Pressure-thermal treatment

Han, J.M. and Ledward, D.A. 2004. High pressure/thermal treatment effects on the texture of beef muscle. Meat Science 68 347-355. 

McKeough, P.J. Johansson, A.A. "Oil production by high-pressure thermal treatment of black liquors aqueous-phase products." In This Volume. 

Oil Production by High-Pressure Thermal Treatment of Black Liquors... 

There are two basic processes for thermal tfeatment of sludge. One, wet air oxidation, is the flameless oxidation of sludge at temperatures of 450 to 550° F and pressures of about 1,200 psig. The other type, heat treatment, is similar but canied out at temperatures of 350 to 400° F and pressures of 150 to 300 psig. Wet air oxidation (WAO) reduces the sludge to an ash and heat treatment improves the dev/aterability of the sludge. The lower temperature and pressure heat treatment is more widely used than the oxidation process. 

Gruner, Ibold and Naumann [589] proposed the performance of thermal treatment of the cake obtained after sodium reduction of K2TaF7 in vacuum. The application of a temperature of 800-1050°C and a residual pressure of 0.013-1.33 Pa was recommended. The process is performed with intermittent vibration in order to promote the separation of the impurities. It is reported that the resulting tantalum contains 31 and 40 ppm of Na and K, respectively. 

More conventional annealing behaviour was found by Zahn, Collins and Collins for Cr(CO)g. Both in vacuo and under a lOO-atm pressure of carbon monoxide, thermal treatment gave reformation of Cr(CO)6 with, at least qualitatively, the usual shape of the annealing curve. This was interpreted as being a simple thermal reaction, represented as ... 

Other antibiotics still require freeze drying, e. g. Na-Cephalotin (Na-CET). Takeda [ 1.32] showed, that thermal treatment of Na-CET was not sufficient to produce pure crystalline Na-CET, as the amorphous fraction discolors during storage and must be avoided. Takeda described the production of pure crystalline Na-CET by adding microcrystals of Na-CET to a saturated solution of Na-CET. If this mixture was frozen and freeze dried, then no amorphous or quasi-crystalline were found. Koyama et al. [3.35] described, that after thermal treatment for 24 h some parts remained incompletely crystallized. After adding 5 % (w/w) isopropylalcohol, a thermal treatment of 1 h was sufficient. Furthermore, the product could be dried at a higher pressure. Thus the drying time could be reduced and 100 % of the product could be used. 

AEA Technology Modified reverse assembly (high-pressure wash, new rocket shearing). Electrochemical oxidation using silver ions in nitric acid (SILVER II ). Treated with SILVER II process. High-pressure acid wash thermal treatment to 5X.b Shredded and treated with SILVER II process. 

A physical approach was also applied to reduce the allergenicity of psyllium and psyllium-containing food products (Wullschleger, 1993). Psyllium was subjected to a thermal treatment imder certain pressure and moisture content for a predetermined time period to destroy the allergenic proteins. The preferred treatment conditions included a temperature of 245-265 °F, pressure range of 14—20 psi, and a time period between 55 and 75 min. This procedure may eliminate up to 100% of the allergenicity of psyllium. 

Films of the polyisoimides were cast from DMAC at 55 °C under reduced pressure (0.1 mm). A study of the isomerization reaction was conducted by FTIR and showed that the isomerization began at approximately 100 °C and was complete after 3 h at 250 °C. In all cases the thermally treated films were insoluble in all solvents tested. Composite films were produced with XVII and three commercial matrix systems a polyarylsulfone (Radel), a polysulfone (Udel), and an acetylene terminated isoimide thermosetting resin (IP-600). Films of the matrix and XVII were cast from DMAC. Slightly cloudy films, indicating some phase separation, resulted with both the Radel and Udel systems. Composite films cast with IP-600, however, were completely clear and showed no signs of phase separation. The structural similarity of the IP-600 resin and XVII may account for the greater homogeneity of the system. Property assessment of these films before and after thermal treatment is currently underway. 

Nowadays, researchers are trying to describe pressure-induced phenomena at the molecular level, to understand which limitations and future applications there could be in the food, pharmaceutical and cosmetic industries. They try to understand the influences of parameters such as temperature, pressure, space time, and the cycle of pressure and pre- and post-thermal treatment on the efficiency of inactivation. 

The most satisfactory nonpressure process is known as thermal treatment. The wood to be treated is immersed in a preservative at an elevated temperature. This causes the air in the wood cells to expand so that when the wood is transferred into a preservative bath of lower temperature, the air contracts forming a partial vacuum and atmospheric pressure forces the liquid into the wood. 

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