Has anyone else noticed flavour, bitterness issue when adding dry hops to the no chill ?
Adding hops to a no-chill beer that is still hot will not be the equivalent to dry-hopping and is basically a flame out addition kettle hops.
Dry hops is added to cooled beer and the fact that it's chilled means that it doesn't readily disolve hop oil, alpha acids etc. Tru dry hopping will give a completely different flavour and aroma impact to kettle hops.
When hops are added to hot wort they readily give up their oils etc, including alpha acids. The alpha acids are isomerised iso-alpha acids, which gives the beer its bitterness. It was believed that for isomerisation to occur you need heat plus agitation, hence a rolling boil. Latest studies have show that isomerisation is a first order reaction and only needs heat to occur (activation energy is 98.6kj per mole - no idea what temp this translate to). However agitation is still need if using plugs or flowers as with pellets they are already much more broken up and the lupin glands have already been burst by the processing making the alpha acids more accessible, unlike plugs and flowers.
So yes there will be some isomerisation of the alpha acids whn added to the hot wort. If you use pellets it will be more pronounced and the hotter the wort the more pronounced. However having said all this, it is likely to be only a slightly increase in bitterness. Remember the same principle applies to brewers who use plate or CFC chillers, where their wort can sit hot with late additions, before it is chilled. If you use a CFC and are used to the impact of late additions, adding hops to the no-chill cube is likely to have a similar result. If you are used to an imersion chiller, you will have to make some adjustments. Or simply use a hop bag/sock and remove all your hops after the desired length of time, then siphon into the cube.