CHEMICAL AND PHYSICAL-PROPERTIES OF THE HIGH MELTING GLYCERIDE FRACTIONS OF COMMERCIAL MARGARINES

The fat obtained from nine commercial margarines purchased from Canada and the U.S.A. were crystallized from acetone at 15, 10, 5 and 0-degrees-C. The high melting triglyceride (HMG) fractions at 15-degrees-C contained high levels of palmitic and stearic acids. The 18:1 levels increased as fractionation temperature decreased. Triglyceride analysis revealed that the HMG fractions contained high levels of carbon 54 and 52. The levels of trans isomers increased, whereas the trans levels in the 18:1 decreased with fractionation temperature. Margarines made from canola oil exhibited beta characteristics whereas canola-palm, soybean and corn margarines showed beta' crystals. The fractions as crystallized from acetone, showed numerous X-ray short spacings, characteristic of beta', beta and intermediate forms. Upon heating and cooling, the 15-degrees-C fraction showed beta' or alpha and beta' characteristics regardless of the polymorphic form present in the original margarines. The differential scanning calorimetry (DSC) melting points of these fractions varied from 53 to 50-degrees-C. The difference between the beta and beta' margarines could be related to the 16:0 and carbon 54 content of the 15-degrees-C fraction. In the beta tending margarines the 16:0 content was below 11%, in the beta' tending margarines above 17%. The carbon 54 content in the 15-degrees-C fraction of the beta tending margarines was close to 70% and that of the beta' tending margarines around 50%. The triglyceride C54 in the 15-degrees-C fraction is beta tending and therefore should be kept as low as possible. In canola margarines this can be achieved by incorporation of palm oil, preferably in a slightly hydrogenated form.