The deal believed to be worth £40m was first revealed by The Grocer at the beginning of March and was completed on Friday.
The company was set up by Herefordshire potato farmer Will Chase six years ago and had sales of £13m for the year to March.
Chase was understood to have wanted to complete the sale before the base rate of capital gains tax increased from 10 to 18 per cent last week. However he is still expected to pay the lower rate as the company had been warehoused before the changes came into force.
Langholm Capital is an investment vehicle backed by Unilever and Rabobank. Last month it sold upmarket cereal supplier Dorset Cereals to Wellness Foods for £50m, around four times its initial investment.