Noticing the difference from non washing to washing them.
I wash mine for 5mins in my thermomix in the simmering basket speed 5 with water level just covering the bottom of the basket.
I always add a dash of non filtered apple cider vinegar to mine.
If you don’t have a thermomix just grab a large bowl place grapes into the bowl. Fill with water to cover the grapes and add a dash of apple cider vinegar.
Gently move the grapes around with a spoon every now and then. And allow to soak in water for 5 mins.
Below is what the grapes looked like before washing, the water after and the grapes after the 5mins.
Water after Washing