The dua before eating is: 'Bismillah' (In the name of Allah). If one forgets at the beginning, say: 'Bismillahi fi awwalihi wa akhirih' — In the name of Allah at its beginning and its end. It is Sunnah to eat with the right hand and from what is nearest to you.
بِسْمِ اللَّهِ وَعَلَى بَرَكَةِ اللَّهِ
Bismillah wa 'ala barakatillah.
Meaning: In the name of Allah and upon the blessings of Allah.
Source: Sahih al-Bukhari #5376Saying Bismillah before eating blesses the food and prevents Shaytan from partaking in the meal. The Prophet (peace be upon him) said: 'When one of you eats, let him mention the name of Allah. If he forgets to mention Allah at the beginning, let him say: Bismillahi fi awwalihi wa akhirih.' (Sunan Abu Dawud 3767)
بِسْمِ اللَّهِ وَعَلَى بَرَكَةِ اللَّهِ
The Messenger of Allah (peace be upon him) said to me: 'O young boy, mention the name of Allah (say Bismillah), eat with your right hand, and eat from what is nearest to you.'