High-temperature short-time method

Pasteurization may be carried out by batch- or continuous-flow processes. In the batch process, each particle of milk must be heated to at least 63°C and held continuously at this temperature for at least 30 min. In the continuous process, milk is heated to at least 72°C for at least 15 s ia what is known as high temperature—short time (HTST) pasteurization, the primary method used for fluid milk. For milk products having a fat content above that of milk or that contain added sweeteners, 66°C is requited for the batch process and 75°C for the HTST process. For either method, foUowiag pasteurization the product should be cooled quickly to <7.2° C. Time—temperature relationships have been estabHshed for other products including ice cream mix, which is heated to 78°C for 15 s, and eggnog, which must be pasteurized at 69°C for 30 min or 80°C for 25 s. 

High Temperature—Short Time Pasteurizers. The principal continuous-flow process is the high temperature—short time (HTST) method. The product is heated to at least 72°C and held at that temperature for not less than 15 s. Other features are similar to the batch hoi ding method. 

To maintain cloud stability in fruit juices, high-temperature-short-time (HTST) pasteurization is used to deactivate pectolytic enzymes. Pectin is a protective colloid that helps to keep insoluble particles in suspension. Cloudiness is required in commercial products to provide a desirable appearance. The destruction of the high levels of pectin-esterase during the production of tomato juice and puree is of vital importance. The pectinesterase will act quite rapidly once the tomato is broken. In the so-called hot-break method, the tomatoes are broken up at high temperature so that the pectic enzymes are destroyed instantaneously. 

HIGH-TEMPERATURE SHORT-TIME (htst) METHOD. The HTST method is used for two purposes in fruit juice technology to sterilize juices for storage and to precipitate thermolabile protein. 

Among the different methods for virus inactivation, high-temperature short-time (HTST) has been used for retrovirus clearance, whereas ultra-violet irradiation is most powerful for the elimination of small, non-enveloped and otherwise very resistant vimses such as porcine parvo-vims (PPV) [169-171]. 

The inactivation of enzymes of fresh plant and animal tissue when the isolation procedure exceeds only a few minutes is essential. A common method used to inactivate enzymes is homogenization in methanol [12,13], This does, however, dilute the sample, decrease the polarity of an aqueous food slurry, and may interfere with later isolation methods. Thermal processes may also be employed if the product is a juice and may be rapidly passed through a high temperature short-time heat... 

HTST (High Temperature Short Time) sterilisation and enzymatic conversion of chlorophylls to chlorophylides or a combination of these methods. It is also necessary to combine these procedures with storage of products at low temperatures. 

The extrapolated values together with results of the second calibration method are shown in Table V. With the exception of cabbage, agreement to better than 0.2% was found in the results of the two methods for the various foods. The proper refluxing time, for a rapid determination, was then selected from the data for the high temperature extraction shown in the last four columns in Table V. The required times varied from 5 minutes for onions and carrots to 30 minutes for celery. The shortness of these times as compared with other methods illustrates the potential usefulness of the Fischer method as a rapid control method, even though its accuracy is uncertain. 

In the laser flash method, the heat is put in by laser flash instead of electric current in the stepwise heating method mentioned above. Thus this method may be classified as a stepwise heating method. A two-layered laser flash method was developed by Tada et al. " The experimental method and the data analysis, including a case involving radiative heat flow, are described in detail in the review article by Waseda and Ohta. A thin metal plate is placed at the surface of a melt. A laser pulse is irradiated onto a metal plate of thickness / having high thermal conductivity. The sample liquid under the metal plate and the inert gas above the plate are designated as the third and first layers, respectively. The temperature of the second layer becomes uniform in a short time" and the response thereafter is expressed by... 

Cycloaddition reactions often require the use of harsh conditions such as high temperatures and long reaction times. These conditions are not compatible with sensitive reagents or products such as natural products. The applicability of Diels-Alder cycloadditions is, moreover, limited by the reversibility of the reaction when a long reaction time is required. The short reaction times associated with microwave activation avoid the decomposition of reagents and products and this prevents polymerization of the diene or dienophile. All these problems have been conveniently solved by the rapid heating induced by microwave irradiation, a situation not accessible in most classical methods. With the aid of microwave irradiation, cydoaddition reactions have been performed with great success [9, 10]. 

Similarly, the use of a higher input power in retro-Diels-Alder reactions of anthracene derivatives has been reported to afford complete reaction in 3-5 min [36], This method is an alternative to the use of flash thermolysis. The use of graphite is a prerequisite for obtaining high temperatures in a short time. 

Chlorination of amide or lactam using oxalyl chloride gives the chloro-iminium salts in situ. They react with tetrathiomolybdate to afford the corresponding thioamides and thiolactams in short-time and at low temperature in high yields. This method affords high yields of secondary or tertiary thioamides on the other hand it gives low yield of primary thioamide (17% yield) (Scheme 12).3 3... 

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