Siman 176 – Eating before the meal

בChelek 2

89. If the table is set for a meal and you will be eating imminently, it is forbidden to eat foods that do not require a beracha during the meal – this will cause you to make a beracha that is otherwise not needed. You should first say Hamotzi and thereby exempt all those other foods. (MB 2)

90. Two exceptions to the above:
91. You specifically enjoy those foods more before eating bread.
92. You want to eat them to stimulate your appetite. Its best to be careful and eat only less than a k’zayis. (MB 2 – ShaH9)

93. Let’s say you ate other food just before netillas yodayim, do you need to say a beracha achrona on them? It depends:
94. Minay Mezonos (like after a morning Kiddush) – argument. It is better not to bless, especially if you will be eating more of it during the seuda. Just, l’chatchila, have them in mind during Birkas Hamazon.
95. Fruit (an example of food that would need a beracha even during the seuda) – if you will continue to eat more during the seuda, Birkas Hamazon will cover all of it. If you don’t plan on eating fruit during the seuda, say a beracha achrona.
96. Meal foods that would be toffel to the bread – if eaten as an appetizer, no separate beracha achrona is required. If not, the food is not considered a part of the seuda – say a Boray Nefashos. (MB 2)