Drying product structure after

The retention or loss of aroma compounds is also influenced by the structure (amorphous or crystallized) of the dried product Structural changes can be used for spray drying encapsulation processes (Bhandari et al., 1992 Re, 1998). Crystallization tends to increase the loss of aroma, because it rejects impurities, including volatiles. Senoussi et al. (1995) measured the loss of diacetyl as a function of the rate of crystallization of lactose during storage. They found that when the lactose was stored at 20 °C above the glass transition temperature Tg, the amorphous product immediately crystallized and practically all diacetyl was lost after 6 days. Levi and Karel (1995) also found increased rates of loss of volatile (1-n-propanol) as a result of crystallization in an initially amorphous sucrose system. 

A Si NMR study (BlOO) showed that for cement, as for CjS pastes, the content of Q° silicate tetrahedra decreases with time and that those of Q and later of tetrahedra increase. After 180 days, the degree of hydration, estimated from the intensities of the NMR peaks, was approximately 90%. These results are consistent with those obtained by the TMS method, and suggest that the hydration products present after 180 days contain at most only a small proportion of monomer. The possible effects on the silicate anion structure of drying, whether during hydration as a result of localized water shortage or subsequently, were considered in Section 5.3.2. 

Diethylzinc reacts with dimethyltriazene to afford the moisture-sensitive complex Zn(MeNNNMe)2 (17). However, a similar reaction involving diphenyltriazene gave a product which, after recrystallization from dry benzene, was found to be Zn40(PhNNNPh)g and to possess a basic beryllium acetate type of structure (48). 

In run 4 Tj g is only 1.4°C higher than in run 1, but the pressure has been low-erd after 3 h and the rised to +40°C. The effect is double In 3 h it is not possible to transfer enough energy for the sublimation of the ice, which remains in the product. Latest after 4 h the already dried product melts back and the structure col-... 

Fig. 32 SEM picture showing starting materials and their corresponding spray-dried products. Fumaric acid milled (A) and spray dried (B), L-leucine milled (C) and spray dried (D). Before spray drying both substances show a layered crystal structure but differ significantly after the spray-drying process.

Basically, all products which contain water can be dried in this manner. After freezing, the ice crystals remain at first at their original location in the structure. If vacuum is applied, the ice sublimates directly without melting. This results in a porous, dry product which has retained its original form. The volume has hardly changed, the cell walls have been little affected, flavour and other main constituents have been treated gently. If the product is to be restored to its former condition - to be reconstituted -only water has to be added. Water sorption in freeze dried materials proceeds faster than in conventionally dried products. For detailed studies on the fundamentals of freeze drying see the literature [1-10]. 

Berbamine occurs in B. vulgaris, B. aquifolium (12, 13), B. thunbergii (22), Stephania cepharantha Hayata (23), and in B. swaseyi Buckley Mahonia swaseyi Fedde) to the extent of about 2 % in the dried roots (24). Santos (21) found that berbamine was isomeric with oxyacanthine and that oxidation of berbamine methyl ether produced 4, 5-dicarboxy-2-methoxy-diphenyl ether (VIII, R = CH3), as in the case of oxyacanthine. The constitution of the isoquinoline portion of the molecule was determined by von Bruchhausen, Oberembt, and Feldhaus (18). The products obtained after a Hofmann degradation of 0-methylberbamine followed by ozonization were the same two dialdehydes, XXXV and 4, 5-diformyl-2-methoxydiphenyl ether (XXXIV), as were obtained from 0-methyloxy-acanthine by similar treatment. On the basis of these facts von Bruchhausen and coworkers concluded that berbamine and oxyacanthine are structural isomers. If o.xyacanthine is assigned the formula XXVI then berbamine must have the formula XXXI or vice versa. 

Structural collapse in freeze-dried products (after sublimation stage) Tc ( )... 

Freeze-drying is mainly used when water or occasionally other solvents must be removed from a temperature sensitive or structurally difficult product - usually of biological origin - without noticeable influence on the quality of the final product. After removal of the water or solvent, the dry product is then easy to store, ft becomes again a product that can be used simply by adding water or the corresponding solvent. 

Polymer 4 was partially soluble in DMSO and amide solvents such as DMF and DMAc. Solution and solid-state NMR were used to confirm the product structure. Peaks due to the adamantane moiety and aramid carbonyls were present indicating reaction. Again, residual solvent peaks were observed in the solid-state NMR spectra, even after extensive extraction and vacuum drying. It appears that hyperbranched structures and adamantane incorporation disrupts crystalline packing and leads to a more open and molecularly-porous branched structure that is capable of taking up and holding solvent. 

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