Composition and crystallization of milk fat fractions

Abstract

Milk fat was fractionated by solvent (acetone) fractionation and dry fractionation. Based on their fatty acid and acyl-carbon profiles, the fractions could be divided into three main groups: high-melting triglycerides (HMT), middle-melting triglycerides (MMT), and low-melting triglycerides (LMT). HMT fractions were enriched in long-chain fatty acids, and reduced in short-chain fatty acids and unsaturated fatty acids. The MMT fractions were enriched in long-chain fatty acids, and reduced in unsaturated fatty acids. The LMT fractions were reduced in long-chain fatty acids, and enriched in short-chain fatty acids and unsaturated fatty acids. Crystallization of these fractions was studied by differential scanning calorimetry and X-ray diffraction techniques. In this study, the stable crystal form appeared to be the β′-form for all fractions. At sufficiently low temperature (different for each fraction), the β′-form is preceded by crystallization in the metastable α-form. An important difference between the fractions is the rate of crystallization in the β′-form, which proceeds at a much lower rate for the lowermelting fat fractions than for the higher-melting fat fractions. This may be due to the much lower affinity for crystallization of the lower-melting fractions, due to the less favorable molecular geometry for packing in the β′-crystal lattice.Milk fat is a natural product obtained from cream, and it forms the main constituent of butter. It has excellent organoleptic properties, which makes it an important ingredient in the bakery and confectionery industry. Despite these good qualifications, the market for milk fat has tended to decline in recent years due to its high price and limited functional properties. Melting characteristics and firmness vary with the season, breed of cow, stage of lactation, and the feed given to the cows. Moreover, the product diversity of milk fat is limited compared to that of margarine, for which a whole range of products exists for applications such as puff pastry, cookies, and cold-spreadable products.The physical properties of milk fat are determined by triglycerides, which are its main components. These triglycerides are composed of a large number of different fatty acids. This leads to a heterogeneous composition of triglycerides and a very broad melting range, which varies between approximately −40 and 35°C. Characteristic for milk fat is the occurrence of large amounts (approximately 25% on a molar basis) of short-chain fatty acids, of which butyric acid is the most important.Polymorphism is a common property of all triglycerides (1,2), including milk fat. The main types of polymorphic crystal forms in triglycerides are the γ-, α-, β′-, and β-forms (3-5). Of these main types, either the β′-or β-form is the stable form, depending on the molecular geometry of the triglyceride (6). The other forms are metastable, although they may persist for a long time. For milk fat, the β′-form is the most stable.The utilization range of milk fat can be broadened by separating it into fractio...

Characteristics and fatty acid composition of milk fat from Saudi Aradi goat

“…High-melting milk fat fractions (10-25 °C) are used in laminated pastries to promote layering and, in the chocolate industry, to inhibit fat blooming. Low-melting milk fat fractions (35-50 °C) can be used for creaming applications in the biscuit and cheese industries (Gibon, 2006;Van Aken et al, 1999).…”

Synchrotron study on crystallization kinetics of milk fat under shear flow

“…Their X-ray diffraction patterns, performed statically after sampling from the stirring vat, show also the presence of form b. Van Aken (van Aken, ten Grotenhuis, van Langevelde, & Schenk, 1999;van Aken & Visser, 2000) carried out a detailed study on the effects of processing conditions, comparing static crystallizations with the operation in actual high shear industrial Votator units. They summarize the crystallization characteristics of milk fat between 10°C and 20°C as follows: Phase a has a clear point of 20°C, and at that temperature HMF forms b 0 after some 35 min, and MMF forms b 0 after more than 60 min.…”

Aeration of low fat dairy emulsions: Effects of saturated–unsaturated triglycerides

“…Its melting behaviour, as observed by differential scanning calorimetry (DSC) indicates three principal melting peaks corresponding to high, middle and low melting temperature fractions containing different proportions of saturated and unsaturated triacylglycerols (Bazmi & Relkin, 2006;Lopez, Bourgaux, Lesieur, & Ollivon, 2002;Timms, 1980;Van Aken, Ten Grotenhuis, van Langvelde, & Schenk, 1999). In the milk fat industry, the Tirtiaux fractionation process is currently applied and the resulting fat fractions, differing in their liquid-solid content, are commonly used to obtain value-added ingredients with nutritional, flavouring or physical effects on food products (Abd El-Rahman et al, 1997;Riaublanc et al, 2005;Herrera, de Leo´n Gatti, & Hartel 1999;Riaublanc et al, 2005).…”