FRANKLINTON, N.C. -- Kosher certification increasingly is being used as a mark of quality when modern food technology meets the centuries-old dietary code of observant Jews.

Conforming to the strict standards of Jewish religious laws can mean surprising sights at some food plants: Like an Orthodox rabbi rappelling inside a huge steel tank to check its cleanliness.

Market research firm Mintel projects kosher food sales will grow by more than 20 per cent from 2008 to this year as more existing products such as Oreos and Tootsie Rolls become certified.

About one out of eight Americans buy kosher products. Sixty per cent who do report quality as the main appeal.

Albany Law School professor Timothy Lytton says some consumers like knowing that someone is performing additional checks now that food is a complex global enterprise.