Spatial mapping of solid and liquid lipid in confectionery products using a 1D centric SPRITE MRI technique

Oil migration is responsible for the poor keeping qualities of composite confectionery products. Quality defects arising from oil migration include softening of the coating, hardening of the filling, deterioration in sensory quality and a greater tendency toward fat bloom formation. For this reason, oil migration has been extensively studied, and yet a clear understanding of the oil migration mechanisms still remains a challenge.Traditional MRI techniques are unable to acquire images from the solid lipid in chocolate. In this paper we employ a newly developed one-dimensional, centric-scan MRI technique to acquire images from the short lived signal components from the solid lipid, as well as the longer timescale components of the liquid lipid in a chocolate sample. We present one-dimensional images of a dynamic hazelnut oil absorption experiment, and one-dimensional solid and liquid distribution maps in a 5 mm thick chocolate sample in which oil migration occurs.     

Oil Migration in a Chocolate Confectionery System Evaluated by Magnetic Resonance Imaging

ABSTRACT: Oil migration is a common problem in composite chocolate confectionery products resulting in softening of chocolate and hardening of the filling. Spatial and temporal changes in the liquid oil content of a 2-layer peanut butter and chocolate model system were evaluated using a magnetic resonance imaging (MRI) technique. The experimental factors were chocolate particle size, milk fat content, emulsifier concentration, degree of temper, and storage temperature. The responses were migration rate and overall change in signal intensity (amount of migration). Based on analysis of variance (ANOVA), particle size, milk fat content, and storage temperature were significant factors for oil migration rates. Milk fat content and temperature were significant factors for overall change in signal intensity.     

Modeling oil migration in two-layer chocolate–almond confectionery products

Migration of oil from high oil content fillings into the surrounding chocolate coatings results in product quality changes of filled confections. The objective of this study was to evaluate the mass transfer of liquid oil in two-layer model confectionery samples prepared from four almond products and dark chocolate. Experimental data were acquired using magnetic resonance imaging (MRI). The spatial and temporal experimental data of the liquid oil signal of the almond product and chocolate were modeled using a Fickian diffusion model. Solutions to the diffusion model were derived using both Laplace transform analytical solution and a finite difference numerical solution. For both methods, the boundary condition between the two layers incorporated a partition coefficient. MatLab’s nlinfit routine coupled with the diffusion equation solution provided estimates of the diffusion coefficients, D_a (almond products) and D_c (chocolate), and the partition coefficient. The diffusion coefficient values for the chocolate region ranged between 3 × 10⁻¹¹ m²/s and 6 × 10⁻¹¹ m²/s; the diffusion coefficient values for the almond products were an order of magnitude greater than that of chocolate.     

Effect of nut oil migration on polymorphic transformation in a model system

Fat migration in confectionery products can lead to significant deterioration in quality. This occurs not only through loss in texture contrast between chocolate and filling but also through the appearance of fat bloom on the surface of the chocolate. This latter aspect is often, although not exclusively, linked to the transformation of the cocoa butter β_V phase into β_VI. In this study, the influence of hazelnut oil on the polymorphic transformation of cocoa butter has been determined, showing that even small additions (1%) of nut oil can have a significant impact on the rate of transformation. Additionally, use of a model system has shown that polymorphic transformation in cocoa butter is linked to the degree of migration of nut oil from a filling. Portions of the cocoa butter close to the filling experience both greater degrees of migration and faster transformation.     

Oil migration in chocolate and almond product confectionery systems

Oil migration from high oil content almond confections into adjacent chocolate causes changes in product quality. The objective of this study was to quantify the oil migration from almond products to dark chocolate. Magnetic resonance imaging (MRI) was used to monitor spatial and temporal changes of liquid lipid content. A multislice spin echo pulse (MSSE) sequence was used to acquire images with a 7.8-ms echo time and a 1000-ms repetition time using a 1.03T Aspect AI MRI spectrometer. Samples were prepared as a 2-layer model system of chocolate and almond confection. Six different almond products and 1 type of dark chocolate were used. Samples were stored at 20, 25, and 30°C for a time frame of several months. Rate and extent of migration were quantified by a kinetic expression based on the linear dependence of oil uptake by chocolate and the square root of the time. Samples showed distinctly different rate and extent of oil migration, as evidenced by quantitative differences in the kinetic rate constants and equilibrium uptake for the different sample types. This work will be helpful to design formulations for almond and almond-based products in confections. PRACTICAL APPLICATION: This work will be helpful to design formulations for almond use in confections.     

Visualisation of Liquid Triacylglycerol Migration in Chocolate by Magnetic Resonance Imaging

This study has demonstrated that magnetic resonance imaging can be used to visualise the migration of liquid triacylglycerols in composite chocolate confectionery. Migration was observed between a layer of hazelnut oil filling (oil+icing sugar) and a layer of dark chocolate used as a model of composite chocolate confectionery products. In addition, low-resolution nuclear magnetic resonance measurements of the solid fat content (%) were also made. Substantial differences were observed between the migration profiles at 19 and 28°C, and in the distribution of liquid triacylglycerols across the chocolate layer after migration. It is suggested that the mechanism of migration involves both diffusion of the liquid triacylglycerols and capillary attraction of the hazelnut oil into the chocolate matrix. © 1997 SCI.     

A discrete stochastic model for oil migration in chocolate-coated confectionery

Oil migration is an important process in the formation of fat bloom on chocolate-coated confectionery, leading to consumer rejection. However, the exact mechanisms behind this phenomenon are still not completely elucidated, which hampers the development of a mathematical simulation model. In this paper, a model based on a cellular automaton (CA) is proposed and parameterized using experimental data obtained from confectionery model systems. This CA-based model is shown to be able to describe the oil migration in an adequate manner and can therefore be used to calculate an effective diffusion coefficient. Further, the potential of a CA-based approach for the further investigation of the fat bloom mechanisms is demonstrated by means of a case study where capillary rise is incorporated in the CA-based model.     

Oil Migration in Chocolate–Peanut Butter Paste Confectionery as a Function of Chocolate Formulation

ABSTRACT:  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 °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 × 10⁻¹¹ m²/s for the chocolate formulations stored at 30 °C. No significant mass transfer took place in the 20 °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.     

Impact of pre-crystallization process on structure and product properties in dark chocolate

Dark chocolate microstructures with different structure densities, i.e., close-packing of the fat crystal lattice, and homogeneity i.e., evenness and connectivity of the fat crystal network, were created by β_VI-seeding or conventional pre-crystallization with various degrees of temper and were evaluated with respect to storage stability. The structure characterization was conducted by measuring the strength of the cocoa butter crystal network with traction tests combined with DSC melting curves. Subsequent storage stability was evaluated with DigiEye technique for fat bloom development and gravimetrical techniques for fat/moisture migration. The two pre-crystallization processes generated significantly different structures and storage stability. Well-tempered β_VI-seeding resulted in a dense and homogenous chocolate structure directly after solidification, which was optimal in order to retard fat bloom and fat migration. However, a too high structure density generated heterogeneous structures with reduced ability to withstand fat bloom. A lower structure density exhibited optimal resistance against moisture migration.     

Effect of cocoa butter structure on oil migration

Oil migration from a high oil content filling into adjacent chocolate causes changes in product quality. The objective of this study was to quantify the oil migration from a cream filling system into cocoa butter, which provided a model for the behavior of chocolate-enrobed confectionery products with a soft, creamy center. Magnetic resonance imaging (MRI) was used to monitor spatial and temporal changes of liquid lipid content. A multislice spin echo pulse sequence was used to acquire images with a 7.8 ms echo time and a 200 ms repetition time using a 1.03 T Aspect Imaging MRI spectrometer. Samples were prepared as a 2-layer model system of cocoa butter and model cream filling. Three methods were used to prepare the cocoa butter: static, seeded, and sheared. Samples were stored at 25 °C for a time frame of 56 d. The rate of oil migration was quantified by a kinetic expression based on the linear dependence of oil uptake by cocoa butter and the square root of the time. Samples showed distinctly different rates of oil migration, as evidenced by quantitative differences in the kinetic rate constant. Practical Application: This work will be helpful to elucidate the influence of crystallization process and structural properties such as crystal nanostructure and crystal habit on the migration of oil through a crystalline fat matrix.     

Comparison of Whiteness Index vs. Fractal Fourier in the Determination of Bloom Chocolate Using Image Analysis

Modeling of bloom is essential to evaluate the effectiveness of processes in chocolate and to determine its shelf life. Computer vision and the fractal kinetic method were used to quantify bloom in samples of chocolate coating and cocoa chocolate subjected to a 3- or 6-h temperature cycle. Bloom was also determined by classical methods (L* lightness and whiteness index). In the results, the kinetic bloom rate derived by the fractal kinetic method was higher than that obtained with the L* or white index. Fractal method can be used to determine kinetic bloom and to detect differences in chocolate coating affected by 3 or 6 h of temperature cycle. The bloom rate derived by the fractal method was higher that the mean L* value and whiteness index methods; no differences could be registered between the last two methods. In general, the fractal method can be seen as a new means of quantifying bloom in chocolate and allows registering the bloom faster than the L* value and white index methods.     

Determination and identification of titanium dioxide nanoparticles in confectionery foods,marketed in South Korea,using inductively coupled plasma optical emission spectrometry and transmission electron microscopy

Food-grade titanium dioxide (TiO₂) is a common and widespread food additive in many processed foods, personal care products, and other industrial categories as it boosts the brightness and whiteness of colours. Although it is generally recognised as safe for humans, there is a growing interest in the health risks associated with its oral intake. This study quantified and identified TiO₂ nanoparticles present in confectionery foods, which are children’s favourite foods, with inductively coupled plasma optical emission spectrometry (ICP-OES) and transmission electron microscopy (TEM). A reliable digestion method using hot sulphuric acid and a digestion catalyst (K₂SO₄:CuSO₄ = 9:1) was suggested for titanium analysis. Validations of the experimental method were quite acceptable in terms of linearity, recoveries, detection limits, and quantification limits. Of all the 88 analysed foods, TiO₂ was detected in 19 products, all except three declared TiO₂ in their labelling. The mean TiO₂ content of candies, chewing gums, and chocolates were 0.36 mg g^?1, 0.04 mg g^?1, and 0.81 mg g^?1, respectively. Whitish particles isolated from the confectionery foods were confirmed as TiO₂ nanoparticles via TEM and energy dispersive X-ray spectroscopy (EDX), in which nanosized particles (<100 nm) were identified.     

Chocolate Swelling during Storage Caused by Fat or Moisture Migration

Abstract: Quantification of swelling in dark chocolate subjected to fat or moisture migration was conducted using a new method based on confocal chromatic displacement sensor. The nondestructive method allowed for the height profile of dark chocolate samples to be scanned with a sensitivity of ± 2.8 μm. By performing multiple scans on each sample prior to and after being subjected to fat or moisture migration, the induced swelling could be quantified. Applying the new method on confectionery systems revealed that fat and moisture migration generate different swelling behavior/kinetics in dark chocolate during storage. Moisture migration resulted in a rapid swelling once a water activity of 0.8 was reached in the chocolate, probably by interaction and absorption of moisture by the particulate solids. Fat migration also affected the swelling behavior in chocolate, possibly by inducing phase transitions in the continuous cocoa butter phase. Migrating fat also proved to induce a more pronounced swelling than the same amount of absorbed moisture which further consolidated that the observed swelling caused by fat or moisture migration is a result of significant different mechanisms.     

Influence of lactic acid ester on chocolate quality

Influence of concentration of emulsifier Lactem P 22 (lactic acid ester of monodiglyceride) as blooming inhibitor on the quality and fat bloom stability of laboratory made samples of chocolate was investigated. This ingredient was added during the pre-crystallization process of chocolate mass. The pre-crystallization was performed in the laboratory crystallizer modified Brabender pharinograph, where the rheological characteristics of the pre-crystallized fluid chocolate mass were measured. The experiments were performed according to the factorial plan 3² (two factors on three levels). Statistical results processing was performed according to the Response Surface Methodology. Physics characteristics of chocolate—hardness and lightness—were obtained by instrumental methods. The results has shown that Lactem P 22 improve fat bloom stability of chocolate samples but decrease sensory quality of chocolate. Better sensory quality of chocolate was achieved with combination of the crystallization promoter—Dynasan 118. The best sensory quality of chocolate has been obtained with 0.5% Dynasan 118 and 1 and 2% Lactem P 22. Samples of chocolate which was pre-crystallized on 23°C and with 3% Lactem P 22, showed the highest fat bloom stability.     

Oil Migration in 2-Component Confectionery Systems

ABSTRACT:  Oil migration from high oil content centers into chocolate coatings results in product quality changes. The objective of this study was to monitor and model peanut oil migration in 2-layer systems of increasing phase complexity. Three 2-layer systems were prepared: peanut oil/cocoa butter; peanut butter paste/cocoa butter; and peanut butter paste/chocolate. Magnetic resonance imaging was used to measure liquid oil signal as a function of position over a storage time of 193 days at 25 °C. The 3 types of samples exhibited appreciably different patterns of oil migration. The peanut oil/cocoa butter samples had mass transfer typical of oil being absorbed into a liquid/solid region. The peanut butter paste/cocoa butter magnetic resonance profiles were characterized by mass transfer with a partition coefficient greater than unity. The peanut butter paste/chocolate samples exhibited a time-dependent peanut oil concentration at the interface between the chocolate and peanut butter paste. The spatial and temporal experimental data of the peanut butter paste/chocolate samples were modeled using a Fickian diffusion model, fitting for the effective diffusivity. Values of the diffusivity for the 6 chocolate formulations ranged from 1.10 to 2.01 × 10⁻¹³ m²/s, with no statistically significant differences.     

Optimization of a scanner imaging technique to accurately study oil migration kinetics

The aim of this study was to refine an image analysis technique that was developed in our laboratory in order to study oil migration in confectionery products (Marty, S., Baker, K., Dibildox-Alvarado, E., Neves Rodrigues, J., & Marangoni, A. G. (2005). Monitoring and quantifying of oil migration in cocoa butter using a flatbed scanner and fluorescence light microscopy. Food Research International). The migration of a nile red stained oily phase (soft fat) was monitored in tempered cocoa butter matrices kept at 18 °C for about 75 days. Oil migration kinetics was quantified using a common flatbed scanner followed by image processing and analysis. The most reliable parameter derived from this analysis is the position of the dye front (I₁₀) where the intensity of the dye is 10% of maximum. The determination of the amount of dye migrated from pixel intensity measurements was found to be highly affected by cocoa butter structure at times greater than 28 days, but I₁₀ was not. The determination of a model-independent oil migration rate (I₁₀/tⁿ) using this method was found to be highly reproducible and accurate. Due to the observed non-linearity of the oil migration process and the effects of matrix structure on the determination of pixel intensity (and thus mass of dye migrated), the quantification of oil migration using the simplified version of Fick’s second law is not recommended.     

Edible Coatings to Inhibit Lipid Migration in a Confectionery Product

Coatings containing hydrocolloids and sweetners were tested for lipid barrier and sensory properties, adhesion to chocolate, viscosity, and a_w. A coating containing high methoxyl pectin, acacia gum, high fructose corn syrup, dextrose, fructose, and sucrose was most effective. Coatings (0.5 mm thick, a_w 0.5) showed no detectable oil migration after 47 days at 30 ± l°C, compared to 11.5 mg/cm² trilinolein equivalents migration in 1 day at 21 ± 2°C. Coatings (0.5 mm thick) were applied between chocolate and peanut butter and tested for sensory characteristics. Except for the color of the coating, no significant difference occurred in overall preference compared to control (no coating) samples.     

Migration of photoinitiators from paper to fatty food simulants: experimental studies and model application

The migration of five different photoinitiators from kraft paper to two fatty food simulants, Tenax^® and 95% ethanol, was investigated under different conditions. The effects of temperature and storage time, as well as the physicochemical properties of the photoinitiators on migration, were discussed. Mathematical models based on Fick’s second law generated from two cases, single- and two-side contacts, were applied to predict the migration behaviour from the paper to the food simulants. The partition coefficients estimated from the model decreased with temperature. The diffusion coefficients of the selected photoinitiators from the paper ranged from 1.55 × 10^–10 to 7.54 × 10^–9 cm² s^?1 for Tenax and from 2.79 × 10^–9 to 8.03 × 10^–8 cm² s^?1 for 95% ethanol. The results indicate that the applied model can predict the migration of photoinitiators in the initial short period before equilibrium, and the migration from paper to Tenax through a single-side contact demonstrated an especially high concordance.     

Effect of storage temperature on texture,polymorphic structure,bloom formation and sensory attributes of filled dark chocolate

The effects of 18 and 30°C storage temperatures on texture, polymorphic structure, bloom formation and sensory attributes of dark chocolate, stored for 8 weeks were studied. Results showed that storage at 18°C for 8 weeks, significantly retarded changes in filled chocolates; the chocolates were free from bloom during the storage period. In contrast, at 30°C there was an increase in the rate of fat migration and rate of change of C36 and C50, and also a decrease in texture and the polymorph structure in the coating changed to β and β′ polymorphs. However, the chocolates bloomed in the third week of storage (2 cycles). Sensory evaluation indicated that, storage at 18°C is better than 30°C, and desiccated coconut gives a pleasant flavour to the chocolate.