Storage and Temperature Effects on the Solubility, Maillard Browning, and Sensory Characteristics of Milk Protein Concentrates
Milk protein concentrates (MPC) are a relatively young, increasingly important category of dairy ingredients. MPC production in the US increased by 38% between 2008 and 2012. MPC are a highly functional protein, however, solubility and a mild flavor across storage are required for success. The objective of this study was to determine the effect of storage time and temperature on the solubility, sensory characteristics, and Maillard browning of low (45%) and high (80%) protein MPC. MPC45 and 80 were manufactured in triplicate and stored at low (4ºC), medium (25ºC) and high (40ºC) temperatures for 0, 1, 3, 6, and 12 mo. Solubility was evaluated by measurement of turbidity and protein at pH 7 before and after centrifugation. Maillard browning was determined by measuring furosine levels by high performance liquid chromatography (HPLC). Descriptive analysis and gas chromatography-mass spectrometry (GC-MS) were also performed to evaluate sensory and volatile compound characteristics. Solubility of MPC45 was higher than MPC80 (p<0.05), and a significant decrease in solubility in both MPC 45 and 80 occurred over time and as temperature increased (p<0.05). Furosine increased with storage time and temperature, and this change was higher for MPC80 than for MPC45 (p<0.05). MPC45 were characterized by sweet aromatic/milky and cardboard flavors while MPC 80 were characterized by lower sweet aromatic/milky and higher cardboard flavors, as well as distinct tortilla/grapey flavor. Cardboard, tortilla/grapey and animal flavors increased with storage time and temperature (p<0.05). Key volatile flavor compounds in MPC were o,p,m 2-amino-acetophenone (tortilla), 2 2-methyl-butanal (green/fruity), 1-octen-3-one (earthy/mushroom), and methional (potato brothy), and concentrations of these compounds increased with storage time and temperature. An understanding of storage and environmental effects on MPC lays the foundation for optimizing quality.
Keywords: milk protein, flavor, solubility