Wild duck (in center of photo)
We are about 3 days into the curing of the duck prosciutto (side note: I have identified my inability to spell “prosciutto” as an intractable character flaw). I’m still not sure how well this product will turn out. For one thing, the wild duck is showing lots of mottled white bloom on its surface, which makes it look really unappetizing. Even the store-bought duck has small patches of this discoloration. I’m not sure if this means it’s too done, or if it’s just a defect.
Another problem: the wild duck pieces have shriveled to an impossibly small size, and the curing process hasn’t improved the aroma much, either. Some people at work, including the fellow that donated the duck, commented that wild duck has an off sort of fishy flavor. I haven’t eaten any yet, but the aroma makes me suspect the drying process has just concentrated the flavor. Without a layer of skin, the w
ild duck has dried much faster than the store-bought variety. Today, the wild duck hit 0.705 water activity units, while the store-bought was still at 0.735.
Lastly, the recipe says to leave the skin on the duck, which for the store-bought variety we did. I’m still unsure how this will taste, but we just have to wait and see. There should be 3 or so more days of drying left, but the wild duck looks as if it is done already. It’s stiff like beef jerky, and its water activity is approaching that of the fridge interior quite quickly. I’ll give it another day, and decide whether to pull it out. In general, though, the duck meat is drying quickly, with the store-bought meat still much softer than the wild duck.
Duck breasts beginning salt cure
The duck prosciutto recipe from Charcuterie sounded relatively easy, and it was. By far, the most difficult aspect was actually getting the duck breast, which in my case came attached to a whole frozen duck. In the book, Ruhlman suggests either buying the duck online (so as to get only the part you want) or getting whole ducks and breaking them down. I did the latter, though they have to be special ordered in a place like Pullman. Nobody I could find stocks them, although this changes with season (I do see duck showing up around the holidays).
I bought 4 birds, and breaking them down proved challenging. I’m kind of familiar with chicken anatomy, but the duck was a little different. Knowing I wanted at the breast, I tried to remove what on a chicken would be the wishbone (this makes slicing off the breast a lot easier). I did manage to get the “wishbones” out, but it took some doing, and I’m not even sure they’re wishbones. The other issue is that chicken breast tends to be massive and thick, while duck is much flatter and longer. This raised the stakes when trying to coax it off the bone, and slip ups caused holes in the duck breast rather easily.
Eventually, all 8 came off the bones. For comparison purposes, a friend from work donated some wild mallard breast he acquired while hunting last year. We’re going to cure them in the same way, and see which we like better. After salting the two kinds of duck breast, we put everything in the fridge until the next day.
We observed the following day that the meat had indeed taken on a “cured” look from all the salt that was in it. Both wild and store meat were harder to the touch. I brought both batches in to work today to cure in our fridge. After stringing them up, we now have about 7 days to wait before we try it.
I tested the water activity of both meats post-salting, and they were exactly the same – 0.843 aw and 0.839 aw respectively. It’s important to note that leaving our meat to cure too long would result in an over-salted product. We don’t know what over-salted is for this product, but since saturated salt is 0.755 water activity units, the 24 hour cure didn’t get us all the way down to that level. With the precision of water activity in that range, establishing “salty enough” and “too salty” values could help producers know when to pull meats out of a salt cure.
Best Before 20 May 2011
Much like Al Gore, cereal bars burst onto the scene in the 90′s. I recall the novelty of the multi-component nutri-grain bars when they hit the shelves – kind of like a thinking man’s pop-tart. Now Kelloggs makes about 4 million of them a day. Although nutritional experts deride the category as a bunch of glorified cookies, sometimes a granola bar is all the breakfast a guy needs.
This brings me to my mom, a remarkable woman who raised nine kids (I’m number six) and lived to tell the tale. Feeding such a large group required lots of food, most of it kept below room temperature in a downstairs “fruit room” that remains well-stocked to this day. Over the past 25 years, all 9 kids have moved out. In short, the fruit room inventory turnover ain’t what it used to be. This fact was confirmed last summer when mom brought an unopened jar of mayonnaise from 2001 to a family picnic. It tasted like motor oil flavored aspic.
The old granola bar that bends
Another family gathering last week saw the appearance of some Nature Valley granola bars that were a year past the “best before” date. Let me first say that they really didn’t taste that bad – maybe a little stale. It was the texture I found interesting. Rather than their normal crispy, brittle texture, I could actually bend these bars (see picture). I thought that maybe the water activity had changed over time, so I took one of the old bars in to work on Monday, and tested the water activity. It came out to 0.386 @ 25C – relatively low. Still, I thought it probably wasn’t as low as a freshly made bar, which I bought from the store. Sure enough, the “fresh” granola bar (that snapped in half as soon as I tried to bend it) had a water activity of 0.247 @ 25.1C.
Crispy, Fresh Granola Bar
So what causes the change over time? The most likely suspect is moisture migration into the package. The “fruit room” humidity is in the 50% range. Although many consumers think of packaging as impermeable to moisture and air, this isn’t true. More expensive packaging can suppress conductance, but can’t stop it completely. Over the 18 months or so that the granola bars sat in the fruit room, they undoubtedly absorbed moisture from the environment. The laws of thermodynamics dictate that the difference in energy levels would cause water to flow from the ambient air (0.5 aw) into the bar (0.247 aw to start with). This probably caused the binder (in this case, brown sugar syrup) to change from a glassy to a rubbery state. Another possibility is a retrogradation of starch, a reaction which can release moisture. This would also have softened the binder over time.
A quick and shameless plug: the real interesting data to gather here would be isotherms. If we could run an isotherm on the bar, we could pinpoint the water activity at which it would lose its crispy texture. We could also calculate, in days, weeks, months, the time it will take for a fresh granola bar to turn into a stale, bendy one. My company makes an instrument that measures these things – it’s called the AquaLab VSA. End of shameless plug.
If you’re interested in a rather amusing Nature Valley granola bar cameo, please check out this old time baseball sketch from Conan O’Brien.
Living in a small town has its benefits. Not fighting with traffic (most of the time), low crime, good schools and having a quiet neighborhood are among them, but the acquisition of specialty foods, including cured meats, isn’t. That’s one good argument for making your own store of preserved proteins.
My recent trip to Toronto led me to a downtown super market with this large collection of prosciutto.
A seemingly unending supply of hams hanging at your beckoned call. Or, if you cure the ham yourself, you can wait out the months.
I started the project of making my own prosciutto nearly one year ago in May, not really comprehending at that time how long of a project it was going to be. The process starts with salting the ham for about 3 weeks or until firm. For one who has never done anything like this before, firm is relative, and being worried about microbial growth I wanted to keep the ham in the salt long enough to bring the water activity of the exterior of the ham down to a safe level. Now, I wonder if I salted for too long.
Here’s a pic of the ham in the salt.
After salting, the ham was rinsed and hung to dry. The recipe suggests drying for at least nine months or until the ham has lost half of its weight. Ten months later, the ham had dropped from 19 lbs to 12 lbs, clearly not half its weight but my patience had run thin, so I declared it done.
During the process of drying, I tracked the water activity of the interior and the exterior of the ham along with the weight. Here’s a graph of its change over time.
Notice that during and after the initial salting of the ham, the water activity level of the exterior and interior diverged significantly, then slowly converged over time. Now they are essentially the same. The weight decreased quickly during the first couple of months, and then decreased more but steadily. The change in water activity flattened over time while the weight continued at a steady rate of decline for several months.
The final water activity of the Prosciutto was fairly low, at 0.80aw. Interesting that the Prosciutto Di Parma I purchased (imported from Italy) had a water activity of 0.90 leading me to believe my prosciutto may have been over salted. Tasting, the difference is clear – the Prosciutto Di Parma is smooth and mellow while mine, though very good, is clearly saltier. Is it possible that it took me almost an entire year to realize I had messed up in the very first step? Fortunately it isn’t too salty to enjoy.
I’ll stray from the usual water activity focused analysis again to detail usage of the product we made: salt cod. I must say, this was really simple to make, but didn’t look much like fine dining when we were done. The fish itself wasn’t totally stiff at the end of 7 days of curing/drying, but it looked pretty durable. With a water activity in the low 0.700′s, it probably wasn’t going to mold, either. I can imagine, though, that ocean-going vessels of the 1500′s probably dried theirs to a wooden plank consistency before socking it away below deck.
Although Charcuterie doesn’t usually serve up a finished dish, the book does drop bread crumbs in the description about how to use the stuff once it’s made. In this case, they suggested cookbooks from Zuni Cafe and Bouchon as good places to start. Seeing that Bouchon was on offer from Amazon for less than $30, and never having had the guts to buy a Thomas Keller cookbook before, I pulled the trigger. A quick aside on Keller: the reason I find him intimidating is that every time I see him on TV or something, he’s talking about how simple and easy food should be. And yet, he runs the best restaurant in the entire country. This suggests he possesses superpowers that make his simple food magically turn out like food for the gods. Also, his recipe for beef stew in The French Laundry Cookbook takes 4 days and 20 pots to make.
There were just 2 cod recipes in Bouchon so I chose the deep fat fried one for using the salt cod. It’s called Cod Brandade, and is made by mixing the poached cod with some mashed russet potatoes and olive oil. This mixture is rolled into 2Tbsp balls, coated with batter, and fried. The resulting snack is both delicious and a little dramatic, with batter streaks clinging to the ball like a comet’s tail. Served, as suggested, on tomato confit, the dish really satisfies. The cod flavor came through clearly. When prepping the salt cod, remember to start soaking it a day ahead. 12 hours wasn’t enough, in my case, even though I chose thin pieces. Bouchon says 12 to 24 hours, but at 12 hours the cod was still on the verge of being too salty for the recipe. Anyway, here’s a picture of how it turned out, but believe me, it was a winner.
Now that the fish has been in the fridge for 5 days, after reposing in salt for the first 24 hours, it seems pretty dried out. The tips of the cod have a very beef jerky-like texture. The thicker parts of the fish still have some softness, but a paper towel pressed onto the surface yield only 2 small blotches of moisture. Also, in the picture, you can see some of the salt from the fish deposited on the surface as it dries out.
As far as water activity, the tip reads 0.704, which is down in jerky territory, and a good indicator that the cod would be shelf stable. The thicker parts of the fish would probably still be in the 0.75 range, but in losing water, the fish has also reduced its water activity. The salt is still a better agent at reducing water activity than drying, though. Over the next day, I’m going to rehydrate the cod and use it in a recipe. This has me thinking of lutefisk, which starts out as food, is turned into poison, and then back into food. No lye has been used in the manufacture of this fish – we’ll see how it turns out.
So the salt cod sat overnight in the fridge with salt pressed loosely
to its surface with cheesecloth. Overnight, the fish took on a stiffer texture, but nothing like the translucent stiffness I see when I cure salmon (see pic. to the right – very little has changed visually from the salting). Though noticeably harder, the fish still felt too “soft” to have really taken on lots of salt. Most of the salt was gone, however, although some flakes clung to the cheesecloth, having refused to melt into the fish. Note that this was the exception, with large sections of the fish showing no salt left at all. Underneath, the salt had actually drained some water out of the fish, which sat in a small puddle underneath the samples.
When I tested the water activity, the soft texture showed itself to be an illusion. The water activity was 0.791, already in the “safe” range for pathogenic bacteria, and much lower than the 0.99 reading for fresh cod. Salt again showes its power to penetrate into tissue like fish at high rates of speed. The next step is to watch the fish as it dries in the fridge for another 4-7 days. Fridge humidity is very low, and Ruhlman says the fish will be stiff when done, so I still expect it to lose a lot more water during the drying phase. Water activity readings will detail the progress of this process.
The world would likely be a different place without salt cod. A few sentences in Ruhlman’s book got me wondering about the history of this fish – how the Vikings learned to dry it, but the Basques learned to salt it so it wou
ld last even longer. Wanting to learn more, I stumbled on an excerpt from Kurlansky’s book “Cod” and ended up fascinated by the subject, and wanting to try my hand at making salt cod.
Turns out, this is the simplest recipe in “Charcuterie” requiring only salt and cod. I dredged the fish in salt, wrapped in cheesecloth, and put in the fridge per the instructions. One aspect of the process I’ll be watching is how much the water activity drops after the salt phase, and how much it changes as it dries in the fridge for 4-7 days. Drying in the fridge reminds me of dry-aging beef, a practice that I’ve used quite a bit, but tends to make food safety people nervous.
One puzzling aspect of this recipe: after going to the trouble of taking the water out of the fish, you have to put it all back in if you want to eat it. Seems a little counterproductive, but I’ll go with it.
Water activity is a geeky concept known mostly to specialists in the field of food safety/quality. Little wonder, then, that a Time article entitled “Food that Lasts Forever” (subscription) came tantalizingly close to mentioning water activity, but failed to do so. Not that we’re bitter. It actually makes sense to avoid the topic in a light piece meant to draw the reader in, since explaining the concept of water activity could take the article down a rabbit hole.
Still, many of the items that show up as long-lasting owe their staying power to water activity. Exhibit A: the “indestructible” sandwich – a bread envelope stuffed with barbecue chicken or pepperoni. These show up in MRE’s used by the US Military, but aren’t really that new. They first garnered attention in 2002 in a news piece that actually does mention water activity. The concept is simple: the bread and the filling must both be formulated at the same water activity, or moisture will move between the two, harming the product. These sandwiches are said to last for three years.
The Time article does focus on a technology that is rather new: using high pressure instead of temperature to kill bacteria. This method tends to result in food that tastes, looks, and feels fresher. Most of these types of foods are high moisture, though, so water activity isn’t much of a factor.
Water activity does have a role to play in shelf life determination for intermediate moisture foods. Most of the reactions that degrade food products like potato chips, crackers, beef jerky, and protein bars are affected by water activity. Sometimes even a small change in water activity can cause rates of degradation to double or triple. This effect is one we are researching at Decagon, so we’ll share more information as it becomes available.
Bacon, pork belly that has been salt cured before cooking, is an American tradition and thus mustn’t be overlooked in our cured meat testing.
To start, I trimmed the pork belly (which came from a local pig we had butchered) and coated it with a salt rub. Different seasonings can be used, but I chose the sweet option with salt, nitrites, and brown sugar. The salt rubbed pork belly was refrigerated for 9 days, then rinsed of the rub and smoked to 170 degrees F. (The recipe called for smoking to 150, but I left it in the smoker a little too long. Fortunately the over cooking didn’t seem to effect the quality of the bacon.)
The picture above shows the bacon, fresh out of the smoker. The smoky aroma was intense, and the meat melted in you mouth – the fatty portions of the bacon were almost buttery and smoky but laced with rich flavors of the meat. This would make an incredible roast.
I was expecting more of the salt to come through, but the meat was surprisingly lacking in salt flavor – it was delicious but not what I expected for bacon. I removed the blackened outer layer from the bacon and left it in the fridge for a couple of days before slicing it.
The pictures to the right depict the sliced bacon before and after baking it in the small toaster oven we have hear at work.
Then it was time for the taste test. In an attempt to compare the homemade bacon with bacon from the store that I thought might be similar, I purchased two products. Wanting to get another whole meat – non sliced bacon that would look similar to the home made, I picked up a salt pork – Hormel brand – in a solid block. Then I sliced and baked it in a similar manor to our bacon. I also purchased a standard thick cut smoked bacon from the local grocery store. It’s slices were similar in thickness to ours and actually looked more like our bacon than the salt pork did.
Below is a picture of the three types of bacon on the plates during taste testing. The water activities of each, taken before cooking them (but after smoking) were as follows…
Salt Pork – 0.85aw, Homemade Bacon – 0.97aw, and Store Bought Bacon – 0.96aw
The plate marked “A” in the picture holds the salt pork, “B” is the home made bacon, and “C” is the store bought smoked bacon. The three types of bacon were tasted by 23 of my fellow employees and ranked on a scale of 1 to 10 based on how well they liked it over all. 1 meaning they hated it, and 10 meaning they loved it.
The results of the testing were rather telling, I thought, and were very polarized. Out of 23 tasters, 11 chose the salt pork as their favorite. Their comments indicated a great like for the saltiness. 12 chose the homemade smoked bacon as there favorite. Comments included good flavor, smokey, melts in your mouth, and soft. Only 3 tasters chose the store bought smoked bacon as their favorite. Note that in some cases the tasters had tied high scores, resulting in 26 favorites even though there were only 23 tasters. Over all, the home made bacon was most favored, but barely.
When looking at average scores, a very different picture is painted. They are as follows…
A (Salt Pork) = 7.04
B (Homemade) = 6.61
C (Store Bough Bacon) = 6.91
So, as you can see, our most favored bacon received the lowest score over all. Why, because those who didn’t like the homemade really didn’t like it. If you look at the least favorite, the salt pork and homemade bacon tied with 9 tasters each giving them their lowest score. But, 6 of the 9 tasters whose least favorite was the homemade bacon gave scores of 3 or lower, pulling down the average. The lowest score of the salt pork was 4, so the low scores of the salt pork didn’t effect the average as much. 5 tasters liked the store bought bacon least.
For some, it appears, salt is the expected flavor in bacon. Others like the flavors of the meat not to be compromised or hidden by the salt. My personal, and biased, preference was for the homemade bacon. I would agree, though, that it could have used more salt. The only thing I would change the next time around is adding more salt rub to the pork belly during the salting stage, but not too much. A little more salt would have likely pulled the water activity down to about the same as the store bought bacon. I loved the tender texture of the homemade bacon and the rich flavors of the meat infused with hickory smoke.