Influence of cocoa varieties on carbohydrate composition and enzymatic activity of cocoa pulp.

In Brazil, after the witch's broom disease incidence, diverse cocoa hybrids were developed, and variations were reported on their composition and characteristics. Based on this, the present study aimed to evaluate the pulp composition of several cocoa hybrids in order to better understand these variations. Results show that cocoa pulp is composed, on average, of 76 % sugar, and a wide variation (20 %) was observed in sugar content between hybrids. Regarding the sugar profile, a prevalence of reducing sugars was observed. Pod origin also plays an important role in pulp composition, with variations between hybrids from Espírito Santo and Bahia states. In relation to the degree of ripeness, ripe pods showed higher fructose and glucose content, while unripe pods presented mainly sucrose. Similar to sugars, the cello-oligossacharides profile was influenced by the degree of pod ripeness and origin and most ripe samples presented mainly cellobiose, cellotriose and cellotetrose. In addition, the prebiotic potential of cocoa pulp was highlighted by cello-oligossacharides digestion assay which exhibited low rates of degradation. Varying enzymatic activity was observed amongst different pulp hybrids, with polyphenol oxidase showing a higher variation when compared to invertase and polygalacturonase ranging. This study shows that the pod hybrid, origin and ripening degree may change the cocoa pulp composition. Therefore, it is very important to understand and evaluate these variations, in order to obtain better results in pulp utilization either in cocoa fermentation or as a coproduct.

Measurement of molten chocolate friction under simulated tongue-palate kinematics: Effect of cocoa solids content and aeration.

The perception of some food attributes is related to mechanical stimulation and friction experienced in the tongue-palate contact during mastication. This paper reports a new bench test to measure friction in the simulated tongue-palate contact. The test consists of a flat PDMS disk, representing the tongue loaded and reciprocating against a stationary lower glass surface representing the palate. The test was applied to molten chocolate samples with and without artificial saliva. Friction was measured over the first few rubbing cycles, simulating mechanical degradation of chocolate in the tongue-palate region. The effects of chocolate composition (cocoa solids content ranging between 28 â€‹wt% and 85 â€‹wt%) and structure (micro-aeration/non-aeration 0-15 â€‹vol%) were studied. The bench test clearly differentiates between the various chocolate samples. The coefficient of friction increases with cocoa solids percentage and decreases with increasing micro-aeration level. The presence of artificial saliva in the contact reduced the friction for all chocolate samples, however the relative ranking remained the same.

Early stages of fat crystallisation evaluated by low-field NMR and small-angle X-ray scattering.

Low-field time-domain nuclear magnetic resonance (NMR; 20 MHz) is commonly used in the studies of fats in the form of solid fat content (SFC) measurements. However, it has the disadvantage of low sensitivity to small amounts of crystalline material (0.5%), thus often incorrectly determining crystallisation induction times. From spin-lattice relaxation rate measurements (R1 ) during the isothermal crystallisation measurements of cocoa butter between 0.01 and 10 MHz using fast field cycling NMR, we learnt previously that the most sensitive frequency region is below 1 MHz. Thus, we focused on analysing our 10-kHz data in detail, by observing the time dependence of R1 and comparing it with standard SFCNMR and SFC determinations from small-angle X-ray scattering (SFCSAXS ). Although not reflecting directly the SFC, the R1 at this low frequency is very sensitive to changes in molecular aggregation and hence potentially serving as an alternative for determination of crystallisation induction times. Alongside R1 , we also show that SFCSAXS is more sensitive to early stages of crystallisation, that is, standard SFCNMR determinations become more relevant when crystal growth starts to dominate the crystallisation process but fail to pick up earlier crystallisation steps. This paper thus demonstrates the potential of studying triacylglycerols at frequencies below 1 MHz for obtaining further understanding of the early crystallisation stages of fats and presents an alternative and complementary method to estimate SFC by SAXS.

Global Small-Angle X-ray Scattering Data Analysis of Triacylglycerols in the α-Phase (Part II).

The early-stage crystallization behavior in a triacylglycerol mixture has been investigated on the nanoscale with a novel global small-angle X-ray scattering analysis technique. This method has been tailored for the determination of the electron density profiles (EDPs) replicating both (i) the nanostructural texture of molten triacylglycerols (TAGs) (refer to "Global Small-Angle X-ray Scattering Data Analysis of Triacylglycerols in the Molten State (Part I)" of this publication series) and (ii) the lamellar structure of the metastable α-polymorph. In a first stage, the α-phase scattering contribution alone was examined by classical Fourier analysis as well as by globally fitting the data, leading to practically identical EDPs. On the basis of these findings, we extended our analysis to the entire X-ray scattering contribution arising from molten TAGs and the solid α-phase fraction. Remarkably, the experimental and theoretical data agree very well, providing for the first time a detailed nanostructural understanding about the coexisting molecular assemblies. This, in turn, also allowed us to quantitatively determine the solid fat content (SFC) with X-ray scattering data. Our new theoretical approach for measurement of SFC is based on the global analysis of small-angle scattering/diffraction patterns, and the SFC results are in good agreement with values obtained from other techniques such as NMR spectroscopy.

Global Small-Angle X-ray Scattering Data Analysis of Triacylglycerols in the Molten State (Part I).

The study of triacylglycerols (TAGs) in their molten state is of fundamental importance for a deeper understanding of the TAG crystallization processes, being highly relevant for both manufacturing and medical applications. Although different models have been proposed to explain the nanostructured nature of the fluid state of TAGs, none of them are fully satisfactory. In this paper, we propose a new model consisting of positionally uncorrelated lamellar TAG assemblies embedded in an isotropic medium that assist as prenucleating structures. This model was validated by applying a novel global fitting method, resulting in an excellent agreement with the small-angle X-ray scattering data. A deeper analysis of the scattering patterns at different temperatures, both in cooling and heating directions, allowed us further to detect the crystalline traces of TAGs even after heating to 40 °C and record, on cooling, the onset of crystallization at 30-25 °C. The application of the presented novel model not only explains the outstandingly structured fluid of molten TAGs, but also lays the basis for analyzing first the crystallization steps in greater detail, which is outlined in our follow-up paper "Global Small-Angle X-ray Scattering Data Analysis of Triacylglycerols in the α-Phase (Part II)".

Whipped oil stabilised by surfactant crystals.

We describe a protocol for preparing very stable air-in-oil foams starting with a one-phase oil solution of a fatty acid (myristic acid) in high oleic sunflower oil at high temperature. Upon cooling below the solubility limit, a two-phase mixture consisting of fatty acid crystals (length around 50 µm) dispersed in an oil solution at its solubility is formed which, after whipping, coat air bubbles in the foam. Foams which do not drain, coalesce or coarsen may be produced either by increasing the fatty acid concentration at fixed temperature or aerating the mixtures at different temperatures at constant concentration. We prove that molecular fatty acid is not surface-active as no foam is possible in the one-phase region. Once the two-phase region is reached, fatty acid crystals are shown to be surface-active enabling foam formation, and excess crystals serve to gel the continuous oil phase enhancing foam stability. A combination of rheology, X-ray diffraction and pulsed nuclear magnetic resonance is used to characterise the crystals and oil gels formed before aeration. The crystal-stabilised foams are temperature-sensitive, being rendered completely unstable on heating around the melting temperature of the crystals. The findings are extended to a range of vegetable oil foams stabilised by a combination of adsorbed crystals and gelling of the oil phase, which destabilise at different temperatures depending on the composition and type of fatty acid chains in the triglyceride molecules.

Tracking Structural Changes in Lipid-based Multicomponent Food Materials due to Oil Migration by Microfocus Small-Angle X-ray Scattering.

One of the major problems in the confectionery industry is chocolate fat blooming, that is, the formation of white defects on the chocolate surface due to fat crystals. Nevertheless, the mechanism responsible for the formation of chocolate fat blooming is not fully understood yet. Chocolate blooming is often related to the migration of lipids to the surface followed by subsequent recrystallization. Here, the migration pathway of oil into a cocoa butter matrix with different dispersed particles was investigated by employing microfocus small-angle X-ray scattering and contact angle measurements. Our results showed that the chocolate powders get wet by the oil during the migration process and that the oil is migrating into the pores within seconds. Subsequently, cocoa butter is dissolved by the oil, and thus, its characteristic crystalline structure is lost. The chemical process provoked by the dissolution is also reflected by microscopical changes of the surface morphology of chocolate model samples after several hours from the addition of oil to the sample. Finally, the surface morphology was investigated before and after oil droplet exposure and compared to that of water exposure, whereby water seems to physically migrate through the particles, namely cocoa powder, sucrose, and milk powder, which dissolve in the presence of water.

Cocoa particles for food emulsion stabilisation.

Emulsifying properties of cocoa particles have been investigated in systems containing purified sunflower oil (PSO) and water at varying pH, concentration and source of cocoa particles including cocoa powders (CP), cocoa fibre (CF) and cocoa mass (CM). The effect of cocoa particle source, pH and cocoa particle concentration on emulsion stability was evaluated by following changes in characteristic droplet diameter. Size distributions acquired on the emulsions and aqueous cocoa particle suspensions overlapped. Based on cryo-SEM imaging of the emulsions, isolation of cocoa particle fines and a process of washing the cocoa particles to remove any water soluble molecules, it was concluded that the cocoa particle fines not captured by the small angle laser diffraction method employed for sizing, act as Pickering particles. This research has demonstrated a universal nature of a natural food particle to stabilise oil-in-water emulsions not requiring particle modification or adjusting of the solution properties of the emulsion phases.