@article{hargrove_barbano_drake_2025, title={A sedimentation test to measure heat stability of milk protein beverages}, DOI={10.3168/jds.2025-26974}, abstractNote={A small-scale oil bath immersion-heating system using sealed stainless-steel process tubes was developed that has the flexibility to evaluate a wide range of holding temperatures and times. After heat treatment and rapid cooling, the liquid product was removed from each stainless-steel tube and a centrifugal protein sedimentation test and laser light scattering particle size analysis were done to determine differences among milk protein beverages in heat stability and casein micelle aggregation before and after thermal processing. The sedimentation and particle size analysis method was able to determine differences in protein sedimentation and casein micelle aggregation of milk protein concentrate (MPC) solutions with 85% protein on a DM basis (MPC85) that were rehydrated at 4°C overnight and heated to 55°C and smoothed by homogenization or not smoothed. The cold rehydrated homogenized MPC85 solutions had a casein micelle size particle distribution similar to skim milk. Smoothing reduced particle size before heat treatment and reduced heat-induced protein aggregation versus no smoothing. The oil bath method was applied to cold rehydrated and smoothed MPC85 high-protein beverages over a range of temperatures typical of retorting and UHT-direct steam injection processing with and without added dipotassium phosphate (DKP). The oil bath heat stability method was able to detect differences in sedimentation and casein micelle aggregation with increasing temperature and the large effect of added DKP in preventing protein sedimentation and casein micelle aggregation. Eight different lots of rehydrated commercial MPC85 powders were rehydrated and smoothed; the method was able to identify 2 out of 8 MPC85 powders that had lower heat stability and more casein micelle aggregation than the others. The heat stability method could be a practical tool to screen heat stability of small volumes of different protein beverage formulations and help avoid pilot plant or preliminary production runs on products that will not be heat stable.}, journal={Journal of Dairy Science}, author={Hargrove, Drew and Barbano, David M. and Drake, MaryAnne}, year={2025}, month={Jul} }
 @article{hargrove_sunkesula_barbano_drake_2025, title={Impact of lactose and soluble milk salts on the heat stability of milk proteins}, DOI={10.3168/jds.2025-27486}, abstractNote={Our objective was to determine the separate effects of lactose, soluble mineral concentration, and added dipotassium phosphate (DKP) on the heat stability of milk protein beverages made from rehydrated milk protein concentrate (MPC) with 85% crude protein on a DM basis (MPC85). Seven batches of rehydrated (7.5% protein) liquid MPC were made from each of 2 lots of MPC85 powder. Treatment 1 was 7.5% MPC85 in deionized (DI) water. Treatment 2 was 7.5% MPC85 that was rehydrated with 4°C Jenness-Koops (JK) buffer, a mix of salts that simulate milk salts. Treatment 3 was 7.5% MPC85 with JK buffer with 4.8% (wt/wt) anhydrous lactose added. Treatment 4 was 7.5% MPC85 with a dilution of JK buffer to ∼14% of its original concentration. Treatment 5 was 7.5% MPC85 with diluted JK buffer with lactose added to 0.6% (wt/wt). Treatment 6 was 7.5% MPC85 in DI water with 0.15% (wt/wt) DKP. Treatment 7 was 7.5% MPC85 rehydrated with 4°C UF permeate. Heat stability testing was conducted using an oil bath with a 30-s hold time at 6 temperatures: 135°C, 140°C, 145°C, 150°C, 155°C, and 160°C. The composition of the solute phase of rehydrated and smoothed dried MPC85 had a large impact on the heat stability and aggregation of milk proteins caused by UHT thermal processing temperatures. When MPC85 was rehydrated in deionized water, it had the highest heat stability and the least protein aggregation, and the heat stability was not increased by the addition of DKP. The heat stability of MPC85 was decreased by rehydration in a typical concentration of milk salts (i.e., JK buffer) and was further decreased by the addition of 4.8% anhydrous lactose to the JK buffer. When the MPC85 was rehydrated in UF milk permeate (i.e., milks salts + lactose), the heat stability was comparable to the JK buffer with added lactose. Using diluted JK buffer (∼14% of the level of milk salts and lactose) in MPC85 resulted in increased heat stability that was similar to rehydration in deionized water.}, journal={Journal of Dairy Science}, author={Hargrove, Drew and Sunkesula, Venkateswarlu and Barbano, David M. and Drake, MaryAnne}, year={2025}, month={Nov} }