EFFECT OF PHASE SEPARATION ON ENZYME KINETICS IN FROZEN SUGAR SOLUTIONS CONTAINING PROTEIN AND POLYSACCHARIDE

• Published in: Journal of food biochemistry Vol. 34; no. 2; pp. 283 - 294
• Main Authors: ROGERS, M.A, ROOS, Y.H, GOFF, H.D
• Format: Journal Article
• Language: English
• Published: Malden, USA Malden, USA : Blackwell Publishing Inc 01.04.2010; Blackwell Publishing Inc; Wiley
• Subjects: Biological and medical sciences; Food industries; Fundamental and applied biological sciences. Psychology; Enzyme; Phase separation; Frozen product; Kinetics; Polysaccharide; Protein; Solution; Sugar
• ISSN: 0145-8884; 1745-4514
• DOI: 10.1111/j.1745-4514.2009.00278.x

Locust bean gum (LBG) or guar and milk proteins were added, individually or in combination, to a solution comprised of sucrose, lactose and milk salts, in formulations designed to have equal freezing point depression and freeze-concentration curves. Alkaline phosphatase and its substrate (disodium ρ-nitrophenyl phosphate) were added and solutions were stored at-10 to-40C for several days. Enzyme reaction kinetics were influenced by phase separation between the biopolymers, with reaction rates being dominated by the protein-rich phase at higher temperatures. Arrhenius calculations revealed a significantly lower activation energy for the LBG, guar, LBG/protein and guar/protein containing systems than for those containing either protein alone or no polymer. Many frozen food systems contain both protein and polysaccharide in solution, as constituents of the foodstuff or added for functional benefit. We studied the effect of protein, polysaccharide and mixtures of the two on enzyme kinetics in frozen sucrose-based systems and showed that phase separation and structural heterogeneity were important considerations in predicting reaction rates from physical parameters of the system. Reactions were dependent not only on the temperature of the sample (which could be modeled by Arrhenius kinetics) but varied highly with composition. The ability to predict reaction rates in more complex systems, such as frozen dairy products or phase-separating systems, presents challenges due to sample inhomogeneity. Careful consideration of how the detrimental enzyme reactions occur and in which phase the various components will be present is required when studying complex systems.