Performance of Cross-linked and Calcium-reduced Milk Protein Concentrate Ingredients in Model High-protein Nutrition Bars
Milk protein concentrate (MPC) and micellar casein concentrate (MCC) have the potential to be the major protein source in high-protein nutrition bars. However, MPCs are known to produce bars that harden too quickly and also result in a crumbly texture. Less is known about the performance of MCC in bars. The objective of this study was to evaluate the performance of transglutaminase (TGase) cross-linked MPC and MCC, and calcium-reduced MPC in high-protein bars.
MPC and MCC retentate were treated with TGase at 0.3 units (low; MPC-L and MCC-L) and 3.0 units (high; MPC-H and MCC-H) per g protein. Controls (MPC-C and MCC-C) were not treated with the enzyme. Separately, CO2 was injected during MPC ultrafiltration to produce calcium-reduced MPC. Retentates were spray-dried to produce ingredients with 72 to 78% protein. Bars were prepared by hand pressing dough containing 30% protein, 8.9% HFCS, 20.7% glycerol, 11% maltitol syrup, and 17.6% palm oil into molds (ID = 21 mm, H = 13 mm) and water activity sample cups. Model bars were stored at 32°C for up to 42 days, during which texture, color, water activity, moisture content, and pH were evaluated. Bar hardness and fracturability were determined with compression, after which a sieve analysis was used to evaluate crumbliness. Data, separated via Tukey’s adjusted p-value (P< 0.05), are the average of two bar preparations.
On day 0, no statistical difference was detected for fracturability and hardness between bars (P < 0.05) and crumbliness reduced when cross-linked ingredients were compared with their respective controls (P < 0.05). Throughout storage, bars formulated with a commercially produced native MPC80 were less crumbly and maintained a larger geometric mean diameter after compression. A high-level of TGase helped maintain cohesiveness in MPC-H and MCC-H compared with their controls through day 16 and day 28, respectively (P < 0.05). Sample moisture content on the day of preparation was the same (P > 0.05), whereas water activity was different (P < 0.05). A significant increase (P < 0.05) in water activity was seen ~24 h after preparation, but after the initial increase it remained stable within each batch. Moisture content and pH remained fairly constant during storage, while visual color change was apparent within the samples. TGase treated and calcium-reduced milk protein ingredients have altered performance in high-protein nutrition bars, which potentially could lead to improved commercial feasibility.
Keywords: milk protein concentrate, micellar casein concentrate, protein bar