Fractionation of fat 211 during refining, as the free fatty acids in a way function as a solvent on some high- melting acylglycerols. Similar behaviour was noted for the olein fraction Crude stearin Crude olein Fig8.2. Influence of refining on dilatation of PKo fractions(Haraldsson, 1978 8.2 DRY FRACTIONATION Dewaxing and winterisation (Thomas Il, 1985)are two limited forms of dry fractionation used for the removal of waxes and high melting triacylglycerols respectively from liquid vegetable oils. For instance, sunflower oil and corn oil contain a small proportion of waxes which give them a cloudy appearance at refrigerated temperatures. While others, such as cottonseed oil, contain triacylglycerols which are rich in saturated fatty acids. Dewaxing and winterisation, respectively, make these oils suit able for use as salad oils and for use in emulsions like mayonnaise. In the case of the latter, without this treatment, the high melting triacylglycerols would crystallise and separate during storage, causing the emulsion to break Cottonseed oil, however, has substantially more palmitic fatty acid, in the range 17 29%, compared with other liquid vegetable oils. This saturated fatty acid whie as palmitic-linoleic-palmitic(PLP) triacylglycerol in cottonseed oil, crystallises out at normal ambient temperatures. This was recognised very early on in the United States where cottonseed oil is widely available, and was as a consequence the first oil to be winterised If the stearin is not removed, the cottonseed oil partially solidifies when stored at temperatures below 10-15.C Nowadays, winterisation of cottonseed oil is carried out at refrigeration temperatures The amount of stearin formed can be large. Although yields can be well in excess of 20%0, filtration is still quite rapid. In view of this, during dry fractionation-winterisation processes, such as that offered by CMB Bernadini of Italy, the crystallisation is carried out in several large horizontal crystallisers, Fig. 8.3, so that, when ready, enough feed isFractionation of fat 21 1 during refining, as the free fatty acids in a way function as a solvent on some high￾melting acylglycerols. Similar behaviour was noted for the olein fraction. 80 - 70- ----- 50 - Temperature (“C) Fig. 8.2. Influence of refining on dilatation of PKO fractions (Haraldsson, 1978). 8.2 DRY FRACTIONATION Dewaxing and winterisation (Thomas 111, 1985) are two limited forms of dry fractionation used for the removal of waxes and high melting triacylglycerols respectively from liquid vegetable oils. For instance, sunflower oil and corn oil contain a small proportion of waxes which give them a cloudy appearance at refrigerated temperatures. While others, such as cottonseed oil, contain triacylglycerols which are rich in saturated fatty acids. Dewaxing and winterisation, respectively, make these oils suit￾able for use as salad oils and for use in emulsions like mayonnaise. In the case of the latter, without this treatment, the high melting triacylglycerols would crystallise and separate during storage, causing the emulsion to break. Cottonseed oil, however, has substantially more palmitic fatty acid, in the range 17- 29%, compared with other liquid vegetable oils. This saturated fatty acid which, present as palmitic-linoleic-palmitic (PLP) triacylglycerol in cottonseed oil, crystallises out at normal ambient temperatures. This was recognised very early on in the United States, where cottonseed oil is widely available, and was as a consequence the first oil to be winterised. If the stearin is not removed, the cottonseed oil partially solidifies when stored at temperatures below 10-15OC. Nowadays, winterisation of cottonseed oil is carried out at refrigeration temperatures. The amount of stearin formed can be large. Although yields can be well in excess of 20%, filtration is still quite rapid. In view of this, during dry fractionation-winterisation processes, such as that offered by CMB Bernadini of Italy, the crystallisation is carried out in several large horizontal crystallisers, Fig. 8.3, so that, when ready, enough feed is