The response to an earlier post about ice cream formulas was such that it seemed a no-brainer to offer the same for sorbet. Because there are fewer variables, sorbet recipes are generally easier to formulate; it could be argued, however, that miscalculations of just a handful of ingredients in sorbet are less forgiving than with ice cream. We've all had examples that were either too soft or too hard, icy from lack of care in storage or gummy due to overuse of stabilizers.
I began using and understanding these formulas in sorbet well before I learned to apply them to ice cream, mostly due to having access to the technical information supplied by the major fruit puree manufacturers. Using these products became a necessity for volume and consistency. Their purees vary, but both Boiron and Ravifruit have published sorbet tables and charts over the years; these formulas alone don't delve deeply into the scientific hows and whys, but studying them can reveal some insight.
The first thing one would notice is the final percentage of solids, or dry matter in the mix- again, for our purposes here, everything that is not water. Lower than that for ice creams (37-42%), the ideal target for sorbets lies right around 33% (technically, if you were to not count the fat in ice cream, the target percentage is the same). So in theory, if we were to spin a mixture of 2 parts water to 1 part sugar, we'd come out with a perfectly textured sorbet. But the fruit bases we use to make a sorbet also contain water, dry matter, and sugars, not to mention their own balance of sweetness and acidity. We can engineer the final product further by concerning ourselves with overrun, conservation, and use of stabilizers.
So before we can fine tune a recipe, we must begin with the fruit. The puree manufacturers usually offer such information as the brix level of their fruits, or as I have, you can begin to assemble and reference your own data on ingredients, which can be helpful far beyond the world of ice cream and sorbet. Olivier Bajard, in his frozen dessert course, also offers general guidelines on the amounts and percentages of any given fruit in a mix, a determination based on flavor, solid content, and acidity/sweetness. For example, according to his formula, a lemon sorbet would be comprised of about 25% juice, while the raspberry puree in its sorbet would account for 50% or more of the total.
Let's make raspberry sorbet, shall we? To start, we need a final yield of syrup plus base puree, which we'll arbitrarily call 1000g. We continue with the knowledge that raspberry puree contains about 85% water, leaving 15% in solids, and that we're shooting for 50% fruit in the total yield. Before we can plug in our water and sugar variables, we need to establish the fixed percentages of our other ingredients. Apart from balancing the overall sweetness, alternative sugars like trimoline and glucose can also aid in texture. Trimoline can usually comprise 1-5% of the total mix, while glucose (which we will use in powder form) is often used in a range between 5-10%. Dry milk can also benefit sorbets (dosed at 2-3%), but I typically only use them in citrus sorbets, which we can discuss another time. Finally, we can choose to employ a stabilizer, which will make up a tiny .2 to .4%. At this point, our recipe is beginning to take shape.
Next we need to find out how much of our total solid content (33% or 333g) we have thus far. Our fruit brings 75g. The solid content of trimoline (we'll use 2%, or 20g) will come to about 16g. Our glucose powder (5%, or 50g of the total) will add 48g in solids. Remember, we're isolating the solids in these ingredients; trimoline is 22% water, and even dry glucose has 3% humidity. On to the stabilizer (.2%), which will contribute 2g to our total. Added together, we come to 141g solids content. Subtracting that number from our target, we determine a need for 192g of solids from added sugar (or sucrose); the humidity of sucrose usually hovers slightly around either side of 1%, so we'll simply round up to a measurement of 200g. Subtracting our new solids total from our yield, we are left with the added water, which comes in at 228g.
Before we draft our final recipe, there is one more quick calculation to be made when using a commercial fruit puree. These purees have sugar added, which is most often labeled as 10%. To adjust our recipe taking this added sugar into account, we need to plug in this equation: weight of puree multiplied by 11.11 then divided by 100. We add this figure (55g) to our measurement of fruit, while subtracting it form our sucrose. Now our recipe will call for 555g of puree and 145g of added sucrose.
Finally, as we would all prefer to construct our recipes on an even 1000g package of puree, multiplying each line by 1.8 will give us our tidy recipe (a couple of measurements rounded slightly up or down), with a new total yield of 1800g.
Download: Raspberry Sorbet-Workbook 28.1.09
As with all recipes, these are mere guidelines; I still tweak and adjust things to suit my needs and I have yet to apply this kind of formula to every single ice cream or sorbet in my repertoire. Again, it's simply the understanding of how and why ingredients function that is most important!
