Influence of water activity and storage temperature on lysine availability of a milk like system

• Published in: Food research international Vol. 35; no. 9; pp. 849 - 853
• Main Authors: Malec, L.S., Pereyra Gonzales, A.S., Naranjo, G.B., Vigo, M.S.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2002; Elsevier
• Subjects: Available lysine; Biological and medical sciences; Casein; Food industries; Fundamental and applied biological sciences. Psychology; Maillard reaction; Milk and cheese industries. Ice creams; Water activity; Available lysine; Maillard reaction; Water activity; Casein; Temperature; Dairy product; Thermal denaturation; Bioavailability; Reducing sugar; Milk protein; Lactose; Warehousing; Lysine; Aminoacid; Models; Milk
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/S0963-9969(02)00088-1

The effect of water activity ( a w) at mild temperatures on the rate constants for available lysine loss was evaluated in a lactose–casein model system. Lactose/casein ratio was the same of milk. Samples were equilibrated at 0.33, 0.43, 0.52, 0.69, 0.85 and 0.98 a w, stored at 37, 50 and 60 °C and lysine damage tested by the o-phthaldialdehyde method. At prolonged storage times, lysine damage became considerable at every a w and temperature studied. At 37 and 50 °C, the reaction rate was the highest at 0.52 a w. However, when the temperature was increased the influence of a w was less steep. At 60 °C, kinetic constants for 0.33, 0.43 and 0.52 a w were not significantly different. The activation energies ranged from 117 to 156 kJ mol −1. The highest values corresponded to 0.33 and 0.43 a w, showing a higher temperature dependence of the reaction with decreasing moisture content.