ISSN:
1750-3841
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
: Nonenzymatic browning (NEB) rates of amorphous, carbohydrate-based, freeze-dried and spray-dried food model systems containing L-lysine and D-xylose as reactants (5% w/w) were investigated at different temperatures (40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C). Samples were exposed to various relative vapor pressure levels (11%, 23%, and 33%) to adjust water contents. Water sorption was determined gravimetrically, and data were modeled using the Brunauer-Emmett-Teller and Guggenheim-Anderson-deBoer equations. Glass transition, Tg, was observed by differential scanning calorimetry. NEB was followed spectrophotometrically. The surface structures of freeze-dried and spray-dried models were observed by scanning electron microscopy. The freeze-dried samples and the spray-dried samples showed different surface structures and slight differences in thermal behavior. Crystallization of component sugars in the freeze-dried samples was slightly more delayed than in spray-dried samples. The glass transition temperatures in spray-dried samples were higher than those of the freeze-dried samples at the same water activity. The temperature dependence of NEB rate in both systems followed the Arrhenius kinetics, but the activation energies were different. Williams-Landel-Ferry equation could be used to model the NEB kinetics in the freeze-dried system, but for the spray-dried system, negative constant values were not within the allowable range.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2621.2004.tb13637.x
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