Glassy lactose

Amorphous or glassy lactose is formed when lactose-containing solutions are dried quickly. The dry lactose is noncrystalline and contains the same ratio of alpha/beta as the... 

Fig. 6.3 Glassy lactose particles obtained from a 20wt% aqueous solution at an outlet air temperature of 90°C Mean particle size / = 65 pm. The transparency of the particles is a clear indicator for the absence of larger crystals.

Eshkenazi et al. [46] Lactose Fresh raw milk /3-Galactosidase, glucose oxidase, and horseradish peroxidase/with PEI and glutaraldehyde Glassy carbon electrode/ 0 V vs. SCE 5-Aminosalicylic acid (in solution)... 

Lactose can occur in two crystalline forms, the a-hydrate and the P-anhydrous forms and can occur in an amorphous or glassy state. The most common form is the a-hydrate (C H On-HjO), which can be obtained by crystallization from a supersaturated solution below 93.5°C. When crystallization is carried out above 93.5°C, the crystals formed are of p-anhydrous type. Some properties of these forms have been listed by Jenness and Patton (1959) (Table 4-6). Under normal conditions the a-... 

Keywords lactose, octa-O-acetyl-lactose, molecular glassy dynamics... 

In most dry foods, starch is the main component responsible for a glassy state. This concerns several dry cereal products, like hard biscuits and various breakfast cereals. Figure 16.5 gives Tg for wheat starch, but if low-molar-mass components, generally sugars, are also present, the curve is shifted to lower temperatures, somewhere between those for starch and those for lactose. Another example is pasta, in the dry form in which it is commonly sold, which consists for the most part of wheat starch. Pasta has an impressive shelf life in the glassy state, and it readily takes up water upon cooking, to attain a soft rubbery texture. 

A fully amorphous (glassy) freeze-dried product, consisting of 5% of a calcitonin gene-related protein (CGRP), 95% lactose and 3% residual water, was heated gently in a sealed DSC capsule. Its Tg is shown by the endothermic step in Scan 1 of Figure 4. Heating beyond Tg makes a material susceptible to more or less rapid physical and/or chemical... 

Moreover, most researchers agree that protection by compounds such as lactose and trehalose depends on the formation of an amorphous phase with the protein [15], The proteins are mechanically immobilized in the glassy, solid matrix during dehydration. The restriction of translational and relaxation processes is thought to prevent protein unfolding, and spatial separation between the protein molecules (i.e dilution of protein molecules within the glassy matrix) is proposed to prevent aggregation [12],... 

High solute and air temperature usually mean higher solubility and higher mass content before the onset of crystallization. (However, some materials do not show increased solubility with increased temperature, as e.g., NaCl). High solubility also means a late onset of crystallization and low solvent content. Due to this fact, particles should form a shell with a thick wall. Materials with low solubility, but still sprayed into the dryer as a solution, are expected to form a thinner shell. However, the nudeation properties, such as nudeation rates and the growth rates of crystals, also play a major role. Some materials do not form crystals but solidify in an amorphous or glassy state. A typical example is lactose, for example, sprayed as a 20 wt% solution into air at an air exit temperature of 90 °C, as shown in Fig. 6.3. 

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