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Title: Role of Glassy and Crystalline Transitions in the Responses of Corn Starches to Heat and High Pressure Treatments: Prediction of solute-induced Barostability from solute-induced Thermostability

Author
item KWEON, MEERA
item SLADE, LOUISE - FD.POLYMER SCI CONSULT.
item LEVINE, HARRY - FD.POLYMER SCI CONSULT.

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2007
Publication Date: 5/5/2008
Citation: Kweon, M., Slade, L., Levine, H. 2008. Role of Glassy and Crystalline Transitions in the Responses of Corn Starches to Heat and High Pressure Treatments: Prediction of solute-induced Barostability from solute-induced Thermostability. Carbohydrate Polymers. 72(2):293-299.

Interpretive Summary: HHP treatment at 25 degrees C showed a significant impact on amorphous and crystalline transitions of corn starches with increasing values of pressure, exhibited as annealing, gelatinization, pasting, and subsequent retrogradation (more notable for dent corn starch), even though the treatment was conducted at a temperature below the characteristic value of the glass transition temperature of amylopectin (gelatinization temperature) at atmospheric pressure. At elevated temperatures for HHP treatment, a further effect on annealing was observed. Also, longer times of HHP treatment at the highest pressure (600 MPa) resulted in further annealing at both 25 degrees C and 70 degrees C. A high (lyotropic) concentration of NaCl or a high (glass-forming) concentration of sucrose showed baroprotective effects against starch gelatinization during HHP treatment at 25 degrees C, but the protective effect of sucrose was more dramatic than that of salt. In summary, it has been demonstrated that the designed use of combined thermal and HHP processing could enable enhanced food quality (novel textures, as well as retained flavors and nutrients), conformance (reduction in process variation), and safety (preservation).

Technical Abstract: In order to explore the effects of heat and high hydrostatic pressure (HHP) on glassy and crystalline transitions of starches, and the distinctive contributions of amylopectin and amylose, with respect to: annealing, gelatinization, pasting, and retrogradation, an experimental design with dent and waxy corn starches was conducted, using pressure (atmospheric to 600 MPa), temperature (room to 70 degrees C), and time (5 to 60 min). The type of diluent was also included as a design factor to study modulation of responses by: water (most efficient plasicizer, lowest Tg), salt-water (non-glass-forming solvent), and sucrose-water (glass-forming plasicizer, high Tg). When 50% w/w starch slurries were HHP-treated for 15 min at 25 degrees C, treatment at 300 MPa showed no effects on glassy or crystalline transitions, but treatment at 600 MPa showed significant extents of gelatinization and annealing, and smaller extents of subsequent retrogradation, for both starches. Longer time of the HHP treatment at 600 MPa showed the role of the glass transition. Elevated temperature of the HHP treatment at 600 MPa showed the roles of both glassy and crystalline transitions. Two molar NaCl (lyotropic concentration) or 50% w/w sucrose (glass-forming concentration) showed protective effects against starch gelatinization during HHP treatment at 600 MPa, 15 min, 25 degrees C, but the protective effect of sucrose was more dramatic than that of salt. In the case of the dent and waxy corn starches, thermostabilization by lyotropic concentrations of NaCl solutions and glass-forming concentrations of sucrose solutions predicted barostabilization.