6 research outputs found
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Methods for detailed study of detergent action in cleaning food soils
Dishwasher detergent formulations contain components which dictate the chemical environment (pH, wettability, solubility) of cleaning solutions. The role of these factors, as well as temperature, in the
mechanisms controlling the cleaning of a baked heterogeneous food soil from stainless steel substrates was studied using a combination of fluid dynamic gauging, real-time imaging, millimanipulation, and solution analysis techniques.
The extent of swelling, which is known to affect cleaning, was determined in situ using a fluid dynamic gauging (FDG) device developed by Wang et al. (2017). A new FDG configuration was developed which enabled measurement of swelling soon after immersion, allowing measurement of initial hydration. These studies were corroborated using a commercial point-light source confocal thickness measurement device. The onset and extent of swelling depended primarily on the solution pH.
At temperatures above 35 á”C swelling was followed by the liberation of mobile fat present within the soil. Monitoring of droplet evolution allowed the growth and detachment of the oil droplets to be quantified and modelled. The rate of total carbonaceous material released from the soil was studied in separate tests using both stagnant and flowing solutions. The onset and volume of oil released was chiefly determined by the solution temperature and concentration of surfactant. Oil release was not directly related to deposit strength.
In millimanipulation the force imposed on a blade being passed through the soil layer is measured. The device was modified to allow submersion and flow of cleaning solution across the sample so that the effect of contact time with the reagent(s) could be studied. The force required to remove the soil changed noticeably after a critical soaking time, from an almost constant value to one which decayed with time. The critical soaking time depended on the temperature, pH, and composition of the
cleaning solution and in many cases was associated with a transition from cohesive to adhesive breakdown. This transition occurred on similar timescales to the swelling of the soil. Some agents promoted faster adhesive breakdown.
Sinnerâs circle is classically used to describe the intentions between temperature, formulation, time and mechanical forces in cleaning. The different techniques allowed these to be quantified, particularly in terms of timescales. The cleaning mechanism was broken into two parallel processes: (I) the hydration and swelling of the soil layer after exposure to aqueous solutions followed by the dewetting and displacement of oils and fats from within the soil structure towards the soil-solution interface, and (II) the ingress of solution at the soil-substrate interface, weakening the adhesive forces attaching the soil to the substrate. Temperature, pH, and surfactant type were demonstrated to act each process to a different extent, influencing the timescales of cleaning.EPSRC iCASE studentship in partnership with P&G
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Quantifying the effect of solution formulation on the removal of soft solid food deposits from stainless steel substrates
The role of detergent formulation on the cleaning of a complex carbohydrate-fat food soil from stainless steel surfaces was studied using a modified version of the millimanipulation device described by Ali et al. (2015b) which allowed the force required to scrape the soil from the surface to be measured as the soil is immersed, in situ and in real time. This allowed the influence of temperature, solution chemistry and time on the mechanical forces (rheology) and removal behaviour of the soil to be studied â in effect quantifying the relationships in Sinnerâs cleaning circle. The soil simulated a burnt-on baked-on deposit and featured regular cracking in the 300 ÎŒm thick layer. The removal force decreased noticeably on hydration: the cleaning mechanism was then determined by the agents present. At 20ÂșC, below the temperature at which the fat phase was mobile, removal was characterised by cohesive failure except in the presence of the cationic surfactant CTAB, which promoted adhesive failure and fast decay in removal force. At 50ÂșC, when the fat was mobile, a transition between cohesive and adhesive failure was observed at pH 7 which was inhibited at higher pH. Adhesive failure and fast decay in removal force was observed at higher pH and 50ÂșC in the presence of the anionic and non-ionic surfactants, SDBS and TX-100, respectively.EPSRC iCASE Studentship
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Pendant drops shed from a liquid lens formed by liquid draining down the inner wall of a wide vertical tube
When a viscous liquid empties from an initially full, wide vertical tube, the drainage behaviour changes from a filament to a regime in which individual drops are shed by a lens formed at the end of the tube: liquid drains down the wall and the lens grows until it becomes unstable. This drop shedding regime was investigated for four Newtonian liquids (rapeseed oil, glycerol, honey and golden syrup) in three tube sizes and two tube materials (Bond number based on tube i.d. > 1 in all cases). The drop mass increased modestly with flow rate and the equivalent sphere diameter, d, was strongly related to the capillary length Lc ⥠(Îł/Ïg)1/2 rather than the tube diameter. The results were fitted to a correlation of the form d/Lc = f(Bond, Reynolds, Morton, sin(contact angle)) derived from dimensional analysis. The data were compared with existing models for drop formation from filled narrow capillaries and a new, simple model based on a quasi-static model of the lens. Agreement with these models was poor, particularly for larger tubes, indicating the need for more detailed analysis. Insights into the dynamics, generated by video analysis of the lens shape, are presented
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Research data supporting 'Fluid-Dynamic Gauging for Studying the Initial Swelling of Soft Solid Layers'
This data set contains experimental data, supplementary material and a Methods description associated with the paper of the same title published in AIChEJ. The data set shows experimental results associated with the calibration and testing of the new SiDG device. The Supplementary Material includes additional experimental material, codes in python and OpenFOAM to allow readers to create similar results, and working diagrams of the experimental apparatus so that the reader can make an SiDG device
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Research data supporting "Quantifying the effect of solution formulation on the removal of soft solid food deposits from stainless steel substrates"
The record contains the numerical data presented in the Figures in the above paper
Four priorities for new links between conservation science and accounting research.
Article impact statement: New collaborations with accounting research can improve conservation impact of ecosystem-based information systems