Deodorization steam refining

Principles of Deodorization/Steam Refining The stripping medium requirements during deodorization/steam refining are described by the following mathematical equation ... 

The efficiency of deodorization/steam refining is usually quantified by the stripping of free fatty acids (FFA). As a result of their relatively low volatility, an efficient... 

Figure 3. Effect of (a) temperature and (b) pressure on FFA removal during deodorization/ steam refining of soybean oil. Conditions (a) 3 mbar, 0.5% sparge steam/h, varying temperature (b) 230°C, 0.5% sparge steam/h, varying pressure.

Typical properties of alkah-refined, bleached canola oil and of acid-water-degummed, acid pretreated, bleached canola oil ready for hydrogenation or steam refining/deodorization are given in Table 16. With the exception of the concentration of free fatty acids, the two process routes produce the same bleached oil quality. 

Physical refining, also called steam refining, combines deacidihcation with deodorization. Physical refining is more efficient for high FFA oils giving better yields of neutrahzed oil than alkali refining (2). 

In literature, the distinction between deodorization and steam refining is rarely and certainly not consistently made. As the process is best known as deodorization, it is used as general term in this chapter as well. 

The simplified Equation 10 is also known as the Bailey Equation. It states that the amount of steam required for deodorization or steam refining is directly proportional to the amount of oil and the absolute pressure in the deodorizer and inversely proportional to the vapor pressure of the pure volatile component at the process temperature and the overall vaporization efficiency E. 

Free sterols are slightly less volatile than tocopherols (Figure 2). Deodorization of soybean oil under varying process conditions (temperature 220-260°C, low pressure 1.5 mbar and 1.5% steam) resulted in a 10-35% reduction of the total sterol content (20). This sterol reduction is totally attributed to the free sterol fraction because esterified sterols are not volatile under the conditions prevailing inside the deodorizer. In case of steam refining, an increase of the steryl ester content can sometimes be observed, probably because of a heat-promoted esterification reaction between free sterols and fatty acids (20). This phenomenon will not take place during deodorization of chemically neutralized oil because the initial FFA concentration is much lower in that case. 

Improvement of the deodorizer design by the installation of baffles and demisters in the vapor chimneys has significantly reduced entrainment losses to 0.1-0.2% in chemical refining. For steam refining, an additional loss directly proportional to the FFA content has to be taken into account. For most oils (soybean oil, pahn oil, etc.), NOL is exclusively due to mechanical carry-over. However, in lauric oils, part of the NOL is a consequence of effective evaporation of volatile short-chain mono- and diacylglycerols (30). (Table 13). This distillation loss of NOL is inherently due to the deodorization conditions, but is not affected by the deodorizer design. 

Alkali-refined oil, or specially degummed crude oil. Is bleached in preparation for hydrogenation or deodorization (including steam refining). Bleaching is an adsorption process in which surface-active clay is suspended in the oil under appropriate conditions to adsorb compounds that are sufficiently polar to be attracted to the active sites of the surfaces of clay particles. The compounds involved are soaps, oxidative breakdown products (Ney, 1964 Pardun eta/., 1968), and also colored compounds such as the chlorophylls, and to a minor extent, phosphatides and the carotenoids. The last are responsible for most of the reddish-yellow color that predominates in the oil, but which is far more efficiently removed by heat breakdown during hydrogenation or deodorization than by adsorption on bleach-... 

The free fatty acids, odor, and flavors are stripped from the oil during deodorization. If the deodorizer was designed for steam refining, there should be no reduction in the rate of production. However, if the steam stripping is inefficient then there might be a need to reduce production rates by as much as 25%. It is possible to make some changes to the design of the... 

Since vegetable oil and other human food grade oils undergo deodorization (steam distillation) and other purification processes (i.e., refining and bleaching) as part of the manufacturing process prior to being used as a food product, they should not contain any of... 

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