A casual observer might say I've become a little too preoccupied with milk, whether it be isolating its solids or its percentage in an ice cream base. Two other pressing issues led me to begin investigating the calcium content of various other ingredients. One, of course, relates to last week's post on pectin. The other goes back a few months to a conversation I had with Chad, about alginate-calcium spheres and the alternative techniques that mimic the effect. We had both recently played around with delicate yogurt 'orbs', but without the boost of any added calcium (usually calcium lactate gluconate). It seemed obvious that since most of us have concentrated calcium at hand in the form of milk powder, wouldn't that work too? He hadn't tried it either, but sent along a graph listing the natural calcium content of a dozen or so common foods. If anything, it inspired me to flesh that list out a bit.
The nutrition labels on virtually all packaged foods, I discovered, don't really offer much useful information. Calcium is listed in terms of daily value, not actual content. Luckily I stumbled on what is likely the best single document for such figures, the data logged by the USDA on over a thousand fresh or processed foods. This list is a behemoth, and it requires sifting through a lot of commercial products to uncover some basic ingredients. But once we do get a better handle on such numbers, we then have to figure out exactly how it reacts with other ingredients and in what concentrations we must apply them to acheive our desired effects.
Download: USDA National Nutrient Database-Calcium
But let's bring pectin back into the fold. Last time, I started with the familiar and basic, apple or high methoxyl pectin, which gels in high sugar/low PH environments with the application of heat. I don't know that it's worth going into the chemical nature of their differences (not that I'd be the one to do it anyway), but suffice it to say, low methoxyl pectin sets in the presence of calcium. Such a difference comes into play in the manufacture of, let's say, low sugar jams. I've worked with LM pectin (sometimes referred to as NH) off and on over the years, but with little understanding of the chemistry or how to determine correct proprtions or the results they would then give. Although I've used it in glazes (where we take advantage of its thermo reversible properties) and even tuiles and nougatine-like mixtures, a lot more attention is given to its HM cousin, at least in pastry circles.
When looking for more than a brief overview of things like the one I just gave, I often find myself leaving culinary texts behind in favor of technical papers on the subject. As I mentioned to a food scientist friend the other day, these things aren't exactly written in kitchen language; it can be frustrating parsing through all the chemistry-speak and diagrams of molecule chains just to extract a few useful nuggets of information. But it can be worth the effort, and I often feel energized and excited by such discovery.
Rather than chase more advanced applications, I wanted to first nail down some parameters. I've seen one or two LM pectin-based versions of conventional pate de fruit, and every once in a while I'll give them a go. But the results often vary wildly, and I had no idea how the formula was structured, or how it might need to be altered when plugging in other ingredients. Even in the technical literature, perecntages of pectin and calcium are given as wide variables. My goal was to establish those ratios in a low-sugar pate de fruit by using that most common source of calcium, milk.
I pieced together some general information to set out on my first attempt: LM pectin is generally dosed in a range of 0.5-1.5%, 2 to 3g per cup of liquid makes up the middle and will give a sufficient gel. When it comes to the calcium needed, the proportion can range anywhere from 10 to 40 milligrams per gram of LM pectin. Again, that's a big window. Knowing that I'm looking for a fairly firm set, I pushed those numbers to the high end of the scale.
Download Blood Orange Pate de Fruit (Dry Milk)-Workbook 10.2.09
I decided to go with a full 1.5% of pectin, mixed with ten times its weight in granulated sugar. In determining the measurement of milk powder, I guessed as to how much I might want for flavor, and then went back to see if I was in the proper range. As 10g of milk powder contains 123mg of calcium, starting with that measurment would put me within the acceptable range of 30mg per 1g pectin. I have discovered, by accident, that you can get a premature set by incorporating the calcium too soon, so I allowed the pectin to dissolve fully before adding my milk powder. The resulting texure and flavor was near perfect; the only problem was a slight graininess as some of the milk powder didn't get a chance to fully hydrate. This tells me that next time, I either have to grind it to a finer consistency, or to perhaps prepare a solution of it. But what if I were to add just plain milk?
Download Blood Orange Pate de Fruit (Skim Milk)-Workbook 10.2.09
Using the same structure as the first recipe, I plugged in an amount of skim milk that I thought might provide the necessary calcium without diluting the blood orange too much. Substituting 75g of milk gave me a total of 94mg of calcium (as opposed to 123mg from the dry milk) and a slightly lower proportion of 25mg per 1g pectin. It didn't seem too far off, and besides, I might be able to determine a tighter range, and if this was too low, I'd certainly find out. For sure, the fluidity of the milk makes it much easier to incorporate, and though the color was not as intense, I was happy with the flavor and texture, which was softer, but only slightly so.
In the end, now have a much cleaner, more vibrant facsimile of a pate de fruit. I'll let you do the math, but remember that the conventional version made with HM pectin has a sugar concentration as high as 80%. Here, it's a fraction of that. While I didn't take into account any naturally occuring calcium in the blood orange, I think this will become a good standard to apply to an infinite number of liquids, and a starting point in exploring new applications...