Fat mixtures

Drain the aqueous acetonitrile (lower) phase into a 500-mL round-bottom flask, and save the separatory funnel for extraction. Extract the hexane-fat mixture by transferring the mixture back to the polypropylene centrifuge bottle and adding 100 mL of acetonitrile-water (4 1, v/v) solution. Balance the duplicate centrifuge bottles, and cap and shake the bottles for 10 min on the shaker. Centrifuge the second extract at 11 000 rpm for 15 min. Decant this second extract into the 250-mL separatory funnel as before. After phase separation, combine the aqueous extracts in the 500-mL round-bottom flask, and discard the top hexane-fat layer. Add 10 drops of Dow Coming Antifoam B emulsion and 3 mL of 10% aqueous Igepal CO-660 (nonionic surfactant) to the flask. 

Guyot, A. (1969) Identification of fat mixtures by analysis of fatty acids and sterols. Bull. Rech. Agron. Gembloux, 4, 484—508. 

Precht, D. (1992b) Detection of foreign fat in milk fat. 2. Quantitative evaluation of foreign fat mixtures. Z. Lebensm. Unters. Forsch., 194, 107-114. 

Schneller, R. and Wullschleger, R. (1992) Quantitative determination of milk fat in fat mixtures by gas chromatographic analysis of triglycerides. Mitt. Gebiete Lebensm. Hyg., 83, 737-744. 

Liew, M., Ghazali, H., Long, K., Lai, O., Yazid, A. 2001. Physical properties of palm kernel olein-anhydrous milk fat mixtures transesterified using mycelium-bound lipase from Rhizomucor miehei. Food Chem. 72, 447 454. 

Lai, O.M, Ghazali, H.M., Cho, F., Chong, C.L. 2000a. Enzymatic transesterification of palm stearin anhydrous milk fat mixtures using 1,3-specific and non-specific lipases. Food Chem. 

Chemical and physical processing methods are not selective and in the starch, protein, fat mixture would hydrolyze all three of the polymers. Thus, by performing specific processing tasks under relatively mild processing conditions, enzymes can offer selected chemical reactions in a heterogeneous mixture, free of undesirable side reactions. 

In mixmres of two or more natural fats, as often occurs in processed foods (e.g., milkfat and cocoa butter in chocolate), it is even more difficult to characterize the true phase behavior for crystallization of fats. One approach that has been used to characterize compatibility of fat mixtures is the isosolids diagram (22). SFC melting curves are obtained (by NMR) for various mixmres of the two fats, as seen for cocoa butter and milkfat in Figure 6. Lines of constant SFC for different temperature and composition are calculated and plotted on an isosolids diagram (Figure 7). 

In the reaction of fat mixtures an exhaust gas containing mainly CO, CO2, Hj, HjO and N2 ( water gas see Section 25.2.4) with extremely low oxygen concentrations is produced. Here, it is useful to consider the relation of lambda to the redox quotient Q defined by Equation (25-31) and the sensor signal based on Equation (25-34). The basis is the stoichiometric equation ... 

In nature one also finds chiral fatty acid or fatty alcohol derivatives with a hydroxyl or amino substituent at the alkyl chain. Common examples are given in Table 2.2.2 of the fatty acids in cheap commercial castor oil (a fat mixture) consist of ricinoleic acid (12-/ -hydroxy-9-Z-octadecene-carboxylic acid). The hydrogenation product (R)-12-hydroxy-stearic acid is the cheapest chiral fatty acid (about 100/g). Sphingosin (2-S-amino-4-E-octadecene-l,3-R-diol) is a chiral a--arnino-diol, which is found in large amounts in nerve tissue ( 5,000/g). Chirality is expensive, if it is localized within the hydrophobic chain. 

Two dimensional 2D ILT was applied in a study addressed to the composition and the physical behaviour of water and fat mixtures. Several dairy products (like milks, cheeses) were measured in the stray field of a superconducting magnet ( H Larmor frequency 5.034 MHz). At g = 0.545 T/m, the samples diffusion properties can be observed, characterized by sample-specific diffusion coefficient ( >) distributions. 

Kloek et al. [32,36] had a similar approach considering a fat mixture of hydrogenated palm oil in sunflower oil as a solute in a solvent. The soluble fraction is calculated with the Hildebrand equation, which is valid for ideal solutions. They calculated the nucleation rate from the same expression as that used by van... 

Whilst the previous discussion gives an idea of the type of information available, often from simple DSC experiments, much work has been directed towards predicting crystallisation behaviour using only the triglyceride composition of the mixture. For example, using the nucleation and growth behaviour, crystal-size distribution and phase diagrams for the components, it maybe possible to predict the functional properties of industrial fat mixtures. 

Interestingly, it is found that certain rates of coohng will produce particular polymorphic forms. For instance, in the PPP/SSS system above, rates greater than about 1 K/min will produce the a form, whereas rates between about 0.2 and 0.5 K/min will produce 3 forms. (3 forms are produced by still lower rates. For many fat mixtures, it is simply not possible to... 

Complex fat mixtures represent a particular challenge to TA. The melting of different polymorphic forms in the fat component of chocolate can be clearly seen (Figure 9.21). 

---