359. Brachos
50:1 Psalms 24:1 tells us that the world and all that it contains belong to God. Just as we may not use consecrated property before it has been redeemed, and doing so would be considered misappropriation, similarly, deriving benefit from this world without blessing God for His goodness is like stealing from Him. The bracha is the thing that “redeems” food and other items from their restricted condition. There is no minimum amount to obligate one in saying a bracha before eating or drinking something; any amount, no matter how small, requires a bracha.
50:2 If a person made a mistake and said the bracha of shehakol, that God caused everything to come into being, over any kind of food – even bread or wine – he has fulfilled his obligation and does not say the bracha normally recited. One must not, however, do this as a first resort. A person is obligated to familiarize himself with the appropriate bracha to recite for different types of food. When there is a doubt, he may discharge his duty to say a bracha with shehakol. (This is only for one who generally knows his brachos; one who hasn’t learned his brachos must inquire – Mishnah Brurah 202:84.) It would be preferable if one is able eat the item whose bracha is in doubt as part of a meal, so that the bracha on his bread would include it.