Melt in the mouth feel

The mouth feeling of substances depends on their chemical composition and on the particle size. Protein particles with a diameter of more than 8 pm are experienced as sandy, those in the range of 3-8 pm as powdery, 0.1-3 pm as creamy, and less than 0.1 pm as watery. Therefore, by means of microparticulation of protein concentrates to particles of 0.1-3 pm, it is possible to achieve the melt-in-the-mouth feeling produced by fat globules. In this process, concentrates of ovalbumin. 

Waxy mouth-feel is associated with the presence of high melting point fats that do not quickly melt in the mouth. 

Incidentally, this argument also explains why the mouth feels cold after the ice has melted, since the energy necessary to melt the ice comes entirely from the mouth. In consequence, the mouth has less energy after the melting than before this statement is wholly in accord with the zeroth law of thermodynamics, since heat energy travels from the hot mouth to the cold ice. Furthermore, if the mouth is considered as an adiabatic chamber (see p. 89), then the only way for the energy to be found for melting is for the temperature of the mouth to fall. 

Processors who want a dry feeling on pickup of the snack may select a fat that is solid at room temperature, but melts rapidly in the mouth to avoid the greasy sensation. Some snacks leave a greasy lining in the mouth if they are eaten at the same time the consumer drinks a cold soda pop. A fat, such as the one marked Nondairy in Fig. 34.20, could be used in coffee whiteners. 

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. 

In the temperature range where the carrageenin is normally employed, viscosity characteristics become dependent on temperature, other solutes, and mode of observation. In a system like this it would be more appropriate to speak of consistency, fluidity, or some similar subjective term, and measuring instruments should be selected to reflect the property desired. The texture of a gel is a combination of strength and elasticity, both of which can be measured. The mouth feel of a paste is a combination of yield, viscosity, and melting temperature, the first two of which can be determined by measurements of thixotropic flow. Of particular significance is that measurements assuming Newtonian viscosity do not show the thixotropic characteristics that influence sensory experience. 

A cooling feeling in the mouth is produced by both fats (cf. 14.3.2.2.2), which melt on consumption, as well as low-molecular compounds which are capable of stimulating receptors for cold perception. Menthol is well known (cf. 5.3.2.4). Its threshold for the cooling effect is 9 pmol/kg of water. In comparison with the cooling effect, however, the retronasal threshold for the characteristic menthol odor is lower by a factor of 9.5, which is a disadvantage for the wider application of menthol. 

Eating ice cream soon causes the mouth to get cold, possibly to the extent of making it feel quite uncomfortable. The mouth of a normal, healthy adult has a temperature of about 37 °C, and the ice cream has a maximum temperature of 0 °C, although it is likely to be in the range —5 to — 10°C if it recently came from the freezer. A large difference in temperature exists, so energy transfers from the mouth to the ice cream, causing it to melt. 

Good quality ice cream can only be made with fats that have a suitable melting profile. Fats that melt at high temperatures produce ice cream with a waxy mouth-feel. Conversely, it is difficult to create stable foams with fats that melt at low temperatures, for reasons that are discussed in Chapters 4 and 7. Dairy fat has the right melting profile to... 

Saturated FA, such as palmitic and stearic acids, are stable toward oxidation and polymerization. Because they have a high melting point, they add structure to certain products. However, due to this characteristic the appearance of a fried food may be adversely affected (e.g., waxy mouth-feel, dry surface of stored fried food). Monoenoic FA, primarily oleic acid, are considered to be beneficial from a health standpoint. Frying oils rich in such FA do not add to the structure they are stable against oxidation and provide a light taste. Polyenoic FA (PEFA) deteriorate more rapidly that monoenoic FA and the shelf life of products fried in oils rich in these acids is shorter. Oxidation products formed from PEFA vary widely, depending on the structure of the FA and the relative concentration of linoleic and linolenic acids. The percentage of linolenic acid in heated oils should be very low. 

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