Bulk fats measurements

Figure 1 Melting enthalpy of bulk fat and emulsified fat of ice cream mix with (+E) and without (-E) emulsifier after cooling at 5°C measured by DSC.

The same techniques developed for bulk fats can be equally employed to measure the crystallization of emulsified oils. In these cases, the experiments tend to be easier as the contraction of the fat on freezing does not lead to the formation of air spaces in the sample, but, on the other hand, because a smaller volume of material is undergoing a phase transition, the magnitude of the signal change, and thus the precision, is lower. 

The interstitial fluid content of the skin is higher than in the subcutaneous fat layer and normal fluid movement is intrinsically finked to lymphatic drainage as governed by mechanical stresses of the tissue. A model of temporal profiles of pressure, stress, and convective ISF velocity has been developed based on hydraulic conductivity, overall fluid drainage (lymphatic function and capillary absorption), and elasticity of the tissue.34 Measurements on excised tissue and in vivo measurement on the one-dimensional rat tail have defined bulk average values for key parameters of the model and the hydration dependence of the hydraulic flow conductivity. Numerous in vivo characterization studies with nanoparticles and vaccines are currently underway, so a more detailed understanding of the interstitial/lymphatic system will likely be forthcoming. 

Any procedure for wood specific gravity or density based on measuring weight and volume can be considered accurate only if the wood sample has been first extracted with suitable organic solvents to remove extraneous resins, oils, fats, gums, etc. (27). These materials bulk cell walls, block potential sites for water adsorption/ab-sorption, alter potential wood swelling/shrinkage, and thereby interfere with the accurate characterization of wood tissue. 

Ultrasonics is in many ways the ideal measurement method for fat crystallization studies. The ultrasonic properties of a fat are strongly sensitive to solids content and can be measured in opaque fats and through container walls. In the present work I will describe the basic physics of ultrasonic waves, their interactions with matter (particularly with semi-solid fats), and their measurement. I will then describe ultrasonic studies of fat crystallization in bulk and emulsified fats. Finally I will use some measurements of the effect of applied shear on fat crystallization as an illustration of a study that could not be easily undertaken by other methods. 

Speed of sound is thus directly and analytically related to bulk-material properties and becomes a useful measure of fat structure. 

Fig, 2. SFC of bulk (lard , PSCO ) and emulsified fats (lard O, PSCO ) as a function of time, measured isothermally at 25°C. See Figure 1 for abbreviations. 

Metabolic energy is measured in terms of adenosine triphosphate (ATP). How the body uses ATP is described in Sections 27.2 and 27.3. Very little ATP is formed in the first three stages of catabolism. However, in the fourth stage of catabolism, every NADH (see Section 25.2) that is formed in the process of carrying out oxidation reactions in the earlier stages is converted into three ATPs in a process known as oxidative phosphorylation. Thus, the bulk of the energy provided by fats, carbohydrates, and proteins is obtained in this fourth stage. 

The application of nuclear magnetic resonance spectroscopy within the food sector has, imtil recently, focussed primarily on the use of time domain (TD) techniques. These enable the quantitative measurement of bulk properties such as water and fat content in whole foods. The measurement relies on the intrinsic relaxation properties of the proton nucleus when a radio frequency pulse is applied to a sample placed in a magnetic field. The differential between the relaxation properties of major food components allows the proportion of these components to be estimated by reference to a calibration safes. This form of NMR spectroscopy is routinely applied for quality and composition checks and is often undertaken in situ as the instrumentation is both inexpensive and robust... 

Palm oil represents about 23% of the world output of vegetable oils and is employed as a food fat in its bulk state, for example in shortening or in emulsions such as margarine and cream [75,76]. The effects of the addition of the SOEs (S-170, P-170, and 0-170) on palm oil in the O/W emulsion were studied by ultrasonic measurements [12], It was shown that S-170 and P-170 reduced the degree of supercooling and hence accelerated the nucleation, yet the effect of 0-170 was negligible. Table 3 shows the Tc of palm oil in bulk and in O/W emulsion, in which the was defined in the same manner as for n-hexadecane. In the bulk without impurities, Tc was 34°C. With the addition of 1 wt% P-170... 

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