Never heard this and would be surprised if anyone got stopped for a jar of coffee as even the Turkish government website says that you are allowed 1kg of coffee. But if you had this amount for a 2 week holiday they may be suspicious.
The rules on the website are that you can import a total of 2kg from the following but only 1kg of each.
Tea
Coffee
Chocolate
Sugary products (sweets)
As with most countries, including the UK, meat, cheese & vegetable products are not allowed.
Remember, your bags may be scanned at the EXIT from
Dalaman airport.
I read a good article in The Metro a couple of weeks ago which said that 60% of people believe that, when on holiday in a foreign country, they are subject to UK law or that rules are relaxed for tourists. They are wrong.
OK, lecture over (did I do good John?)