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Effect of Different Enzymes on the Textural Stability of Shelf-Stable Bread

¹Performance Enhancement and Food Safety Team, Combat Feeding Directorate, U.S. Army Natick Soldier Center, Natick MA 01760-5018. ²Frito-Lay, Inc., Plano, TX. ³The Ohio State University, Department of Food, Agricultural, and Biological Engineering, Columbus, OH. ⁴Corresponding author. Phone: 614-292-0419. Fax: 614-292-9448. E-mail: kaletunc.1@osu.edu

Three enzyme systems (2 amylase-based and 1 protease-based) were tested in shelf-stable bread to determine effectiveness in preserving texture during storage for eight weeks. Each enzyme was tested in formulations without glycerol or with 6% glycerol. Bread samples were analyzed to determine physical properties (crumb density, crust-to-crumb ratio, rate of moisture distribution from crumb to crust), mechanical properties (modulus, and a parameter [C1] describing resistance to high levels of deformation obtained by fitting stress-strain data to a three-parameter function), and thermal properties (thermal stability and enthalpy of transitions) as a function of storage time. Mechanical properties were further analyzed to predict asymptotic firmness. Bread firmness after storage as evaluated in terms of modulus and C1 were lower in all enzyme-added systems, the effect of protease being the most significant. Enzymes had less effect on glycerol-containing systems with no apparent trend. The breads had complex thermal behavior and exhibited multiple transitions. Both amylase preparations in the presence of glycerol reduced the amount of starch recrystallization.