S. Bakalis

Mass Transfer and Nutrient Absorption in a Simulated Model of Small Intestine

There is an increasing need to understand how food formulations behave in vivo from both food and pharma industries. A number of models have been proposed for the stomach, but few are available for the other parts of the gastrointestinal tract. An experimental rig that simulates the segmentation motion occurring in the small intestine has been developed. The objective of developing such an experimental apparatus was to study mass transport phenomena occurring in the lumen and their potential effect on the concentration of species available for absorption. When segmentation motion was applied the mass transfer coefficient in the lumen side was increased up to a factor of 7. The viscosity of the lumen, as influenced by guar gum concentration, had a profound effect on the mass transfer coefficient. The experimental model was also used to demonstrate that glucose available for absorption, resulting from starch hydrolysis, can be significantly reduced by altering the lumen viscosity. Results suggest that absorption of nutrients could be controlled by mass transfer. Practical Application: To address health-related diseases such as obesity, novel foods that provide advanced functions are required. To achieve the full potential offered by the latest developments in the field of food material science, a fundamental understanding of the behavior of food structures in vivo is required. Using the developed gut model we have demonstrated that absorption of nutrients can be controlled by mass transfer limitations.

Using discrete multi-physics for detailed exploration of hydrodynamics in an in vitro colon system

We developed a mathematical model that describes the motion of viscous fluids in the partially-filled colon caused by the periodic contractions of flexible walls (peristalsis). In-vitro data are used to validate the model. The model is then used to identify two fundamental mechanisms of mass transport: the surfing mode and the pouring mode. The first mechanism is faster, but only involves the surface of the liquid. The second mechanism causes deeper mixing, and appears to be the main transport mechanism. Based on the gained understanding, we propose a series of measures that can improve the reliability of in-vitro models. The tracer in PET-like experiments, in particular, should not be injected in the first pocket, and its viscosity should be as close as possible to that of the fluid. If these conditions are not met, the dynamics of the tracer and the fluid diverge, compromising the accuracy of the in-vitro data.

Evaluation of dry heat treatment of soft wheat flour for the production of high ratio cakes

An accurate method to heat treat flour samples has been used to quantify the effects of heat treatment on flour functionality. A variety of analytical methods has been used such as oscillatory rheology, rheomixer, solvent retention capacity tests, and Rapid Visco Analysis (RVA) in water and in aqueous solutions of sucrose, lactic acid, and sodium carbonate. This work supports the hypothesis that heat treatment facilitates the swelling of starch granules at elevated temperature. Results furthermore indicated improved swelling ability and increased interactions of flour polymers (in particular arabinoxylans) of heat treated flour at ambient conditions. The significant denaturation of the proteins was indicated by a lack of gluten network formation after severe heat treatments as shown by rheomixer traces. Results of these analyses were used to develop a possible cake flour specification. A method was developed using response surfaces of heat treated flour samples in the RVA using i) water and ii) 50% sucrose solution. This can uniquely characterise the heat treatment a flour sample has received and to establish a cake flour specification. This approach might be useful for the characterisation of processed samples, rather than by baking cakes. Hence, it may no longer be needed to bake a cake after flour heat treatment to assess the suitability of the flour for high ratio cake production, but 2 types of RVA tests suffice.

Modelling, Simulation and Economical Evaluation of Dry Food Manufacture at Different Production Scales.

Abstract In this work, a modelling platform by which different manufacturing scenarios can be assessed both in terms of their financial performance and energy demand is presented. The production of a dried food product (cereal baby porridge) has been chosen as case study and four production scales were assessed: (i) Homemade, (ii) Food Incubator (FI), (iii) Distributed Net (DN) and (iv) Plant & Multi-plant Production, with throughput values ranging from 0.5 kg/h to 6500 kg/h. The proposed tool has been also applied to the UK dry baby food demand scale. Results show that DN represents the most convenient scale up to 275 kg/h of production rate, achieving similar profitability than centralised scenarios but providing more flexibility to product demand shifts.

Coating of sodium percarbonate particles using water soluble materials in a fluidised bed to achieve delayed release in aqueous environment

Abstract Three coating materials, namely sodium sulphate, 1.6R and 2.35R sodium silicate, were respectively used to coat sodium percarbonate (SPC) particles in a fluidised bed coater to achieve its delayed release in aqueous environment. The size of SPC particles was measured using image analysis. The thickness and porosity of the shell materials were analysed using scanning electron microscopy (SEM) and helium pycnometry respectively. The rates of SPC release from uncoated and the coated particles were measured using an iodide molybdate titration method coupled with UV-vis spectrometry. The results indicate that sodium sulphate coating with an average thickness of 53 ± 9 μm only reduced the release rate of SPC as no delayed release was observed. In contrast, sodium silicate coating generated a significant delayed release. 1.6R sodium silicate coating with a thickness of 109 ± 8 μm delayed the release of SPC by approximate 60 s under a static condition. At the same condition, 2.35R sodium silicate coating with a thickness of 71 ± 10 μm delayed the release by approximately 7 min. When the coated SPC particles immersed in water were shaken using an orbital shaker at 150 rpm, the delayed time was reduced by 50% in comparison with the static condition. The 1.6R sodium silicate shell in solid phase transformed to gel-like structure during dissolution and the hydrodynamic forces generated in the shaker accelerated its dissolution. However, there was no significant change of 2.35R sodium silicate shell when the capsules were immersed in water under the static condition, and they broke into pieces in the shaker. For both 1.6R and 2.35R sodium silicate, the further increase in shell thickness increased their shell porosity, which facilitated the water penetration and thus resulted in no significant benefit to additional delay. Moreover, the thermal stability of SPC after coating was slightly improved and the flowability did not change significantly. This study demonstrates that a significant delay in release of SPC can be achieved using 2.35R sodium silicate as a coating material.

Heat Transfer to Foods: Safety and Structure

Heat transfer in foods is a commonplace operation in the home and restaurant, but is also the basis for a very large industry. Foods are complex non-Newtonian soft solids or structured liquids whose thermal behaviour is difficult to model; but engineering understanding is needed to develop processes that are safe and products that are attractive to the consumer. The increasing incidence of obesity in the developed world, and of food shortage elsewhere, demands that the industry adopts processes that give nutritious products in environmentally acceptable ways. This paper reviews the heat transfer problems that are found in food processing, with particular reference to the modelling of heating operations to ensure safety, problems that are found in the fouling and cleaning and process plant, and how heating and cooling are used to generate structure. Research challenges for the future are outlined.Copyright

Evaluating The Applicability Of Time Temperature Integrators As Process Exploration And Validation Tools

AbstractKnowledge of the impact of thermal processing in the food industry is crucial in order to deliver high quality safe foods to the consumer. Time Temperature Integrators (TTIs) have been developed as quality control and process exploration tools for processes where use of other thermal sensors is impossible. TTIs are encapsulated enzymatic suspensions with well characterized thermal inactivation kinetics, whose activity can be measured easily before and after processing. From the reduction of the TTI activity it is possible to estimate the inactivation of pathogens and spoilage organisms, as well as nutrients in the product. Although TTIs are currently used in many industries a thorough review of their applicability to evaluate thermal processes has not yet been published. Here, experimental validation of an α-amylase TTI is shown with the intention of accurately characterising the variability of the technique. In an attempt to describe the thermal variability of real food processes the heat and mass transport in typical food processes where TTIs might be used were simulated using CFD. Monte Carlo simulations to study the effect of (i) process variability and (ii) the measurement variability inherent within TTI response. Results indicate that TTIs can be used both to validate thermal processes; and as a process exploration tool. In the latter form, they can be used to derive information about variation, although a larger number of TTIs would be required.