I made wine this spring from petals I pick & cleaned, vacuum sealed and froze last year. It was the ugliest looking olive green mud I had ever seen. But - it fermented fine, all the disgusting looking green mud settled out by the 3rd rack and it tastes & smells great. btw - I poured a bit of the boiling water into each bag to clean out the yellow pollen when I started. I have picked and vacuum sealed enough for 2 gallons so far.
Additional notes - 1 full gallon bucket of blossoms will yield about 8 cups of petals loosely packed and weighs about 320 g. That's enough for 1 gallon of wine.
I have picked blossoms and put them in the 'fridge over night and there was no "sour" smell. But if they smell funky, I wouldn't use them. I found I can pick a gallon bucket of blossoms in about 1/2 hour and it takes about an hour to remove the petals.
Here's my "beheading" technique - I put 3 buckets in front of me - blossom bucket in the center, petals go to the bucket on my left, bottom of flower head to my right. Flower in the Left hand, stem end in the right - bring your thumbnails together under the blossom and ABOVE the leaves that curl down - twist and roll the petals off the flower. Once you get a rhythm going, it moves pretty quick.