Isolation and thermal characterization of high-melting seed crystals formed during cocoa butter solidification

Seed crystals which formed during early stages of cocoa butter solidification have been isolated and determined to have extremely high melting points. The melting points of the seed crystals generally exceeded 60°C, in contrast to cocoa butter, which melts between 30–35°C. In addition, the melting point of the seed crystals decreased as a function of crystal growth time. Evidence suggests that the high-melting seed crystal is not an additional polymorphic form of cocoa butter, but rather a distinct crystalline entity. Consequently, a unique compositional make-up is suspected as being responsible for the elevated melting point. A technique to separate seed crystals from the molten cocoa butter mass has been developed. The procedure has been shown not to alter the thermal and compositional properties of the isolated seed crystals.     

Characterizing cocoa butter seed crystals by the oil-in-water emulsion crystallization method

Unambiguous quantitative evidence for the catalytic action of seed crystals in cocoa butter is presented. We used an ultrasound velocity technique to determine the isothermal growth of solid fat content in cocoa butter oil-in-water emulsions, in which the probability of finding a seed crystal in any one droplet was around 0.37 at 14.2°C. The upper limit for the size of seed crystals in West African cocoa butter was around 0.09 μm, the Gibbs free energy for nucleation was 0.11 mj m⁻², and the concentration of seed crystals was in the range of 10¹⁶ to 10¹⁷ m⁻³. X-ray diffraction measurements showed that emulsified cocoa butter crystallizes in the α polymorph and does not appear to transform to the β′ form within the first 25 min of crystallization. Primary nucleation events in cocoa butter emulsions are accounted for by seed crystals. Collision-mediated nucleation, a secondary nucleation mechanism, in which solid droplets (containing seed crystals) catalyze nucleation in liquid droplets, is shown to account for subsequent crystallization. This secondary nucleation mechanism is enhanced by stirring.     

Phospholipid composition of lipid seed crystal isolates from ivory coast cocoa butter

Seed crystals isolated from Ivory Coast cocoa butter were shown to differ in chemical and thermal characteristics from solidified Ivory Coast butter. Higher concentrations of complex lipids in the seed crystals have led to speculation on the role these polar molecules play in lipid crystallization events. Phospholipids separated from lipid seed crystal isolates were twelve-fold more concentrated than the original cocoa butter. Seed crystals contained 3.99% phospholipids while cocoa butter samples contained 0.34%. Phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, lysophosphatidylcholine, phosphatidylserine, and phosphatidic acid were identified in cocoa butter with phosphatidylcholine (37.7%), phosphatidylglycerol (27.3%) and phosphatidyl-ethanolamine (15.6%) being the major phospholipid constituents. Two phospholipids not previously reported in cocoa butter were identified as phosphatidylglycerol and diphosphatidylglycerol based on co-migration of standards. Cocoa butter and its seed crystals contained the same phospholipid entities; however, individual phospholipids differed significantly in concentration. Phosphatidylethanolamine (30.4%) and phosphatidylcholine (30.2%) were the major phospholipids in seed crystal samples. Fatty acid composition of cocoa butter and seed crystal phospholipids were found to be similar, with the exception of myristic, stearic and oleic acids. Myristic acid was three-fold higher in phosphatidylglycerol and phosphatidylethanolamine in the seed crystals, whereas stearic acid was significantly lower in the seed crystals when compared to the cocoa butter. Concentrations of oleic acid were twice as high in seed crystal phosphatidylethanol-amine and almost four times as high in seed crystal phosphatidylcholine than in corresponding cocoa butter samples. The possible role phospholipids play in seed crystal development and in crystallization events is discussed.     

Dynamic crystallization of cocoa butter. I. characterization of simple lipids in rapid- and slow-nucleating cocoa butters and their seed crystals

Six cocoa butters with different crystallization induction times and their seed crystals were analyzed for simple lipid composition. The rapid-nucleating cocoa butter samples had higher concentrations of 1-palmitoyl-2-oleoyl-3-stearoylglycerol and 1,3-stearoyl-2-oleoylglycerol (SOS), and lower concentrations of the diunsaturated triacylglycerols, 1-palmitoyl-2,3-oleoylglycerol and 1-stearoyl-2,3-oleoylglycerol, as well as higher stearic acid concentrations within their diacylglycerol fractions when compared to the slow-nucleating samples. At the early stages of crystallization, under agitation conditions at 26.5°C, cocoa butters solidified into two fractions, high-melting and low-melting. The low-melting fractions were composed of polymorphs IV and V of cocoa butter, as indicated by the onset melting temperatures of the endotherms from differential scanning calorimetry. The high-melting fractions, which had wide melting ranges, had peak maxima of 38.5–52.2°C. Seed crystals isolated at the early stage of crystallization were characterized by high concentrations of complex lipids, saturated triacylglycerols, saturated fatty acid-rich diacylglycerols, and monoacylglycerols. The rapid-nucleating seed crystals had higher concentrations of SOS when compared to their respective cocoa butters. The slow-nucleating seed crystals did not exhibit this characteristic.     

Seeding effects on solidification behavior of cocoa butter and dark chocolate. I. Kinetics of solidification

Effects of seeding of fat crystals on the crystallization kinetics of cocoa butter and dark chocolate were examined with a rotational viscometer. The seed crystals employed were cocoa butter, 1,3-distearoyl-2-oleoylglycerol (SOS), 1,3-dibehenoyl-2-oleoylglycerol (BOB) and 1,2,3-tristearoylglycerol (SSS). The seed powders were prepared by pulverization below —50°C, the dimensions being in a range from 20–70 μm. Particular attention was paid to the influence of polymorphism of the seed crystal. We found that all of the above seed materials accelerated the crystallization, the degree of acceleration being in a following order; SOS (β ₁) > cocoa butter (Form V) > SOS (a mixture ofβ’ andβ ₂) > BOB (β ₂) > BOB (pseudo-β’) > SSS (β). Precise measurements of the crystallization kinetics showed that the most influential factors in the seeding effects are the physical properties of the seed materials—above all, thermodynamic stability, and similarity in the crystal structure to cocoa butter are the most determinative.     

Polymorphism of cocoa butter

Largely by x-ray diffraction six crystalline states, I–VI, in order of increasing melting point, have been identified for cocoa butter. Of these states II, IV, V and VI are pure and identifiable with previously (or presently) identified polymorphs of 2-oleoylpalmitoyl stearin (POS), namelyα-2,β′-2,β-3 (“V”) andβ-3 (“VI”); V and VI representing distinct but very closely related crystalline structures. State I is a definite but fleeting and not readily characterized subα state and may be a phase mixture, as state III may be also. Melting points, heats of fusion and dilatometric data are reported for all states to the extent that their stability permits. The normal state of cocoa butter in chocolate is apparently V, certainlyβ-3. While it is true that “bloom” has not been observed for pure V nor observed to exist in the absence of VI, it is premature to say that VI is specifically the phase of chocolate “bloom”.     

Solidification of cocoa butter

Cocoa butter and other confectionery fats do not behave alike on molding. Explanations for the behavior of cocoa butter generally are unavailable. The linear contraction of molded cocoa butter on solidification under various conditions was determined. Maximum linear contraction of about 2% was measured when a well-seeded sample was solidified at 16C. Nearly all of this contraction occurred during the first half hour. A theoretical explanation for this contraction was developed. Linear contraction takes place after the well-seeded cocoa butter has solidified in the next-to-highest melting form and while this solid form is transforming to the most stable polymorph. Addition information was developed on the polymorphic forms of cocoa butter, the permanence of seed crystals at various temps, rates of solidification, and solidification characteristics of unseeded cocoa butter. The data were obtained by dilatometric examination of a small sample using a volumetric dilatometer and direct measurement of linear contraction during solidification in a mold. Presented at the AOCS Meeting in Atlanta, April, 1963.     

Characterization of cocoa butter substitutes,milk fat and cocoa butter mixtures

The melting properties and polymorphic behavior of binary and ternary blends of cocoa butter substitutes (CBS), cocoa butter (CB), and milk fat (MF) were studied by using pulsed nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and X‐ray diffractometry (XRD). Hydrogenated palm kernel stearin (HPKS) and hydrogenated palm kernel olein (HPKO) were chosen as the two CBS feedstock fats. Both CBS/CB binary blends displayed significant eutectic behaviors. Multiple melting peaks and eutectic effects were observed at 30–50% addition levels of CB to HPKS. The range was broader in HPKO/CB blends. Dilution effect was observed in both CBS/MF blends while slight monotectic effect was also observed in HPKO/MF blends. Ternary phase diagrams and melting curves showed that eutectic effects existed in both ternary blends and the degree of interaction depended on the content of CB and MF. XRD results showed that when pure fat component in each blend exceeded 80%, its polymorphism dominated in the ternary blends. However, when CBS/CB or MF /CB were added at a comparative content (blends D and F), both β and β′ form existed. Practical applications: Phase properties of fat blends may have significant effects on the sensory characteristics and physical properties of the final products, such as hardness, brittleness, and the bloom formation. This study evaluates the melting properties and the polymorphic characteristics of fat blends of constituents with potential use in the manufacture of confectionery products. A comprehensive analysis of binary and ternary fat blends was conducted in order to provide a guide for compound chocolate production formulation.     

巧克力中可可脂及其代用品分析技术研究进展

介绍了天然可可脂的特性,可可脂代用品如类可可脂和代可可脂的分类和特性,并从晶体性能研究、组分对比研究、鉴定研究和检测方法研究等4个方面,重点阐述了国内外巧克力中可可脂及其代用品的分析技术研究进展,对巧克力及巧克力制品产业的发展前景进行了预测和展望。     

巧克力中可可脂及其代用品分析技术研究进展

介绍了天然可可脂的特性,可可脂代用品如类可可脂和代可可脂的分类和特性,并从晶体性能研究、组分对比研究、鉴定研究和检测方法研究等4个方面,重点阐述了国内外巧克力中可可脂及其代用品的分析技术研究进展,对巧克力及巧克力制品产业的发展前景进行了预测和展望。     

Lipid composition of perilla seed

The composition of lipids and oil characteristics from perilla [Perilla frutescens (L.) Britt.] seed cultivars are reported. Total lipid contents of the five perilla seed cultivars ranged from 38.6 to 47.8% on a dry weight basis. The lipids consisted of 91.2–93.9% neutral lipids, 3.9–5.8% glycolipids and 2.0–3.0% phospholipids. Neutral lipids consisted mostly of triacylglycerols (88.1–91.0%) and small amounts of sterol esters, hydrocarbons, free fatty acids, free sterols and partial glycerides. Among the glycolipids, esterified sterylglycoside (48.9–53.2%) and sterylglycoside (22.1–25.4%) were the most abundant, while monogalactosyldiacylglycerol and digalactosyldiacylglycerol were present as minor components. Of the phospholipids, phosphatidylethanolamine (50.4–57.1%) and phosphatidylcholines (17.6–20.6%) were the major components, and phosphatidic acid, lysophosphatidylcholine, phosphatidylserine and phosphatidylinositol were present in small quantities. The major fatty acids of the perilla oil were linolenic (61.1–64.0%), linoleic (14.3–17.0%) and oleic acids (13.2–14.9%). Some of the physicochemical characteristics and the tocopherol composition of perilla oil were determined.     

Thermal and compositional properties of cocoa butter during static crystallization

Studies were conducted using differential scanning calorimetry (DSC) and high performance liquid chromatography (HPLC) to determine the thermal properties and glyceride composition of cocoa butter crystals formed under static conditions. In addition to these studies, visual characterization of the crystallites was obtained with polarized light microscopy (PLM). Crystals were formed under controlled static or motionless conditions at formation temperatures of 26.0, 28.0, 30.0, 32.0 and 33.0 C. Preparatory techniques were developed using laminated polyethylene with plastic hoops in order to grow the crystals for isolation and visual identification by PLM prior to DSC assay. Cocoa butter was also crystallized from liquid oil directly in the DSC pans prior to thermal assay. At each crystal formation temperature (26–33 C), various crystallite types grew, each with varying triglyceride composition (PLiP, POO, PLiS, POP, SOO, SLiS, POS, SOS, SOA). As an example, the ‘feather’ and ‘individual’ crystals formed at 26.0 C exhibited significant increases in SOS and significant decreases in POP compared to the original butter. It was determined that the original amount of SOS significantly increased in the cocoa butter crystallite as the incubation temperature increased from 26–32 C.     

On the configuration of cocoa butter

Summary It is concluded from x-ray diffraction, thermal curve, and enzymatic hydrolysis that the predominant glyceride of cocoa butter is 2-oleoyl palmitoyl stearin (POS) instead of 2-palmitoyl oleoyl stearin (OPS), the configuration which has been rather generally accepted. Accordingly it is suggested that a fully satisfactory cocoa butter extender should be largely of symmetrical, disaturated configuration since only thus is the characteristic beta-3 form of cocoa butter likely to be preserved. An important aspect of this finding is that all disaturated vegetable glycerides which have been well characterized are of symmetrical, disaturated configuration. This not only supports the idea of the formation of specific glycerides in natural fats as opposed torandom fatty acid distribution but also points to some important common feature in vegetable glyceride metabolism.     

The flash devolatilization of cocoa butter

A water-induced flash devolatilization process has been developed for the deodorization of cocoa butter. Per flash devolatilization efficiencies of 65⊋ash;75% are high enough to give commercial quality products in a single flash.     

Lipid composition of murraya koenigii seed

Total seed lipids extracted fromMurraya koenigii (Linn), Rutaceae amounted to 4.4% of the dry seed. The total lipids consisted of 85.4% neutral lipids, 5.1% glycolipids and 9.5% phospholipids. Neutral lipids consisted of 73.9% triacylglycerols, 10.2% free fatty acids and small amounts of diacylglycerols, monoacylglycerols and sterols. At least five glycolipids and seven phospholipids were identified. Sterylglucoside and acylated sterylglucoside were major glycolipids, while digalactosyldiacylglycerol, monogalac-tosyldiacylglycerol and monogalactosylmonoacylglycerol were present in small quantities. The phospholipids consisted of phosphatidylethanolamine, phosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidylcholine as major phospholipids and minor quantities of phosphatidylinositol, phosphatidylglycerol and phosphatidic acid. The fatty acid composition of these different neutral lipids, glycolipids and phospholipids were determined.     

Chemical and physical characteristics of cocoa butter substitutes, milk fat and malaysian cocoa butter blends

Two ternary systems of confectionery fats were studied. In the first system, lauric cocoa butter substitutes (CBS), anhydrous milk fat (AMF), and Malaysian cocoa butter (MCB) were blended. In the second system, high-melting fraction of milk fat (HMF42) was used to replace AMF and also was blended with CBS and MCB. CBS contained high concentrations of lauric (C_12:0) and myristic (C_14:0) acids, whereas palmitic (C_16:0), stearic (C_18:0), and oleic (C_18:1) acid concentrations were higher in MCB. In addition, AMF and HMF42 contained appreciable amounts of short-chain fatty acids. CBS showed the highest melting enthalpy (143.1 J/g), followed by MCB (138.8 J/g), HMF42 (97.1 J/g), and AMF (72.9 J/g). The partial melting enthalpies at 20 and 30°C demonstrated formation of a eutectic along the binary blends of CBS/MCB, AMF/MCB, and HMF42/MCB. However, no eutectic effect was observed along the binary lines of AMF/CBS and HMF42/CBS. Characteristics of CBS included two strong spacings at 4.20 and 3.8 Å. MCB showed a strong spacing at 4.60 Å and a weak short-spacing at 4.20 Å. On the other hand, AMF exhibited a very weak short-spacing at 4.60 Å and two strong spacings at 4.20 and 3.8 Å, while HMF42 showed an intermediate short-spacing at 4.60 Å and also two strong short-spacings at 4.20 and 3.8 Å. Solid fat content (SFC) analyses at 20°C showed that CBS possessed the highest solid fat (91%), followed by MCB (82.4%), HMF42 (41.4%), and AMF (15.6%). However, at 30°C, MCB showed the highest SFC compared to the other fats. Results showed that a higher SFC in blends that contain HMF does not necessarily correlate with a stronger tendency to form the β polymorph.     

Effect of liquid fat on melting point and polymorphic behavior of cocoa butter and a cocoa butter fraction

The polymorphic behavior of cocoa butter and a high-melting fraction of cocoa butter (CBF) was investigated by differential scanning calorimetry. The effect of liquid fat on melting point and polymorphic behavior was established for six mixtures: 83.5% cocoa butter and 16.5% of a low-melting fraction of cocoa butter (CBF-LM), 90% cocoa butter and 10% olive oil, and four mixtures of CBF and olive oil containing 10%, 20%, 30%, and 50% olive oil. Six polymorphs were found for cocoa butter and at least five for CBF. The melting points for cocoa butter and CBF were 35 and 38 C, respectively. Addition of CBF-LM to cocoa butter reduced the observable polymorphs to four and the melting point to 32.5 C. In cocoa butter, 10% olive oil reduced the observable polymorphs to three and the melting point to 31.5C. Similarly, 10% olive oil in CBF reduced the observable polymorphs to three and the melting point to 37 C. Amounts of 20%, 30%, and 50% olive oil in CBF reduced the polymorphs to two and the final melting point to 34.5, 33, and 32 C, respectively. Possible explanations for the observed polymorphic behavior are advanced. Changes in the rates of tempering of cocoa butter and CBF on addition of various amounts of liquid fat are discussed.     

Detection of cocoa butter equivalents in chocolate

The fatty acids at the sn-2 position and the sterol composition of cocoa butter and three common cocoa butter equivalents (CBE), namely Coberine, Choclin and Calvetta, were studied comparatively, in order to develop a sensitive method for detecting CBE in chocolate. Differences observed in the composition of saturated fatty acids at position-sn-2 present some interest in detecting CBE in chocolate. Differences found in 4-desmethyl and 4-methylsterol compositions, although quite significant, did not present any practical interest because of the relatively small amounts present in CBE. The 4,4′-dimethylsterol or triterpene alcohol fraction was found to have a potential for determining CBE in chocolate. Thus, the triterpene alcohols of Coberine were further fractionated on argentation thin layer chromatography (TLC) and analyzed by gas liquid chromatography (GLC) and gas chromatography-mass spectrometry (GC-MS). α-Amyrin was found in 48.2% of the triterpene alcohols of Coberine and was absent from cocoa butter. Cycloartenol, the main 4,4′-dimethylsterol of cocoa butter, and α-amyrin were well resolved on an OV-17 glass capillary column.