Shares in the company swiftly tumbled by 12.5p to 127p, wiping pounds 15m off its stock market value.
The share price performance has been steady over the past year, rising from a low of 95p to a peak of 142p.
Mr Matthews said that profits in the second quarter of the year would not compare favourably with the excellent figures a year ago.
This time last year, the company benefited from the BSE scare which caused a flight of beef consumers to other meat products. The company was also able to push through price increases with little adverse impact on sales.
However, the chairman attempted to temper yesterday's warning with a hint of optimism on prospects. He said: "We believe this to be a short- term situation and remain cautiously optimistic for the year as a whole, as we continue the expansion of our branded added-value business."
Hardest hit by the share price fall yesterday was Mr Matthews himself and his family which still owns almost 40 per cent of the company and was actively buying more a month ago.