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The lipolytic behaviors and postprandial effects of butterfat and its fractions (30L and 30S) procured by dry fractionation at 30 °C were investigated using in vivo digestion. A total of 142 triacylglycerols (TAGs), 64 diacylglycerols (DAGs), 14 monoacylglycerols (MAGs), and 7 free fatty acids (FFAs) in the butterfat fractions and their hydrolysates were identified by combining high-performance liquid chromatography coupled with electrospray ionization-tandem quadrupole time-of-flight mass spectrometry with solid-phase extraction. The first-step hydrolysis from TAGs to sn-1,2 DAGs occurred slower in the high-melting-temperature solid fat (30S) fraction, which is rich in long-chain FAs compared to that of the low-melting-temperature liquid oil (30L) fraction, which is rich in short-chain unsaturated FAs (the hydrolysis rates were 39.22% vs 60.11%, respectively, in the 30 min gastric phase), and these differences were also reflected in the delayed and relatively flat postprandial lipemia levels in rats force-fed with 30S fraction. This study revealed the importance of TAG composition and lipid physical state in regulating digestion and absorption, which is related to nutrition science and the dairy or pharmaceutical industry.

High-melting-temperature solid triacylglycerol (TAG) is the main source of controversy with regard to the nutritional assessment of milk fat. This study investigated the microscopic changes and hydrolysis kinetics of milk fat globules (MFGs) reconstituted with butterfat and its primary fractions (30S, 20S, and 20L) during in vitro digestion. The 30S, 20S, and 20L on behalf of high-, medium- and low-melting-temperature fractions, respectively, had well-distinguished melting temperatures (42.1, 38.9, and 22.0 °C) and long-chain saturated TAG contents (19.3, 3.2, and 1.8%). The results revealed that the gastrointestinal fate of these butterfat fractions varied greatly with their TAG composition, and the gastric phase was a sensitive target in terms of the physiological site. The 20S- and 30S-reconstituted MFG emulsions during gastric digestion compared to that of 20L had higher extensive aggregation, lower hydrolysis extent (29.8, 28.0, and 57.3%, respectively), and slower apparent hydrolysis rate constants k (2.4, 2.1, and 6.1 min-1, respectively).

Lipase from Rhizopus oryzae immobilized on polysiloxane–poly(vinyl alcohol) (SiO2–PVA) was used to study the interesterification reaction of the milkfat with soybean oil in a stirred tank reactor (STR) containing baskets for the immobilized enzyme retention in two different configurations: central or lateral. The progress of the reaction was followed by determining free fatty acids, composition in triacylglycerols (TAGs), and consistency. The central basket was chosen for assessing the biocatalyst operational stability by running 10 consecutive batch assays lasting 6 h each. Non-notable deactivation of the biocatalyst was observed during the total operation time (60 h). The potential of the evaluated system to make the milkfat-based fat more spreadable under cooling temperature and with lower saturated fatty acids content was demonstrated in this study. Both evaluated basket reactor designs have shown potential to be used in interesterification reactions of industrial interest.

Fatty acid methyl esters (FAME) were produced from cow's milk (Bostaurus) butter by esterification/transesterification in the presence of methanol. The product was assayed according to the Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels (ASTM D 6751). The preparation failed to meet the specifications for flash point, free and total glycerin contents, total sulfur, and oxidation stability. Failures to meet the flash point and free/total glycerin specifications were determined to be due to interference with standard assays for these parameters by short-chain-length fatty acid esters. The oxidation stability of the butterfat FAME was improved by supplementation with a commercial antioxidant formulation. Approximately 725 ppm of antioxidant was required to meet the ASTM-specified stability value for biodiesel. This work indicates that, without further purification to reduce a slightly excessive sulfur content, fatty acid ester preparations produced from butter are unacceptable as sole components of a biodiesel fuel. However, it is possible that even without further purification a butter-based ester preparation could be mixed with biodiesel from other feedstocks to produce a blend that meets the current quality standards for biodiesel. The results presented here also illustrate some potential weaknesses in the accepted methods for biodiesel characterization when employed in the analysis of FAME preparations containing mid- and short-chain fatty acid esters.

Partitioning of volatile compounds between lipid and aqueous phases may influence flavor perception and availability to participate in flavor-generating reactions. The objective of this research was to characterize the partitioning of short-chain alkan-1-ols between milkfat and aqueous phases, as influenced by temperature, as compared to an octan-1-ol/water biphasic system (Log P). Temperature has a positive, but nonlinear, influence on Log P values for alkan-1-ols. There is an approximately 1 log decrease in Log P values of milkfat/water as compared to octan-1-ol/water systems; similar trends were observed across chain length. Temperature has a greater effect on alkan-1-ol partitioning in milkfat/water systems than octan-1-ol/water. The latter observation is primarily attributed to the solidification of milkfat at temperatures below 40 degrees C and the resulting reduction in liquid lipid solvent volume.

Time-resolved synchrotron X-ray diffraction techniques were used to study the effect of cooling rates and temperature on the crystallization dynamics and polymorphism of anhydrous milk fat (AMF) and milk fat triacylglycerols (MFTs). The crystallization of AMF at fast cooling rates and low final temperatures proceeded through the metastable phase a and resulted in the formation of a mixture of phases β' and β. Slow cooling rates and high final temperatures resulted in the formation of phase β' only, with no formation of phase a nor phase β. Moreover, in the absence of polar lipids, MFTs had a decreased tendency to form the a and β phases. The formation of the β phase was largely dependent on the initial amount of a phase formed. At high cooling rates and low crystallization temperatures, polar lipids may have initiated the crystallization process together with a high melting fraction of milk fat in the a phase. In time, this metastable phase transformed to the β phase. When no a phase was initially formed (high temperatures and/or slow cooling rates), no β phase was formed either. Small-angle X-ray diffraction could be used to monitor compositional variation of crystals over time, and demonstrated that minor polar lipids present in the milk fat delayed the onset of crystallization and reduced the rate of crystal growth.

Thermogravimetric analysis was used to determine the oxidative stability of various edible oils (olive oil, milkfat) and triacylglycerides (triolein, trilinolein), while the effect of natural (alpha-tocopherol, ascorbic acid) and synthetic antioxidants (butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and tertiary butyl hydroquinone were evaluated by addition to trilinolein. Oil resistance to oxidation was obtained by measuring the increase in sample weight due to the uptake of molecular oxygen, the temperature at maximum sample weight, and the temperature at the onset of oxidation. When comparing sample weight increase, trilinolein proved to be oxidatively less stable than triolein, olive oil, and milk fat, while triolein was less stable than olive oil and milk fat. Olive oil showed significantly higher stability than milkfat when comparing the temperature at the onset of oxidation. When comparing effectiveness of antioxidants, a combination of 0.01% BHA and 0.01% BHT increased trilinolein stability the most.

The addition of 0.10% glycerol or Tween 60 increased the yield force of a 70:30 (w/w) mixture of triolein/HMF (high-melting fraction of milkfat) at 5 °C. Further increases in glycerol or Tween 60 c...

Dairy systems formulated with fractionated milkfat and milk-derived components have compositional differences that may affect functionality and nutritional aspects as compared to natural dairy products. The composition of 20% milkfat creams formulated with emulsifying components (skim milk, sweet buttermilk, and butter-derived aqueous phase) and low- or medium-melt fractionated butteroil was compared with natural cream. Cream separation temperatures (49 and 55 degrees C) and processing conditions (commercial and pilot plant) in obtaining emulsifying components were examined for effect on content of surface active agents. Individual fatty acids, lipids, cholesterol, phospholipids, protein levels, and types varied with components. Separation temperature influenced the cholesterol level in the aqueous phase. A commercially produced aqueous phase contained less total lipid, protein, cholesterol, and phospholipid than aqueous phase obtained in the pilot plant. Milkfat globule membrane concentration of emulsifying components affected phospholipid and cholesterol content of formulated creams. Butteroil type affected cholesterol levels and cream formulations.

A novel variable temperature range, variable shear range in-situ processing cell is used to examine crystallization and polymorphic phase transformations in cocoa butter fat. Under static conditions, polymorphs III and IV are observed, while under sheared conditions polymorphs III and V are present at a specified range of temperatures. Increased shearing rate significantly raises the temperature at which the polymorphs are observed resulting in an associated reduction in induction times. Also, as the base holding temperature is lowered the induction times for forms IV and V decrease (depending on whether the sample is sheared).

The water vapor permeability (WVP) and mechanical properties of whey protein isolate (WPI) and WPI-lipid emulsion films dried at different conditions were investigated. As drying temperature increased, WVPs decreased significantly. Significantly lower WVP was observed for emulsion films compared to WPI films. WPI-Beeswax (BW) and WPI-anhydrous milkfat fraction emulsion films dried at 80 degrees C and 40% RH gave the lowest WVP compared to 25 degrees C, 40% RH and 40 degrees C, 40% RH. A large drop in WVP of WPI-BW emulsion films was observed at 20% BW content. The decrease in WVP for emulsion films as drying temperature increased could be due to change in the lipid crystalline morphology and/or lipid distribution within the matrix. Mechanical properties of WPI and WPI-lipid emulsion films, on the other hand, were not modified by drying conditions.

A new technique using solid-phase microextraction, mass spectrometry, and multivariate analysis (SPME-MS-MVA) was developed for the study of off-flavors in milk. The analytical column of a GC/MS system was replaced with a 1-m deactivated fused-silica column, which served as a transfer line to deliver volatiles extracted from milk samples with a Carboxen-SPME fiber to the mass spectrometer. Mass fragmentation data resulting from the unresolved milk volatile components were subjected to MVA. Principal component analysis based on SPME-MS-MVA provided rapid differentiation of control reduced-fat milk (2% butterfat content) samples from reduced-fat milk samples abused by light, heat, copper, and microbial contamination. The three psychrotrophic bacteria studied included Pseudomonas fluorescens, Pseudomonas aureofaciens, and Pseudomonas putrefaciens. SPME-MS-MVA is rapid and offers significant advantages over commercial electronic nose instruments currently being used as quality assurance tools to differentiate normal-tasting food and beverage samples from those containing off-flavors and malodors.

The effects of sn-1,3 specific Rhizopus arrhizus lipase-catalyzed enzymatic interesterification on the physical properties of butter fat/canola oil blends [100% butter fat (w/w) to 60% butter fat/40% canola oil (w/w) (60:40)] were determined. Enzymatic interesterification (EIE) lowered and linearized the solid fat content (SFC) versus temperature profile of all noninteresterified (NIE) blends in the 5−40 °C range. The largest drops in SFC as a result of EIE occurred with native butter fat between 5 and 10 °C. Dropping points (DP) decreased 1−3 °C for all blends upon interesterification, and the decrease in DP as a function of canola oil proportion in the blend was more pronounced for the EIE than for the NIE blends (0.16 °C/wt % versus 0.10 °C/wt %, respectively). Isothermal crystallization behavior monitored turbidimetrically (onset of crystallization) showed that EIE did not alter the crystallization behavior of butter fat, yet did alter that of the blends. Rheological characterization included large an...

A bifunctional fusion protein was constructed by fusion of the streptavidin gene from Streptomyces avidinii to the lipase gene from Pseudomonas fluorescens, and the resulting streptavidin−lipase was expressed in Escherichia coli. Immobilized streptavidin−lipase was prepared by direct bioselective adsorption from crude cell lysates on biotinylated controlled-pore glass and used to catalyze interesterification of anhydrous butteroil. Changes in the triacylglycerol composition indicated that those with equivalent carbon numbers (ECN) ranging from 36 to 42 decreased, while those with ECN values from 48 to 50 increased following interesterification for 120 h in hexane at 42 °C. Both the melting temperatures and the solid fat content at various temperatures were lower as compared to those of the unmodified butteroil. Addition of unsaturated fatty acids, linoleic and linolenic, yielded modified butteroils with lower melting points and solid fat content, whereas addition of saturated fatty acids, palmitic and ste...

Multivariate statistical analysis of fatty acid data was used to quantitate tallow in tallow/milkfat mixtures. These techniques proved to be superior in terms of reliability of the estimates in relation to quantitation via the butyric acid (C4 :0) content of the fat blend or simple regression analysis of C4 :0. Of the three multivariate regression techniques compared, partial least-squares (PLS) regression was best suited for the problem, followed by multiple regression analysis with stepwise variable selection. Calibration functions were derived by computer-simulated fatty acid profiles, and the calibration equations derived were validated by actually analyzed samples with known mixture proportions. The root mean squared difference figure for the validation data set, an indicator for the average error in the analysis, was 1.2% tallow in milkfat in the case of the PLS regression, in contrast to 3.5% for the simple regression solution.

In situ wide angle X-ray scattering studies have confirmed that the initial nucleating phase involved in the tempering of cocoa butter fat is consistent with the form III polymorphic structure rather than the form II alternative.

The compositions of two solid and two liquid fractions of butterfat obtained by the Tirtiaux melt fractionation process were studied. The triacypglycerols of each of the four fractions and butterfat were separated by silver ion high-performance liquid chromatography (Ag-HPLC) into sir subfractions. Each was analyzed for fatty acid composition by gas chromatography and was separated by reversed-phase HPLC. The liquid Tirtiaux fractions contained higher proportions of saturated short-chain and monoenoic fatty acids, especially cia-18:1, than the solid ones. Every Tirtiaux fraction comprised at least 64% saturated fatty acids

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