Kinetics of the migration of lipids in composite chocolate measured by magnetic resonance imaging

Impact of composition and aeration on the migration of TAGs in sandwich type confectionery products

A sandwich type confectionery product is made with a soft filling and a chocolate coating. The fats used for these two parts are generally different to provide specific organoleptic sensations. Thus, their compositions, in terms of the triacylglycerols (TAGs) profile, are different. Depending on the ambient temperature conditions, the chemical potential gradient at the interface for TAGs, and the microstructures in the bulk of two parts, the migration of TAGs is influenced. We have studied the impact of different filling recipes on the migration of specific TAGs from the filling to the coating and vice versa with a newly developed tool, referred to as lipstick method. Also, the influence of the micro-aeration of the filling on the transfer process is evaluated. Furthermore, Fick's law of diffusion-based model is developed. The migration of TAGs as predicted by the model is compared to the experimental measurements, and limitations of the model are discussed. This approach can be used to tune the recipes of coating and filling to enhance the shelf-life stability of such products while delivering on specific liking attributes of taste.

Pre-Crystallization of Nougat by Seeding with Cocoa Butter Crystals Enhances the Bloom Stability of Nougat Pralines

Fat bloom is an outstanding quality defect especially in filled chocolate, which usually comprises oils of different origins and with different physical properties. Dark chocolate pralines filled with nougat contain a significant amount of hazelnut oil in their center and have been reported as being notably susceptible to oil migration. The current study was designed to test the assumption that a targeted crystallization of nougat with cocoa butter seed crystals is an appropriate technological tool to reduce filling oil transfer to the outside of the praline and, hence, to counteract chocolate shell weakening and the development of fat bloom. For this purpose, the hardness of nougat/chocolate layer models and the thermal properties of chocolate on top of nougat were analyzed during storage at 23 °C for up to 84 days. Pronounced differences between layer models with seeded nougat and with control nougat that was traditionally tempered were observed. The facts that chocolate hardness increased rather than decreased during storage, that the cocoa butter melting peak was shifted towards a lower temperature, and that the hazelnut oil content in the chocolate was reduced can be taken as explicit indicators for the contribution of seeded nougat to the fat bloom stability of filled chocolate.

Effect of ultrasonic on deterioration of oil in microwave vacuum frying and prediction of frying oil quality based on low field nuclear magnetic resonance (LF-NMR)

The ultrasound assisted microwave vacuum frying system was investigated to achieve higher physicochemical and quality attributes of frying oil. In this study, the effect of ultrasonic on peroxide value, acid value, carbonyl value, polar component, fatty acid, color, viscosity, dielectric properties and low field nuclear magnetic resonance (LF-NMR) relaxation characteristics of frying oil under microwave vacuum frying were analyzed; the principal component regression (PCR) analysis was used to establish a correlation model for predicting physicochemical properties through LF-NMR relaxation characteristics. The results indicated that the acid value, carbonyl value, polar component, color, viscosity, dielectric constant and saturated fatty acids of the oil samples increased with the prolongation of frying time, and the peroxide value increased first and then decreased with the extension of frying time. Furthermore the relaxation time of peak T₂₁, T₂₂ and T₂₃ decreased gradually of frying oil, and the peak area ratio of S₂₁ gradually increased as the frying time goes on. Good correlations were found between the LF-NMR relaxation characteristics and the physicochemical properties using PCR, and the analysis results are credible. In conclusion, compared with the microwave vacuum frying, the ultrasonic combined with microwave vacuum frying can delay the deterioration of the frying oil and the physicochemical properties of frying oil could be well predicted by the LF-NMR T₂ relaxation characteristics during the frying process.

Shear effects on the diffusive movement of oil in triacylglycerol networks

Correlation between the macroscopic D_eff obtained through the Ziegleder model and D_mol obtained by NMR in fat crystal networks.

Oil diffusivity through fat crystal networks

Oil migration in chocolate and chocolate-based confections leads to undesirable visual and textural changes. Establishing ways to slow this unavoidable process would increase shelf life and reduce consumer rejection. Diffusion is most often credited as the main pathway by which oil migration occurs. Here, we use fluorescence recovery after photobleaching (FRAP) to explore the diffusion coefficients of vegetable and mineral oil through fat crystal networks at different solid fat contents (SFC). Differences in compatibility between the fat and oil lead to unique primary crystal clusters, yet those variations do not affect diffusion at low SFCs. Trends deviate at higher SFCs, which we ascribe to the influence of the differing crystal cluster structures. We relate our results to the strong and weak-link rheological regimes of fat crystal networks. Finally, we connect the results to relationships developed for polymer gel systems.

Fat crystal migration and aggregation and polymorphism evolution during the formation of granular crystals in beef tallow and palm oil

Six rectangular block all beef tallow (BT)-based and all palm oil (PO)-based model shortenings prepared on a laboratory scale, denoted BTMS and POMS, respectively, were stored under two storage conditions, (1) constant temperatures (5 and 20 °C, respectively and (2) temperature fluctuations (5 °C for 12 h and 20 °C for 12 h for a cycle), to induce granular crystals. The fat crystal migration and aggregation, sensory evaluations, and polymorphism evolutions during the formation of granular crystals in the above samples were investigated systematically. In comparison to the constant temperature storage, the crystal growth and hierarchical aggregation process were more quick and the conversion rate of the β-form crystal was also faster in both BTMS and POMS under temperature cycling storage and, concomitantly, easier to induce the formation of granular crystals. From the comprehensive analysis of crystal sizes and the sensory evaluation results, it can be concluded that the detection threshold for graininess ranged from 40 to 90 μm, with the smaller size being perceived only at higher crystal concentrations. The possible formation mechanism and the realistic control approaches for granular crystals in plastic fats also are clarified in the present study.

Oil migration in chocolate-peanut butter paste confectionery as a function of chocolate formulation

Migration of oil from high oil content filling to the chocolate coating can result in undesirable quality changes in filled chocolate confectionery products. The objective of this study was to monitor and model peanut oil migration in a 2-layer chocolate-peanut butter paste model confectionery. Spatial and temporal oil content changes were evaluated using magnetic resonance imaging. Five formulations of chocolate, which varied in chocolate particle size, milk fat content, and emulsifier level, were assessed at 2 temperatures, 20 and 30 degrees C. The spatial and temporal experimental data were modeled using a Fickian-based diffusion model, fitting for the diffusion coefficient, D, over a time frame of 17 d. Values of the diffusion coefficient ranged from 1.82 to 3.23 x 10(-11) m2/s for the chocolate formulations stored at 30 degrees C. No significant mass transfer took place in the 20 degrees C samples over the experimental time frame. This study describes the dynamic nature of the interface between the chocolate and peanut butter paste layers, quantifies the mass transfer from the peanut butter paste to the chocolate, and reinforces the importance of temperature control.

Microstructure of fat bloom development in plain and filled chocolate confections

Temperature-controlled environmental scanning electron microscopy was used to examine the microstructural changes in plain solid chocolate and its counterpart stored against a tricaprylin-based filling cream. Sample storage at 26 °C for 40 days led to significant changes in microstructure as a function of time. Surface imperfections (pores, pits, etc.) initially present on the filled confection disappeared within two days whereas those on the control did not throughout the storage period. Morphological changes on the surface of the control were dominated by the growth of needle-like crystals whereas spherulites appeared on the filled chocolate, with large crystals (upwards of 100 microns in length, in some cases) observed in both cases. From a microstructural perspective, both diffusion and capillarity appear to have a part in fat bloom initiation and propagation, though temperature and the presence of a filling fat strongly dictate which mechanism will dominate.