Elucidating enzyme-based cleaning of protein soils (gelatine and egg yolk) using a scanning fluid dynamic gauge

Improving Cleaning Efficiency through the Measurement of Food Fouling Adhesive Strength

This study aims to investigate the impacts of factors, including textural properties, surface roughness, and contact angle, on the cleaning performance of food soils and develop a preliminary mathematical model to predict the cleaning score, depending on the soil-surface properties. The force required to remove soil from the surface was determined by a texture analyzer equipped with a newly designed probe. Potato puree and egg yolk soils showed high adhesive forces compared to other deposits. Margarine required the lowest force to detach from the surfaces. A soil-surface characteristic number (SSCN) was constructed from the results of contact angle, roughness, and textural analysis to predict the cleaning score depending on the soil-surface properties. The experimental work presented indicates that a higher SSCN was associated with lower cleaning scores for soil-surface combinations. Furthermore, a predictive model was developed to define the relationship between cleaning scores and SSCN. The applicability of the model was validated by measuring the cleaning performance of caramel and pudding soils on glass, porcelain, and stainless-steel household surfaces by using an automatic method. Therefore, it can be concluded that the SSCN approach can be improved in further studies to predict cleaning scores of soil-surface combinations in the experimental rig or automatic dishwasher.

Assessing the Impact of Germination and Sporulation Conditions on the Adhesion of Bacillus Spores to Glass and Stainless Steel by Fluid Dynamic Gauging

The adhesion of spores of 3 Bacillus species with distinctive morphologies to stainless steel and borosilicate glass was studied using the fluid dynamic gauging technique. Marked differences were observed between different species of spores, and also between spores of the same species prepared under different sporulation conditions. Spores of the food-borne pathogen B. cereus were demonstrated to be capable of withstanding shear stresses greater than 1500 Pa when adhered to stainless steel, in contrast to spores of Bacillus subtilis and Bacillus megaterium, which detached in response to lower shear stress. An extended DLVO model was shown to be capable of predicting the relative differences in spore adhesion between spores of different species and different culture conditions, but did not predict absolute values of force of adhesion well. Applying the model to germinating spores showed a significant reduction in adhesion force shortly after triggering germination, indicating a potential strategy to achieve enhanced removal of spores from surfaces in response to shear stress, such as during cleaning-in-place procedures.

PRACTICAL APPLICATION

Spore-forming bacteria are a concern to the food industry because they have the potential to cause food-borne illness and product spoilage, while being strongly adhesive to processing surfaces and resistant to cleaning-in-place procedures. This work is of significance to the food processors and manufacturers because it offers insight to the properties of spore adhesion and identifies a potential strategy to facilitate the removal of spores during cleaning procedures.

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

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 [Formula: see text]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.

Characterising the structure of photosynthetic biofilms using fluid dynamic gauging

A new configuration of the fluid dynamic gauging technique for measuring soft layers on surfaces was used to monitor the growth of a cyanobacterium, Synechococcus sp. WH 5701, on stainless steel (SS), glass and an indium tin oxide (ITO) on a polyethylene terephthalate (PET) substratum. The biofilm thickness increased steadily over 4 weeks and exhibited noticeable changes in microstructure and strength. The biofilms all exhibited a two-layer structure, with a compact layer next to the substratum and a loose layer above. Biofilms on ITO or SS exhibited cohesive failure when removed by fluid shear whereas those on glass exhibited adhesive failure. The technique is able to elucidate various aspects of biofilm behaviour, as illustrated by the action of a biocide (NaOCl) on a mature biofilm.