Material properties of cocoa butter emulsions: effect of dispersed phase droplet size and compression speed on mechanical response

Water-in-cocoa butter (CB) emulsions material properties were investigated using uniaxial compression test. Emulsions containing 20% (wt%) water and with a range of droplet size were manufactured to assess the role of defect size on emulsions mechanical properties. Although differences were not significant within the tested droplet size range, results showed a decreasing trend in the values of mechanical parameters at fracture with increasing structural defect size. The mechanical response of bulk CB and emulsions was also investigated at different compressive rates. Materials visco-elastic behaviour was confirmed by their strain-hardening behaviour at increasing test speed with bulk CB always displaying the highest mechanical strength. In the light of these results and microscopy evidences, it was hypothesised that droplets are only partially bonded to the CB network therefore playing a stress-concentration role by promoting fracture initiation. The addition of water droplets also resulted in a reduction of the overall network internal degree of connectivity: when large deformations are applied, droplet-matrix de-bonding occurs at the particle-fat network interface promoting fracture propagation and thus explaining the weakening structural effect of droplets

Preparation and characterisation of whey protein fluid gels:the effects of shear and thermal history

AbstractWith the potential use of fluid gels in structuring fluids, whey protein isolate (WPI) was used as a prerequisite to prepare fluid gels: owing to its high nutritional value and thermal stability on gelling. Fluid gels were prepared via heat-induced gelation of a 10 wt% protein solution under controlled temperature and shear. Physical properties of the resulting gel particles (e.g. size and particle–particle interactions) were found to be dependent on the combination of shear and thermal history. Discrete large aggregates (>120 μm) were obtained at low shear, with aggregate size decreasing (<40 μm) at higher shear. Such microstructural changes in the particles led to the control of the suspension rheology. All suspensions showed a marked shear thinning behaviour associated with particle break-up which was observed to be more apparent for larger aggregates, originally made at low shear. The viscoelastic properties of the particulate systems, once in intimate contact (e.g. high volume fraction) resembled a pseudo solid material. In addition, it was shown that at a given volume fraction, the elasticity of the suspension varied dependant on their original processing conditions, owing to the degree of particle–particle interactions. A qualitative model has therefore been presented for the formation of particles by which the rheology is determined

Fabrication of sub-micron protein-chitosan electrostatic complexes for encapsulation and pH-Modulated delivery of model hydrophilic active compounds

AbstractElectrostatic sub-micron complexes of a protein (sodium caseinate (NaCAS) or bovine serum albumin (BSA)) and a polysaccharide (chitosan) were fabricated by associative phase separation and investigated for use in encapsulation and pH-triggered delivery applications. Various factors have been studied with respect to the extent of complexing and the size and morphology of the complexes produced, including protein type and the biopolymer mixing ratio. The effect of applying ultrasound has been considered with a view to comminuting precipitates produced under low shear to the colloidal scale to form coacervates. A simple model is suggested to explain how the biopolymer mixing ratio influences the ability for application of ultrasound to convert macroscopically phase-separated complex precipitates into coacervates. Different factors, both from a formulation and processing viewpoint, were studied with respect to encapsulation efficiency (EE) of model hydrophilic actives: fluorescein, rhodamine B, and riboflavin. Release of fluorescein and rhodamine B was measured as function of pH in order to investigate the pH-responsive molecular release capability of the fabricated structures. It is envisaged this work will add to the current tool-box of pH-responsive molecular delivery approaches, including those in the areas of foods, pharmaceuticals, and agrochemicals

Processing effects during rotating membrane emulsification

AbstractIn this study, a rotating membrane emulsification setup incorporating a 6.1μm pore diameter SPG membrane was used to produce O/W emulsions of average droplet sizes between 23.4 and 216.6μm. All emulsions consisted of 10vol% of sunflower oil or silicone oil stabilised by 1wt% Tween 20. The transmembrane pressure (0.1–1.8bar), rotational speeds (100–2000RPM) annular gap width (5–45mm), dispersed and continuous phase viscosity were all investigated as to their effect on emulsion droplet size and dispersed phase flux. Modification of the dispersed phase flow properties alters the droplet size with four regions being suggested; a decrease in size (as droplet coalescence is minimised), a plateau (size-stable zone), a gradual increase in size (due to transfer of mass via droplet neck) and then a rapid increase (due to jetting). The importance of Taylor vortices development was seen with larger droplets formed in their absence; typically at low rotational speeds, narrow vessel diameters and more viscous continuous phases. It was concluded that the flow behaviour of each phase requires careful consideration to understand the likely formation mechanism(s) during operation. Across the pressure and viscosity ranges investigated, the dispersed phase flux ranged between 50 and 12,500Lm−2h−1 and pore activity was within the range of 0.5–2.7%

The neuronal encoding of oral fat by the coefficient of sliding friction in the cerebral cortex and amygdala

Fat in the diet contributes to the pleasant mouthfeel of many foods, but overconsumption may contribute to obesity. Here we analyze what properties of fat in the mouth are sensed, by analyzing the responses of neurons in the macaque insular taste cortex, and two areas to which it projects the orbitofrontal cortex where the pleasantness of fat is represented, and the amygdala. We discovered that the firing rate responses of these fat-responsive neurons are correlated with the coefficient of sliding friction (CSF) and not with viscosity which reflects food thickness. Other, not fat-sensitive, neurons encoded viscosity and not the CSF. Neuronal population analyses confirmed that fat-responsive neurons conveyed information about the CSF but not about viscosity. Conversely the viscosity-sensitive neuronal population conveyed information about viscosity but not about the CSF. This new understanding of the representation of oral fat in the cerebral cortex and amygdala opens the way for the systematic development of foods with the pleasant mouthfeel of fat, together with ideal nutritional content and has great potential to contribute to healthy eating and a healthy body weight

Exploring the impact of pedagogic approaches in technology practice upon the construction of feminine identity

Females participate to a limited extent in science, engineering and technology (SET) industries that are central to innovation and building national economies. The causes of this under representation, in part, have their roots embedded in how females perceive school mathematics, science and technology subjects as being inconsistent with their gender identity. A participatory action research methodology was used to investigate the effect of two different pedagogical approaches for teaching middle school mathematics and science through technology practice on female students’ attitudes to SET. Quantitative and qualitative data related to enjoyment, intention to undertake further such study, perceived usefulness and interest in career options involving SET, and perceptions of the investigative nature of the two approaches, were sought using, interviews, classroom observations, and a modified survey instrument. The findings indicated that female students responded in a more positive manner when careful scaffolding and the establishment of explicit linkages between the construction activity and mathematics principles were part of the pedagogical approach. In addition, there were specific types of projects that females found authentic. The implications of these findings for SET syllabus authors, pre- and inservice teacher educators, and classroom teachers are explored