14B-8 |
Kinetics of acid-catalyzed sucrose hydrolysis in solution under ambient storage conditions: effect of pH and reducing sugars |
S. Chuy, Nutrition and Food Science, Auburn University, 328 Spidle Hall, Auburn, AL 36849 and L. N. BELL, Dept. of Nutrition & Food Science, Auburn Univ., 328 Spidle Hall, Auburn, AL 36849.
Sucrose is commonly added to foods as a sweetener, humectant, and texturizer. Its hydrolysis would therefore change the sweetness profile, humectancy, and texture of the food product as well as providing reducing sugars that could promote the Maillard reaction. Stability studies under processing conditions indicate that fructose decomposition products enhance sucrose inversion. However, processing conditions are not synonymous with storage conditions. Factors contributing to sucrose inversion during storage should also be evaluated. The objective of this project was to study the kinetics of acid-catalyzed sucrose hydrolysis during ambient storage as affected by pH and reducing sugars. Three experimental solutions were each prepared from pH 5 to 7.4: 0.14 M phosphate buffer/1.4 M sucrose, 0.14 M phosphate buffer/0.14 M glucose/1.4 M sucrose, and 0.14 M phosphate buffer/0.14 M fructose/1.4 M sucrose. Aliquots of each solution were stored at 25ºC. At regular time intervals over a 9 month period, samples were removed for glucose analysis via an enzymatic assay. Glucose concentrations were converted into sucrose concentrations. Sucrose loss was modeled using pseudo first order kinetics. Sucrose hydrolysis occurred at all pH levels, being fastest at pH 5. The presence of glucose or fructose had no effect on sucrose hydrolysis at pH 5 and 25ºC, with the rate constant being 1.3E-4 d -1. At higher pH levels, both glucose and fructose enhanced the hydrolysis of sucrose. At pH 6.5, glucose increased the hydrolysis rate 10-fold in comparison to that without reducing sugars. The rate-enhancing effect of fructose became increasingly significant as pH increased. However, glucose caused a larger increase in the rate constant than fructose. Sucrose hydrolysis can occur in neutral solutions during ambient storage, produce reducing sugars in sufficient amounts to cause non-enzymatic browning, and ultimately have a negative effect on food quality. These effects should be recognized during product development.
Session 14B, Food Chemistry: Physicochemical properties
|