Developing and testing a new quantitative near infrared spectroscopy online tracking measuring system for soil detection during automatic dishwashing

Near infrared (NIR) measurements have been used for several years to examine the processes taking place in the dishwasher during dishwashing. It is possible to differentiate between the soil components butterfat, oatmeal and egg-yolk and to determine their concentration in the dishwashing liquor quantitatively. Consequently, time-consuming dishwashing tests can be avoided by weighing the dishes. However, this method is also based on a small number of NIR measurements which are carried out intrusively during the dishwashing process, i.e. outside the dishwasher. These few NIR measurements make it difficult to investigate the dynamics of a dishwashing process. In this study, the development, testing and usage of a new online tracking measuring system is presented. The latter was used to perform 38 dishwashing processes, each containing 51 NIR spectra, to develop a calibration model using the partial least squares regression method with cross-validation. This new online tracking measuring system, based on the calibration, can determine the concentrations of three different soil components in the dishwashing liquor during automatic dishwashing. By recording the 51 spectra, it is possible to display a tracking curve for each soil component, i.e. the concentration courses of the dishwashing process over time. This results in a significantly better time resolution and it was possible to investigate the first dynamic part of the tracking curve, i.e. the beginning of the dishwashing process. This could lead to the opportunity to change the state of the dishwasher depending on the concentrations detected in the first step and, secondly, to a more environmentally friendly and cost-reducing dishwashing process.

Features reported after exposure to automatic dishwashing rinse aids

Introduction: Automatic dishwashing rinse aids are drying aids which contain non-ionic surfactants, usually ethoxylated alcohols, typically at concentrations of ≤30%. Objective: To assess the reported toxicity of rinse aids. Methods: Telephone enquiries to the UK National Poisons Information Service were analysed from January 2008 to June 2019. Results: Ingestion: Ingestion was involved in 976 cases and produced gastrointestinal features, coughing and central nervous system depression, particularly in young children. In those in whom the amount ingested was known, the majority (56%) of children <18 years and of adults (57%) ingested <50 mL of rinse aid. Although moderate or severe exposures (Poisoning Severity Score (PSS) ≥ 2) were uncommon, they occurred significantly ( p < 0.0008) more often in adults (9.0%) than in children (1.8%); however, three of the four adults with PSS ≥ 2 co-ingested other substances. Eye exposure: Ocular exposure was reported in 35 cases, of whom 29 developed features. Eye irritation ( n = 10, 28.6%) and eye pain ( n = 10, 28.6%) were reported most commonly, and three patients (8.6%) developed corneal abrasions (PSS 2). Dermal exposure: Thirty-four patients were exposed dermally, and six (17.6%) reported features, including rash, numbness, pruritus and burns (PSS 1). Conclusions: Overall, clinical features developed in 47% of patients exposed to rinse aids, but more severe features (PSS ≥ 2) were rare (<3%) following exposure by any route.

Toxicity of traditional and soluble film automatic dishwashing tablets

Introduction: Detergents used in automatic dishwashing machines are of two main types: traditional tablets that require removal from an external wrapper and newer soluble film tablets. Objective: To determine the toxicity of automatic dishwashing tablets. Methods: Telephone enquiries to the UK National Poisons Information Service were analysed for the period January 2008 to June 2019. Results: Ingestion: Ingestion was involved in 798 traditional tablet exposures and 725 soluble film exposures. Clinical features (Poisoning Severity Score ≥ 1) developed in 22.2% of patients ingesting traditional tablets and in 28.8% ingesting soluble film tablets; moderate or severe toxicity was rare (<0.5% for both traditional and soluble film tablets). Children (≤5 years) significantly ( p < 0.0001) more often developed features following ingestion of soluble film ( n = 193, 28.2%) than traditional tablets ( n = 134, 19.1%). In contrast, adults more often developed features following ingestion of traditional than soluble film tablets, although this difference was not statistically significant. Eye exposure: The eye was involved in only 26 of 1539 exposures; 17 of 26 exposures resulted in ocular features. The most commonly reported features were conjunctivitis, eye pain and blurred vision, although one patient sustained a corneal abrasion and developed loss of vision. Skin exposure: Thirty-four of 1539 exposures involved the skin but only 3 developed dermal features which were minor. Conclusions: Children (≤5 years) significantly more often developed features following ingestion of soluble film than traditional tablets, although the likelihood of a child developing features was relatively low (<30%) and features that did develop were almost always mild. In contrast, adults more often developed features following the ingestion of traditional than soluble film tablets. Overall, the eye was involved in only 1.7% of exposures and only one patient sustained a corneal abrasion.

Applicability of near infrared spectroscopy for real-time soil detection during automatic dishwashing

The purpose of this study was to utilize NIR spectrometry to develop a novel method to detect and determine concentrations of different soils in dishwashing liquor during automatic dishwashing in real-time. If it is possible to differentiate between soils, this could be an opportunity to react specifically to them (e.g. by increasing the water temperature if fat components are not sufficiently emulsifying). The possibility of an automatic adaptation of the dishwashing process to different soils and soil levels could lead to a shorter, more environmentally friendly and cost-reducing process. In a first approach, an emulsion containing three soil types (oatmeal, egg-yolk and butterfat), water and detergent were used to develop NIR spectrometry prediction models. Transmittance spectra obtained with an Fourier transform near infrared (FT-NIR) spectrometer of testing standards of 76 automatic dishwashing cycles with seven samples per cycle were taken at various times during the main washing process for calibration (and validation) of the NIR spectrometry prediction models. The spectra were pretreated to develop NIR spectrometry prediction models for each type of soil using the partial least squares regression method with cross-validation. Overall, the coefficients of determination in cross-validation are R2 > 0.92 for all NIR spectrometry prediction models developed. The results of the prediction models developed show that NIR spectrometry technology is a promising method to predict different levels of predefined soils in dishwashing liquor. The NIR spectrometry models were applied to an automatic dishwashing process with soiled dishes instead of emulsions containing soils to test their applicability. The resulting dishwashing process could be tracked in real-time by the dissolved soil concentrations, observed in the dishwashing liquor.