The greatest benefits from foods and the most efficient digestion come from simple meals with minimal food combinations. Thus, the first principle of Food Combining is simplicity and compatibility in meal planning.
Fruits digest best when eaten by themselves as an entire meal. In general, fruits should not be eaten with other foods. If they are, they will be detained in the stomach causing them to begin formation.
Alcohol, coffee, tea, vinegar, condiments retard digestion considerably.
Acid Fruits & nuts - Cheeses are ok because the high fat content of nuts & cheeses acts like a separate meal from the Acid frutis by digesting more slowly.
Acid fruits delay the digestion of sweet fruits.
Tomatoes - May be combined with Low Starch vegetables and either avocados or nuts, and not with starches or proteins.
Sugar & Protein - Fruit & other sugars inhibit gastric juice delaying protein digestion
Melons - Because they decompose even faster than the other fruits. It is advised to eat melons separately from other fuits.
Avocados combine BEST with non starchy vegetables. FAIR with acid fruits & starches. Avocados do not combine well with sweet fruits or proteins.
Source: perigreen.blogspot.in/2012/08/food-combination-of-fruits-for-better.html