Machine Dishwashing Research Articles

A guide to household manual and machine dishwashing through a life cycle perspective

This study evaluates and provides guidance on improving the life cycle environmental performance of dishwashing in the typical U.S. household. Typical user behaviors and recommended best practices for manual dishwashing as well as machine dishwasher use are evaluated. A sensitivity analysis shows the influence of varying grid carbon intensity, water heater type, regional water scarcity, and behaviors such as pre-rinsing and machine loading on overall results. Use-phase behaviors are observed through a small-scale laboratory study. Dishwashing following typical manual and machine practices produces 5,620 and 2,090 kg CO2e life cycle greenhouse gas (GHG) emissions respectively based on washing 4 loads (8 place settings per load) a week for 10 years. Avoiding typical behaviors like pre-rinsing and selecting heated dry can decrease life cycle GHG emissions for machine dishwashing by 3% and 11%, respectively. The running tap style of manual dishwashing results in the highest life cycle GHG emissions of the alternatives in the lab study. Manual dishwashing has the potential to have the lowest GHG emmisions (1,610 kg) when recommended behaviors are followed, less than the 1,960 kg CO2e for recommended machine dishwasher use. When life cycle water consumption burdens are evaluated, typical manual and machine dishwashing use 34,200 and 16,300 gallons respectively and these results are contextualized to regions with different water scarcity. A life cycle cost (LCC) analysis finds that machine dishwashing costs more than manual dishwashing over a 10-year lifetime even if best practices are followed. However, when a user’s time spent washing is valued, machine dishwashers pay for themselves within a year of use.

Allergy in Children in Hand Versus Machine Dishwashing

To investigate whether dishwashing methods by variably altering microbial exposure could impact the risk of allergy development.Children (N = 1029) 7 to 8 years of age from Kiruna and Mölndal, 2 cities in Sweden.Questionnaire-based study, including questions on asthma, eczema, and rhinoconjunctivitis taken from the International Study of Asthma and Allergies in Childhood questionnaire.Hand dishwashing was associated with a reduced risk of allergic disease development (multivariate: odds ratio 0.57; 95% confidence interval: 0.37–0.85). This risk was further reduced in a dose-dependent manner if the children were also served fermented food and if the family bought food directly from farms.Allergic diseases are less common in children whose families use hand dishwashing versus machine dishwashing. This phenomenon may be due to increased microbial exposure with a less efficient dishwashing method leading to more induction of allergen tolerance.Over the past 20 years, the hygiene hypothesis has been proposed as 1 reason for the rising prevalence of allergic diseases in the later part of the 20th century. The hypothesis proposes that microbial exposure early in life stimulates the immune system in a manner that helps induce allergen tolerance. Several studies including those by von Mutius and others in farming communities lend credence to this hypothesis. The goal of this study was to also see whether simple variations in daily life exposure patterns (eg, due to varied dishwashing practices) might also play a role. The authors do point out that this was an observational study, and as such the observed trend is not necessarily causal; despite multivariate analysis, the outcome could also be due to associated lifestyle factors (eg, overcrowded housing, low socioeconomic status, immigration status) where hand dishwashing may simply be more common.

Allergy in children in hand versus machine dishwashing.

The hygiene hypothesis stipulates that microbial exposure during early life induces immunologic tolerance via immune stimulation, and hence reduces the risk of allergy development. Several common lifestyle factors and household practices, such as dishwashing methods, may increase microbial exposure. The aim of this study was to investigate if such lifestyle factors are associated with allergy prevalence. Questionnaire-based study of 1029 children aged 7 to 8 years from Kiruna, in the north of Sweden, and Mölndal, in the Gothenburg area on the southwest coast of Sweden. Questions on asthma, eczema, and rhinoconjunctivitis were taken from the International Study of Asthma and Allergies in Childhood questionnaire. Hand dishwashing was associated with a reduced risk of allergic disease development (multivariate analysis, odds ratio 0.57; 95% confidence interval: 0.37-0.85). The risk was further reduced in a dose-response pattern if the children were also served fermented food and if the family bought food directly from farms. In families who use hand dishwashing, allergic diseases in children are less common than in children from families who use machine dishwashing. We speculate that a less-efficient dishwashing method may induce tolerance via increased microbial exposure.

Allergy in Children in Hand Versus Machine Dishwashing

Allergy in Children in Hand Versus Machine Dishwashing

Attitudes and behaviour of consumers regarding dishwashing: The case of Patras, Greece

Washing the dishes, which comes at the expense of natural resources consumption, is one of the cornerstones of hygiene in modern households. Dishwashing can be performed either manually or by the use of dishwashers. Even though machine dishwashing has clear advantages over manual, the latter is still used by a great portion of the households.The aim of this study, the first if its kind originating from Greece, is to investigate, analyse and report the attitudes and behavioural patterns of Greek consumers regarding both manual- and machine-dishwashing; to account for the rate of penetration of dishwashers in the household; and draw the profile of the households that own a dishwasher. The research took place in Patras, the third largest city in Greece using a closed-type questionnaire.The rate of penetration of dishwashers in this study, 39%, is below the European average but close to the one reported for southern European countries. The profile of the dishwasher owner outlined by our research is close to the one reported in the literature. In addition, habits of dishwasher owners have been identified. Our analysis indicates convenience, and not the conservation of water and energy, is the main reason for owning a dishwasher in Greece. An encouraging result is that Greeks are well informed and dedicated consumers of the low tariff electricity when using the dishwasher. Finally, despite the presence of a dishwasher in a Greek household, manual dishwashing using hot water is far from obsolete. The environmental impacts of heating the water for dishwashing can be alleviated by engaging solar heaters, the penetration of which proved to be quite high in the present research. Education and training of the consumers on both the advantages as well as the proper use of dishwashers is identified as the major requirement towards the reduction of the environmental impacts associated to dishwashing.

The effect of dishwater parameters on the survival of Staphylococcus aureus and vegetative cells and spores of Bacillus cereus

AbstractIn this study, the effect of dishwater parameters on the survival of Staphylococcus aureus and vegetative cells and spores of Bacillus cereus was evaluated. Both types of bacteria have been found in dishwater and are presumed to be pathogenic; both have also been reported to cause outbreaks of foodborne illness. Experiments were conducted in a 2‐L beaker, and temperature, pH, type of detergent and broth concentrations were altered. The influence of nutrition, which normally exists in dishwater, has a substantial effect on the survival rate of S. aureus. The survival of S. aureus in dishwater solutions at 45°C and pH 7 is similar for two different types of detergents, hand dishwashing and machine dishwashing, after a longer time exposure (50 min). The effect of the temperatures on the survival of S. aureus and B. cerus was investigated for the range typical for professional dishwashers and hand dishwashing (45°−65°C). Only a slight reduction of S. aureus takes place at 45°C; however, at 55°C, no more than seven minutes is required to achieve a 3‐log10 reduction. Vegetative cells of B. cereus revealed a similar temperature dependence; however, for the spores of B. cereus, not even a temperature of 65°C is enough to reduce the bacterial counts. The influence of pH on the bacteria was also investigated. For S. aureus and vegetative cells of B. cereus, the pH influence is moderate and is only apparent after longer exposure times. For B. cereus spores, the results showed that they are not influenced by pH up to 10.6. This investigation points out that the most effective strategy for reducing bacterial counts in dishwashing solutions is to use high temperatures (>55°C) in the dishwater, which reduces the risk for cross‐contamination from dishwater to dishware.

Role of Hydration via Alkaline Wash Liquor in the Removal of Starchy Soil during Machine Dishwashing

A materials science approach is applied to understanding the removal of starchy soils from crockery in a dishwasher. Specifically, the action of hydration and the role of alkalinity in reducing the cohesion of a retrograded Cream-of-Wheat soil are studied using the rigidity modulus of the soil as a measure of cohesive strength. Cream-of-Wheat gels prepared undersaturated with water were exposed to simple wash liquors buffered in the alkaline pH range. The gain in water content by the gel was analyzed via a differential and an integral approach, both treating the process of swelling with wash liquor as a one-dimensional diffusion problem. A phenomenological diffusion coefficient describing the swelling process is determined as 3x10 -11 m 2 /s at pH 10 and 10 -10 m 2 /s at pH 12. The ingress of alkalinity into the soil was followed by having an acid/base color indicator uniformly distributed throughout the gel. Treating the progress of the color change into the soil as one-dimensional diffusion, diffusion coefficients were obtained for the ingress of alkalinity: 10 -9 m 2 /s at pH 10 and 3x10 -9 m 2 /s at pH 12. The decay in the soil layer cohesion with exposure to wash liquor occurs on a time scale too rapid to be related to the swelling process but in keeping with that of alkaline ingress. The penetrating hydroxyl ions deprotonate a portion of the hydroxyl groups which cross-link starch, making the soil more easily removed by mechanical forces in a dishwasher.

SD&C Technical phosphates as energy savers in machine dishwash performance

AbstractA savings of 20% in the energy consumption of machine dishwashers to meet government guidelines requires a significant reduction in the amount of water used or in the temperature of the wash. Performance testing has shown that a reduction in wash temperature from 140 F to 100 F results in a significant increase in the spotting and filming of glassware. This performance loss to conserve energy can be reduced by increasing the sodium tripolyphosphate (STP) content of the machine dishwash formulation. A reduction in the STP content of the formulation from the typical 40–45% level that would be required to comply with restrictive phosphate (8.7% P) legislation coupled with a decrease in wash temperature for energy conservation results in extremely poor washing performance.

Detergent‐hard water interactions in machine dishwashing

AbstractInsufficient detergent concentration has recently been recognized as a major contributor to film formation on glassware in machine dishwashing. The film is shown to consist largely of calcium tripolyphosphate, Ca5(P3O10)2; evidence is cited for the presence of a silicate, probably calcium metasilicate, as well. Systematic variation of detergent concentration and of water hardness allows construction of a response surface describing conditions of maximum and minimum rates of film formation. The extent of film formation is minimized when the ionic ratio of Ca or Mg or both to tripolyphosphate is 1:1 and maximized when the ratio is 5:2. These ratios correspond to the 1:1 chelate and the uncharged precipitate, Ca5(P3O10)2, respectively. The implications of this treatment to other detergency processes are also considered.

Chlorine‐stable machine dishwashing products

AbstractThe increasing use of active chlorinecontaining compounds in machine dishwashing has led to the need for chlorine‐stable, low foaming detergent formulations. To avoid oxidative degradation of nonionic surfactant and simultaneous loss of available chlorine, a new basic formulation process has been devised. This obviates the need for modifying nonionic surfactants. The process requires a preferred order of addition and the use of tetrasodium pyrophosphate builder as an integral part of the composition. The detergent product is free‐flowing, granular, readily soluble and exhibits no tendency to cake on storage. A suggested machine dishwashing formulation is given, and data are presented which show good chlorine stability and excellent dishwashing performance.

Protein soil defoaming in machine dishwashers

AbstractThe machine washing of dishes that are heavily loaded with proteinaceous soil has been a problem facing consumers and the surfactant industry alike for many years. The rapid growth in the machine dishwasher market and the trend toward the use of lower water temperatures have tended to aggravate the resulting foaming problem for both the household and the industrial consumer of machine dishwashing detergents. Although many surfactants have been recommended for use in defoaming protein soils, no one product which satisfactorily defoams protein soils over a temperature range of 100−160F has been available. A systematic study undertaken with the primary objective of defoaming egg and milk soils in machine dishwashers over wide temperature ranges has now led to the development of an effective protein soil defoaming system. This consists of monostearyl ester of phosphoric acid blended with special nonionic surfactants, in a mixture of alkaline builders, and provides excellent control of protein foam from 100−160F. Studies have been undertaken to show the effects of variations in monoalkyl ester concentration, types of surfactant, soil load, water temperature, water hardness and builder systems.

Machine dishwashers' nightmare

Machine dishwashers' nightmare

Machine dishwashers' nightmare

Machine dishwashers' nightmare

Critical Study of Machine Dishwashing

Critical Study of Machine Dishwashing Affiliation W. L. Mallmann, Paul DeKoning, and Leo Zaikowski CopyRight*Presented before the Engineering Section of the American Public Health Association at the Seventy-fourth Annual Meeting in Cleveland, Ohio, November 12, 1946. https://doi.org/10.2105/AJPH.37.4.390 Published Online: August 29, 2011

COMPARISON OF THE BACTERIAL COUNTS FROM MACHINE AND HAND WASHED DISHES AND THEIR SIGNIFICANCE

More and more it becomes evident that carelessly washed dishes and utensils in eating places and at soda fountains are potential disseminators of infections. Principles like this, however, need to be confirmed by observation. This paper furnishes practical facts that point to the health value of machine dish washing.