(166n) Effect of the Addition of Hydrolyzed Soybean Protein Isolate, Transglutaminase and CaCl2 on the Production of Panela-Type Cheeses with Partial Substitution of Milk Protein

The use of soybean protein for partial or total substitution of the milk protein in the production of fresh cheeses such as panela, one of the most consumed in Latin America, is promising to reduce raw material costs and follow current market trends. Nevertheless, it is a challenge from the process point of view to achieve characteristics similar to those made entirely with milk, where casein plays a fundamental role in creating the structure of the product.

Considering vegetable proteins have very different functional characteristics in terms of water absorption, solubility, and interaction with the fat fraction, soy hydrolysates were created to facilitate the incorporation of these proteins through low-molecular-weight peptides in the casein-fat network.

The use of transglutaminase (TG) has also been explored to improve texture and stability, through the formation of isopeptide bonds (Jaros et al., 2006). Additionally, the coagulation process can be greatly influenced by the addition of calcium chloride, as the calcium ions neutralize the charge of the caseins and allow an increased aggregation of the renneted micelles (Dalgeish, 1983). These could favor the incorporation of soy hydrolysates and develop an interpenetrated network of the components during the production of the panela-type cheese structure.

The objective of this research was to evaluate the effect of the hydrolysis of soy isolate, the addition of transglutaminase and calcium chloride on the development of an interpenetrated network during the production of panela-type cheese with partial substitution of 41.6% of milk protein, evaluated on its texture, proximal, and sensory characteristics.

To achieve the objectives of this investigation, the following five treatments were prepared: control without vegetable protein (A); soybean isolate with CaCl₂, TG, and hydrolysis (B); soybean isolate with CaCl₂ and TG (C); soybean isolate with CaCl₂ and hydrolysis (D); soybean isolate with CaCl₂ (E).

Milk was pasteurized for 30 min at 63ºC and cooled to 32ºC. Calcium chloride (0.125% w/v) was added to some treatments and mixed. All treatments with vegetable protein underwent a heat treatment for 15 min at 85ºC. The protein hydrolysis was performed with an alkaline protease at pH 8.0 for 3 h at 60ºC and was inactivated with heat treatment. Subsequently, the protein solution was added to the milk (corresponding to 1.25% of the total volume and 41.6% of the total protein present in the original raw material) and mixed. Dairy-vegetable protein mixtures were prepared considering a total solids content of 12.5%, using distilled water for the adjustment. According to experimental design, 1.92% TG (of total protein in dairy-vegetable mixtures) was added immediately prior to rennet (0.03% v/v) for the cheesemaking. Content of protein, fat, ash, moisture, sensory analysis, and texture were evaluated.

Experimental results indicated a higher moisture content in treatments with hydrolysis (A with 67% and C with 69%), but lower protein content (39% and 43%, respectively) compared to those with only heat treatment (B with 66% and 44% and D with 66% and 45%, respectively). The missing protein is expected to be present in the whey. All vegetable protein treatments had slightly lower fat content than control, except for C. TG treatments showed slightly lower moisture content and higher yield than their counterparts. A small difference was found regarding the ash content in hydrolyzed treatments.

On the other hand, the sensory analysis showed higher acceptability in A and C (6.0 and 6.3), in comparison with B and D (5.7 and 5.8), but lower with A (7.8). The category appearance affected the acceptability the most because the soybean protein in the treatments was visibly distinguishable. Since treatments A and C had low-molecular-weight peptides, the final product had a more homogenized appearance, and therefore a slightly higher general opinion. Additionally, TG seemed to slightly influence the flavor negatively, while improving the appearance.

Texture profile analysis revealed that treatments A and C had the lowest values in all four categories: hardness, cohesiveness, springiness, and chewiness. Samples B and D had similar cohesiveness and springiness values, but higher hardness and chewiness than A. Treatments A and B had higher values in all texture categories than C and D, respectively, due to the presence of transglutaminase.

The findings show the potential of the partial substitution of milk protein with soybean protein implementing processing techniques to create an interpenetrated network during the cheesemaking of panela-type cheeses. Although the protein content and texture profile must be improved in the hydrolysis treatments to achieve better acceptance by consumers, sensory aspects are promising. Transglutaminase along with calcium chloride improved texture (specifically hardness and chewiness), but impaired sensory aspects like flavor, which suggests the concentration might need adjustment. Further research including a microscopic approach is suggested to gain a deeper understanding of the interactions among the factors.

References

Dalgleish, D. G. (1983). Coagulation of renneted bovine casein micelles: dependence on temperature, calcium ion concentration and ionic strength. Journal of Dairy Research, 50(3), 331-340.

Jaros, D., Partschefeld, C., Henle, T., & Rohm, H. (2006). Transglutaminase in dairy products: chemistry, physics, applications. Journal of texture studies, 37(2), 113-155.