Thermal and Mechanical Properties of Cocoa Butter Crystallized under an External Laminar Shear Field

Abstract

In this work, the effects of laminar shear on nanoscale structure and physical properties of triglyceride crystal networks were quantified. Cocoa butter (CB) was crystallized in the presence and absence of an external shear field. Samples were crystallized under a shear rate of approximately 340 s À1 in two different ways, by using a continuous Couette-type laminar shear crystallizer and by using a standard paddle mixer. Using different analytical methods and physical models, the mechanical strength and thermal properties of the crystallized CB were characterized. Cocoa butter crystallized under an external shear field had a stronger network with higher breaking force, Young's, and storage modulus than statically crystallized samples. The sheared samples also had a smaller crystallite size (300 nm length, 130 nm width). Here we also show that the arrangement of the crystalline component influences the material's strength. The Young's modulus was increased by about 30% in samples that exhibited crystalline alignment. Moreover, higher average peak melting temperature (∼0.8 °C) and full width at half maximum of the thermogram curves, fwhm, (∼0.9 °C) were observed for the statically crystallized samples. In the presence of crystalline alignment, the melting point of cocoa butter was decreased slightly, about 0.5 °C. This work demonstrates the substantial effects of laminar shear applied during crystallization of cocoa butter on its functional properties including melting, hardness, and rigidity.

Effects of external shear forces on crystallisation kinetics of model fat blends

“…However, the statically crystallised CB displayed a broader melting range compared to the sheared sample. These observations support previous findings that suggest a more uniform crystallisation behaviour when shear is applied during crystallisation (Dhonsi & Stapley, ; Maleky & Marangoni, ).…”

“…For instance, Marty & Marangoni () reported the influences of cocoa butter fatty acid profile on its physical properties and structural behaviour. On the other hand, in the manufacture of confectionery products, shear is usually applied to improve heat and mass transfer in cocoa butter as well as to promote the formation of a desirable polymorph (Rousset & Rappaz, ; Padar et al ., ; Maleky & Marangoni, ,b; Mazzanti et al ., ). Furthermore, shear has been shown to affect the crystallisation kinetics and microstructure of CB (Sonwai & Mackley, ; Marty & Marangoni, ; Mazzanti et al ., ), resulting in a stronger crystal network that could affect the quality and stability of confectionery products (Humphrey & Narine, ; Acevedo et al ., ; Ghosh & Rousseau, ; Maleky et al ., ).…”

Shear and Rapeseed Oil Addition Affect the Crystal Polymorphic Behavior of Milk Fat

“…In AMF, the 3L packing was not destroyed by shear. It is known that shear decreases the crystal cluster size of a crystallized fat [17,27]. The effect of the crystal cluster size on the solid state decay constant was not examined.…”

“…Le Botlan and Ouguerram [13] proposed a method to quantify an amorphous and a solidlike phase in milk fat by analyzing the transversal relaxation decay constant from free induction decay (FID) data obtained on a low field NMR spectrometer. Since then, a number of papers using NMR to determine and characterize the polymorphic forms present in model TAG systems [14][15][16] and in milk fat [17] have been published. So far, NMR has been shown to successfully distinguish a and b 0 , however, the b modification cannot be distinguished unambiguously from b 0 [14,18].…”

Nonspherical Nanoparticle Shape Stability Is Affected by Complex Manufacturing Aspects: Its Implications for Drug Delivery and Targeting

“…Whereas the latter instance is exhibited by the crystalline lipids (e.g., triglycerides) in spherical solid lipid nanoparticles, which is stored in aqueous medium at room temperature . Triglyceride has high degree of hydrophobicity (Figure e; represented as cocoa butter), bulk Young's modulus ≈0.25–0.47 × 10 −6 GPa, and average T m 31–34 °C (actual T m ranging 11‐73 °C due to the variation of trilaurin‐tristearin as well as α‐ & β‐polymorph). Considering these unsupportive properties for nonsphericity, it is really astonishing to know that triglyceride nanoparticles can arrange themselves into nonspherical nanoparticles during storage.…”