Fractioning insect garums

Added on by Josh Evans.

by Josh Evans

In the beginning, our original grasshopper garum recipe yielded one product: grasshopper garum. Sometimes we also used the paste.

400 g whole grasshoppers
600 g wax moth larvae
225 g pearled barley koji
300 g filtered water
240 g salt

Blend insects until broken up but not into a smooth purée and keep in a container. Mix insect purée, barley, water and salt together. Place in a non-reactive container with cling film directly covering the surface. Place container in a 40˚C incubator or suitable area, and allow at least 10 weeks to ferment. The garum will separate and remain on the bottom of the vessel, and should be decanted/siphoned with an appropriate pipette/tube. The paste is also excellent, and should be passed through a fine sauce net.

In the summer of 2013, we began to make two 'pressings', as one does with olive oil. The first 'pressing' involved filtering the fermented mixture through a filter paper solely by gravity, obtaining a translucent liquid with few impurities—we called this 'Extra Virgin Grasshopper Garum'. The second pressing actually involved some real pressing, where we took what remained in the filter and pressed it through a superbag to obtain 'Second Press Grasshopper Garum', analogous in some sense to pomace oil.

Extra Virgin Grasshopper Garum on the equator in Uganda.

Extra Virgin Grasshopper Garum on the equator in Uganda.

Last summer, in 2015, we took things a bit further. Firstly, we made production batches of five 'single-species' garums using the same basic recipe as the original, and only one species per batch (based on trials we had conducted the previous summer, in 2014). The species were: grasshopper (Locusta migratoria), cricket (Acheta domesticus), wax moth larvae (Galleria mellonella), bee larvae (Apis mellifera), and mealworm (Tenebrio molitor).

1000 g insects (55.9%)
250 g barley koji (14%)
300 g water (16.8%)
240 g salt (13.4%)
Incubate at 40°C  for >10 weeks
Filter, bottle, pasteurise at 72°C for 15s

When it came time to filter, we realised that we could go into more detail than we had before—particularly because we had Bernat's PhD rigour with us, and were thus well-positioned to go deeper into the post-fermentation part of the process.

Figure 1. Flow chart drawn by Bernat illustrating our most recent garum fractioning process.

Figure 1. Flow chart drawn by Bernat illustrating our most recent garum fractioning process.

We began with the complete garum mixture, post-fermentation. We passed this mixture through a chinois without filter paper, to begin to separate the liquid and solid phases. We then let the liquid phase pass through filter paper by gravity, yielding a fine liquid that had passed through the paper and an emulsion left on it, which we suspect contained residual compounds and water suspended in fats. The filtered liquid we allowed to further separate into lipid and water phases, yielding 'Virgin Oil' and 'Insect Garum 1st fraction' respectively. We passed the emulsion left in the filter paper through a sauce net and called it 'Paste B'—because we were not expecting to have it and had already named its analogue 'Paste A'.

Fractioning garums by gravity through filter paper.

Fractioning garums by gravity through filter paper.

Meanwhile, the solids reserved from the very first filtration through the chinois we pressed through a superbag, yielding a cloudy liquid, and a bit of solids—mainly chitin, small bits of barley etc.—that we discarded. The liquid we then let pass through a superbag by gravity, yielding a more opaque liquid than the 1st fraction, which we called 'Insect Garum 2nd fraction', and an emulsion left in the superbag that we called 'Paste A'.

We also tried using a vacuum filter to extract more of the liquid, but that didn't end up working so well..

Bernat and the vacuum filter. We had high hopes.

Bernat and the vacuum filter. We had high hopes.

Bernat and Roberto try to collaborate with the vacuum filter

Bernat and Roberto try to collaborate with the vacuum filter

Good old gravity took a bit longer but yielded a better product.

Thus, in total, we obtained five products from this fractioning process: Virgin Oil, Garum 1st fraction, Garum 2nd fraction, Paste A, and Paste B.
Our more rigourous fractioning also gave us higher total yields—see Table 1, which does not take into account the Virgin Oil or Pastes A and B.

Table 1. Garum yield as a function of total starting mass. Does not include yield of Virgin Oil or Pastes A and B.

Table 1. Garum yield as a function of total starting mass. Does not include yield of Virgin Oil or Pastes A and B.

Most importantly, the single-species garums are delicious (except for the Mealworm, which is quite thin and unremarkable) and distinct from one another. We are keen on experimenting further with the pastes, which are just as distinct in taste as the garums—they range in colour from pastel peach to ombré ochre, and some of them have a unique, silky texture. Tobyn started working on some compound butters; we can imagine particular pastes being well-suited to different particular applications.

The range of pastes.

The range of pastes.

Now the next step is to re-obtain a centrifuge and take the fractioning further—and to see for what, if anything, we can use the discarded fragments of exoskeleton..