In the monastery I live, we are taught to bless the food by way of offering it, before each meal (or even before simply drinking a glass of water, tea, coffee or so).
The short Tibetan version goes:
Tönpa la mä sangye rinpoche
Kyobpa la mä dam chö rinpoche
Dren pa la mä gendün rinpoche
Kyab nä kön chok sum la chö par bül
Its English translation goes:
To the precious Buddha, the unsurpassable teacher,
To the precious Dharma, the unsurpassable protection,
To the precious Sangha, the unsurpassable guides—
To you, the three rare and supreme sources of refuge, I offer.
It is what we recite (just once, no need for thee recitations) when we have no time (or no heart to take the time). Usually, we recite this short version in the context of 'blessing, offering the food during puja' or when we eat outside of the monastery. An even shorter version for lazy people like me consists in saying "Om Ah Hum" three times.
We also have a longer (clearly Mahayana) version. It is the one we recite every day before the communal lunch:
Om Ah Hum (3x)
Field of merit and ocean of qualities,
Tathagata, to you I pay homage.
Through purity free of attachment,
Through virtue free of the lower realms,
Uniquely ultimate supreme,
Peaceful Dharma, to you I pay homage.
Showing the path which frees those seeking freedom,
Well established in the trainings,
Pure among fields possessing qualities:
To the Sangha, I also pay homage.
To the principal Buddha homage.
The Dharma, which protects homage.
To the Sangha assembly homage.
Homage to the three always.
The qualities of Buddha are inconceivable.
The qualities of the Dharma are inconceivable.
The Arya Sangha are inconceivable.
Through generating faith in the inconceivable,
The karmic ripening result will also be inconceivable:
May we be born in the pure realm.
To the precious Buddha, peerless guide,
To the precious Dharma, peerless refuge,
To the precious Sangha, peerless liberators:
We offer to the three jewels of refuge.
This food with a hundred of flavours,
Which is mouth-watering and well made,
To the Conqueror and his children we offer with faith.
By this, may all migrators become wealthy,
And enjoy the food of concentration.
Seeing this food as medicine,
We eat it without attachment or hatred,
Not to have an enviable body, not out of pride,
Not to look strong, only to sustain the body.
Through the connection of making charity
To the sentient beings living in my body,
May they become human beings and I will reveal to them the
Dharma and lead them to enlightenment.
For this purpose I am going to enjoy this food.