 0.5% whey protein increased the moisture content of LFC, while the fat, protein and calcium content of cheese was slightly decreased or remained unaffected. Second, the quality and functional properties of LFC were improved due to the addition of whey protein, which can be reflected in the increased color and browning L* values and meltability, decreased hardness and stretch force, and better pizza bake and stretch performance of LFC containing whey protein. Besides, DWP improved the quality of Mozzarella cheeses better than WPC. Third, the micro-structure results showed that serum pores and channels of LFC with whey proteins were slightly reduced than those of the cheeses without whey proteins, suggesting that LFC obtained a denser casein network upon whey protein addition. Fourth, the texture, meltability, pizza bake and stretch performance of all the Mozzarella cheeses were improved with advancement in the 28 days of storage at 4 ℃ due to proteolysis. Finally, pre-acidification of cheese milk also improved the functionality, color and browning and softness of cheeses because of the increased interactions between protein and surrounding serum. Using part-acidification (acidifying agent was prepared by mixing an equal volume of 100 mM citric acid and 100 mM lactic acid ) to adjust cheese milk containing 0.5% DWP to pH 5.8 resulted in a LFC with the best stretch and pizza bake performance, indicating its great potential to be used as a FFC substitute. The addition of 2-8% soy protein or pea protein hydrolysate powder in cheese milk or curd also improved the functionality of LFC. It was observed that the color and browning L* values of LFC decreased proportionally to the level of plant protein hydrolysates in milk. The assessments of baking and stretching quality parameters demonstrated that the addition of plant protein hydrolysates in the range of 2% to 6% enhanced the baking and stretching performance of cheese. However, when the concentration of the hydrolysates was above 6%, the stretch performance of cheeses containing plant protein hydrolysates was reduced due to the hindrance of casein network caused by protein hydrolysate. The CSLM and SEM images showed that protein network became denser and exhibited irregular honeycomb structure as the levels of plant protein hydrolysates increased. Overall, the addition of 0.5% DWP or 6% plant protein hydrolysates improved the quality and functionality of LFCs, and made their overall performance closer to that of the FFC, indicating that these protein additives could be potential texturizers for use in dairy food.