Monday, November 25, 2019

Hint: How to Break Down an Onion

Recorded October 30, 2013. Revised November 25, 2019. Onions are used widely in cooking, and usually need to be broken down before use. The methods described here respect the anatomy of the onion, and exploit its properties for culinary purposes. Two forms of slicing are described, one which favors retention of form and the other its loss. A combination of the two slicing methods leads to dice or mince.

The globe of an onion plant, 'an onion', is formed by concentric layers of pale watery leaves, the lamellae, that grow from the root below ground, and continue above ground as green leaves.  Onions are monocots, meaning their vessels run parallel to each other from root to leaf tip. This means that a slice in the 'polar' direction, that is, parallel to polar axis along a radius, will cause the least cellular damage. I refer to this as a 'blossom cut' because it results in petal-like pieces. Use this when you want onion pieces to keep their shape after cooking. Alternatively, a cut in the equatorial plane, the 'cross cut', slices through all the cells that make up the vessels, the xylem and phloem, that conduct the watery solutions up and down the plant during growth. This produces maximal cellular injury (and release of syn-propanethial-S-oxide, the tearful chemical). Use this cut when you want the onions to break down, such as for caramelized onions.

By combining cuts in the polar and equatorial planes, of course, dice result. A single piece of onion can't be any thicker than the thickness of the lamella from which it was cut. The lamellae change in thickness across the radius and so uniform dice are not possible irrespective of the slicing strategy. For large dice, I cut thick, equatorial slices and then, holding the slices together, along the radii toward the center following the shallow grooves on the surface. Fast, safe, and optimal uniformity.