Common lore on the internet is that liquid laundry detergents go bad 1-2 years after they are purchased. Is this true? I'd like to understand the chemistry behind this. This is the laundry detergent I am researching for o-chem.
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1$\begingroup$ A year or two? Mine gets exhausted long before then. $\endgroup$– Oscar LanziCommented Aug 7, 2023 at 19:07
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1$\begingroup$ Hanging out with the wrong crowd will do it. $\endgroup$– Todd MinehardtCommented Aug 7, 2023 at 23:51
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1 Answer
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"Common lore" is not exactly evidence. Can you cite anything to back that up the lifetime of laundry detergents? What happens after that time -- are they no longer effective?
That said, many laundry (and dishwasher) detergents now contain enzymes, e.g., fungal alkaline proteases, to break down protein-containing dirt and stains(foods, blood, etc.). Since proteases are enzymes that break down proteins (cleavage),and since these enzymes are themselves proteins, they might shred themselves over time. In organisms, "Proteases... are synthesized in the inactive form so that they may be safely stored in cells... " Postponing self-cleavage could extend the shelf life of proteases.
Perhaps laundry detergents contain inhibitors to extend shelf life; some companies use dry granules for that purpose. Others are designing proteases more resistant to self-cleavage.
However, I've not noticed a difference in cleaning effect with old detergent; perhaps the issue of self-cleavage has been effectively ameliorated.
answered Aug 7, 2023 at 17:09