Posted by Mindy Lvoff
Purpose: Change the flavor of a raw oyster through live-infusion
Equipment Used: Rotor-stator homogenizer
Oysters are little filters, eating what they strain out of the saltwater around them, ultimately tasting like what they have consumedâ€”they are what they eat. Dave and Nils were discussing French Marennes oysters, which are green because of the type of algae they eat. Dave spoke to an oyster physiologist who told him that Marennes oysters are now so prized that oyster farmers actually move them from location to location to feed where a particular type of algae is growing. This idea of diet control gave Nils and Dave an idea for their own way to manipulate the flavor of the oyster before ever shucking it: live-infusion. Asking Dave later how they came up with the idea, he stared at me blankly (as if to say, â€œWell, this is where logical thinking would lead youâ€) and explained, â€œI have a tank. I can keep oysters alive. Why the hell not?â€
Nils and Dave wanted to re-create the green color of the Marennes oyster, but they also wanted to impart unique flavor. The natural culinary inclination is to pair oysters with some form of acidity, but with live-infusion, acidity will kill the oysters. Saltwater is basic, so any acidity at all would be a problem. First, they decided to try a broth of dashi & dill, which would both color the oysters and impart a distinct flavor. Next, they considered the salinity level of the broth. Luckily, Dave Arnold Hobby #612 just so happens to be keeping saltwater fish, so he had a bag of aquarium salt handy. We added just under the recommended dosage for saltwater in order to simulate the brackish water in which oysters feed. Finally, the broth temperature needed to be between 41-70Â°F (anything higher would make for potentially toxic conditions) so the oysters would be active and eating instead of hibernating.
Normally you strain the kombu and bonito flakes from dashi broth, but we wanted the oysters to eat these solids and take on color. So we needed to find a way to make the kombu and bonito particles small enough for the oysters to actually be able to take them in. We used our Vita-Prep blender to blend the broth, bonito flakes, dill, and aquarium salt until the particles were as fine as possible. We poured the mixture into a medium-sized cambro, added the oysters (belly-side down) in a single layer, covered the container and put it in a dark, cool, and quiet corner. We waited 3-4 hours and then shucked one to take a look. Inside, the oyster was swimming in a greenish liquidâ€”so far, so good. Next up was a taste test. Not so good, but at least the idea had worked.
Dave took a closer look and noticed that the bonito and dill particles were actually too big and had gotten caught, clogging the gills and basically choking the oysters. Dave cold-called an oyster physiologist (who took his call and took his questions) about our experiment and got a few crucial facts for our next attempt: 1) the flavor infusion will occur over a period of time no longer than 4 hoursâ€”flavor comes from whatâ€™s in the gills and ingested, not digested; and 2) bacteria can breed in an oyster that is harmless to them, but toxic for humans, so donâ€™t keep oysters in a captive tank too long. There was no specification for how long â€œtooâ€ long was, so we chose to adhere to the food code danger zone of no longer than 4 hours. Typically, we generally go no longer than 2 hours.
Dave also found that in order for an oyster to eat without its gills getting clogged, particles can be no bigger than 10 microns, much smaller that the 20 microns a Vita-Prep can grind down to. From the depths of his equipment room, Dave pulled out a rotor-stator homogenizer, which can grind well below 10 microns. He held out both arms and began swinging it in front of him, cutting the air, and explained, â€œIf the Vita-Prep is like running around with two butter knives, this is like running around with two scissors.â€
So now we had refined the process, but still needed a better flavor profile and we also wanted to try different color. We decided on beet and bacon; beet would impart a vivid red color and baconâ€”well, itâ€™s bacon. Beets are messy. Juicing beets is just obnoxious. Oh yeah, and when using the rotor-stator homogenizer, remember to hold it as vertically as possible as holding it at an angle will shoot colored liquid everywhere. The oysters went in and two hours later, we started fishing them out. The end color was fantastic and, like I said, we all love bacon. Unfortunately, there was a slight â€œdirtâ€ taste from the beets that was enhanced by the brackishness of the oyster. We didnâ€™t love it, but we now had a working process for live-infusion. (We havenâ€™t tried this flavor combo again since then, but we havenâ€™t given up on it yet.)
The next idea was to try carrot and cardamom. We peeled, juiced, and strained a little over 25 lbs of carrots and added in ground cardamom. Then we added the aquarium salt and hit it with the rotor-stator homogenizer. Allow me to state for the record one more time, itâ€™s important not to hold the rotor-stator at an angle… . Again, we laid the oysters, Duxbury this time, in a single layer, belly-side down, and put them aside for two hours. Jackpot. Nils popped open the first oyster, revealing bright orange liquid surrounding its belly. He tasted itâ€”delicious. Then he added lime crÃ¨me fraÃ®che and a little paddlefish caviar (because Nils needs food to go beyond delicious) and the oyster was perfect.
Weâ€™ve served this dish several times now, and can now successfully get 75% of the oysters to feed (we call this our â€œeat rateâ€). You can juice the carrots a day ahead, but itâ€™s best to juice them fresh so you donâ€™t get that woodsy, old carrot taste. We always cover the tank and put the oysters somewhere cool, quiet, and dark to encourage them to start chowing down on the liquid surrounding them. In case you skipped ahead and are just reading this summary, we also learned not to put the rotor-stator homogenizer into the juice at an angle, since it will splash out and cover anyone near it with carrot juice (thanks, Dave). Finally, weâ€™ve used the same technique to make French Onion Soup Clams. We cooked, strained, and chilled French Onion soup (with added bacon and GruyÃ¨re rinds), hit it with aquarium salt and the rotor-stator, then let Littlenecks hang out in it for 2 hours. The result is amazingâ€”the GruyÃ¨re and bacon complement the natural salty, briny taste in the clams while the onion brings out the sweetness. Itâ€™s my personal favorite.