Jenny Ruhl has a good explanation on the difference between first and second phases of insulin release (emphasis mine):

When a healthy person starts to eat a meal, the beta-cells kick into high gear. Their stored insulin is released immediately. Then, if the blood sugar concentration rises over 100 mg/dl, (5.5 mmol/L) the beta-cells start secreting more insulin into the blood stream. This early release of stored insulin after a meal is called "First Phase Insulin Release." In a healthy person it keeps the blood sugar from rising very high because it is available to meet most of the glucose that comes from the digestion of the current meal.

The amount of insulin secreted in the first phase response to a meal is usually determined by the amount of glucose encountered in the previous meal. In a healthy person, this first phase response peaks a few minutes after you've started your a meal. The blood sugar rise caused by the meal peaks about half an hour after you start eating.

After completing the first phase insulin release, the beta-cells pause. Then, if blood sugar is still not back under 100 mg/dl (5.5 mmol/L) ten to twenty minutes later, they push out another, smaller second phase insulin response which, in a healthy person, brings the blood sugar back down to its starting level, usually within an hour to an hour and a half after the start of a meal.

So it's not just the presence of carbs or sweet taste that affects insulin response. As I recall, this was part of the rationale for the Carb Addicts Diet where you'd eat two low-carb meals and one reward meal a day.

"All sweet tastes trigger insulin like sugars" has become a bona fide urban myth.

Whether or not it is also factually true, is another question.

I'm inclined to think the facticity is dubious and that it's simply something that keeps getting repeated because of its "just so" quality. You know: sounds like it should be true, so that makes it true.

I'm prepared to stand correct if someone can present evidence other than opinion, which is what my own stance comes down to.

Everyone's MMV, so a glucose test would be the best, but a glucose meter won't measure insulin levels. Then again, you can use your information to confirm that you are going low-carb successfully. When I am on a strict low-carb protocol, even celery and lemon juice taste sweet.

There has been some research, all of which is in overweights/diabetics if I recall, that showed artificial sweeteners trigger an insulin response. However, such an insulin spike would be very transient and small.

As far as liver goes, of course it triggers insulin release, as it has protein in it. The protein would have far more of an effect than sweetness.

Why are you so concerned anyway? Insulin is good for you. And insulinogenic foods don't spike blood glucose per se, as the liver would also stimulate glucagon which would raise blood sugar.

I just ate a piece of liver that tasted sweet. I ate only liver because I cooked up a bunch to portion and freeze and that one somehow made it to my mouth rather than the freezer.

I have a BG meter so I'll test in an hour and come back to let you know.

EDIT: Those above who pointed out my meter won't measure insulin make great sense. For the record, after 33 minutes my BG is slightly lower than it was after my 2 mugs of coffee with cream/honey. I assume that may mean it was on the way down anyhow and the liver had no effect or I released some insulin after the liver which dropped my BG a little. We're talking small differences, BTW.

This makes for some interesting reading.

liver is a organ that stores sugar in a poly state so that it is not water soluble. the glycosides are called liver glycogen. the chemical is very closely related to amylose or starch found in vegetables differing only in the length and branching of the chains. So, is liver sweet because your tongue has sugar receptors or because its full of sugar, i will let you decide that one. i will just repeat that the liver stores sugar as liver glycogen, enough to power a body for days if required.

I think the sweet part was the onion. YUMMY

According to the article "Do Artificial Sweeteners Cause an Insulin Spike?" on Mark's Daily Apple, most artificial sweeteners do not cause insulin spikes in humans.

The Wikipedia article "Sugar subsitute" states that a sweet taste will cause an insulin spike in rats. This may be why some people believe this happens in humans.

However, artificial sweeteners have been linked to weight gain, possibly through increasing food reward. The blog post "The Skinny on Artificial Sweeteners" describes a plausible reason:

Artificial sweeteners do not activate the food reward pathways the same way as natural sweeteners do. Their non caloric nature, eliminates the postingestive reaction and offers partial activation of the food reward pathways. The failure to provide complete satisfaction leads to further seeking of food.