Kinetics of amino acid loss in carrot juice concentrate during storage

The loss of total amino acid (TAA) and individual leading amino acids (LAAs) in 20, 40, 60 Brix carrot juice concentrate (CJC) stored at −18 C, 0, 25 and 37 °C is investigated. The LAAs are histidine, proline, serine, aspartic acid, glutamic acid, arginine and alanine in CJC, their summation account for about 86 percent in TAA. As the storage temperature increase and the storage time extend, the loss of TAA and LAAs concentration is significantly increased (P<0.05). The higher the storage temperature such as 37 °C is, the greater the loss of TAA and LAAs concentration is. After 6 month storage, the TAA loss percentage is 72.85, 70.13 and 78.32 in 20, 40, 60 Brix CJC at 37 °C, respectively. The loss kinetics of TAA concentration is well fitted using the first-order reaction and the zero-order reaction. As compared to the zero-order reaction, the first-order reaction provides a perfect fit with better model performance parameters, which included accuracy factor (Af), bias factor (Bf), the sum of the squares of the differences of the natural logarithm of observed and predicted values (SS), and root mean square error (RMSE). Similarly, the loss kinetics of LAAs also followed the first-order reaction. After 6 months storage at 37 °C, the loss percentage of histidine, proline, serine, aspartic acid, glutamic acid, arginine and alanine is 95.46, 93.52, 78.05, 73.14, 70.35, 67.14 and 62.72 in 60 Brix CJC, respectively, the histidine is the most reactive one of LAAs in the study.