Recently I made 2 separate batches of salsa from the same ingredients: 1x Red Capsicum 1x Brown Onion 3x Green chilis Half a head of garlic Salt Sugar Lime Juice

The first batch was great. I dirced all ingredients to smaller than 2mm pieces, mixed it all together and it was lovely. For the second batch I decided that I didn't have the time to dice everything by hand (I am not very fast with a knife) and so I threw everything in the blender and blended until it was a frothy brown liquid.

The second batch was very bitter despite being made from the same quantities of each ingredient, all of which had been purchased on the day and everything was fresh.

Is there something about the liquifying my ingredients that caused my second batch to be bitter that would not have been caused by dicing them?

2 Answers 2


While I haven't heard of it happening for the specific ingredients you list, yes, the blender can make stuff really bitter.

There are two ways this can happen. First, a chemical reaction. A blender really churns the stuff through, driving lots of air bubbles into the mixture with some force. It also causes friction heat, especially professional grade blenders like vitamix. The heat, force and large reaction surface can cause the oxygen in the air to enter a reaction with the ingredients which doesn't happen when using a milder method for cutting up. Olive oil is a known culprit here, it usually turns bitter when blended, but it can happen with other stuff too.

Besides oxygen, a chemical reaction can also happen between two ingredients coming from two different vegetables, which would not have been mixed well enough in the knife scenario to produce noticeable amounts of reaction product.

The second possibility is releasing stuff which would have stayed "packed" without the blender. A knife will only damage the plant cells at the cut surfaces, and a blunt knife, if used with a somewhat inefficient technique, might even break very ripe vegetables along the cell walls instead of cutting through the cells. If there are mini-droplets of something bitter within the plant cells, it is possible that the blender (which really cuts cells into pieces) released these things. On a more macro level, it is also possible that we are not talking mini-droplets, but just plant parts which didn't get cut with the knife. Stray pepper seeds come in mind: you probably didn't cut any with the knife, they tend to be pushed by a knife instead of cut when you are cutting the pepper. The blender pulverizes everything that hits the blades, including these seeds.

I cannot know which of these is the most probable source, or which plant contained the bitter matter exposed/created by the blender. But the different methods of mincing vegetables are not equivalent, and can have very noticeable effects on taste and texture beyond the obvious chunk size. The bitterness you encountered is only one example. In general, use the method specified in a recipe. If you are not working from a written recipe, try out a few and see which works best.

  • 1
    If I had to point to one most likely cause, I'd say the ribs and seeds within the peppers; those can be very bitter and were likely pulverized by the blades. Overall, you're better off dicing, but if you want to use the blender, cut into larger chunks and just pulse a few times - don't liquify.
    – logophobe
    Jul 31, 2014 at 14:14
  • Thanks for the responses. This happened a few weeks ago so I can't be sure if there were any seeds involved but I tend to strip them out.
    – Chris
    Aug 1, 2014 at 1:12
  • If there's bitterness from the garlic, at all, blending it to nearly a liquid would make a huge difference vs chopped. Sep 28, 2016 at 18:34
  • +1 to olive oil in blender - this isn't theoretical or subtle, it can get grossly bitter! Friends don't let friends serve them a blender pesto ;) Sep 29, 2016 at 8:26

I'm pretty sure it's the onions, some are a lot stronger than others and even different sizes can vary. I have to add extra tomato to even it out sometimes.

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