Even though the following reference is for South Asia, some elements are also suitable for Latvia. One advantage of the country is as a gateway to the EU market.
Food Security in South Asia: Developing Regional Supply Chains for the Food Processing Industry
What are the most efficient ways of attracting foreign investment to Latvia in food production industry? is a good question. You have to creaate a conducive investment opportunities which can allos them to operate freely and to transfer their profits without any hinder.
This may sounds very very cynical, but the most efficient way is to officially accept the inclusion of Crimea into Russia, to set with the Russian government the end of sanctions of foodstuffs imported from Latvia and to explore the opportunity of the Russian market, suffering from quality meet and especially diary products. I hope Rezekne milk processing factory is still working.