Food relaxation

SKELETAL MUSCLE RELAXANTS. The nurse gives these drug with food to minimize gastrointestinal distress, hi addition to drug therapy, rest, physical therapy, and other measures may be part of treatment. 

The relatively low entry level instrumentation cost and the relatively simple experimental methods associated with GARField - both comparable to a standard bench-top relaxation analysis spectrometer as commonly used by the food industry, for example, for water/fat ratio determinations - offer potential advantages to the industrial based user. Indeed, the overwhelming majority of the applications development work described here has been carried out in collaboration with major multi-national industrial corporations such as ICI Paints, Unilever and Uniqema, with industry sponsored research laboratories and associations such as Traetek, and with a range of small-medium sized enterprises. 

NMR spectroscopy is one of the most widely used analytical tools for the study of molecular structure and dynamics. Spin relaxation and diffusion have been used to characterize protein dynamics [1, 2], polymer systems[3, 4], porous media [5-8], and heterogeneous fluids such as crude oils [9-12]. There has been a growing body of work to extend NMR to other areas of applications, such as material science [13] and the petroleum industry [11, 14—16]. NMR and MRI have been used extensively for research in food science and in production quality control [17-20]. For example, NMR is used to determine moisture content and solid fat fraction [20]. Multi-component analysis techniques, such as chemometrics as used by Brown et al. [21], are often employed to distinguish the components, e.g., oil and water. 

The measurement of viscosity is important for many food products as the flow properties of the material relate directly to how the product will perform or be perceived by the consumer. Measurements of fluid viscosity were based on a correlation between relaxation times and fluid viscosity. The dependence of relaxation times on fluid viscosity was predicted and demonstrated in the late 1940 s [29]. This type of correlation has been found to hold for a large number of simple fluid foods including molten hard candies, concentrated coffee and concentrated milk. Shown in Figure 4.7.6 are the relaxation times measured at 10 MHz for solutions of rehydrated instant coffee compared with measured Newtonian viscosities of the solution. The correlations and the measurement provide an accurate estimate of viscosity at a specific shear rate. 

The lower esophageal sphincter is a manometrically-defined zone of the distal esophagus with an elevated basal resting pressure. The sphincter is normally in a tonic, contracted state, preventing the reflux of gastric material from the stomach. It relaxes on swallowing to permit the free passage of food into the stomach. 

Food is stored in the body of the stomach, which may expand to hold as much as 11 of chyme. As food enters the stomach, it undergoes a reflex relaxation referred to as receptive relaxation. It enhances the ability of the stomach to accommodate an increase in volume with only a small increase in stomach pressure. The fundus does not typically store food because it is located above the esophageal opening into the stomach. Instead, it usually contains a pocket of gas. 

For the most part, the resting pH of the stomach is nearer to 2 than 1 however, during feeding the meal causes a transient rise in pH to 4—5 depending on the volume and nature of the meal consumed. The fundus undergoes receptive relaxation to allow the proximal stomach to accommodate the food mass in the distal stomach, the food is triturated to form chyme, which is ejected into the duodenum in spurts of 2-5 mL. The division of function causes significant inhomogeneity in... 

In some cases, gastroesophageal reflux is associated with defective lower esophageal sphincter (LES) pressure or function. Patients may have decreased LES pressures related to spontaneous transient LES relaxations, transient increases in intraabdominal pressure, or an atonic LES. A variety of foods and medications may decrease LES pressure (Table 24-1). 

NMR relaxation time measurements (7) and T2) can provide valuable information for investigating the molecular dynamics of water in food systems. However, a number of factors can seriously complicate the analysis... 

FIG. 23 A schematic illustration of the molecular motions and associated T2 relaxation curve behavior for the three major domains in foods—liquid, viscous liquid, and solid (crystalline and glassy). Typical H T2 NMR relaxation time values observed in these domains, and values specific for water in liquid and crystalline domains, are listed. 

Using the time-dependent aspect of state diagrams, Roos (2003) illustrated the effects of temperature, water activity, or water content on relaxation times and relative rates of mechanical changes in amorphous systems (Figure 36). This diagram can be considered as a type of mobility map, where mobility increases (relaxation time decreases) as temperature and/or water content/activity increases. Le Meste et al. (2002) suggested the establishment of mobility maps for food materials showing characteristic relaxation times for different types of molecular motions as a function of temperature and water content. 

Champion, D., Le Meste, M., and Simatos, D. 2000. Towards an improved understanding of glass transition and relaxations in foods Molecular mobility in the glass transition range. Trends Food Sci. Technol. 11, 41—55. 

In Spectral Methods in Food Analysis (M.M. Mossoba, ed.), pp. 1-88. Dekker, New York. Eads, T.M. and Axelson, D.E. 1995. Nuclear cross relaxation spectroscopy and single point imaging measurements of solids and solidity in foods. In Magnetic Resonance in Food Science (P.S. Belton, F Delgadillo, A.M. Gil, and G.A. Webb, eds), pp. 230-242. Royal Society of Chemistry, Cambridge, UK. 

Hills, B.P., Ridge, C.E., and Brocklehurst, T. 1996b. NMR water relaxation, water activity, and bacterial survival in porous media. J. Sci. Food Agric. 71, 185-194. 

Fito, P., Andres, A., Chiralt, A., and Pardo, P. 1996. Coupling of hydrodynamic mechanism and deformation-relaxation phenomena during vacuum treatments in solid porous food-liquid systems. J. Food Engineer. 27, 229-240. 

Fito, P., Chiralt, A., Barat, J.M., and Martinez-Monzo, J. 2002. Mass transport and deformation relaxation phenomena in plant tissues. In Engineering and Food for the 21st Century (J. Welti-Chanes, G.V. Barbosa-Canovas, and J.M. Aguilera, eds), pp. 235-252. CRC Press, Boca Raton, FL. 

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