The Shiurim for Brocha Rishona and Achrona
General Rule: If you eat or drink any amount for the sake of eating or drinking and not just to taste it – then you need to say a Bracha Rishona. However, in order to make a Bracha Achrona on the food you ate – you would need to eat a Shiur Chashuv (an important amount).
Tasting: If one tasted from a dish in order to know if it was good (i.e. enough spices in the dish, or if the milk is too hot for a baby) then he wouldn’t make a bracha, even had he tasted from it several times. However, if he tasted a k’zayis of food (or a reviit of liquid) then he would need to make the brocha rishona and achrona, since it is not considered tasting when one consumes that large an amount.
Amount - there is NO minumum amount of food that must be consumed to say the bracha rishona.
Time Limit (min) - NONE
Time Lapse (max) - How long does a bracha rishona last for? Potentially, it could last all day. The things that conclude bracha rishona's are: (1) a mental decision that one is done eating, (2) saying a bracha achrona, (3) changing locations, or (4) going to sleep.
Bracha Achrona for Liquids
Amount – The final halacha is that the size of a revi’it of liquid is defined as 3oz and this is in accordance to R’ Chaim Na’eh. (Rav Moshe holds it’s 3.3 oz of liquid, and if interested you can be machmir.)
Time Limit (min) – How much time does one have to consume the revi'it amount: As for the final halacha, the drink would need to be consumed without interruption. There is no set amount of gulps necessary, rather as long as there is a continuous flow. (Some advise stricter guidelines, such as: two normal gulps with one really quick break in between). Therefore, the cup would need to remain at one’s mouth the entire time, and he would need to be drinking the entire time. Thus, if one drinks 2oz and then pauses and removes the cup from his lips, and then afterwards drinks more – he wouldn’t have qualified to say the brocha achrona.
Example: Hot drinks (i.e. tea and coffee) – Since one drinks them sip by sip over a long time – he wouldn’t say a bracha achrona on these drinks. There are some opinions that argue since this is the normal manner for these types of hot drinks, one would need a bracha achrona; nevertheless, the Minhag Olam (common practice) is not to make a bracha achrona on them. Many people do have the practice, however, to leave over the last 3 oz and let it cool down in order that he can drink it in one shot and then make a bracha achrona.
Time Lapse (max): Ideally, one should make the borei nefashot as soon as possible, because once you begin to feel thirsty again, you have missed your opportunity. When it comes to drinks, one can feel thirsty again within 30 minutes, especially on hot summer days and can easily run into issues. If one can not tell if he is thirsty or just not full of drinks - then as long as within 30 minutes, he can make the borei nefashot. Beyond 30 minutes he should (1) hear a friend, (2) drink more water, or (3) eat another borei nefashot food.
Bracha Achrona for Foods
Amount – The Final halacha: A k’zayis is defined as the volume used to displace slightly less than one fluid once. (For more on Shiur K’zayis and how to practically calculate it, click here.)
Time Limit (min) – How much time does one have to consume the kazayis amount: The consensus among most poskim is that the time of “Kdei Achilat Pras” is 4 minutes, but there are minority opinions that range from 2-9 minutes, and in some circumstances it would be advisable to be cautious for these minority opinions.
Time Lapse (max) - From when you are done eating, how long do you have to say the bracha achrona? There is a difference between Bread and all other items in this regard:
Safek if a Food or a Drink
What about an item which is eaten like a food but isn’t chewed rather just turns into liquid and is drunk – is it halachically treated as a food or a drink?
Examples include: ice cream, yogurt, honey, cream, and thick blended drinks. (If the blended drink is thin, then there is no question that it is treated as a drink.)
The practical difference is whether one would make a bracha achrona on such food items since if the ice cream is treated as a food, then one would only have to eat 1 oz in 4 minutes; whereas if it is considered a liquid than one would need to consume 3oz without pause, which is practically impossible.
The Halacha: Since there is uncertainty in the matter, the halacha is that one generally wouldn’t make a beracha achrona on ice cream.
For Ashkenazim only, there is one exception where one consumed 3 oz of ice cream in 2 minutes. The logic is perhaps ice cream is halachically food, and even if it is a drink there are opinions (GRA) that hold that drinks can be consumed within “Kdei Achilat Pras” and still receive a brocha achrona. The reason 2 minutes was chosen is because that amount qualifies for “Kdei Achilat Pras” according to all opinions. Rav Elyashiv contends that this is even stronger than a typical safek Sfeika because it seems that the poskim hold the Ikar halacha is like the GRA except out of concern we are normally cautious for the opinions that argue on the GRA. That is why ideally we require the 3 oz to be drunk continuously, however in this case, one could rely on the GRA and wouldn’t have to take into consideration the opposing opinions.