Chocolate physical properties

Cocoa butters have a natural variation in physical properties related to the triacylglycerol structure Malaysian, Indian and Indonesian butters are harder than those from Africa, and Brazilian butters are the softest. The hardness of typical butters from some continents has changed over the years (Timms and Stewart, 1999). Because the hardness affects the processing required for chocolate manufacture, suppliers of cocoa butter to that trade blend butters to attempt to produce a uniform product. 

Non-cocoa fats are added to certain chocolates for a number of reasons. Their introduction was prompted by a sharp rise in the cost of cocoa butter in the 1960s which coincided with the emergence of technologies suitable to analyse butter composition and produce substitute fats. Principally, chocolate manufacture can be made more economical by using more stable processing conditions when other fats are added. The variations in processing required by changes in the chemical composition and physical properties of different batches of cocoa butters, and the effects of erratic harvests, can be ameliorated by the incorporation of the tailored non-cocoa fats. 

Verhey, J.G.P. 1986. Physical properties of dried milk in relation to chocolate manufacture. 

The sensory properties, especially texture and appearance, of milk fat-based products such as butter, cream, cheese, ice cream and milk chocolate are largely dependent on the physical properties of the product, especially properties governed by the phase change behavior of the fat, used here to mean melting and crystallisation behavior, crystal polymorphism and microstructure (Birker and Padley, 1987 O Brien, 2003). The same may be said of the functional properties of milk fat, milk fat fractions and milk fat-based products when these are used as food ingredients. 

From the snap, gloss and texture of chocolate to the shelf life of frozen foods, crystalline microstructure plays a very important role in the texture, appearance, shelf life and overall quality of many foods. The total amount of crystaUine phase in a food, as well as the size distribution and shape of the crystals within the food, can affect the physical properties of the product. Furthermore, some mataials in food can crystallize in different polymorphic forms so that control of polymorphic transformations may also be necessary. 

Fats provide fundamental structural and textural attributes to a wide range of consumer products, including lipstick, chocolate, and everyday products such as butter and margarine (1, 2). Within these fat-based products, certain textural properties are required to meet desirable sensory attributes to gain consumer acceptance (3). This has led to an increase in research efforts on the physical properties of fats, particularly their rheology. 

Pastry, Cake, and Biscuit Products. In general, fats play several essential nutritional, technological, functional, and organoleptic roles in most all-bakery applications. As a result of its physical properties, fat plays a major part in the production of the majority of items in the pastry, cake, biscuit, and chocolate confectionery sector for example, in the preparation of pastry cream and in the desired appearance and texture of the end product. These physical properties include, above all, the rheological properties (consistency, plasticity, texture, etc.), and the properties of fusion and crystallization depend on the type of fat, the temperature, and the working conditions of the product. 

Confectionery-Liquors and Liqueur. In chocolate confectionery and for pastry creams, it is the physical properties linked to the fusion and the crystallization of the fat that are essential. For milk chocolate, for coating or in bars, AMF can be used in proportions that depend on its compatibility with cocoa butter, whose properties of hardness and rapid fusion at 35°C cannot be altered. Thus it is currently accepted that AMF with high fusion levels obtained by the fractionation technique can be used. In general, milkfat has an interesting characteristic it inhibits the appearance of fat bloom (133). 

Have you ever had candy apples like those shown in Figure i Or have you had strawberries dipped in chocolate When you make these treats, you can see a substance in two states. The fruit is dipped into the liquid candy or chocolate to coat it. But the liquid becomes solid when cooled. However, the substance has the same identity—and delicious taste—in both states. Most substances, such as the mercury shown in Figure 2, can be in three states solid, liquid, and gas. The physical properties of each state come from the arrangement of particles. 

The new European Chocolate Directive [14] allows the addition of up to 5% of vegetable fats other than cocoa butter (CB), the so-called cocoa butter equivalents (CBEs), in chocolate. CBEs resemble the chemical composition and physical properties of CB very closely, making them therefore extremely difficult to quantify and even in some cases to detect (especially at very low levels). There is a perceived need within official control laboratories for reliable analytical methods for the quantification (around the 5% level) of CBEs in chocolate, as Member States laws and administrative provisions need to comply with the new Chocolate Directive before August 2003. All proposed analytical methods have been evaluated by the JRC in collaboration with EU expert laboratories [15]. The performance of several methods has been compared and a final method based on the analysis of the main components, triglycerides, has been proposed for further validation. 

The chocolate paste needs tempering before further operations take place. Tempering is required because of the polymorph property of the cocoa butter. Polymorphy is a phenomenon when a given material is able to produce crystal-modifications of different physical properties. Out of four possible modifications only one, the P-crystal modification is stable. Through tempering it is possible to obtain P -crystal modification which is transformed into stable P-modification in the finished product. 

The physical properties of PKOs resemble particularly closely those of cocoa butter, and it is generally acknowledged that the best types of CBS are made from this fat. Substantial quantities of PKO are therefore fractionated in Western Europe, the US and Malaysia for this purpose. Coconut stearin, on the other hand, while having exceptionally sharp melting properties and mouth feel, has a melting point which is too low for substitute chocolate and most coatings. It is also obtained in lower yield and so is more costly to produce. Its uses, therefore, are restricted to the finest biscuit creams and a small number of luxury products. 

PHYSICAL PROPERTIES eolorless to white crystalline solid bitter, chocolate-like odor soluble in ethyl acetate, ethyl silicate, ethyl borate, 1-bromopropane, carbon disulfide. 

For chocolate fats in particular, it is often necessary to know the composition of the TAGs based simply upon the level and position of unsaturation. The SOS (1-saturated, 2-monoimsaturated, 3-satu-rated) type TAGs are responsible for the particular physical properties of cocoa butter and its equivalents. The information can be obtained from the reversed-phase method mentioned above, but a simpler profile is obtained by using 5% silver nitrate-impregnated silica as a 25 cm column. 

Proper control of the crystalline microstructure leads to products with the desired textural properties and physical characteristics. For example, tempering of chocolate prior to molding or enrobing is designed to control crystallization of the cocoa butter into a large number of very small crystals that are aU in the desired polymorphic form. When controlled properly, the cocoa butter crystals in chocolate contribute to the desired appearance (shine or gloss), snap, flavor release, meltdown rate upon consumption, and stability during shelf life (fat bloom). Similar... 

The dispersion of the crystalline fat phase in a material determines the physical and textural properties of a lipid-based product. For example, the hardness, snap, and glossy appearance of chocolate is caused by crystallization of cocoa butter in the form of numerous, very small (1 pm or less) crystals of the most stable polymorph (p form). The size distribution (mean size and range of sizes), polymorphic form, and shape of the fat crystals, as well as the network formed among the crystals, all play important roles in determining physical attributes of lipid-based products. 

The candy technologist, in manufacturing the various types of product ranging from hard candy and caramel to liquid-center chocolates, employs many of the physical and chemical properties of sucrose (71). In hard candies, crystallization and stickiness are the two most common problems limiting shelf life (23). Use of the proper amount of an acidic doctor, such as cream of tartar, causes enough... 

In many cases of application it is not sufficient to measure a size distribution with respect to an arbitrary physical particle property, but to the one which is as closely as possible related to the desired product property. In most cases it would anyhow be better, to measure the product property directly and not the particle size distribution of the product. Only if the dependency between product property and particle size distribution is known, can conclusions be drawn between both. Sugar in chocolate feels gritty between onds teeth if its coarsest particles are bigger than 15 im. The strength of concrete depends on the size distribution of its binder,that is cement, and so on. 

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