Anhydrous goat's milk fat: thermal and structural behaviors studied by coupled differential scanning calorimetry and X-ray diffraction. 2. Influence of cooling rate

Crystallization and melting properties of triacylglycerols (TGs) in anhydrous goat's milk fat (AGMF) are investigated by X-ray diffraction as a function of temperature (XRDT) coupled with high-sensitivity differential scanning calorimetry (DSC), using synchrotron radiation and Microcalix. The polymorphic behavior of AGMF was monitored by varying the cooling rates between 5 and 1 degrees C/min from 45 to -20 degrees C with their subsequent melting at 1 degrees C/min. Quenching of AGMF at -20 degrees C was also examined to determine the metastable polymorphic form of AGMF. At intermediate cooling rates, TGs in AGMF crystallize, from about 18 degrees C in two different lamellar structures with triple chain length 3Lalpha stacking of 72 A and a double chain length 2Lalpha stacking of 48 A, which are correlated to two overlapped exothermic peaks recorded by DSC. A reversible transition sub alpha <--> alpha was observed. Subsequent heating at 1 degrees C/min shows numerous structural rearrangements before final melting. At fast cooling of AGMF (5 degrees C/min), similar unstable crystalline varieties are formed while three endotherms are recorded. Several new unstable lamellar structures are observed after quenching. All of these data are compared to those previously reported at slow cooling (0.1 degrees C/min) showing a relative stability of the structures formed. In spite of general similitude, the thermal and structural behavior of the goat's milk is more complex than that of the cow's milk.     

Ultrasonic spectroscopy and differential scanning calorimetry of liposomal-encapsulated nisin

The thermal stability of phosphatidylcholine (PC) liposomes (colloidal dispersions of bilayer-forming polar lipids in aqueous solvents) in the presence and absence of the antimicrobial polypeptide nisin was evaluated using differential scanning calorimetry (DSC) and low-intensity ultrasonic spectroscopy (US). PC liposome mixtures with varying acyl chain lengths (C16:0 and C18:0) were formed in buffer with or without entrapped nisin. Gel-to-liquid crystalline phase transition temperatures (T(M)) of liposomes determined from DSC thermograms were in excellent agreement with those determined by ultrasonic velocity and attenuation coefficient measurements recorded at 5 MHz. The dipalmitoylphosphatidylcholine (DPPC) T(M) measured by DSC was approximately 41.3 and approximately 40.7 degrees C when measured by ultrasonic spectroscopy. The T(M) of distearoylphosphatidylcholine (DSPC) and DPPC/DSPC 1:1 liposomes was 54.3 and 54.9 degrees C and approximately 44.8 and approximately 47.3 degrees C when measured by DSC and US, respectively. The thermotropic stability generally increased upon addition of nisin. Analysis of the stepwise decrease in ultrasonic velocity with temperature indicated an increased compressibility corresponding to a loss of structure upon heating.     

Differences in polymer formation through disulfide bonding of recombinant light meromyosin between white croaker and walleye pollack and their possible relation to species specific differences in thermal unfolding

Fast skeletal light meromyosins (LMMs) of white croaker and walleye pollack were prepared in our expression system using Escherichia coli and determined for their polymer-forming ability and thermodynamic properties by using sodium dodecyl sulfate polyacrylamide gel electrophoresis and differential scanning calorimetry (DSC), respectively. White croaker LMM formed dimer by heating at 80 degrees C and showed only a single peak at 32.1 degrees C of temperature transition in DSC. On the other hand, walleye pollack LMM hardly formed polymer and showed four peaks at 27.7, 30.5, 35.8, and 43.9 degrees C. When Cys525 of white croaker LMM was replaced by alanine, this point-mutated LMM showed no change in its DSC profile but formed no dimer upon heating, suggesting a possible role of Cys525 in dimer formation. On the other hand, walleye pollack LMM where Cys491 was substituted by alanine changed its DSC profile, showing four peaks at 27.9, 29.1, 38.4, and 43.9 degrees C. However, this point-mutated LMM formed no dimer upon heating as in the case of native LMM. These results suggest that cysteine residue(s) participates in thermal gel formation of LMM when it locates in a suitable position of the sequence.     

Crystallization properties and polymorphism of triacylglycerols in goat's milk fat globules

The sensorial, functional, and nutritional properties of goat dairy products result from the specific fatty acid composition of goat's milk fat. However, information on the physical and thermal properties of goat's milk fat is scarce. In this study, crystallization of triacylglycerols (TG) in goat's milk fat globules was investigated using polarized light microscopy and the coupling of time-resolved synchrotron radiation X-ray diffraction (XRD) and high-sensitivity differential scanning calorimetry (DSC). The molecular organization of the solid fat phase was characterized for cooling rates between 3 and 0.1 degrees C/min. Quenching of goat's milk fat globules from 50 to -8 degrees C and 4 degrees C was also examined to identify the most unstable polymorphic forms of TG. Then, the melting behavior of fat crystals was studied on subsequent heating at 1 degrees C/min. Triple chain length (3L: 68.6-70 A) and double chain length (2L: 37-45.4 A) structures were characterized and 5 polymorphic forms, alpha, sub-alpha, beta' 1, beta' 2, and beta were identified. Polymorphic transitions were observed within goat's milk fat globules as a function of time after quenching and as a function of temperature on heating. From a technological point of view, this work will contribute to a better understanding of the rheological properties as well as on the flavor evolutions of goat's milk-based products.     

Can the thermodynamic melting temperature of sucrose, glucose, and fructose be measured using rapid-scanning differential scanning calorimetry (DSC)?

The loss of crystalline structure in sucrose, glucose, and fructose has been shown to be due to the kinetic process of thermal decomposition (termed apparent melting), rather than thermodynamic melting. The purpose of this research was to investigate whether or not it is possible to scan quickly enough to suppress the kinetic process of thermal decomposition and reach the thermodynamic melting temperature of these sugars using a new rapid-scanning DSC. Indium, a thermodynamic melting material, and sucrose, glucose, and fructose were analyzed at three heating rates from 1 to 25 °C/min using standard DSC and at seven heating rates from 50 to 2000 °C/min using rapid-scanning DSC. Thermodynamic melting was achieved when the onset temperature (T(m onset)) of the endothermic peak leveled off to a constant value independent of heating rate. The T(m onset) for indium was constant (156.74 ± 0.42 °C) at all heating rates. In the case of fructose, the T(m onset) increased considerably until a heating rate of approximately 698 °C/min, after which the average T(m onset) for the remaining three heating rates was constant at 135.83 ± 1.14 °C. Thus, 135.83 °C is proposed to be the thermodynamic melting temperature of fructose. It is important to note that the heating rate at which this thermodynamic melting temperature is achieved is most likely influenced by the type and amount of trace components (e.g., water and salts) contained in the fructose, which are known to vary widely in sugars. In the case of sucrose and glucose, thermodynamic melting temperatures were not able to be obtained, because the upper limit heating rate used was not fast enough to suppress thermal decomposition and achieve thermodynamic melting, perhaps due to the higher apparent T(m onset) for sucrose and glucose compared to that for fructose.     

Modeling Starch Gelatinization Kinetics of Milled Rice Flour

Milled long‐grain rice samples were evaluated by differential scanning calorimetry (DSC) to determine the kinetics of starch gelatinization. The experiments were conducted with milled rice flour with a 10.6% degree of milling. DSC thermograms were obtained from 35 to 110°C using heating rates between 1°C/min and 15°C/min. The rate constants were evaluated, and two activation energies were found for different temperature ranges. At <70.1°C gelatinization was not completed. It was assumed that at <70.1°C gelatinization would only affect the amorphous regions. During the subsequent phase the crystalline regions destabilized by the amorphous component begin to gelatinize. For moisture content of 70%, wet basis, and a heating rate of 12°C/min, the enthalpy of gelatinization reaches a constant value of 7.3 J/g.     

Isolation and thermal characterization of an acidic isoperoxidase from turnip roots

An acidic peroxidase (pI approximately 2.5) was purified from turnip roots (TAP), and its thermal properties were evaluated. TAP is a monomeric protein having a molecular weight (MW) of 49 kDa and a carbohydrate content accounting for 18% of the MW. The yield of pure TAP was relatively high ( approximately 2 mg/kg of fresh roots), with a specific activity of 1810 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) units/mg at pH 6. The activity increased 4-fold at the optimum pH (4.0) to 7250 ABTS units/mg, higher than that of most peroxidases. TAP was heat stable; heat treatment of 25 min at 60 degrees C resulted in 90% initial activity retention, whereas an activity of 20% was retained after 25 min of heating at 80 degrees C. TAP regained 85% of its original activity within 90 min of incubation at 25 degrees C, following heat treatment at 70 degrees C for 25 min. Thermal inactivation caused noticeable changes in the heme environment as evaluated by circular dichroism and visible spectrophotometry. TAP was rapidly denatured by heating in the presence of 1.0 mM ethylene glycol bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid, but the Soret band and activity were fully recovered by adding an excess of Ca(2+). This is further evidence that Ca(2+) plays an important role in the stability of TAP. The high specific activity of TAP, together with its relatively high thermal stability, has high potential for applications in which a thermally stable enzyme is required.     

A DSC study on the gel-sol transition of a starch and hsian-tsao leaf gum mixed system

Differential scanning calorimetric analysis was performed on the admixture of 4% hsian-tsao leaf gum and 8% wheat starch as a function of salt types and concentrations. The salt concentrations (C(s)) studied were 5-100 mM for sodium and potassium chloride, and 3.4-34 mM for calcium and magnesium chloride. It was found that hsian-tsao leaf gum or starch alone did not present a readily recognizable exothermic peak or endothermic peak during cooling or heating in DSC. However, mixing these two polymers promoted the intermolecular binding and subsequent gelation of the mixtures as evidenced by the DSC exothermic and endothermic peaks during cooling and heating, respectively. The setting and melting temperatures of such a mixed system shifted progressively to higher temperatures with increasing concentrations of added salts. It was considered that the aggregated mixed polymers formed thermally stable junction zones with higher binding energies. The thermal behavior change was more remarkable by the addition of K(+) than by Na(+), and by Ca(2+) than by Mg(2+). For monovalent cations, the DSC heating and cooling curves showed a single endothermic and exothermic peak. For divalent cations at low concentration, the DSC curves showed a single peak. However, with sufficient divalent cations, the DSC curves eventually developed a bimodal character. A mixed system with sufficient Ca(2+) could form firm gel that was difficult to remelt completely upon heating to 130 degrees C, indicating the possibility of the formation of ionic bonds through cross-links with the carboxyl groups in hsian-tsao leaf gum.     

Thermomechanical Behavior of Concentrated Starch-Water Preparations

The rheological behavior of concentrated starch preparations from various origins was studied by dynamic mechanical thermal analysis (DMTA). Four types of starch were used: wheat, potato, normal, and waxy corn adjusted to moisture contents in the 42–49% (w/w) range. The thermal treatments of the starch-water mixtures consisted of heating to 85°C and cooling to room temperature, both at a rate of 1°C/min. During heating, the storage modulus (E′) appearance was first characterized by an increase with a maximum at ≈70°C (or potato starch at 63°C) followed by a decrease to 85°C. During cooling, storage modulus increased steadily down to room temperature. The magnitude of these variations depended on the starch type. Despite some differences, all the loss tangent curves showed a decrease during heating from 60–70°C to 85°C, followed by a plateau during cooling. To propose an interpretation for the DMTA results, we measured, by laser-light diffraction, the influence of heating (up to the maximum E′ peak) on the distribution of the granule sizes of the different starches. Moreover, differential scanning calorimetry (DSC) was used to measure the temperature range where the melting of starches ordered regions occurred. Partial melting enthalpies were plotted against temperature. The hypothesis of a relationship between swelling and an increase in rigidity during heating seemed to be confirmed by laser-light diffraction, whereas DSC indicated the decrease in rigidity was caused predominantly by order-disorder transitions. During cooling, amylose gelation plays a major role in the rigidity increase, but a contribution of amylopectin is not excluded.     

Differential scanning calorimetry and circular dichroism spectrometry of walleye pollack myosin and light meromyosin

The thermodynamic properties of myosin and its C-terminal fragment, light meromyosin (LMM), from walleye pollack, a typical cold-water fish efficiently utilized on an industrial scale, were analyzed by using differential scanning calorimetry (DSC) and circular dichroism (CD) spectrometry. Recombinant walleye pollack LMM expressed in Escherichia coli was also subjected to DSC and CD measurements for reference. The two proteins prepared from frozen surimi showed three endothermic peaks, the transition temperatures (T(m)) of which were quite similar, although overall DSC patterns differed considerably from one another. Their alpha-helical contents determined by CD were low compared to values reported before for other species. On the other hand, recombinant LMM gave four endothermic peaks at 27.4, 30.8, 36.5, and 43.4 degrees C in DSC and showed an alpha-helical content of approximately 80%. The peak at 27.4 degrees C could not be observed in walleye pollack LMM prepared from frozen surimi and thus was possibly attributed to its C terminus, because this extreme C-terminal region is supposedly truncated during preparation of LMM by tryptic digestion.     

Use of differential scanning calorimetry to study lipid oxidation. 1. Oxidative stability of lecithin and linolenic acid

The oxidation of linolenic acid (LNA) and soy lecithin was studied by differential scanning calorimetry (DSC) with linear programmed heating rates (non-isothermal mode). The interpretation of the shape of DSC curves is discussed, and it has been concluded that temperatures of the extrapolated start of heat release are the most reliable data for the rapid estimation of the oxidative stability of lipid materials. The Ozawa-Flynn-Wall method was used to calculate the kinetic parameters of the process: for LNA autoxidation the activation energy, Ea, and pre-exponential factor, Z, are 66 +/- 4 kJ/mol and 1.5 x 10(7) s(-1), respectively, and the autoxidation of lecithin is described by Ea = 98 +/- 6 kJ/mol and Z = 9.1 x 10(10) s(-1). Values of Ea and Z can be applied for calculation of the overall first-order rate constant of autoxidation at various temperatures, k(T). For the two studied lipids the comparison of k(T) values shows the inversion of their oxidative stabilities; that is, below 167 degrees C lecithin is more stable than LNA, k(T)lecithin < k(T)LNA, and above that temperature (termed the isokinetic temperature) k(T)lecithin > k(T)LNA. The calculated inversion of oxidative stabilities can be an explanation of similar observations for other pairs of lipids if the results of accelerated tests measured at temperatures above 100 degrees C are compared with the results obtained at temperatures below 100 degrees C.     

Capillary electrophoresis analysis of orange juice pectinesterases

Pectinesterase (PE) was extracted from orange juice and pulp with 1 M NaCl, desalted, and separated using capillary electrophoresis (CE) gel procedures (CE-SDS-CGE) and isoelectric focusing (CE-IEF). PE resolved as a single peak using noncoated fused silica columns with CE-SDS-CGE. CE-IEF separation of PE required acryloylaminoethoxyethanol-coated columns, which had limited stability. Thermal stability of PE extracts before and after heating at 75 degrees C for 30 min and at 95 degrees C for 5 min established heat labile and heat stabile fractions with identical PE migration times by CE-SDS-CGE or CE-IEF. Peak magnitude decreased to a constant value as heating time increased at 75 degrees C. Regression analysis of CE-SDS-CGE peak migration times of molecular weight (MW) standards estimated both heat labile and heat stable PE at MW approximately 36 900. Traditional SDS-PAGE gel separation of MW standards and active PE isolated by IEF allowed estimation of MW approximately 36 000. CE-SDS-CGE allowed presumptive, but not quantitative, detection of active PE in fresh juice.     

Effect of heat treatment on the antioxidant activity of extracts from citrus peels

The effect of heat treatment on the antioxidant activity of extracts from Citrus unshiu peels was evaluated. Citrus peels (CP) (5 g) were placed in Pyrex Petri dishes (8.0 cm diameter) and heat-treated at 50, 100, or 150 degrees C for 10, 20, 30, 40, 50, and 60 min in an electric muffle furnace. After heat treatment, 70% ethanol extract (EE) and water extract (WE) (0.1 g/10 mL) of CP were prepared, and total phenol contents (TPC), radical scavenging activity (RSA), and reducing power of the extracts were determined. The antioxidant activities of CP extracts increased as heating temperature increased. For example, heat treatment of CP at 150 degrees C for 60 min increased the TPC, RSA, and reducing power of EE from 71.8 to 171.0 microM, from 29.64 to 64.25%, and from 0.45 to 0.82, respectively, compared to non-heat-treated control. In the case of WE from CP heat-treated at the same conditions (150 degrees C for 60 min), the TPC, RSA, and reducing power also increased from 84.4 to 204.9 microM, from 15.81 to 58.26%, and from 0.27 to 0.96, respectively. Several low molecular weight phenolic compounds such as 2,3-diacetyl-1-phenylnaphthalene, ferulic acid, p-hydroxybenzaldoxime, 5-hydroxyvaleric acid, 2,3-diacetyl-1-phenylnaphthalene, and vanillic acid were newly formed in the CP heated at 150 degrees C for 30 min. These results indicated that the antioxidant activity of CP extracts was significantly affected by heating temperature and duration of treatment on CP and that the heating process can be used as a tool for increasing the antioxidant activity of CP.     

Microwave heating of tea residue yields polysaccharides, polyphenols, and plant biopolyester

Microwave heating was used to produce aqueous-soluble components from green, oolong, and black tea residues. Heating at 200-230 degrees C for 2 min extracted 40-50% of polysaccharides and 60-70% of the polyphenols. Solubilization of arabinose and galactose by autohydrolysis occurred with heating above 170 degrees C, whereas heating above 200 degrees C was necessary to solubilize xylose. Catechins were soluble in water by heating at low temperature (110 degrees C); however, new polyphenols having strong antioxidant activity were produced above 200 degrees C. The amount of solubilized materials and antioxidant activity increased with increased fermentation of harvested tea leaves (green tea < oolong tea < black tea). Cutin, a plant biopolyester, remained in the residue after heating as did cellulose and lignin/tannin. The predominant cutin monomer that was recovered was 9,10-epoxy-18-hydroxyoctadecanoic acid, followed by dihydroxyhexadecanoic acid and 9,10,18-trihydroxyoctadecanoic acid.     

Influence of different drying and aging conditions on saffron constituents

A dehydration postharvesting treatment is necessary to convert Crocus sativus L. stigmas into saffron spice. Three different dehydration treatments were evaluated: dehydration at room temperature; dehydration with hot air at different temperatures (70, 90, and 110 degrees C); and dehydration following traditional processing in Castille-La Mancha (Spain) with three different heating sources (vineshoot charcoal, gas cooker, and electric coil). The time (between 28 and 55 min) and mean temperature (between 54 and 83 degrees C) conditions for traditional dehydration were established for the first time. The highest coloring strength was obtained when saffron was submitted to higher temperatures and lower times. These findings may be supported by the fact that samples dehydrated at high temperature were more porous than those dehydrated at room temperature, as was observed by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The higher the temperature during the process, the higher the proportion of trans-crocetin di-(beta-D-gentibiosyl) ester, although trans-crocetin (beta-D-glucosyl)-(beta-D-gentibiosyl) and trans-crocetin di-(beta-D-glucosyl) ester decrease while cis-crocins did not change significantly. A thermal aging process reveals that the trans-crocetin di-(beta-D-gentibiosyl) ester increases when saffron is resubmitted to a heating treatment before it is decomposed by the extreme conditions. The picrocrocin extinction during the aging process does not imply a consistent generation of safranal.     

Determination of the molecular and structural characteristics of okenia, mango, and banana starches

Starches were isolated from nonconventional sources (banana, mango, and okenia) and their characteristics were examined using polarized light microscopy, X-ray diffraction pattern, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). Banana starch granules were of an ellipsoidal shape with size between approximately 8 and 20 microm; okenia had the smallest granule size, between approximately 2 and 5 microm. The three starches showed the Maltese cross, indicative of an intact granule structure. Okenia and mango starches had the A-type X-ray diffraction pattern, common to native cereal starches, whereas banana starch showed a mixture between A- and B-type pattern. Banana starch had the highest temperature (77.6 degrees C) and enthalpy (23.4 J/g) of gelatinization in excess water conditions; okenia had the lowest temperature (71.2 degrees C) and enthalpy (15 J/g), which may be related to the X-ray diffraction pattern and its small granule size. Both the okenia and mango starches had a higher molar mass and gyration radius than banana starch, which may be related to the differences determined in their crystalline structures.     

Stability of sterols in phytosterol-enriched milk under different heating conditions

Commercially available phytosterol-enriched milk was subjected to usual and drastic heating conditions to evaluate the stability of the sterols at different treatments. Products showed 422.2 mg of phytosterols/100 g of milk and 132 microg of sterol oxidation products (SOPs)/g of fat (277 microg of SOPs/100 g of milk). Schaal oven conditions (24 h/65 degrees C, equivalent to 1 month of storage at room temperature) reduced the phytosterol content by only 4%. Drastic heating treatments (2 min of microwave heating at 900 W or 15 min of electrical heating at 90 degrees C) led to a 60% decrease of total phytosterol content, with a significant increase of TBARs. The oxysterol amount under those conditions (which was higher in microwave-treated samples) was lower than expected, probably because of the degradation of the oxidation products. Usual heating conditions (1.5 min of microwaves) maintained phytosterol content on physiologically active values (301 mg/100 g of milk) with oxidation percentages around 0.12-0.40% for phytosterols and 1.13% for cholesterol.     

Gelation of edible blue-green algae protein isolate (Spirulina platensis Strain Pacifica): thermal transitions, rheological properties, and molecular forces involved

Proteins isolated from blue-green algae Spirulina platensis strain Pacifica were characterized by visible absorption, differential scanning calorimetry (DSC), viscometry, and dynamic oscillatory rheological measurements. Unique thermal unfolding, denaturation, aggregation, and gelation of the algal protein isolate are presented. DSC analysis showed that thermal transitions occur at about 67 and 109 degrees C at neutral pH. Calcium chloride stabilized the quaternary structure against denaturation and shifted the transitions at higher temperatures. Viscometric studies of Spirulina protein isolate as a function of temperature showed that the onset of the viscosity increase is closely related to the dissociation-denaturation process. Lower viscosities were observed for the protein solutions dissolved at pH 9 due to an increased protein solubility. Solutions of Spirulina protein isolate form elastic gels during heating to 90 degrees C. Subsequent cooling at ambient temperatures caused a further pronounced increase in the elastic moduli and network elasticity. Spirulina protein isolate has good gelling properties with fairly low minimum critical gelling concentrations of about 1.5 and 2.5 wt % in 0.1 M Tris buffer, pH 7, and with 0.02 M CaCl(2) in the same buffer, respectively. It is suggested that mainly the interactions of exposed hydrophobic regions generate the molecular association, initial aggregation, and gelation of the protein isolate during the thermal treatment. Hydrogen bonds reinforce the network rigidity of the protein on cooling and further stabilize the structure of Spirulina protein gels but alone are not sufficient to form a network structure. Intermolecular sulfhydryl and disulfide bonds were found to play a minor role for the network strength of Spirulina protein gels but affect the elasticity of the structures formed. Both time and temperature at isothermal heat-induced gelation within 40-80 degrees C affect substantially the network formation and the development of elastic modulus of Spirulina protein gels. This is also attributed to the strong temperature dependence of hydrophobic interactions. The aggregation, denaturation, and gelation properties of Spirulina algal protein isolate are likely to be controlled from protein-protein complexes rather than individual protein molecules.     

A kinetic study on the isomerization of hop alpha-acids

In this article, a detailed study on hop alpha-acid isomerization kinetics is presented. Because of the complex wort matrix and interfering interactions occurring during real wort boiling (i.e., trub formation and alpha-acids/iso-alpha-acids complexation), this investigation on alpha-acid isomerization kinetics was performed in aqueous buffer solution as a function of time (0-90 min) and heating temperature (80-100 degrees C). Rate constants and activation energies for the formation of individual iso-alpha-acids were determined. It was found that iso-alpha-acid formation follows first-order kinetics and Arrhenius behavior. Differences in activation energies for the formation of trans- and cis-isomers were noticed, the activation energy for the formation of trans-iso-alpha-acids being approximately 9 kJmol (-1) lower.     

Complex coacervates for thermally sensitive controlled release of flavor compounds

To improve the appeal of frozen baked foods upon heating, we have encapsulated flavor oil in complex coacervate microcapsules using gelatin and gum Arabic. Variation of polyion concentrations and homogenization rate affected particle morphology, size distribution, and oil release upon heating. Release of the oil from formulations was determined by a simple spectroscopic method based on separation of oil labeled with a lipophilic dye from unaffected particles. When heated to 100 degrees C or higher, univesicular microcapsules (prepared with a lower homogenization rate) released almost all of the encapsulated oil, while multivesicular microcapsules (produced by high homogenization rates) resulted had lesser degrees of release. The oil remained encapsulated during 4 weeks of storage at 4 and -20 degrees C (freezing and thawing) but was released by exposure to 100 mM NaCl at room temperature. When particles were cooled after releasing their oil content, the oil was re-encapsulated.