Increasing long-term storage stability

The stability of freeze-dried materials is dictated by various factors two of the most important of which are moisture and oxygen. 

By nature, freeze-dried produets are hygroscopic, so exposure to moisture during storage can destabilize them. Packaging used for freeze-dried materials must be impermeable 

Freeze-drying converts one second at refrigeration temperature into one minute at room temperature. By changing the rate of the kinetic clock, the formulation that was only stable for 2 weeks at 4-8°C is now stable for 120 weeks (2.3 years). In slowing down the clock, the manufacturer now has time to test the product before releasing it to the public. In addition, the product no longer requires refrigeration at 4-8°C, which makes worldwide distribution much easier and safer. Also, there is less chance that the product will not be available for a patient or that it will expire and need to be discarded. 

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A diesel fuel stabilizer containing a blend of amines, polyamines, and alkyl ammonium alkyl phosphate as specified under MIL-S-53021 is recommended for federal diesel fuel oil. This stabilizer is to be used at a treat rate of 25 lb/1,000 barrels. It is not intended for use in routine applications, but for situations where increased stability protection is required. Typical applications include fueled equipment undergoing long-term storage in a warehouse or depot, prepositioned equipment or equipment maintained in a high-temperature environment. 

Proteins derived from varions natnral sonrces such as plant, animal, and milk are converted into dry powder form to enhance their stability and for long-term storage. Even therapeutic proteins such as antibodies, which are usually delivered after reconstitution, are also first converted into powder (Sane et al., 2004). Dry therapeutic proteins are being increasingly used in their native form for inhalation and pulmonary and transdermal delivery (Johnson, 1997). Nontherapeutic proteins such as milk proteins are important ingredients in manufactured functional and health foods. They are also converted into dry powder form. 

Water. Latices should be made with deionized water or condensate water. The resistivity of the water should be at least 10 2. Long-term storage of water should be avoided to prevent bacteria growth. If the ionic nature of the water is poor, problems of poor latex stability and failed redox systems can occur. Antifreeze additives are added to the water when polymerization below 0°C is required (99). Low temperature polymerization is used to limit polymer branching, thereby increasing crystallinity. 

Stability was determined by measuring the settling rate and the sedimentation volume. As the stability increases, the settling rate decreases and the sedimentation volume formed in long-term storage (about one month) decreases. The stability was graded 0 (very unstable) to 5 (very stable) by an overall evaluation. 

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