Water-soluble powders, from drying processes

Instant tea is manufactured in the United States, Japan, Kenya, Chile, Sri Lanka, India, and China. Production and consumption in the United States is greater than in the rest of the world. World production capacity of instant teas depends on market demand but is in the range of 8,000 to 11,000 t/yr (3). The basic process for manufacture of instant tea as a soluble powder from dry tea leaf includes extraction, concentration, and drying. In practice, the process is considerably more compHcated because of the need to preserve the volatile aroma fraction, and produce a product which provides color yet is soluble in cold water, all of which are attributes important to iced tea products (88). 

Milk from cows contains 3.2% protein, about 80% of which is casein. Casein is isolated by a precipitation process from milk, involving heating, rinsing to remove whey, and drying to a powder. The yield is about 3 kg/ 100 kg skim milk. Rennet casein is obtained when the casein is precipitated by chymosin enzyme, also known as rennet, and acid casein is produced when precipitation is accomplished by acidification. Acid casein is usually found in the form of sodium caseinate or calcium caseinate, which are water-soluble salts. Caseinates are made by reacting NaOH or CaOH with a slurry of casein curd or powder and then spray drying (Southward, 2010). 

Both carmine and cochineal extract are made from the dried female insect, Dactylopius coccus costa, commonly known as cochineal. The cochineal live on specific cacti and the main prodnction is in Pern, bnt cochineal are also produced in Chile, Bolivia and the Canary Islands. There are nsnally two harvests per year, where the cochineal are removed mannally with snitable tools from leaves of the cacti. Following harvest the insects are snn dried before further processing. The cochineal insects are extracted nsing an aqueous alkaline solution. The resnlting cochineal extract can either be formulated to different cochineal products in powder or liquid form or further processed to carmine. Cochineal products are water-soluble and orange in low pH applications. The colour intensity is relatively low. 

Aqueous solutions of salts of acrylic acid that may contain between 0.5% and 3.0% of a water-soluble initiator have been sprayed into a chamber in which the air is heated between 150° and 485°C. The polymer forms rapidly by this spray-drying-polymerization process [105]. Solutions of mixtures of salts of acrylic acid have also been dripped onto oppositely rotating, steam-heated rolls. The dried powder could be scraped from the rolls before the end of a revolution of the roll. In this procedure, 0.5% on the monomer of a persulfate salt was added to the monomer solution. The rolls were 1 ft in diameter, 4 mils apart, rotating at 5.5 rpm. Table IX gives some observations made on this method of polymerization [106]. 

Although vinyl chloride has been polymerized with organometallics [2], commercial poly(vinyl chloride) (PVC) is made by a free radical polymerization. The dominant process is the suspension process. Vinyl chloride (most commonly referred to as vinyl chloride monomer or VCM) is suspended as droplets in water and an initiator that is soluble in the VCM is added. VCM has a boiling point of -13 °C. It is reacted under pressure as a liquid. The resultant PVC powder is separated from the water and dried. PVC can also be prepared by a mass or bulk polymerization where the initiator is added to the liquid VCM. A third polymerization technique, an emulsion polymerization, employs liquid VCM, water, and an emulsifier. A water soluble initiator is added to the VCM/water emulsion. 

Though povidone is used in a variety of pharmaceutical formulations, it is primarily used in solid-dosage forms. In tableting, povidone solutions are used as binders in wet-granulation processes. Povidone is also added to powder blends in the dry form and granulated in situ by the addition of water, alcohol, or hydroalcoholic solutions. Povidone is used as a solubilizer in oral and parenteral formulations, and has been shown to enhance dissolution of poorly soluble drugs from solid-dosage forms. 

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