Syllabus - Science, Technology, And Society CHEDFull description
Space Science and Technology has many application areas such as in agriculture, education, transportation, health, business, administration, oil explorations, water, environment, and many more, but this work looks at its applications in administratio
ye, Owen - Pottery Technology Principles and Reconstruction
Pharmacology - Principles and Applications, 3rd Edition
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ye, Owen - Pottery Technology Principles and Reconstruction
by Prashanta Pokhrel Intended for Lok Sewa Aayog of Nepal Gov.
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Fig. 6.4. Glass
1990)
transition temperature ( T g) of zein protein as a function of moisture. (Reprinted from Lawton
Fig. 6.5. Farinogram
of a zein-starch dough mixed at 35°C. The r esistance of the dough against the rotating blades of the farinograph instrument is measured as torque, expressed in farinograph units (FU), and recorded and plotted on-line as a function of time. (Reprinted from Lawton 1990) STARCH
Starch, as it occurs in nature, is a partially crystalline polymer system (see Chapter 2). As such, it should go through a glass transition. The granules take up only about 30% water at room temperature. Figure 6.6 shows its T g as a function of moisture content. When gelatinized, all the crystals are melted, and the resulting starch freely hydrates and swells in water. With excess water, the T g of gelatinized starch has been shown to be about −7°C. When the T g levels of native and pregelatinized starches are compared as a function of moisture content, under limited moisture contents, the T g of the native starch is always higher than that of the pregelatinized starch. One way to explain this difference is to consider the native, partially crystalline starch as a form of cross-linked (see above) starch, in which the free movement of the chains is restricted and which therefore has a higher T g than its gelatinized counterpart. However, Figure 6.6 is not universally accepted. Other workers have suggested that the glass transition of native starch occurs at higher temperatures. A thorough discussion of the arguments is beyond the scope of this book.