99E-11 |
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K. RIEDL, Food Science and Technology, The Ohio State Univ., 2015 Fyffe Rd, Columbus, OH 43210 and Y. Vodovotz, Dept. of Food Science and Technology, Ohio State Univ., 2015 Fyffe Ct., 227 Parker Food Science Bldg., Columbus, OH 43210-1007. Reports suggest High Pressure Processing (HPP) of starchy foods can alter starch properties related to staling. The physical properties of gels cooked by HPP or conventional means were compared during storage at 4° C. Starch slurries (tapioca and rice, 30 %(w/w) in water) were cooked by HPP (100° C for 10 minutes at 690 MPa), conventional (100° C for 2 minutes at ambient pressure) or a combination of conventional cooking with HPP (100° C for 2 minutes then 10 minutes at 100° C and 690 MPa). The resulting gels were stored at 4° C and characterized by thermo-mechanical techniques (DSC, DMA, TGA) and according to water mobility (proton relaxation NMR) on a weekly basis for 8 weeks. All gels staled maximally within 3 weeks of refrigeration as indicated by amylopectin retrogradation and firming. During rapid staling proton T1 values peaked while proton T2 relaxation and “freezable” water (by DSC) dipped to a minimum then rebounded. These transient features were unexpected since parameters of starchy foods typically change in only one direction with staling. HPP delayed firming of rice gels by 2 weeks although retrogradation was similar. HPP-cooked tapioca gels had a delayed peak in proton relaxation and a later rise in retrogradation although the firming rate was similar. The transient changes observed in this study have not been reported previously and may be peculiar to low solids conditions (30%). The increase in T1 and drop in T2 are consistent with increased solid character of water protons in amylopectin crystal hydrates. The temporary nature of the changes (peaks and valleys) might reflect re-equilibration of water within the amorphous starch phase after rapid crystal growth. The basis for delayed staling deserves further study since similar phenomena may occur in other high moisture starch foods, e.g. cooked rice.
Session 99E, Nonthermal Processing: General II
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |