A Pinch of Culinary Science

by Anu Inkeri Hopia

  Stock cooking commented

  ^The figure shows the steps of cooking stock together with recommendations and comments for each step. Based on the studies by Snitkjær Bailey (2010)

  It is an interesting reflection for us that, just as in the case of cooking eggs in water, this research had not been done earlier. After all, it is about a practice that is carried out in thousands of restaurants and homes across the world every day, and the research provides knowledge that may change those practices in fundamental ways. If only these stock-makers had all been aware of it. Surely quality science communication may be an important activity.

  Making a red wine sauce. There are at least two basic ways to make a red wine stock.

  1. You reduce a mixture of wine and chopped onions. Add meat stock prepared beforehand and continue reducing until you are satisfied.

  2. Add red wine to your broth after the straining step and let them reduce together from the start.

  If you are running a restaurant, the first approach may be convenient since you can have a basic meat stock that is used in various ways – with or without wine. If you make stock for a single meal at home, you could choose the one you find most convenient.

  Pia Snitkjær Bailey wanted to examine how red wines with different flavor characteristics affected the flavor of the stock. And since tannins react with proteins upon heating, she was also interested in studying how red wines with different tannin levels affected the meat proteins. She analyzed ten different stock samples based on beef stock combined with two different wines chosen for their different tannin levels: a Cabernet Sauvignon (high in tannins) and a Zinfandel (low in tannins).

  She found that the aroma of the red wine was to a large degree lost in the reduction step. This is quite self-evident because volatile substances, which are those reaching our nose, evaporate easily. After all, if they didn’t evaporate we wouldn’t be able to smell them. The advice is, therefore, that wine for cooking should not be chosen based on its aroma, but rather on its mouthfeel and taste, such as sweetness, acidity, and astringency (the drying sensation in the mouth imparted by tannins). So, if you want to make an effort choosing a wine for your sauce, hold your nose while evaluating it. This would probably require that you are an experienced taster and sauce maker, however. Consequently, the most expensive wines are most likely wasted in a sauce.

  Tannins from red wine and proteins from meat stock react to precipitate, complex, insoluble substances. If the meat stock and wine are reduced separately and thereafter combined, the result might therefore be a slightly grainy/sandy mouthfeel. Snitkjær Bailey also reported that this procedure led to a more astringent and perhaps bitter sauce. Therefore, reducing the meat stock and wine together gives a less astringent sauce than that made by reducing stock and wine separately. Not surprisingly, this effect is more pronounced when using a wine rich in tannins. If you still choose to reduce stock and wine separately, you may combine them and reduce for 30–45 minutes and finish it off by a filtration to avoid the risk of a slight grainy and astringent mouthfeel.

  The components of a red wine stock

  ^Before reduction, red wine and broth is mostly water. After several hours’ reduction, the water content is reduced from the original 90% to 25%. At the same time, the concentration of non-volatile compounds such as sugars, acids, and amino acids increases markedly. In addition, numerous new substances are produced as result of chemical reactions.

  A fine wine experiment Red wine sauce, similar to, for example, puff pastry and some other products, is a laborious ingredient where the industrially prepared alternatives may be competitive for the occasions where you don’t have time to carry out all the time-consuming steps. Although maybe a disappearing skill in home kitchens, we were inspired by Snitkjær Bailey’s work and decided to have a closer look at what happens in the pan during the reduction step in one of our food workshops. We were curious to see with our own eyes, and taste with our own palates, which roles the red wine could play in the sauce.

  The point of departure was a basic recipe for red wine sauce: take half a liter of good meat stock and half a bottle of red wine and reduce it down to one deciliter. The procedure is not ideal according to Snitkjær Bailey’s research, but the approach would give us two stocks that would be directly comparable in terms of reduction time. To which degree would the characteristics of the wine affect the flavor of the final product? Would minor differences in acidity, sweetness and mouthfeel in the wines show up in stocks cooked for several hours? If so, how are the differences experienced?

  We prepared three different red wine stocks with three different red wines with increasing body, aroma intensity, and amount of dry extract: a light Beaujolais, a medium-bodied Rioja, and a full-bodied Argentinian Malbec. The differences in acidity, sweetness, and body were clear but not dramatic. For example, the acidity varied from moderate (5.0 g/l total acids in the Beaujolais) to high (5.7 g/l total acids in the Malbec). The dry extract is the amount of solids left when all water is evaporated and gives indications towards the quality and body of the wine. In these wines, this parameter varied between 24 g/l in the light-bodied Beaujolais to 35 g/l in the full-bodied Malbec. The Rioja was in between these two extremes both in acidity and dry extract content. Would these differences reflect in the stock when tasted by the panel consisting of workshop participants?

  The sauces were cooked, coded, and served as blind samples for the tasting panel. The differences in sauces were obvious already to the naked eye. The Beaujolais came out lightest, the Malbec darkest. The participants were asked to rank the three sauces in order of increased body, bitterness, acidity, sweetness, and aroma intensity. The values were summarized and displayed as a radar diagram often used in sensory science to visualize how the different characteristics were evaluated by the panelists.

  Blind tasting of three red wine stocks

  ^Results of red wine stock blind tasting (panel of 12 participants): The radar diagram shows that the three wines gave stocks with very different sensory characteristics.

  The differences in the three red wine sauces were quite obvious, and there was no question about the important role of wine in cooking (see diagram). The full-bodied Malbec gave, except for aroma intensity, a stock with more of everything: body, acidity, sweetness, and bitterness. The Rioja gave a stock that was fairly similar to the one with the lightest of the wines, but somewhat more body and clearly higher aroma intensity. The result was quite unambiguous: the wine makes the sauce!

  Naturally, we also asked the question that most choose to ask right away: which stock would you prefer? Liking is always a matter of personal taste and more or less up for debate. In this case, nine out of 12 participants considered the stock made with the full-bodied Malbec as the best, the three remaining preferring the Rioja-based stock. However, this time, the liking-issue raised some harmonious debate among the participants. Everyone agreed that a sauce should match the main ingredient of the dish and that it cannot be evaluated alone. Every dish requires its own tailored sauce.

  15

  Salt Shapes the Pasta

  How does a non-Italian know when the pasta is ready? S/he throws it on the wall and if the pasta sticks to the wall, it is ready. More often than not, jokes contain a kernel of truth. This one describes two important things about pasta: 1) Italians love pasta and have a passionate relation to how to cook it properly; 2) pasta is considered overcooked when it becomes gluey and sticks to the plate, the wall, ceiling, and so forth.

  Italian recipes for cooking pasta usually put a great emphasis on achieving the ideal texture. The exactly right al dente structure, literally “for the teeth,” means that the pasta should have a certain firmness or resistance to the bite, but without being hard or brittle. In the case of dry pasta, the al dente structure is said to be reached the moment that the hard and white center in pasta is no longer visible. Careful monitoring and testing of the softness of pasta using one’s teeth during cooking is a common advice to ensure a good stru
cture. Another advice is to stop the cooking slightly before the pasta reaches the desired structure, as the cooking continues for a short while after the pasta has been strained. For an Italian, cooking pasta can be a play with seconds, whereas many others would only count minutes. No wonder they make jokes about the pasta-ignorant people from other countries.

  Pasta = starch trapped in a network of proteins. The most important chemical substances in pasta are water, starch, and gluten proteins—the very same elements that make up a good bread. Both pasta and bread are built up by a strong and elastic gluten network. Microscopic starch granules in the flour swell as they absorb water during heating and get trapped in the gluten network.

  Overcooked pasta becomes sticky because the starch granules absorb so much water that they burst open, leaking out long starch molecules that form an adhesive, sticky layer that makes individual pasta strands or pieces stick to each other, and, for that sake, to the wall. In a properly cooked pasta, the starch granules are swollen and soft, but still intact, with the starch molecules in place inside the swollen granules. Gluten does a good job of keeping the starch in place, inside the pasta, rather than letting it escape and float around in the water as a thickening agent.

  Gluten is a strong network of wheat proteins permeating the entire dough to make it both plastic and elastic. This network gives a dough that can change shape upon pressure or stretching (plastic), but can still return to its original shape when the pressure of stretching is relieved (elastic). To build such a network, we need a good amount of gluten-forming proteins. Untouched, these proteins are globular in shape, like a ball of woolen thread twisted and folded and swimming in the wet dough slurry of flour and water. In a watery environment, part of these proteins (glutenins) unfold and and entangle to form a web-like network that ultimately permeates the entire dough. The web-forming reactions speed up during kneading, surely noticed by any baker. The second type of proteins (gliadins) keep their original ball-like shape but bind lightly to the glutenin network. Solubilized in water, these small balls increase the viscosity of the dough, and they act like plasticizers, tiny ball bearings, in the network, thus enhancing both the plastic and elastic nature of the dough. A dough with a strong gluten network will stretch when you pull it but return to its original shape once you release it. Just imagine the wonderful dough in the hands of an experienced pizza maker, at the same time malleable like a play dough and elastic like a rubber band. The gluten network is this rubber band; actually, it is thousands and thousands of microscopic rubber bands bound to each other as a three-dimensional network throughout the dough.

  Gelatinization of wheat starch in pasta

  ^Starch granules in pasta swell in hot water to give a gel, kept in place by the gluten network. The chef’s challenge is to stop the cooking at the moment where the granules in the middle have swollen just enough, while those at the surface are still intact. Otherwise, the pasta will be too hard in the center (undercooked) or starch molecules leak out at the surface to form a gluey layer.

  What about salt in the cooking water? The role of salt seems to be important in Italian pasta recipes especially, as they seem to contain significantly more salt as compared to, for example, most Nordic pasta cooking recipes. The Italian rule of thumb is 100:10:1, where the numbers indicate the relative amount of ingredients: 100 grams pasta requires 10 grams salt in 1 liter of water. In a world where we are commonly advised to cut our salt intake, this sounds like an awful lot. Indeed, many recipes seem to manage with significantly less salt, and ratios as low as 5 grams of salt for 2 liters of water are not uncommon. Compared to the Italian rule of thumb, 100:10:1, we have seen recipes asking for as little as 100:2.5:1.

  Why are these recommendations so different? Looking through literature and various cooking forums revealed different sorts of reasoning behind the role of salt in the pasta cooking water. A common reason is obviously taste, and salt is claimed to be absorbed by the pasta. This sounds logical as dry pasta absorbs significant amounts of cooking liquid, and that other flavorings should tag along with the water into the pasta. Another explanation is related to the structure. Salt is said to help pasta remain firm and less sticky during cooking. This is usually explained by the fact that salt is known to retard the gelatinization of starch, the phenomenon where microscopic starch granules from the flour absorb water. Thus, pasta cooked in salty water does not so easily become sticky. Third, salt is known to promote formation of the gluten network. Salt ions interact with the charged parts of the glutenin molecules, to decrease the repulsive forces between glutenin molecules. This allows them to come closer to each other and thus react more easily to give a strong gluten network.

  In summary, salt might affect the structure in pasta either to strengthen the gluten network, to prevent the starch becoming gluey, or both. However, in many discussion forums, there are many claims about salt having no effect on the structure of pasta whatsoever, and we would assume that at least some of these should be based on experience. It seems that we have a nice mixture of contradictory claims, which clearly asks for an experiment, and a suitable topic for a food workshop. We decided to let the following “double research question” guide our inquiry: does salt have a firming effect on pasta structure as claimed or is the role of salt, and thus difference in recipes, only a matter of taste?

  The pasta experiment. We invited participants to a workshop and cooked pasta in four pans with two different concentrations of salt. Two pans had salt content based on the Italian recommendation 10g/l and the other two contained cooking water with a lower salt content, namely 2.5 g/l. In order to expand the experiment we used two different types of pasta: one made of durum wheat traditionally used for pasta and another made of regular wheat. These two wheat varieties should expectedly give different structures to the cooked pasta. While normal wheat flour contains approximately 12% protein, durum wheat has a protein content of around 15%. Also, the starch is slightly different between these two types of wheat. The starch in durum wheat has a lower gelatinization temperature, and it also binds more water than the starch in common wheat. So, this could potentially give us two answers from one experiment: we might get a clue of both the effect of salt and the effect of wheat variety on the structure of cooked pasta. The four parallels were:

  – Regular wheat pasta cooked in low salt (2.5 g/l) water for 3 minutes.

  – Durum wheat pasta cooked in low salt (2.5 g/l) water for 3 minutes.

  – Regular wheat pasta cooked in high salt (10 g/l) water for 3 minutes.

  – Durum wheat pasta cooked in high salt (10 g/l) water for 3 minutes.

  The pastas were freshly made at a small pasta factory in Helsinki based on a recipe of 70% flour, 20% eggs and 10% water. The pasta dough did not contain any salt to ensure that the only salt experienced by the pasta should come from the cooking water.

  The four parallels were coded for blind tasting and served with good tomato sauce made by chef Tatu. The 16 participants of the experiment were asked to evaluate which parallels were the softest and the firmest of the four alternatives. We also asked them to state which they would prefer most and shortly explain their choice.

  Indeed, the results convinced us that both the salt level in the cooking water and the wheat variety used are important parameters in the quest for a firm structure in the ready-cooked pasta. Ten out of the 16 participants on this evening evaluated the durum pasta cooked in high-salt water to be the firmest, and nine considered the regular wheat pasta cooked in low-salt water to be softest. The pasta made of regular wheat flour cooked in high-salt water also got a few votes as the firmest, indicating the salt contributes to a firmer pasta even if the flour is not high in protein. The important role of high protein flour became obvious as neither of the durum pastas got any “softest pasta” votes.

  Blind tasting of pasta

  ^The illustration summarizes the result from the pasta experiment, percent of votes. The two leftmost columns/bars show that both type of flour and amount of s
alt affect the firmness of the pasta, but that type of flour most likely has a greater effect of the two. The two rightmost columns show that personal taste preferences vary considerably.

  Within pair comparisons of wheat variety and salt level also gave an indication of the importance of these two parameters. Of the two durum wheat pastas, the high-salt version received more votes as the firmest (green vs. blue bar), and within the regular wheat versions only the high-salt version received votes as firmest (purple vs. red bar). When comparing the two durum wheat pastas on the one side (green and blue) with the regular wheat versions (purple and red) on the other, the former dominate the votes for firmest, while the latter are the only ones receiving votes for being softest, clearly showing that the wheat variety is important. But which parameter is the most important; the amount of salt or wheat variety? If we compare the durum wheat pasta in low salt (blue) with regular wheat pasta in high salt (purple), we get some sort of measure of this. Both received votes for being firmest, but of the two, only the high-salt regular pasta received votes for being the softest of all. With great caution, we could say that the nature of the wheat has a somewhat stronger effect on the texture than the amount of salt in the cooking water. The salt content obviously affected the taste of pasta, so the high-salt versions were easy to identify. From an experimental perspective, this may be source of error because the tasting was not entirely blind. Some panelists might have been affected by their preconceptions, conscious or unconscious. The evaluation of wheat variety was hence more unbiased because the two high-salt and the two low-salt parallels were compared internally.