Recent content by PenderJ

My understanding is that the largest component in the lipid fraction of brewed coffee is triglycerides.

The vast majority of the cafestol and kahweol recovered from a brew is found in the retained grounds. So it may simply be a matter of filtration efficiency being much higher in a paper filtered coffee. The brew methods that produce the highest amounts are unfiltered (e.g. Turkish). Metal...

Excuse my ignorance but by lambda/pi do you mean roughly 1/3 the wavelength of light? The particles I'm talking about are larger than 450nm.

I'm using 0.45 micron filters. The liquid is translucent and a little cloudy prior to filtration and has good clarity afterwards. The liquid is espresso coffee. I have an el cheapo ($25) hand held optical refractometer, the kind where you look for the shadow line through the eyepiece. Prior to...

So when I filter out these particles and observe a lower reading in a refractometer I'm actually observing a change due to the elimination of scattering. And predicting this quantitatively would be complicated. Is that correct?

I guess it isn't an intermediate question. How do you edit it to change the level? Is there a level that corresponds to it being too hard for this forum? :smile:

Do suspended sub-micron sized particles influence the index of refraction of a liquid?

It's not my presumption; it's a more standard belief. It stems from the notion that under/over-extracted coffee tends to be sour/bitter. So an uneven extraction, whether due to an uneven grind (bad grinder) or uneven percolation, is assumed to result in inferior coffee, one that can be both sour...

I don't know what you mean by "Manufacturer's". But the basic answer is yes. While a ring pattern is common it is also not uncommon to have an even pattern. With the same equipment. The ones in that video are actually fairly mild. Here's a more typical example. So this evidence doesn't answer...

While not really relevant to the question I asked, the guy, the "coffee expert", offered a hypothesis about why some holes get clogged. But he didn't actually offer any real evidence for his idea. What he did show was that a particular brand of precision basket, which they sell, worked better...

If that gets out of hand it's referred to as "side channeling". Many of these cylinders also include some amount of taper. And the way the water is introduced to the top of the bed varies. I suppose it's complicated. People do all sorts of things to try to get the flow to appear as even as...

Thanks. What I'm actually interested in is an example of the former. Specifically, an espresso portafilter. The tamped coffee powder provides the vast majority of the pressure drop, typically 7-9 bar over a distance of a couple of centimeters. It's quite common to see the initial droplets of...

I did a brief search prior to posting but concluded that I wouldn't be able to figure it out on my own easily. In the scenario I described the holes are all the same distance apart but there is an area with no holes. But it sounds like what you're suggesting is that the difference in flow...

Suppose you have a cylindrical column filled with packed, irregularly shaped particles. The bottom of the cylinder is flat and closed except for an array of small circular holes, regularly spaced except for a ring around the edge of the bottom where there are no holes. So, holes everywhere on...