My fingers are burning as I’m typing this story. Chilli seeds are a pain (gloves Sheere, gloves!), but I found in my experiment that they are crucial to making a well-balanced and moist sambal belacan ­­­— if using the right method.

Many cooks talk about a mortar and pestle producing better spice pastes than a blender, although few can say why. Kenji Lopez of Serious Eats has by far the best explanation. Pounding crushes the cells of the vegetables, he says, whereas a blender cuts them. Since crushing ruptures the cells to release more aromatic compounds, a mortar and pestle produces more flavourful results.

I wanted to know how well this theory applies to sambal belacan, a chilli paste consisting only of chillies and belacan, a sun-dried, fermented shrimp paste. Unlike other aromatics like garlic and shallots, there are two parts to a chilli, the fruit and the seeds. The latter are spicier than the former, that’s why people sometimes remove the seeds to tone down the heat of what they are cooking.

Chillies are spicy because they contain capsaicin. According to Harold McGhee, chillies produce capsaicin from its placenta, the pale, spongey tissue in the middle of the fruit that holds the seed. From the placenta, capsaicin spreads to the seeds and then the fruit, where it becomes less concentrated.

I already know that chilli seeds escape the blades intact (unless you have a Vitamix), whereas a pestle could beat them beyond recognition. What I wanted to find out is:

1. If this difference has any impact, besides spiciness, on the resulting sambal.
2. If the recipe calls for seeded chillies, would pounding and blending produce a significantly different flavour profile?

To answer these questions, I made four sambal belacan using the two methods, and with each method I made a sambal with chilli seeds and one without. The ingredients are standardised by weight:

32 g big red chillies, pre-cut into chunks
9 g red chilli padi, pre-cut into chunks
10g toasted belacan

Here are my findings:

Pounded, without seeds
This sambal tasted bright and refreshing like a capsicum. While it was spicy, it didn’t cause my tongue too much pain. The chillies released its juice as I pounded them and more accumulated at the bottom of the resulting paste as it sat longer. Belacan is meant to make the sambal pungent and salty but I found these two qualities a little too prominent in this sample.

Blended, without seeds
I used a handheld blender because the sample size was too small for a regular blender to do its job. That’s a downside of the machine: you’ll need to be making enough for the blades to reach the ingredients and blend them well. My handheld blender wasn’t capable of melding the belacan with the chillies either, leaving tiny bits of shrimp paste in the sambal. But other than that, I didn’t think this sample tastes any different from the pounded version. So if I were to make a sambal with seeded chillies, I would use a blender for convenience. Toasted belacan could be broken down into powder first to mix well with the chillies.

Pounded, with seeds
I removed the chilli seeds to pound them first, so that the juice of the fruit wouldn’t get in the way. They turned into a fibrous mass similar to a dried-out ginger. I took a bite, and it was awfully spicy as expected. In terms of flavour, it was somewhat dull. There might be a hint of nuttiness but by then my tongue was too swollen to tell for sure. It turned out that the fibres are great for keeping moisture within the paste. There was no liquid at the bottom of the sample even after hours. It appeared that the pounded seeds functioned as a binder like what candlenuts does for spice pastes. They may have also helped subdued the strong belacan flavour a little, creating the most well-balanced sambal of all the samples.

Blended, with seeds
As expected, the seeds remained intact. This sample had bits of belacan in one bite, and too much seeds in another — a far cry from the pounded version. Maybe it wouldn’t be so inconsistent if I had made a bigger portion with a regular blender, but I believe the outcome would still be less than ideal.

Conclusion
If spiciness isn’t a problem, I would include chilli seeds in my sambal anytime and pound instead of blending it.

If seeded chillies will be used, then a blender will do just fine. It is faster and produces similar results to a mortar and pestle’s.

Unless I’m making a small amount. Then, I would do it manually. A mortar and pestle can do the work in less than five minutes and they are easier to clean than the machines.