Fat globules

Bacteria are capable of storing fat in the form of globules. Fat globules may be demonstrated in 24-hr. cultures and usually reach a maximum in about 48 hr. 

Some cells may contain only one large globule others may show the presence of a number of small, scattered globules. 

---

In milk fat, cholesterol is associated with Hpoproteins in the milk fat globule. It is also a component of animal membranes and controls rigidity and permeabihty of the membranes. Cholesterol has interesting surface properties and can occur in Hquid crystalline forms. Plants contain sterols such as P-sitosterol [83-46-5] (4b) or stigmasterol [83-48-7] (4c). Their functions in plant metaboHsm are not yet well understood. Analysis of sterols has proven useful for detection of adulteration of edible fats (9). 

Fig. 1. Diagrammatic representation of fat globule separation in a centrifugal separator (5).

Fett-industrie, /. fat industry. kalk, m. fat lime, -kohle, /. fat coal, coal rich in volatile matter, -kdrper, m. fatty compound, fat aliphatic compound fatty or greasy matter. kUgelchen, n. fat globule, fett-lickern, .f. (Leather) fat-liquor. -Idsend, a. fat-dissolving. 

Sodium citrate is used in ice cream to keep the fat globules from sticking together. Citrates and phosphates both have this property. It is also an anticoagulant. 

Citric acid is also highly astringent it can be used as a skin toner. Like the related compound sodium citrate, citric acid is often an ingredient in ice creams, where it helps keep the fat globules separate. 

Some ice creams contain sodium citrate to decrease the tendency of fat globules to coalesce, and to decrease protein aggregation. This results in a wetter ice cream. The citrates and phosphates are both used for this effect. Calcium and magnesium salts have the opposite effect, making a dryer ice cream. 

The structure of whipped cream is quite complex. A coating of milk protein surrounds small globules of milk fat containing both solid and liquid fats. These globules stack into chains and nets around air bubbles. The air bubbles are also formed from the milk proteins, which create a thin membrane around the air pockets. The three-dimensional network of joined fat globules and protein films stabilizes the foam, keeping the whipped cream stiff. 

When an organism is in steady state, the rates of production and consumption of biomolecules are equal, and there is no net addition to the body on a time scale longer than a few hours (e.g., temporary storage of glucose as glycogen or FAs as fat globules). This is an adequate description of a mature... 

Emulsifiers assist the stabilizing hydrocolloids in controlling crystal structure. They accentuate the function of the homogenizer in reducing the size of the fat globules. They also reduce the interfacial tension between the fat and water phases of the mix. The result is smaller ice particles and air cells when the mix is frozen and a smoother and creamier finished product. 

Fluorescent probes are divided in two categories, i.e., intrinsic and extrinsic probes. Tryptophan is the most widely used intrinsic probe. The absorption spectrum, centered at 280 nm, displays two overlapping absorbance transitions. In contrast, the fluorescence emission spectrum is broad and is characterized by a large Stokes shift, which varies with the polarity of the environment. The fluorescence emission peak is at about 350 nm in water but the peak shifts to about 315 nm in nonpolar media, such as within the hydrophobic core of folded proteins. Vitamin A, located in milk fat globules, may be used as an intrinsic probe to follow, for example, the changes of triglyceride physical state as a function of temperature [20]. Extrinsic probes are used to characterize molecular events when intrinsic fluorophores are absent or are so numerous that the interpretation of the data becomes ambiguous. Extrinsic probes may also be used to obtain additional or complementary information from a specific macromolecular domain or from an oil water interface. 

These assumptions were confirmed by the electrophoresis study of the washed creams. Electrophoresis of purified fat globules is a convenient method to characterize and quantify proteins adsorbed at the oil-water interface [35]. Electrophoretic data indicate that no casein, nor whey proteins, were adsorbed at the surface of raw-milk fat globule. Upon homogenization, caseins adsorbed preferentially at the lipid-water interface. In this case, bound a-lactalbumin accounted for 16% of the total interfacial proteins. Heat treatment also induced the interaction of proteins with the fat globules. The amount of bound proteins (per mg of lipids) for heated raw milk was half that for homogenized milk. 

THE EFFECTS OF THE COMPOSITION OF THE FAT GLOBULE SURFACE ON THE COAGULATION OF MILK... 

Skimming fresh whole milk allowed us to obtain milk fat globules with natural membranes that were blended at a concentration of 35 g/L with hydrated skim milk powder (35g/L). This reconstituted milk was coded CREAM. 

TABLE 1 Average Diameter of the Natural Milk Fat Globules and Emulsified Milk Fat Droplets Stabilized by Different Fat-Water Interfaces in Reconstituted Milks... 

Reconstituted milks with natural milk fat globules (CREAM) or emulsified milk fat droplets stabilized by jS-casein (BCAS), /i-lactoglobulin 5g/L (BLG5), skim milk proteins (MP). 

This study has shown that the process used to coagulate milk has a broad effect on fat globule-protein interactions and on the molecular structure of the gel. In addition we have shown that the different molecular structures of the three coagula correspond to different rheological properties. 

Food products can generally be considered as a mixture of many components. For example, milk, cream and cheeses are primarily a mixture of water, fat globules and macromolecules. The concentrations of the components are important parameters in the food industry for the control of production processes, quality assurance and the development of new products. NMR has been used extensively to quantify the amount of each component, and also their states [59, 60]. For example, lipid crystallization has been studied in model systems and in actual food systems [61, 62]. Callaghan et al. [63] have shown that the fat in Cheddar cheese was diffusion-restricted and was most probably associated with small droplets. Many pioneering applications of NMR and MRI in food science and processing have been reviewed in Refs. [19, 20, 59]. 

---