Binary Phase Behavior of 1,3-Distearoyl-2-oleoyl-sn-glycerol (SOS) and Trilaurin (LLL).

Shinichi Yoshikawa,Fumitoshi Kaneko,Yoshinori Yamamoto,Shimpei Watanabe

doi:10.3390/molecules25225313

Shinichi Yoshikawa, Fumitoshi Kaneko + Show 2 more

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https://doi.org/10.3390/molecules25225313

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Abstract

This paper reports the precise analysis of the eutectic mixing behavior of 1,3-distearoyl-2-oleoyl-sn-glycerol (SOS) and trilaurin (LLL), as a typical model case of the mixture of cocoa butter (CB) and cocoa butter substitute (CBS). SOS was mixed with LLL at several mass fractions of LLL (wLLL); the mixtures obtained were analyzed for polymorphic phase behavior using differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffractometry (SR-XRD). In melt crystallization with constant-rate cooling, SOS and LLL formed eutectics in their metastable polymorphs, allowing the occurrence of a compatible solid solution at wLLL ≥ 0.925. With subsequent heating, the resultant crystals transformed toward more stable polymorphs, then melted in a eutectic manner. For mixtures aged at 25 °C after melt crystallization, eutectics were found in the extended wLLL region, even at wLLL = 0.975. These results indicate that phase separation between SOS and LLL progressed in their solid solution under stabilization. The crystal growth of the separated SOS fraction may cause fat-bloom formation in compound chocolate containing CB and CBS. To solve this problem, the development of retardation techniques against phase separation is expected.

Highlights

Cocoa butter (CB), a material fat for chocolate products, is obtained from the beans of the cacao plant (Theobroma cacao L.) by press, expeller, or solvent extraction [1,2,3].The predominant constituents are about 95% to 97% triacylglycerols (TAGs) enriched with stearic acid (S, C18:0), oleic acid (O, C18:1), and palmitic acid (P, C16:0) as the major fatty-acid moieties
differential scanning calorimetry (DSC) measurements were conducted to examine the crystallization kinetics of the mixtures in terms of heat flow changing with varying temperature during cooling and heating
Crystals and crystallizes to form a new solid phase during aging. Such phase separation and crystallization of the separated phase are considered the crucial cause of fat bloom in cocoa butter substitute (CBS)-based compound chocolate

Summary

Introduction

Cocoa butter (CB), a material fat for chocolate products, is obtained from the beans of the cacao plant (Theobroma cacao L.) by press, expeller, or solvent extraction [1,2,3].The predominant constituents are about 95% to 97% triacylglycerols (TAGs) enriched with stearic acid (S, C18:0), oleic acid (O, C18:1), and palmitic acid (P, C16:0) as the major fatty-acid moieties. Unlike most naturally occurring fats, the symmetrical 1,3-disaturated-2-oleoyl-sn-glycerols of 1(3)-palmitoyl-2-oleoyl-3(1)-stearoyl-sn-glycerol (POS), 1,3-distearoyl-2-oleoyl-sn-glycerol (SOS), and 1,3-dipalmitoyl-2-oleoyl-sn-glycerol (POP) comprise at least 70% of the total TAGs in CB [3,4,5,6,7]. Due to this unique TAG composition, CB is solid at temperatures below ~25 ◦ C and liquid at the body temperature of ~37 ◦ C, resulting in sharp melting in the mouth [8,9]. Categorized as the fat of β-polymorphic tendency [15,16], CB requires a tempering (pre-crystallization) process for controlled crystallization in form V [10,13,14,17]

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