Green builders for automatic dishwashing
Automatic dishwashers are highly popular in Western European and North American households. In Eastern Europe and Turkey their market penetration is growing significantly. In institutions like hospitals and hotels, automatic dishwashing is even more common. Indeed dishwashers offer convenience and allow water and energy savings. Dishwashers however require special detergent formulations for optimal results.
Automatic Dishwashing Detergents (ADWDs) contain builders, special additives (e.g. enzymes, bleaching agents), surfactants and fillers (e.g. sodium sulfate). The common builders in household ADWDs are phosphates; also common in institutional ADWDs is NTA (sodium nitrilotriacetate). For environmental, toxicological and legal reasons there is great interest to replace phosphates and NTA by safer alternatives. Citrates and gluconates have unique properties that make them ideal ingredients for formulations that combine cleaning efficacy and environmental care.
In the USA, a number of states will ban phosphates from household ADWD formulations by July 1st 2010. In Europe, the use of phosphates in ADWDs is not yet limited on EU level, but individual member states like Italy, France and Sweden have already implemented or announced limitations.
NTA is not yet banned from ADWDs in the EU. However, because of its listing as substance being suspected of causing cancer, products containing NTA now have to be labelled with the risk phrase “limited evidence of a carcinogenic effect” when the NTA content is ≥ 5%. In the USA, some states have banned NTA generally from all household detergents.
Environmental and health concerns are also reflected in the criteria for the award of ecolabels to household ADWDs. NTA is banned and the use of phosphates is limited in such products. On the contrary the main ecolabels permit citrates and gluconates without any limitation in household ADWDs.
Citrates and Gluconates in household ADWDs
Trisodium citrate is an ideal ingredient to replace phosphates. It represents an excellent combination of environmental care and good complexing properties and moreover it is a non-toxic, readily biodegradable ingredient which does not promote the growth of algae. Trisodium citrate is able to sequester calcium and magnesium, but also iron and other metal ions, even at higher temperatures.
Jungbunzlauer trisodium citrate is available in two different structures. It naturally crystallizes together with two molecules of water to form trisodium citrate dihydrate (TSC) but can be further processed to obtain the anhydrous form.
Trisodium citrate anhydrous (TSA) contains approximately 14% more active substance per kg than TSC. Its crystals have a porous structure that can serve as carrier for various substances.
TSA can for example absorb water from the surrounding area in a fast process without losing flowability. Thus it allows increased storage stability of dishwashing formulations which contain bleach and enzymes because these ingredients lose their activity in presence of water during storage.
TSA can also be loaded with other liquids such as surfactants or perfume and still remain a free flowing powder. These liquid absorption properties allow to optimize the dry-mixing production process of dishwashing powders and the pressing of dishwashing tablets.
Like sodium citrate, Jungbunzlauer sodium gluconate is a non-toxic, non-ecotoxic and readily biodegradable sequestrant, but its optimal calcium chelating capacity is at a higher pH than for TSC. Thus its best performance is achieved in institutional ADWDs, but it can be used as a co-builder in household ADWDs or as main builder if borates are contained or can be added to the formula as it can form stable calcium borogluconate chelates at pH 9-11.
Sodium gluconate further acts as a corrosion inhibitor for metals as steel and aluminium, thus helping to protect the cutlery, pans, pots and the dishwasher itself. When combining sodium gluconate and a mineral zinc salt in the formula, zinc gluconate is formed in situ during the washing process and contributes to protect glassware from corrosion.
Gluconates in institutional ADWDs
Crucial for institutional dishwashing is an efficient cleaning of a large number of items in shortest time. Specifics of commercial warewash are thus very short wash cycles, higher temperatures and more alkaline formulations.
As sodium gluconate performs best as calcium chelant at a pH between 13 and 14 it fits ideally into institutional ADWDs. In such conditions sodium gluconate easily exceeds sodium tripolyphosphate (STPP) in calcium sequestration. If the pH is adjusted at the very optimal value, the calcium chelation capacity of sodium gluconate is even higher than that of NTA.
Made by fermentation of natural raw materials, non-toxic and readily biodegradable, sodium gluconate is the real sustainable builder in such products.
The green builders trisodium citrate and sodium gluconate are part of Jungbunzlauer’s QualityChoices portfolio.