Phospholipids in chocolate: Structural insights and mechanistic explanations of rheological behavior by coarse-grained molecular dynamics simulations

Isotropic liquid state of cocoa butter

The complex crystal structure of coca butter (CB) is responsible for the unique melting behavior, surface gloss, and mechanical properties of chocolate. While most studies concentrated on the crystalline state of CB, few studied the isotropic liquid state, which has a major impact on the crystallization process and the characteristics of the resulting crystals. In this study, the molecular organizations of the main CB triacylglycerols (TAGs; 1,3-dipalmitoyl-2-oleoylglycerol, palmitoyl-oleoyl-stearoylglycerol, POS, and 1,3-distearoyl-2-oleoylglycerol) were studied. The findings revealed the tunning-fork (Tf) conformation, commonly found in the crystalline state, is the least abundant in the isotropic liquid state of CB and pure TAGs. Notably, POS was found to interact with itself in CB, while its molecules with Tf conformation, although in small amounts in the mixture, tend to pair with each other at lower temperatures. These results highlight the significance of POS in CB crystallization and provide insights for developing CB alternatives.

Sugar-sugar interactions in oil suspensions containing surfactants and effects on macroscopic phenomena

Surfactants are used in confectionery production to control the viscosity and yield value of molten chocolate. To develop a deeper understanding of the structure-function relationship of surfactants in food-related particle suspensions, the apparent viscosity, yield value, sedimentation, and particle interactions of 10 wt% confectioner's sugar-in-canola oil suspensions were investigated in the presence of up to 1 wt% commercial soy lecithin, polyglycerol polyricinoleate (PGPR), citric acid esters of monoacylglycerols (CITREM) or ammonium phosphatides (AMP). Atomic force microscopy (AFM) was used to measure attractive forces at the nano-Newton scale between a sugar substrate and a sugar crystal-functionalized AFM cantilever in an oil environment. For all but PGPR, addition of surfactant reduced the adhesion force between sugar surfaces up to a critical concentration above which the force increased, implying the presence of additional interactions. This critical concentration was assumed to be when monolayer coverage of the sugar surfaces by surfactant occurred (0.05 wt% for lecithin, 0.10 wt% for CITREM and AMP). No critical concentration was found for PGPR, with its greatest effect for each analysis occurring at the highest concentrations tested (0.60 and 1.00 wt%). The significance of these interactions on macroscopic phenomena such as apparent viscosity and sedimentation was also assessed. Like with the AFM data, there was an optimal concentration of added surfactant above which viscosity increased. Sedimentation rate greatly decreased with addition of PGPR while being only slightly affected by addition of lecithin, CITREM and AMP. An argument regarding their efficacy was made based on the relative sizes of the polar headgroup and nonpolar tail groups of the molecules, which contributed to how they adsorbed to the sugar surface. Overall, these results suggested that surfactant properties such as molecular weight and head group properties played an important role in modifying the interactions between sugar crystals in an oil-continuous environment.

Assessment of bioaccessible and dialyzable fractions of nickel in food products and their impact on the chronic exposure of Belgian population to nickel

This study aimed to investigate bioaccessible/dialyzable fractions of nickel in selected foods and to clarify the impact of the food digestion/absorption on the final exposure of consumers to nickel. In vitro gastrointestinal incubation experiments were conducted to estimate the bioaccessibility of nickel in different foods. For estimation of a dialyzable fraction, dialysis filtration was conducted. Highest bioaccessibility (99.6%) was observed for wheat-based breakfast cereals. Lowest bioaccessibilities was observed for dried-fruits (on average 20.4%). Highest (61.5%) and lowest (24.5%) dialyzable fractions were observed for wheat-based breakfast cereal and chocolate respectively. Bioaccessible/dialyzable fractions based exposure assessments were highlighted the overestimation of exposures calculated based on total nickel concentrations in foods. This is particularly important when exposure values were compared with toxicological thresholds in a risk characterization study. When threshold values have been obtained through animal studies in which nickel was dosed at 100% accessibility/availability, e.g. nickel salts this is even more important.