The Science of Ice Cream (RSC Paperbacks)
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Ice cream as we recognize it today has been in existence for at least 300 years, though its origins probably go much further back in time. Though no one knows who invented ice cream, the first improvement in its manufacture was made by Nancy Johnson, of Philadelphia, who invented the first ice cream making machine in the 1840s.
The Science of Ice Cream begins with an introductory chapter on the history of ice cream. Subsequent chapters outline the physical chemistry underlying its manufacture, describe the ingredients and industrial production of ice cream and ice cream products respectively, detail the wide range of different physical and sensory techniques used to measure and assess ice cream, describe its microstructure (i.e. ice crystals, air bubbles, fat droplets and sugar solution), and how this relates to the physical properties and ultimately the texture that you experience when you eat it. Finally, some suggestions are provided for experiments relating to ice cream and ways to make ice cream at home or in a school laboratory.
overcome these forces and move past each other. The result of this at the macroscopic level is that the whole liquid flows less easily, i.e. its viscosity increases. Conversely, as the temperature increases the molecules move faster and more freely so the viscosity decreases. This is illustrated in Figure 2.13, which shows the viscosity of a 20% sugar solution as a function of temperature. Figure 2.14 shows that the viscosity of sucrose solutions increases as a function of solute concentration. 3
invert sugar, which is occasionally used as an ice cream ingredient. Lactose Lactose (C12H220Jis a disaccharide of dextrose and galactose and is present in milk (Figure 3.5). Lactose is substantially less sweet than sucrose. It also has a relatively low solubility, as a result of which it can crystallize out of ice cream as a monohydrate (i.e. for each lactose molecule there is also a water molecule in the crystal). The crystals CH20H CH20H 0 0 0 H OH Figure 3.5 Lactose molecule H OH
production process, such as the length of time required to harden the ice cream, depend on the thermal properties, as does the rate at which ice cream warms up and melts. This is important in storage and distribution and also when the ice cream is consumed. It should not melt so rapidly that it falls off the stick before it can be eaten. The thermal properties also affect the sensory properties such as the perception of coldness in the mouth. Furthermore, the freezing point and glass transition
Figure 6.18 how changes in formulation and storage conditions (which alter the microstructure) affect the sensory attributes. Another example is the relationship between the ice and air microstructure, the thermal conductivity and the perception of coldness in the mouth. The high thermal conductivity of water ice means that heat is rapidly removed from your mouth when you eat the product. This is one of the reasons why an ice lolly feels colder than an ice cream even if they are actually at the
in the corn flour so the solution thickens. Make two marks on the funnel, one near the top and one about halfway down. Place the funnel in the stand above the beaker (Figure 8.1). Hold the card against the bottom of the funnel and fill the funnel with water to the top mark. Measure the time it takes for the level to fall to the second mark when you remove the card. Refill, repeat the measurement several times and calculate the mean time. Then repeat with the sugar solution and the polymer