Anhydrous milkfat

Figure 17.18. Linear correlation between solid fat content and yield force. Data represent several cooling rates and storage times for anhydrous milkfat (Rye, Litwinenko, and Marangoni 2005).

Figure 17.21. Illustration of the calculation of D from plot of InG versus ln(SFC/100) for anhydrous milkfat.

Figure 7. Isosolids diagram for mixtures of anhydrous milkfat (AMF) and cocoa butter (ICB) (4).

As for the polymorphism of milkfat, a and p forms frequently appear, and p form appears under special conditions when HMF and milkfat are stored for long duration (99-101). In regard to the effects of thermal treatment and emulsification on the polymorphic crystallization of milkfat, Lopez et al. recently performed synchrotron radiation X-ray diffraction and DSC studies, using anhydrous milkfat... 

TABLE 9. Comparison of Thermal and Structural Behaviors of Anhydrous Milkfat and Cream Observed at a Slow Cooling Rate. 

Figure 24. Relative intensity of small-angle X-ray diffraction peaks and DCS thermopeaks of bulk anhydrous milkfat taken during a slow cooling process.

Figure 4. Solid fat content of anhydrous milkfat cooled at 0.1°C/min, 1°C/min, and 5°C/min and stored for a period of 14 days at 5°C.

Figure 5. Crystallization and crystal growth of anhydrous milkfat at controlled cooling rates of 0. PC/min, 1°C/min, and 5°C/min monitored using SFC by pNMR.

Figure 7. Differential scanning calorimetry curves for anhydrous milkfat cooled at rates of 0.1° C/ min, TC/min, and 5° C/min to 5° C and stored for time periods (A) 10 minutes, (B) 1 day, (C) 7 days, and (D) 14 days.

TABLE 2. Rheologically Determined Fractal Dimensions (Dr) and Pre-Exponential Terms X) for Anhydrous Milkfat Crystallized at Various Rates of Cooling and Storage Times at 5°C. 

Figure 12. Polarized light micrographs of anhydrous milkfat cooled at 0. PC/min, PC/min, and 5°C/min. Images were acquired during crystallization in the range of 30°C to 5°C at intervals of 5°C.

The process for cholesterol removal from anhydrous milkfat was patented by General Mills (41). Fractionment Tirtiaux also disclosed the development of a vacuum steam distillation system called the LAN cylinder (38). The steam distillation process (Figure 2) was commercialized, producing a 90-95% cholesterol reduction in anhydrous milkfat with a 95% yield that was reconstituted into 2% fat fluid milk (42). The major disadvantage to the process is that it strips or removes most all volatile flavor components from the fat. These flavor components must be captured (i.e., vacreation) before the distillation process to attempt to reproduce the delicate flavors so desired for reconstitution into a butter product. 

The process has been applied to strip oil-soluble vitamins, sterols, and fatty acids from fats and oils. Cholesterol has been successfully removed from anhydrous milkfat in the range of 70-90% (44, 45). Extensive smdies were performed and various temperatures and pressures were used to fractionate milkfat (46). Unfortunately, the process has not proved to be economically feasible due to the low butter fat yield when significant cholesterol was removed (Land O Lakes research). 

TABLE 15. Standards for Anhydrous Milkfat, Anhydrous Butter Oil, and Butter Oil (65). ... 

Butter should be stored at 4.4°C or lower or at less than — 17.8°C, if it is to be held for more than 30 days (62). The International Dairy Federation (IDF) has produced specifications for milkfat (64), which include reference to the feedstock. (These specifications relate to the time of manufacture but are often used as purchase standards.) The highest grade, anhydrous milkfat (AMF), must be produced from fresh milk, cream, or butter, to which no neutralizing substances have been added. It should have a clean, bland flavor when tasted at 20-25°C and a peroxide value (PV) of less than 0.2 meq oxygen/1 kg fat. Anhydrous butter oil may be produced from butter or cream of different ages and has no pronounced, unclean, or other objectionable taste or flavor. The term butter oil should be used where there is no pronounced unclean or other objectionable taste or odor. The FAOAVHO Codex standard for milkfat is shown in Table 15 (65). 

Currently, dry fractionation of anhydrous milkfat is performed by two conventional systems—Tirtiaux and De Smet (both from Belgium)—which are bulk crystallization processes. The widely used Tirtiaux dry fractionation process enables one-step or up to hve-step fractionation of anhydrous butter oil at any temperature, ranging from 50°C to 2°C (37, 110-113). The milkfat fractions thus obtained can be used as such or the fractions can be blended in various proportions for use as ingredients in various food-fat formulations. The major shortcoming inherent in this system is the long residence time (8-12 h) for nucleation and crystal growth. 

Figure 17. Solid fat content profiles of the control and anhydrous milkfat (--------) the low-...

The quality assurance program for manufacture of butter oil, or anhydrous milkfat (AMF), also focuses on the quality of the raw materials. Naturally, many of the same considerations apply to handling raw cream for AMF manufacmre that apply to butter, except that vacreation is not used. As it is stored under ambient conditions, care against oxidation is essential. Oxidation is perhaps the most important mechanism by which milkfat deteriorates in quality. As the oxidation reaction is autocatalytic (i.e., the products of the reaction act as catalysts to promote further reaction), the normal quality-control tests, peroxide value and free fat acidity, could give misleading results when applied to stored butter. Methods of deaeration have been developed that could reduce potential oxidation (74). 

By definition, ghee is a product obtained exclusively from milk or fat-enriched milk products of various animal species by means of processes that result in the near total removal of water and nonfat solids (similar to anhydrous milkfat) and in the development of a characteristic flavor and texture. Even so, most ghee contains some nonfat solids to enhance the flavor. 

Other Uses. The use of butter or anhydrous milkfat requires more added emulsifiers in ice creams and ice milks, because the naturally occurring milkfat emulsion will have been destroyed in the manufacturing process. Milkfat is also used in fresh cream, frozen cream, dry cream, and plastic cream. Ice creams contain a high level of milkfat, and its manufacture uses substantial quantities of milkfat worldwide. 

Hypoallergenic Butter. A U.S. patent was granted in 1992 for the manufacture of hypoallergenic butter (136). The patent has limited claims. The product is a sterile butter-like product made from anhydrous milkfat it contains no nonfat solids (99.9% free of NFS). 

Lipase-catalyzed esterification of fatty acids with alcohols [oleic acid + ethanol (141, 152, 163, 169, 178, 195-197), oleic acid + oleyl alcohol (144, 179, 198-200), lauric acid + butanol (142), myristic acid + ethanol (138, 139, 143, 201), stearic acid + ethanol (202), anhydrous milkfat fatty acids + ethanol (197)] in SCCO2 has been widely studied to understand the kinetics/mechanism of the reaction and to determine the effect of operating conditions, substrate concentration, and water content on enzyme activity. Alternative catalysts such as p-toluenesulfonic... 

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