Dairy Crest said sales of the brands had fallen in a butter and spreads market that continued to decline in the three months to June 30.
But its flagship Cathedral City cheddar did better, increasing sales and market share to become the UK's 16th largest grocery brand.
The group said the full year outlook was unchanged but sales would be weighted towards the second half.
"We expect sales of our key brands to perform strongly as the year progresses," the group said.
Dairy Crest is selling its milk and dairy business to Germany's Müller.
The deal depends on concessions offered by Müller, which the Competition & Markets Authority is considering.
Shares pared early losses to stand flat at 566p just before midday in London.
Shore Capital, which has a 'buy' recommendation on the stock at 559p, expects the Müller deal to complete by the end of September.
Analyst Clive Black said: "With the dairies business, including the Frijj brand, under the auspices of the rapidly advancing Müller UK & Ireland, Dairy Crest becomes a very different and much more attractive business."