I made a batch of wild raspberry jelly last week using the Ball brand pectin for low sugar recipes. After carefully straining the seeds out of the raspberries I followed the proportions of liquid to pectin and used four cups of sugar instead of six.and carefully timed the addition of pectin to one minute of boiling time. When I put the jelly in the jars it was beautifully liquid with no lumps. However the finished product after processing in the canner has lumps throughout. It tastes fine, and the consistency of the rest of the surrounding jelly is fine, but it is extremely lumpy and the lumps are rather hard. Not so hard that I need to throw the batch away, but definitely a different consistency than the surrounding jelly which is soft and yummy.

What did I do wrong, and how do I prevent this in the future? Should I use the regular pectin and not cut back on the sugar? I made blueberry jam with regular pectin and that turned out fine, so I'm wondering if there is something about the low sugar recipe pectin that requires special handling.