The grapes needed a fairly direct hard light.

Lets get back to that ghostly phantom thing, I like it to create distinct and obvious highlights. Throw in a blurry quality and you're away! Ghostly Phantom even.

What I do to achieve the ghostly highlight is a double exposure. The first exposure is done with no diffusion at the camera, minus the light causing  the "spectral highlight".

For the second exposure drop a diffusion filter over the lens and use only the light that creates the "spectral highlight", pop!