A Pinch of Culinary Science

by Anu Inkeri Hopia

  Chef Tatu made two identical portions of fish stock used for steaming two portions of mussels, the only thing different being the acidity during cooking. Both stocks ended up with the same amount of citric acid, but in one parallel the acid was added before cooking the mussels, while in the other, the mussels were cooked and the acid was added afterwards. Thus, both portions had the same amount of acid when served, but only one portion of the mussels had actually experienced acidic conditions during cooking. This way, we reckoned, the panelists would not perceive any taste difference in terms of acidity, and the main difference would be any changes occurring in the mussels.

  Steamed mussels

  Ingredients per portion

  50 g olive oil

  150 g shallot onions, finely chopped

  36 g garlic, thinly sliced

  30 g parsley, chopped

  1 l good fish stock

  2.5 kg mussels

  2.5 g citric acid

  Procedure

  The shallots and garlic were sautéed in oil and the fish stock was added. Citric acid was added to one of the portions. The two portions of mussels were steamed in their respective stocks for 6 minutes, after which citric acid was added to the second portion. Parsley was added; the two portions were given codes for blind tasting and served.

  The workshop participants were asked to rate the two portions in terms of tenderness, chewiness, acidity, and finally, which they would prefer. While we summarized the results, the panelists were allowed to enjoy the rest of the mussels together with fresh bread and aïoli. After all, it is no bad thing to keep your taste panelists happy!

  The difference between the two batches of mussels was surprisingly clear. Two out of three considered the mussels cooked without acid to be more tender. The differences in chewiness or tartness were less clear cut, but the results still pointed toward the same conclusion: cooking in acidic medium gave both a less tender and chewier texture. The more tender mussels were considered more pleasant by 2/3 of the participants.

  Blind tasting of mussels

  ^The diagram shows how the panel of 2g participants judged the mussels. One portion was steamed with citric acid, and the other had citric acid added after steaming.

  Which recommendations should we give based on this experiment? At the very least, if you want to cook your mussels in white wine, you might want to pick a wine with moderate acidity. But beer or good fish stock may also be good alternatives.

  Acids in cooking. Protein chemistry plays a key role when it comes to structural changes of food during cooking. When protein-rich foods such as fish, meat, or egg are exposed to heat, the natural structure of proteins is disturbed. The protein molecules denature and eventually coagulate, resulting in changes such as firmer structure and changes in appearance. In addition to heat, there are at least three other strategies to changing the protein structure in food: we can use acids to “cook” protein-rich foods. An example is the Peruvian dish ceviche, where the cook sprinkles lime juice over raw fish cut in small pieces, or the Nordic pickled herring, where herring or Baltic herring is “cooked” in vinegar, often with added spices and herbs. The acid in lime juice or vinegar affect the structure of the fish meat: the almost transparent and soft structure turns opaque and takes a firmer “cooked” structure. The second strategy is cooking with ethanol, or, in everyday language, alcohol. In some recipes for carpaccio, which is based on thin slices of raw meat, we are asked to add a dash of brandy or other strong spirit. Doing the same with salmon, and adding some salt and sugar, as well, we get gravlax. The spirit does not only add flavor, but the alcohol also gives a more tender meat because high concentrations of ethanol make proteins denature. The third strategy is described in the chapter on foams, such as when we converted the clear fluid of egg white into an opaque and stiff foam by sheer physical movement of a whisk. The change of appearance from clear to opaque indicates that we have actually “cooked” the egg white proteins by our vigorous whisking, spreading and stretching the egg white protein bundles around the surface of air bubbles.

  Combine any of these treatments and you get new kinds of solid structures because you expose the raw material to more than one treatment. What we observed in our mussel experiment can also be seen when you poach an egg. Recipes for poached eggs recommend a little vinegar in the cooking water. The egg white coagulates faster and you get a characteristic firmer structure on the outer layer of the egg white. Without vinegar you simply get a more classic soft-boiled egg. Thus, playing with acid and combining it with heat or other methods that affect protein structure adds diversity to the culinary structures of everyday food. But be aware that combining such strategies can also result in overcooking your mussels, such as using a too acidic wine or not reducing the heat treatment when combining it with acid.

  Acids can also result in less pleasant surprises when cooking. We experienced this when baking a traditional Finnish spice commonly made for Christmas. The cake batter contains a special mixture of gingerbread spices as well as a significant amount of lingonberries, a tart and somewhat bitter wild berry commonly used in the Nordic countries.

  Spice cake with lingonberries

  Ingredients

  100 g butter or margarine

  2 dl brown sugar

  3 eggs

  2.5 dl flour

  2 tsp baking soda

  1 dl mashed lingonberries

  1–2 tsp cinnamon

  1–2 tsp ginger

  0.5 tsp cloves

  Procedure

  1. Whisk butter/margarine and sugar into a dense foam.

  2. Whisk the eggs into the butter/sugar foam one by one.

  3. Mix baking soda and spices into the flour and fold it gently into the foam.

  4. Add lingonberries and transfer to a 1.25 l springform pan.

  5. Bake at 175°C for 45 minutes or until the cake is ready (poke a knitting needle or wooden cocktail stick into it. If the batter doesn’t cling to the stick, it should be ready).

  The unexpected happened when we, in a hurry, added the ingredients in a different order than instructed by the recipe; the flour and lingonberries changed order. Rather than beating sugar and butter with eggs, adding flour and finally lingonberries, we beat sugar and butter with eggs, added lingonberries, and stirred in the flour at the end. The acidic lingonberries made a significant part of the egg proteins, which were supposed to maintain a foamy and spongy structure, denature already in the cold batter—well before the cake went into the oven. This coagulation should not take place until after the cake is in the oven. The foam is a delicate structure, and the batter must first be allowed to rise (by effect of the leavening agent and water evaporating), and thereafter solidify into a firm but porous cake. But since some of the egg proteins had already coagulated in the batter due to the acids from the berries, there was not much flexible protein network left to form a structure around the bubbles in the foam. The hard work of beating and whisking air into the sugar, butter, and eggs had been in vain. Ready baked, the cake came out as a sad, flat, and crumbly specimen. Damn acids! Luckily the cake was served to a chemist colleague, so one positive side effect of the accident was the pleasure of a discussion about protein chemistry.

  5

  Sausage Engineering

  How many sausage recipes could there be in the world? Bratwurst, chorizo, kiełbasa biała, frankfurter, chipolata, salami, blood sausage, seitan sausage, baloney. The sausage is part of culinary heritages all over the world, and has since prehistoric times been a method to prepare and preserve meat, making use of all parts of the animal. Salted meat, offal, or blood is mixed with spices and perhaps some cereals, stuffed into casings made from various natural materials such as stomach, lungs or intestines of cattle, pigs, or sheep. The resulting neat packages can be dried, smoked, fermented, cooked or a combination of these treatments, to be enjoyed at a later point. Even after new storage techniques were invented such as ice houses, fridges, and freezers, the sausage was not abandoned—perhaps because it is
such a practical technique to deal with meat, and the end result so delicious. On the contrary, the idea of sausage has been carried on and developed further by modern home and professional butchers, and later in large scale by the food industry. And the fact that more and more sausages based on vegetarian protein sources are making their way to the consumers is another sign that the popularity of sausages seems to increase rather than decrease.

  No doubt that the sausage is an important part of the world’s food heritage. For example, in the United States, the National Hot Dog and Sausage Council reported that only during summer, the three-month-long peak hot dog season, 320 million American citizens typically consume 7 billion hot dogs. Around 20 hot dogs per person. Also, Europeans and those in Nordic countries love sausages. The Finns eat approximately 20 kg sausages per capita a year, which is about half a barbeque sausage every single day for every Finn on earth. Although Norwegians are not the winners in this somewhat peculiar sausage consumption competition, they are reported to consume around 115 sausages per capita annually, one sausage every third day. Of course, many are not sausage fans, so if we remove these from the statistics it is obvious that those who eat them have one or two per day, around the year. Consequently, which type of sausages we make or eat is no small issue, and worthy of closer inspection.

  Mixtures of things that do not mix. Substances that make up food come in various forms, or states (phases) of matter: solid, liquid or gas (plus a couple of other, rather rare ones of little relevance to home cooking).

  Food commonly consist of a mixture of substances in various states, and more often than not it is a mixture of substances of rather different natures that do not normally mix. Oil and water are two liquids that will not dissolve into each other but remain separate even after vigorous mixing, returning to separate layers shortly after you stop mixing. To get these two mutually opposing materials to form a fairly stable mixture, an intermediary is required: an emulsifier. The emulsifier does not make the oil dissolve in water, but makes sure they are kept together; we have an emulsion. Emulsifying agents are usually molecules with both water-loving (hydrophilic) and fat-loving (lipophilic) properties in different parts of one and the same molecule. Examples of such emulsifiers are lecithin found in, for example, egg yolks and soybeans, phospholipids that make up the cell membranes of cells, certain proteins and many more.

  What about making your sausages at home? Although most of us let the food industry make our sausages, stuffing one’s own sausages at home has become increasingly popular. It is not particularly difficult and can be done with relatively simple means. All you need is meat (or some plant protein such as seitan), casings and grinding and a stuffing attachment for your kitchen machine. All of it is available from the shelf or fridge in any well-stocked supermarket and a kitchen equipment shop.

  Regardless of type, sausages are all complex mixtures where fat and water form a delicate and mutual relationship. The key ingredients of a typical sausage are meat, fat, and water. Making good sausages, be it in industry or at home, is based on quality raw materials and the building of a stable emulsion where fat droplets are dispersed in a water-based continuous phase (see info box and diagram). In this mixture, the basis is a water-based, protein-rich mixture into which fat is emulsified into oil droplets or solid fat particles. Some sausages have a coarse structure with noticeable bits of meat and fat, such as salami or the Spanish-cured salchichón. However, if we want smooth and juicy sausages, the fat droplets need to be really small in size to give that creamy sensation on the tongue rather than clumps of fat rolling around in the mouth. Furthermore, small fat droplets are better retained in the sausage during cooking, rather than leaking into the pan, taking with it the good flavor and juicy texture into the water. Too little fat will give hard, crumbly and dry sausages. In order to get a juicy and smooth texture it is recommended to use at least 20% fat.

  In sausage mince, the most important emulsifying agents are the meat proteins, with both water soluble and fat-soluble properties. They make sure that the fat particles don’t separate out. In addition to the casings you will at least need meat/protein, fat, salt, and water to make a good sausage. All of these four play their own important roles in achieving a good texture. If one is missing, you will probably fail, or you might struggle convincing others that you have made a sausage. The bulk of the sausage is meat, which provides the important proteins that emulsify the fat particles as well as water. In some recipes the water bound up in the meat is not sufficient, and you are asked to add some additional water. Upon cooking, the proteins coagulate to form a firm but nicely elastic structure in the ready-cooked sausage. Salt helps dissolve some of the proteins in the water which in turn helps the fat becoming evenly dispersed and emulsified in the mass/dough.

  Mayonnaise is an emulsion classic, where small oil droplets are surrounded by lecithin from the egg yolk and evenly distributed in water from lemon juice or vinegar. In that case, the oil is the dispersed phase while the water is the continuous phase, both still being liquid. We have a water-in-oil (w/o) emulsion. Milk and cream are emulsions of the same kind, where either oil droplets or fat particles (depending on the temperature) are dispersed in water. The same applies to butter and margarine, but in those cases water droplets are dispersed in oil or fat: an oil-in-water (o/w) emulsion. Many such mixtures consisting of otherwise non-miscible or difficult-to-solve substance pairs exist (see the diagram). Examples are suspensions (solid particles floating in a liquid), foams (gas bubbles trapped in a solid or liquid) and gels (liquid bound in a solid network). When whisking double cream, three difficult-to-mix materials dance together in an airy whipped cream while the whisk gives the rhythm: air, water, and fat. A general term for such mixtures of immiscible substances is dispersions. Indeed, we should all praise the chef who can organize mutually repellent molecules into a wide range of different structures for our mouth to enjoy!

  But why introduce all these new and foreign words? Well, because they give us a language that allows us to talk about food as general structures, and thereby make sense of the food from a structural perspective. A chef can, for example, use the term “emulsion sauce” as a general term for sauces with certain properties (Béarnaise, Hollandaise and so forth). The language that follows with this is then a tool that helps us in understanding and dealing with them in practice, such as understanding why the sauce occasionally splits, how to keep it stable and so forth. ×

  The structures of foods and other mixed materials

  ^ Diagram with possible dispersions. Both components of a dispersion (the dispersed and continuous phase) can be either gas, liquid, or solid, giving nine possible combinations. The gas mixture in the upper left-hand corner is the only exception, not being a dispersion but one single homogeneous phase. Thus, there exist eight basic dispersions.

  ^ Sausages are dispersions: The most important components are water (blue, continuous phase), fat (yellow, dispersed phase), meat proteins (red) and connective tissue proteins (green). The meat proteins surround the fat and function as an emulsifier. The two types of proteins permeate the mixture and makes a sausage both an emulsion and a gel.

  The Food and Agriculture Organization of United Nations, FAO, have much information on their web sites, including detailed descriptions of what happens during the various steps in sausage making:

  1. During grinding the meat, muscle- and connective tissue fragments are mixed to form a homogeneous mass.

  2. Addition of salt and water causes meat fragments to swell. Furthermore, part of the proteins will dissolve in the salt water to form networks in the liquid—a gel. Other parts of the muscle proteins remain intact and fairly unaffected, floating in the water to form a suspension.

  3. Fat is then added, resulting in an emulsion in which the complex water-meat mixture described above forms the continuous phase and fat taking role as dispersed phase.

  4. During heating the protein molecules go through structural change to coagulate and firm up to form a rig
id network: The soft and pliable sausage mass turns into cooked sausage. The connective tissue fragments mainly consist of the protein collagen with a triple helix structure. Upon heating, this untangles into single strands of gelatin proteins which dissolve in the hot water, eventually to form a gelatin gel when the sausage is later cooled (see figure). The more connective tissue in the meat, the higher more gelatin in the cooked sausage.

  The process gives a product that consists of several states of matter and various structures at the same time, giving the texture and mouthfeel we have learnt to enjoy. A sausage is at the same time an emulsion, a suspension, and a gel. Sometimes there are air bubbles or -pockets in the structure, so foam can also be said to occur in some sausages. Evidently, foods are often not only dispersions, but mixtures of dispersions.

  Sausage on the rocks. In some sausage recipes, especially from old cookbooks, a rather specific and peculiar advice is given. Namely that the water should be added in the form of ice. In more modern recipes this is not usually mentioned, but the advice to keep the ingredients cold during the mixing is not uncommon. Why not just use water from the tap? This is one of those questions that begs for an experiment to be done during one of our scientific food workshops. Why ice? Why cold? Is it simply because the raw materials are easily perishable, or could there be another reason?

  We prepared two batches of basic pork sausages with only four ingredients: meat, fat, salt, and water. The sausage batches were identical except for the water temperature. In one batch water was added as crushed ice while the other batch got room-tempered water. The outcome was then blind tasted by the nine participants who were to evaluate, without mustard or any other condiments, which sausage was most juicy, which had the smoothest texture and which was most salty. Naturally we also asked them to point out which of the two they would prefer. We also collected data of somewhat “harder” nature: the weight of the samples before and after cooking, and the temperature of the sausage mass at the end of mixing.