The word Sattvic is originated from Sattva (सत्त्व) which is a ancient Sanskrit phrase. Sattva means one which is “pure, natural, vital, energy, clean, conscious, strong, courage, true, honest, wise, goodness”.
Sattva is one of the three gunas as mentioned by Lord Krishna in Bhagavad Gita . The other two qualities are Rajas or passion and Tamas or ignorance. The concept that contrasts with Sattva is Tamas.
Foods in the mode of goodness or Sattva increase the duration of life, purify one’s existence and give strength, health, happiness and satisfaction. Such nourishing foods are sweet, juicy, fattening and palatable. Foods that are too bitter, too sour, salty, pungent, dry and hot, are liked by people in the modes of passion. Such foods cause pain, distress, and disease. Food cooked more than three hours before being eaten, which is tasteless, stale, putrid, decomposed and unclean, is food liked by people in the mode of ignorance. (BG Ch 17 Verse 8-10)