Study of Water in Dough Using Nuclear Magnetic Resonance

Abstract

Cereal Chem. 76(2):231-235The amount and state of water play an important role in the preparation and properties of wheat flour doughs and their products. A new method for presentation and analysis of relaxation time measurements of protons in dough is described in this article. This new method acknowledges a continuous probability distribution of protons having different relaxation times in heterogeneous systems such as dough, which is dramatically different from the conventional discrete methods that rely on prior assumptions of a number of discrete relaxation components. In the present study, pulsed proton nuclear magnetic resonance was used to study the relaxation characteristics of dough systems at moisture levels of 12-45%. The relaxation curves obtained using a 90-degree pulse (Onepulse) sequence and the Carr-Purcell-Meiboom-Gill pulse sequence were analyzed using a multiexponential discrete model and a continuum model. The discrete model produced three fractions of protons relaxing in three different time domains. The continuum model produced spectra of spin-spin relaxation time vs. amplitude, from which two to five peaks, depending on the moisture content, could be identified. At moisture contents of 23 and 35%, dramatic changes in relaxation time and amplitude were observed with both models. The continuum model provided additional information about the homogeneity of the morphology and physical state of the dough systems.

Effect of aging and ice-structuring proteins on the physical properties of frozen flour–water mixtures

“…Experimental error of the mean of the distributions was approximately 2% for all samples studied. These compare reasonably well with T 2 relaxation values found in the literature for the same system (Assifaoui, Champion, Chiotelli, & Verel, 2006;Engelsen, Jensen, Pedersen, Norgaard, & Munck, 2001;Kim & Cornillon, 2001;Ruan, Wang, Chen, & Fulcher, 1999). The first distribution has been assigned to water that exhibits strong interactions with gluten and starch (Assifaoui et al, 2006;Engelsen et al, 2001;Kim & Cornillon, 2001;Ruan et al, 1999).…”

The effects of soy on freezable bread dough: A magnetic resonance study

“…frozen storage time for both soy and wheat dough varieties (Table 2). Although the observed T 1 times may be slightly less than actual T 1 spin-lattice values due to cross-relaxation behaviours (Watanabe, Fukuoka, & Watanabe, 1995), soy dough exhibited shorter T 1 times for the majority population at every time point, suggesting that the water molecules were more translationally and/or rotationally hindered than those in the wheat dough (Ruan et al, 1999). Literature on spin-lattice relaxation experiments in dough performed using high field NMR (>7.05 T, 300 MHz 1 H frequency) is sparse and, due to the strong dependence of T 1 relaxation times on field strength, it is not appropriate to compare results to data collected at low field strength (ca.…”

“…4.5-5.0 ppm; Lodi, Tiziani, & Vodovotz, 2007) vs. delay time was used to fit an exponential rise to maximum equation to attain T 1 relaxation times. The relaxation curves fit best to a double exponential equation (1), thereby distinguishing two distinct 1 H water populations [attributed to different water populations (Ruan et al, 1999)]. …”

Effect of Fat Content on Water Sorption Properties of Biscuits Studied by Nuclear Magnetic Resonance

“…It was revealed that 1 H transverse relaxation time T 2 is able to reflect the availability and mobility of water inside the foods [16,17]. Monolayer of water molecules is almost immobilized, and it behaves so in many aspects (also in NMR spectroscopy) as part of a solid.…”