Using the Scanning Fluid Dynamic Gauging Device to Understand the Cleaning of Baked Lard Soiling Layers

Abstract

Extended or repeated heating of food fats promotes polymerisation reactions that produce difficult-to-remove soil layers. Cleaning of these baked-on/burnt-on fat deposits was investigated using model layers generated by baking lard on 316 stainless steel discs. Rigorous characterisation of the layer material was difficult, as it was insoluble in most solvents. Cleaning was studied using the scanning fluid dynamic gauging technique developed by Gordon et al. (Meas Sci Technol 21:85–103, 2010), which provides non-contact in situ measurement of layer thickness at several sites on a sample in real time. Tests at 50 C with alkali (sodium hydroxide, pH 10.4–11) and three surfactant solutions indicated two removal mechanisms, related to the (1) roll-up and (2) dispersion mechanisms reported for oily oils, namely (1) penetration of solvent at the soil–liquid interface, resulting in detachment of the soil layer as a coherent film, observed with linear alkylbenzene sulfonic acid (LAS) and Triton X-100 and aqueous sodium hydroxide at pH 10.4–11; and (2) the breakdown promoted by the agent penetrating through the layer, observed with cetyl trimethyl ammonium bromide (CTAB), in which CTAB antagonised the cleaning action of LAS.

Quantifying the effect of solution formulation on the removal of soft solid food deposits from stainless steel substrates

“…The cleaning mechanism and behaviour is ultimately determined by the nature and microstructure of the soil. For example, Ali et al (2015a) studied the cleaning of polymerised lard soil layers on stainless steel and reported that solutions of TX-100 and LAS at pH 10.4-11 promoted solution ingress and soil detachment at the soil-substrate interface, while CTAB promoted penetration through the soil layer (rather than promoting ingress as observed in this work). These differences illustrate how, like coatings to prevent deposition and fouling, detergent solutions need to be matched to the soil.…”

“…Whereas denatured whey proteins were reported to swell and erode in alkali, gelatin and egg proteins both swelled but both require shear forces to effect removal (Gordon et al, 2010;Perez-Mohedano et al, 2016). Ali et al (2015a) observed little swelling with burnt oil soils in aqueous cleaning solutions and removal of these was characterised by a 'cohesive blistering' mechanism.…”

“…The active agent must therefore be soluble (or encapsulated) in water, preferentially adsorb on to the soil surface, remove the soil from the substrate, and stabilise removed residues in the solution. Highly polymerised lipids such as those found in burnt oil soils have limited solubility in organic solutions and no recorded solubility in water (Ali et al, 2015a).…”

“…High pH or long soaking times are often required, in combination with mechanical shear, to remove such soils from the substrate (Dunstan and Fletcher, 2014). Surfactants can promote detachment of mobile components at the soil-substrate interface (Ali et al, 2015a(Ali et al, , 2015b. A combination of saponification, mechanical cleaning and surfactant action will be required to clean burnt oil soils as the existing literature does not report a single mechanism being entirely effective.…”

Analysis of Cleaning Process for Several Kinds of Soil by Probability Density Functional Method

“…In order to analyze the mechanism of oily soil removal during washing, many studies have been conducted by applying various methods such as molecular dynamics simulations 22 , combined molecular dynamics and quantum mechanics 23 , lattice Monte Carlo simulations 24 , confocal laser scanning microscopy 25 , a scanning fluid dynamic gauging device 26 , and the quartz crystal microbalance technique 27 .…”