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 ^circ 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.
Highlights
The problem of cleaning difficult-to-remove food soils is ubiquitous in the food industry
Tests at 50 C with alkali 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
Separate tests found that unbaked lard was soluble in chloroform, toluene, benzene and tetrahydrofuran
Summary
The problem of cleaning difficult-to-remove food soils is ubiquitous in the food industry. Fats and oils undergo a series of polymerisation reactions that can leave undesirable, unwanted deposits on food processing surfaces such as baking trays and frying pans. This accumulation of material generated by thermal processing is called fouling, and the deposits formed are known as ‘soils’. Fouling is defined as the unwanted accumulation of material on and/or into process surfaces. Any deposit that needs to be cleaned is initially generated by a fouling step. Understanding how a deposit forms can yield insight into how best to remove it and how to prevent its formation
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