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Water uptake mechanism in crispy bread crust

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Author: Nieuwenhuijzen, N.H. van · Meinders, M.B.J. · Tromp, R.H. · Hamer, R.J. · Vliet, T. van
Institution: TNO Kwaliteit van Leven · KvL
Source:Journal of Agricultural and Food Chemistry, 15, 56, 6439-6446
Identifier: 240953
doi: doi:10.1021/jf800537b
Keywords: Nutrition · Food technology · water · adsorption · article · bread · chemistry · comparative study · humidity · kinetics · physical chemistry · sensation · Adsorption · Bread · Chemistry, Physical · Humidity · Kinetics · Sensation · Water


Crispness is an important quality characteristic of dry solid food products such as crispy rolls. Its retention is directly related to the kinetics of water uptake by the crust. In this study, a method for the evaluation of the water sorption kinetics in bread crust is proposed. Two different sorption experiments were used: an oscillatory sorption test and a sorption test in which the air relative humidity (RH) was increased stepwise. These two experiments had different time scales, which made it possible to get a better understanding of the mechanisms involved. Results show that the adsorption and desorption dynamics of the oscillatory sorption test could be described by a single exponential in time. The water uptake rate (k) was one of the fitting parameters. A maximum in the water uptake rate was found for a RH value between 50 and 70%. The rate parameters of the experiment where RH was increased stepwise were around a factor 10 lower tharj those derived from oscillatory sorption experiments. This is an important factor when designing experiments for the determination of water uptake rates. In addition, also a parameter describing the time dependence of the rate parameters of the oscillatory sorption experiment was calculated (C), again by fitting a single exponential to the rate parameters. C was in the same range as the rate parameter of the isotherm experiment. This indicates that different (relaxation) processes are acting at the same time in the bread crust during water uptake. © 2008 American Chemical Society.