Gastronomy and Food Science

By Charis M. Galanakis

Gastronomy and Food Science fills the transfer knowledge gap between academia and industry by covering the interrelation of gastronomy and food and culinary science in one integral reference. Coverage of the holistic cuisine, culinary textures with food ingredients, the application of new technologies and gastronomy in shaping a healthy diet, and the recycling of culinary by-products using new is also covered in this important reference. Written for food scientists and technologists, food chemists, and nutritionists, researchers, academics, and professionals working in culinary science, culinary professionals and other food industry personnel, this book is sure to be a welcomed reference.

• Discusses the role of gastronomy and new technologies in shaping healthy diets
• Describes a toolkit to capture diversity and drivers of food choice of a target population and to identify entry points for nutrition interventions
• Presents the experiential value of the Mediterranean diet, elaio-gastronomy, and bioactive food ingredients in culinary science
• Explores gastronomic tourism and the senior foodies market

• Language: English
• Publisher: Academic Press
• Release date: Sep 22, 2020
• ISBN: 9780128204382

Book preview

Israel

Chapter 1

The impact of molecular gastronomy within the food science community

Nicola Caporaso¹,²,    ¹1Department of Agriculture and Food Science, University of Naples Federico II, Naples, Italy,    ²2Department of Food Sciences, School of Biosciences, University of Nottingham, Sutton Bonington, United Kingdom

Abstract

Molecular gastronomy is a novel discipline within the food science area. Its main difference with the traditional food science and technology studies is its focus on kitchen restaurant and home kitchen levels. The collaboration among food scientists (food chemists, food engineers, sensory scientists, etc.) and innovative chefs led to the implementation of a new approach to cooking, often referred to as science-based cooking or molecular cooking. This implies implementing new techniques, tools, or ingredients borrowed from scientific laboratories. In parallel, a closer look at the kitchen led scientists to investigate phenomena or methods that are often ignored by food scientists. The difference between molecular gastronomy and conventional food science has been discussed in this chapter, with some examples related to studies on olive oil, sous-vide cooking, the use of liquid nitrogen and ultrasound treatment, as well as the technique called spherification. The importance of food pairing in haute-cuisine restaurants and for researchers in the area of sensory science has been highlighted, with the presentation of the theoretical/computational approach based on the so-called flavor network and reporting some results based on empirical laboratory-based studies. The negative outcome of these investigations proves the difficulties of simplifying such a complex system, in which odor, taste-active compounds, texture, and other factors interact, and additional complexity is added by cooking itself. Also, the final consumers’ experience depends on other factors such as the dish presentation and their general expectations.

Keywords

Molecular gastronomy; flavor; food pairing; science-based cooking; culinary techniques

1.1 Molecular gastronomy: definition, aims, and development

The word gastronomy indicates a set of techniques and culinary arts to prepare good food, and it is commonly intended, in a broad sense, as the study of the relationship between culture and food. Within the scientific community, a new discipline timidly appeared. It was named molecular gastronomy and differentiates itself from conventional food science or close disciplines for its focus on the phenomena occurring during dish preparation and consumption. Its application brings transformations to the kitchen practices from an empirical discipline to a real science, or in a more rigorous language, it applies the scientific approach to cooking. There is debate among scientists and experts on the definition of molecular gastronomy, which aims to understand the basic principles of food transformation, and its application which is often named molecular cooking or science-based cooking, or sometimes experimental cooking. (1) Molecular gastronomy has been defined as a branch of food science that studies the physical and chemical transformations of food during cooking, and the sensory phenomena or impact on the consumer. It could be considered as a part of food science and technology, because it includes the application of knowledge from this field to improve dishes’ quality, focusing mainly on home cooking or restaurant. (2) The application of molecular gastronomy principles in the restaurant kitchen or home cooking is called molecular cooking, which is, in other words, the application of science in the kitchen.

This and Rutledge (2009) reported that the appearance of molecular gastronomy happened in 1992, in occasion of the celebration of the first international conference on Science and Gastronomy called Molecular and Physical Gastronomy in Erice, Sicily (Italy). The meeting was supposed to be called Science and gastronomy (the name that was kept until 1992), but then the name was changed to appear more scientific to the academic world. The chairs of this meeting thus added the word molecular because it is similar to molecular biology in its wording. The setup of the workshop in Erice was organized mainly by Myhrvold and Smith (2011).

Molecular cooking is different from traditional cooking methods because it uses new tools that were until recently unknown to professional cooks, and they are mostly adaptions from tools used in scientific laboratories, such as rotary evaporators, sintered glass filters, and ultrasound probes. In addition to the tools or techniques, it also uses ingredients that are not common in the kitchen, whereas they are applied in food industries, for example, sodium alginate, calcium lactate, phenols extracted from grape juice, flavors, and ascorbic acid (This, 2011a,b).

For details about the development of molecular gastronomy in several European countries, the reader can refer to the following publications related to several counties: France (This, 2011a,b), Ireland (Valverde et al., 2011), Lebanon (Barbar and This, 2012), United Kingdom (Edwards-Stuart, 2012), Denmark (Risbo et al., 2013), and Spain (García-Segovia et al., 2014).

One of the approaches of molecular gastronomy is the construction of culinary tests, moving from scientific laboratory to the kitchen, in order to verify the so-called culinary myths, which are saying, provers of traditional/conventional culinary knowledge to verify whether it has a sound scientific basis. These are false statements, which are sometimes traditionally found in cookbooks and are common knowledge among professional cooks. The scientist or chef will then verify with a scientific approach the traditional cooking practices and verify if they are based on true assumptions (de Solier, 2010). Another aspect of molecular gastronomy related to the investigation of the so-called kitchen tales has a positive impact on educating chefs and cooking passion.

An example of these tales is the sealing of meat when it is roasted in a pan before cooking it in the oven or boiling/brazing it. It is now well known that this process does not avoid dehydration of the meat. However, the Maillard reaction on the outside part of the meat brings a new flavor to the final product, and therefore it might be desirable for this purpose.

Another goal of this discipline, as described by This and Rutledge (2009), is the creation of a universal scientific language culinary, which involves the translation of recipes from the usual language into the so-called language of science.

This approach led to the analysis of traditional culinary practices, which were synthesized as follows:

1. Definition: The technical parts of a recipe, leading to the production of the dish, consisting of an operating protocol (recipe).

2. Culinary precisions: All the technical details that are not included in the definition; for example, to make a fruit jam, there is the culinary concept that the cooking must go on until a drop of the liquid forms a gel on a cold plate.

3. A third part, which is made of information different from the technique and could be related to the artistic or social dimension (Burke et al., 2016).

Scientists attempted to describe dishes by using formalisms, as they are neither solid nor liquid but complex disperse systems (CDS), thus developing their own scientific language called CDS formalism. However, there is no information in the literature related to whether this formalism has been applied in practice, and so far only one author, the one who proposed this approach, has intensively published on this topic.

de Solier (2010) reported that molecular gastronomy has different aims for scientists, for chefs, or for the user (diner): for the scientist, it is the enlightenment related to the phenomena taking place during cooking, while for the check it is an inspiration to get more creative ideas, finally for the foodie the goal is often the gastronomic education, that is, expanding their knowledge of ingredients, origins, tools, and ways to prepare dishes. In the laboratory, for example, it is used by the scientist to discover chemical and physical reactions that take place and the effect of different culinary practices, while the chef aims to create new innovative dishes. At home, it can be mostly used to entertain foodies and educating consumers on food composition and innovation. In fact, according to This and Rutledge (2009), three components can be summarized for the culinary activity, that is, social, art, and technique, therefore the scientific program of MG has three parts: the technical part of cooking (tools, method, etc.), the artistic component (presentation, appearance, description), and its social component (the enjoyment of the diner, the effect of having a meal with others in a nice environment, etc.).

Cooking as a process is not just science or technology but also the artistic part related to cooking, which needs to be investigated and understood. Creativity has a great importance in the activity of a top-restaurant chef, or to anyone approaching cooking. A dish is not just judged as a technical product, but its success depends also—and sometimes mostly—on the aesthetic and sensory aspects. The aesthetic component of cooking has such a large importance that it has been described as a form of art (Adria et al., 2010).

1.2 Collaboration among scientists and haute-cuisine chefs

Very often, when reporting on the development of molecular gastronomy, the most recurring names of scientists or experts interested in this discipline are Hervé This, Nicholas Kurti, Harold McGee, and Peter Barham (Ivanovic et al., 2011). Hervé This is a French chemist who is often reported as the cofounder of molecular gastronomy as a discipline. He carried out studies on the ideal temperature for cooking eggs (at about 65°C the yolk does not coagulate but the egg white does), smoked salmon treated by electric fields, the creation of the Chocolate Chantilly which is made using baking chocolate and water. Nicholas Kurti was a physicist who applied microwave treatment to make a variation of Baked Alaska, naming it Frozen Florida: the variation consists in the fact that it is cold outside and warm inside (Ivanovic et al., 2011). Harold McGee, an American writer, disseminated food chemistry, history, and cooking, while not being a scientist, wrote several books on cooking, and gathered the reader’s attention about applying science in the kitchen. The physicist Peter Barham published a book entitled The Science of Cooking in collaboration with some chefs, for example, Heston Blumenthal. Spanish chef Ferran Adrià is often pointed out as an innovator in the kitchen, as he applied new methods, tools, and ingredients in his restaurant, for example, using liquid nitrogen, or applied a technique named spherification. Moreover, he also used the so-called air which is a very light foam. He also applied several additives usually applied in the food-processing industry into restaurant preparations, and he created a business on selling these solutions for other chefs. Along with British chef Heston Blumenthal, Adrià is very often associated with molecular gastronomy, although he does not call himself as a molecular gastronomy chef or his cooking style as molecular gastronomy or molecular cooking. In fact, he refers to it as unstructured cuisine. He claimed that as the goal of his cuisine is to create innovative and unexpected contrasts of flavor, temperature, and texture, therefore the chef wants to provoke, surprise, and delight. In other words, the chef Adrià claimed that the ideal diner does not go to elBulli just to eat but to look for a sensory experience (Andrews, 2010).

Heston Blumenthal is an English chef who has so far published books, participated in television series, and collaborated with researchers for experimental tests. He introduced some food-processing tools or methods in restaurant cooking, for example, the sous-vide, which means cooking meat at lower temperature and much longer times compared to usual meat cooking, and some new recipes like the ice cream bacon and eggs. It should be noted, however, that the first introduction of this technique in restaurants was done by the French Georges Pralus in 1974, for foie gras. With television programs, he presented his approach to make the perfect chips by using a triple cooking technique (nothing molecular, by the way). Blumenthal also collaborates with scientists, Peter Barham and the experimental psychologist Charles Spence. He also collaborated with research institutes studying aroma and taste perception, for example, through the collaboration with the Food Sciences Department of the University of Nottingham (United Kingdom) for a PhD project entitled Creating Innovative Flavour and Texture Experiences carried out by Edwards-Stuart (2009).

Other chefs are often reported in review papers and press articles on molecular gastronomy (Ivanovic et al., 2011), for example, Homaro Cantu, for the use of the laser in the kitchen; Grant Achatz, for innovations in dish presentation and for the spray-dried instant pudding; Pierre Gagnaire is a French chef who used jarring juxtapositions of flavors instead of the traditional cooking methods, in order to improve the taste and texture; finally, the Italian chef Massimo Bottura was a pioneer of innovations in restaurant cooking but looking at the traditional recipes and dishes, at his restaurant Osteria Francescana, which has been named for several years among the top restaurants in the world.

1.3 The outcome of scientific research applied at the kitchen restaurant level

In recent years, scientists and chefs have been carrying out fruitful collaborations that can be seen as a clear example of a win–win situation: chefs can get more knowledge about the phenomena that they usually see in the kitchen so that they can add more insight in what they do empirically; scientists can also benefit from this collaboration as they have actual production conditions, can understand the challenges and the needs of the chefs, as well as carry out research directly in a kitchen. This is somehow comparable to a situation in which food scientists want to go beyond the laboratory investigation of something innovative and want to investigate these effects when applying them on a large-scale production plant directly in the food-processing industry.

Other examples of collaboration among scientists and chefs include Heston Blumenthal collaboration with the physicist Peter Barham, Michelin-starred chef Pierre Gagnaire who collaborated with the scientist Hervé This, and the Italian scientist Davide Cassi carried out some research with the chef Ettore Bocchia. This collaboration demonstrates the needs of understanding phenomena that are not only practically and empirically observed by chefs, from a scientific and deeper point of view, but also the need of researchers to face actual kitchen problems, and therefore to apply the scientific approach to cooking. An example of publication about science-based cooking is the book authored by McGee (2004) entitled On science and Cooking. This book has been one of the first to be published on this topic and aimed to help cooks in improving their scientific understanding of food, as well as the public to understand a more scientific approach to cooking.

The collaboration among scientists and top-restaurant chefs has brought to the publication of some scientific papers that have been coauthored by chefs applying molecular gastronomy, for example, Heston Blumenthal or Ferran Adria. Blumenthal is the coauthor of a research on the sensory study and consumer science (Yeomans et al., 2008), as well as a paper on the study of the umami taste in tomato (Oruna-Concha et al., 2007; Dermiki et al., 2013). Studies on how diners react to food that has been named wrongly have been also published, to understand the effect of the expectation of a dish and the actual sensory impact of new foods, for example, in the case of dish named smoked-salmon ice-cream. Dermiki et al. (2013) reported a significant difference in terms of organoleptic impact when tasting the tomato flesh or its inner pulp. It was explained by the different concentration of compounds, such as glutamic acid, that are responsible for the umami taste. Vignoli et al. (2014) presented the culinary concept of the bollito misto non-bollito, by modifying a classical Italian dish to enhance the sensory impact and nutritional properties, basically using low temperatures and sous-vide cooking.

Ferran Adrià coauthored another scientific publication that reports the use of encapsulation (Fu et al., 2014). This research reports the application of encapsulation by using sodium alginate spheres, a technique that is usually referred to as spherification. It is one of the most famous examples of molecular cooking. The paper goes in a detailed description of the free-energy calculations that explain the formation of egg-box structures in the three-dimensional organization, as well as the spontaneous growth of polysaccharide membranes. The technique of spherification was investigated for liquids of different types, in which the charge changes due to the presence of different hydrophilic and hydrophobic compounds.

Chefs can benefit by collaborating with food scientists, because they can take advantage in their cooking of a more systematic knowledge and use an approach that can be defined as science-assisted cooking (Vega and Mercadé-Prieto, 2011). Vega and Mercadé-Prieto (2011) described some experiments aimed to challenge the culinary assertion that slow boiling of eggs is strongly influenced by a critical temperature. The authors reported that for so the so-called 6X°C eggs there is only limited influence of the initial heating temperature, when reducing the isothermal cooking temperature. In other words, the time needed for the initial temperature increase inside the egg is faster than the gelation kinetics of the yolk. Gelation is possible even at lower temperatures the ones defined 6X°C, but obviously longer cooking times are needed. For example, an egg can be cooked at 58°C but 16 hours are necessary. Using higher temperatures, above 67°C, leads to a shorter gelation and remains constant at c. 28 minutes.

These researchers are examples of molecular gastronomy studies, whose results can be applied to cooking at the home level or restaurant cooking level. Regarding this approach, it has been suggested that the target texture could be defined by the chef not empirically but using literature knowledge about texture and viscosity of the main food ingredients and choosing the most appropriate cooking time/temperature profile to obtain the desired texture. This can be done by building an iso-viscosity plot to link the texture with the cooking conditions (Vega and Mercadé-Prieto, 2011).

1.4 Molecular gastronomy and food science

1.4.1 Differences among molecular gastronomy and traditional food science and technology

A comprehensive review describing molecular gastronomy dated 2010 mostly report information that are typically attributed to the traditional topics of food science and technology, such as flavor release and perception, food texture, flavor changes during storage and food processing, matrix interactions and thermodynamic aspects, and food colors (Barham et al., 2010). Also, other important topics in food science and technology were already published decades before the appearance of molecular gastronomy, for example, the quality and characterization of primary ingredients used in food preparations, the impact of animal diet on meat or milk (and cheese) quality (Urbach, 1990; Melton, 1990).

Investigations on meat flavor development, and especially changes due to the cooking process, for example, time or temperature or the way meat is cut, are found in the literature since several years before molecular gastronomy appeared as a separate discipline. Other publications (Cambero et al., 2000; Pereira-Lima et al., 2000) described the change of the chemical composition and its sensory effect due to meat cooking, in particular for its flavor. However, it is difficult to attribute these studies to the field of molecular gastronomy, first because these cooking practices are usually applied at the industrial level, and they are well-known topics within the food science community. Therefore it is somehow difficult to draw a separation line between conventional food science and technology studies and molecular gastronomy.

Meat is often reported as the preferred ingredient for several molecular gastronomy studies, not surprisingly. However, fruits and vegetables are also abundantly investigated in molecular gastronomy studies and in kitchen books, given its versatility and nutritional interest. Some compounds largely found in fruits and vegetables are known to be responsible for positive healthy properties, as well as for other reasons (e.g., giving an appealing color). Pigments in fruits and vegetables, carotenoids, phenolic compounds, and other constituents are well-studied targets in agricultural science and in food science, for example, the changes in the color of green vegetables due to the loss of chlorophyll magnesium ion coordinated to the center of the porphyry ring, resulting in a color change from bright green to light brown. In the kitchen, this color change can be prevented with slightly alkaline water in which to boil the vegetables, for example, with the addition of sodium bicarbonate. Therefore research paper describing means to keep green beans color during cooking seems not so innovative (This, 2011a,b).

Anthocyanins are compounds found in many flowers and fruits and influence the color of the ingredient. However, their color can be subject to modifications when the pH changes. This information can have, consequently, some kitchen applications for some foods or dishes, in which the pH change during cooking (Francis, 1985).

Many conventional cooking methods apply heat, by using different methods, like boiling, steaming, frying, or baking (Barham et al., 2010). Innovative cooking methods often use alternative means to heat the food ingredients, for example, in the case of microwave treatment (an alternating field causes the rotation of the dipoles), or others use alternatives, for example, through high-pressure treatments. Examples of microwave cooking and high-pressure treatments are not to be necessarily pointed out as examples of molecular cooking. In fact, microwave treatment has been introduced to the food industry and for home applications for many decades. About high-pressure treatment, there are still some technological limitations, and there is no current application in restaurant kitchens.

A big part of molecular gastronomy is investigating culinary proverbs or so-called grandmothers stories, which mostly focus on local cuisine and not the large-scale food production (This, 2010). There has been a clear opening toward the use of chemical or pure compounds, in other words food additives, for their use also in the home or restaurant kitchens, to help expanding the range of flavor or texture (This, 2011a). In the home environment and food, there is certain reluctance in the use of these chemicals, but there is a cultural lack in accepting these changes, therefore they are likely to be very slow.

Some examples of scientific cooking can be found only in a limited number of scientific papers, being more diffused in journals for the general public rather than for the scientific community. Some papers are called kitchen challenges, for example, transformation of chlorophyll in food and therefore how to keep the green color in cooked beans (This, 2011b). It is well known that during cooking chlorophylls lose the magnesium ion in the ring porphyry, in a process called pheophytinization. A simple and effective technique avoiding the typical browning of green beans due to boiling is to put them in very cold water after very few minutes of boiling, so that in this way the intense green color is maintained over time. There is an alternative chemical solution to this problem, commonly used in the food industry. It is based on the use of chlorophylls in which the copper ion is replaced by magnesium ion, so that the color can be kept for a much longer time (additives E141i and E141ii). For some foods, for example, green table olives, the addition of this coloring agent is not allowed due to marketing reasons, but there is no safety concern related to their use (Roca et al., 2009). The green bean challenge was reported by This (2010, 2011b), who registered a new additive in which the copper ion is replaced by zinc. However, as demonstrated before, the study of food color is not something new in food science. This makes the assessment of molecular gastronomy as a separate discipline more challenging, as sometimes the topics under investigation belong to food chemistry, food engineer, sensory science, or even to culinary arts or humanistic disciplines. However, it also makes this discipline interesting because of these overlaps and connections with other fields.

One must also consider that the scientific approach and the empirical testing of new flavors, combinations, techniques, not always go together, in fact. Declarations from several top chefs suggest that molecular gastronomy or in general science are used more as inspiration for creativity for the creation of new dishes rather than the end goal of discover kitchen phenomena (Spence and Youssef, 2018). Ferran Adria stated that molecular gastronomy is a marketing operation and not a new cooking style.

On the other side, one should reflect on the fact that natural science relies on observation of natural phenomena in order to understand and describe them, and find a general (universal) law that rules them.

In the book Principles of Modernist Cuisine, it is stated that science and technology are a means to an end, which is the creation of a new culinary invention, rather than the final goal for a chef. Therefore it seems that food science and technology, food chemistry, and biochemistry and food engineering are disciplines borrowed by chefs as valuable sources of information and ideas, but there is no constraint under their point of view in properly or fully using the scientific method.

In fact, chefs often decline the application of the scientific approach but they attribute their creations and innovation to observation and curiosity.

1.4.2 Example on olive oil and (molecular?) gastronomy studies

Olive oil, and especially its most precious category extra virgin olive oil, can be used as an example for the development and use of an ingredient in gastronomy and food science, even regarding the molecular gastronomy movement. Sacchi et al. (2014) in an interesting chapter entitled Extra Virgin Olive Oil: From Composition to Molecular Gastronomy described the use of olive oil in gastronomy and the link between the use and the food chemistry knowledge. The authors reported examples of interaction between food ingredients, such as olive oil used for tuna canning, showing the positive effects of EVOO in protecting tuna during storage. This was explained by the partitioning of the hydrolyzed higher molecular weight phenolic compounds from EVOO. The more hydrophilic phenolic compounds mostly partitioned in the water phase (brine), thus providing an additional protective effect to the tuna flesh. This application is a simple yet interesting way in which food science and food chemistry can be applied to the food industry and culinary applications, also showing why this happens. These results can also be applied in restaurants or home cooking, by using EVOO for marinating food or fish products before cooking, instead of using other fats.

The science behind marinating has been addressed by the same research group, who studied the effect of using EVOO for marinating meat before roasting. A model system was used, with pure phenolic compounds, successfully showing inhibition of mutagenic heterocyclic amine formation. Results like this are not just useful for gastronomy applications to enhance flavor or consumer’s appreciation but in fact to design and produce a final dish that contains the lowest content of potentially harmful compounds, thus protecting consumer’s health.

A similar approach was carried out for frying. Frying is an ancient cooking operation that has several benefits including low cooking times, flavor production, and dramatic change in the texture (e.g., crispness), but it has been under debate especially in Western countries for the consequent fat intake in the fried food. Another issue is related to the formation of acrylamide, a compound showing toxic effects on the nervous system and fertility, and under investigations for its potential cancerogenic effects. Acrylamide is produced in foods submitted to prolonged high temperatures, from potato chips to roasted coffee to peanuts, etc. It is produced by the reaction of the amino acid asparagine with reducing sugars or reactive carbonyls. As frying implies heating at very high temperatures, it is not surprising that fried foods typically contain an appreciable amount of acrylamide. However, the type of oil used for frying makes a difference, as different oils were shown to lead to a lower formation of alka-2,4-dienals in EVOO, explained by the lower content of linolenic and linoleic acids compared to other vegetable oils. During frying, there is an exchange between the food being fried and the frying media, therefore using EVOO for frying also leads to an update of some important minor constituents of the oil such as phenolic compounds.

The interaction between ingredients during cooking has been studied by several authors. Some of the staple ingredients used in the Mediterranean typical cuisine are represented by olive oil and tomato sauce. A study reported a loss of antioxidant activity after cooking tomato sauce (Pernice et al., 2007). The interaction among tomato sauce and olive oil was shown, on the contrary, to be beneficial in terms of final antioxidant activity during cooking, as an increase was reported by Sacchi et al. (2014), and results were linked to the potential anticancer preventive effects of such preparations.

1.5 Outcomes of molecular gastronomy

1.5.1 Practical applications of molecular gastronomy

A major practical application of molecular gastronomy was the scientific cooking or molecular cooking. Examples can be found in the use of precise temperature control in food preparation. Food scientists and food chemists know well that many reactions are temperature-dependent and thus their impact is important, for example, on oxidation, enzymatic (Maillard) reaction (García-Segovia et al., 2007), flavor release, and many others, whereas chefs usually control cooking temperature in an empirical and not very precise way. This not only influences the way a specific recipe is created, but it also affects the repeatability: in other terms, without a good temperature control, a dish can be made in an optimal manner, while the second one might not be identical to the previous, for the consequent disappointment of the diner. A precise temperature control allows many types of cooking that are not possible with other techniques. Eggs have been often used as a good example ingredient to show the effect of cooking temperature, as boiling it in water at 52°C allows the albumin (white) to coagulate, while the yolk is still fluid. Another example can be cooking meat at much lower temperature (and longer time), allowing the production of a more tender and juicy meat, which also has more positive impact on its color (Barham et al., 2010). It is normally applied using the so-called sous-vide technique. It is today almost a common practice, among the top-level restaurant kitchen, to use sous-vide cooking. The spread of this technique is also related to the simplicity of applying it, and the consistency of the results obtained. Monitoring cooking time and setting specific temperature even in a more automatic way, while food is sealed in plastic bags, are easier than using conventional methods in which the chef has to check several times and always decide if it is good enough or not by a trial–error manner. In summary, exact monitoring of temperature and time allows better results. Roca et al. (2009) reported that restaurant chefs tend to cook meat at lower temperatures compared to the foodservice industry or home kitchen level. The temperature chosen by the chefs to cook pork is approximately 60°C–63°C (Myhrvold and Smith, 2011). Beef cooking at 56.5°C has been reported as the optimal temperature, similar to other meats such as bison, lamb, tenderloin, pork chops, and duck breast. Fish or seafood such as lobster and scallops could be cooked at this temperature as well, while pork roast and spare ribs need higher temperatures, in the range of 71°C–80°C. The temperature increase is positively correlated to the firmness of the meat. A temperature of 63.5°C has been reported for chicken breast, while 71°C is suggested for chicken legs, and 80°C for turkey or duck legs. Lower temperature is ideal for fish, that is, 52°C, but there are exceptions, for example, of shrimp are cooked at 60°C. The cooking temperature for vegetables and fruit can vary to a more limited extent, being 84°C regarded as the optimal one, with cooking times that can typically from 30 minutes up to 4 hours.

Roca and Bruguès (Roca et al., 2009) reported that the main changes of the meat subjected to long cooking at moderate temperatures are mainly textural parameters. Longer cooking times influence collagen solubilization, and solubilized collagen brings to a larger formation of gelatine, and a decrease of meat hardness. This effect happens when the temperature is 65°C in the connective tissue of mammals. In addition, the cooking of meat at moderate temperatures would lead to coagulation of myofibrillar protein, which for most of the proteins of this type happens at temperatures above 70°C–80°C (Palka, 2003). Moreover, the use of under vacuum bags allows air removal, improving the uniformity of heating; it also avoids the formation of some undesired flavor, whose generation needs oxygen. Removing oxygen from the food can bring an improvement of the product under the point of view of the oxidation as well as the overall acceptability, also in the case of vegetables cooked sous-vide. One disadvantage could be the cost of instrumentation, in particular for applications in the field of catering for a limited number of requests or utilities. In addition, the shape of the food products might be compromised, especially when excessive vacuum level is set by the pump or by the compression of the food by the plastic bag used (Myhrvold and Smith, 2011).

1.5.2 Example of sous-vide cooking of pork meat

del Pulgar et al. (2012) analyzed the effect of time and temperature when cooking pork cheeks using vacuum packaging, with different compositions. They used eight combinations of time (between 5 and 12 hours) and temperatures (ranging from 60°C to 80°C) cooking sous-vide, and they compared normal cooking by boiling in a saucepan for 30 minutes. Cooking time and temperature, not surprisingly, affected meat texture in a statistically significant manner. The authors reported that meat boiled for 30 minutes in traditional saucepan had a water loss similar to the meat cooked at 80°C by using sous-vide. Sous-vide cooking of meat has been reported to result in a more juicy meat as well as more concentrated nutrient preservation of meat, but it does not seem to be directly related to the cooking method (vacuum or cooked in boiling water). Cooking time was described to exert a limited or no influence on the color of cooked meat, when the temperature is not excessive, and even if the cooking time is prolonged. However, a trend was reported about a more intense red color for meat cooked by sous-vide at 60°C for 12 hours, compared to those packaged just with air. It is clear that temperature control is dramatic in sous-vide cooking of pork cheek due to its influence on water loss, in other terms of the moisture content of the cooked meat, and the color and texture of the meat. The results suggest that vacuum packaging by itself does not significantly bring an improvement of the physicochemical parameters (del Pulgar et al., 2012).

1.5.3 Using liquid nitrogen in cooking

New recipes that use low temperatures have been reported in kitchen applications since a few years, including the use of liquid nitrogen. It is particularly useful since it is a quick and easy way to rapidly cool foods and thus prevents the growth of large ice crystals, as those with high dimensions often damage frozen foods. Two examples are the herbs grinding, by simply mixing herbs with liquid nitrogen in a mortar and pestle, and quickly freezing in brittle solids, and the formulation of ice cream. In one case, it avoids oxidation phenomena that involve the color changes and the loss of aroma compounds, while in the second case, it allows the formulation of an instantaneous ice cream with a very smooth taste due to the small size of the ice crystals.

It is known that liquid nitrogen does not have any negative impact on the consumer’s health, but chefs and home cooks need to put care when they use it, in particular protecting their eyes while pouring the liquid in bowls or glasses, but also for the consumer. Ingestion is rare but can lead to catastrophic complications due to barotrauma in the gastrointestinal tract. A case has been reported in a study by Berrizbeitia et al. (2010), where ingestion of liquid nitrogen caused gastric perforation and respiratory failure. Also, newspapers reported some few cases of people having serious health problems (stomach removal) after drinking cocktails in which liquid nitrogen was used and it still was not completely evaporated (Gladwell, 2012). One should also point out that there are some practical limitations in using liquid nitrogen, as it needs special storage and transport containers (Dewar), which are not available to typical restaurant kitchens.

1.5.4 Using ultrasound to prepare molecular gastronomy food

When referring to ultrasound, one indicates the range of wavelengths below the ones of the radio frequencies (audible to the human ear), generally below 20 kHz (Chandrapala et al., 2012). The technique of ultrasound treatment is applied in food technology to improve the final quality of the products, but it applied to food chemistry during food analysis for several applications. Ultrasound is applied to food products in a wide extent, for example, to obtain better emulsification (Chemat and Khan, 2011), generation of nanoemulsions (Kentish et al., 2008), milk homogenization (Bermúdez-Aguirre et al., 2008; Bosiljkov et al., 2011), aroma encapsulation in cheese (Mongenot et al., 2000), for lipolysis enhancement (Ramachandran et al., 2006), emulsion stabilization (Ogawa et al., 2004; Juliano et al., 2011), etc. Nevertheless, these applications can be seen as belonging to the broader field of food science and technology, and it is very difficult to attribute them to molecular gastronomy.

An example of ultrasound application at the kitchen level could be the control of the viscosity. A study by Iida et al. (2008) evaluated the impact of ultrasonic treatment for depolymerization and modulating the viscosity of solutions made of polysaccharide starch after gelatinization, by testing a range of starchy ingredients. Ultrasound treatment can lead to positive effects, for example, there is no need to use chemicals or additives, and the process is easy and rapid. Other researchers investigated the impact of sonication on food texture (Ashokkumar et al., 2010), but also in this case, the application is of industrial scale and of general interest for food scientists, thus not specifically related to the field of molecular gastronomy.

An interesting use of ultrasound at the restaurant level has been for tenderizing meat. Jayasooriya et al. (2007) applied ultrasound treatment to improve the meat texture. The authors used an ultrasonic probe of lower intensity (12 W/cm²) for a treatment time of 30–240 seconds. There are, however, researches that report no change in meat tenderness by using higher intensities and shorter time (a few seconds). Others such as Jayasooriya et al. (2007) describe a temperature increase of the meat of about 15°C–30°C, depending on the length of ultrasound treatment. This temperature results in increased protease activity in the muscle that consequently causes color changes to the meat, that is, higher brightness.

One of the first attempts that can be directly labeled as a molecular gastronomy study of the impact of ultrasound treatment has been reported by Pingret et al. (2011) (Fig. 1.1). Dishes prepared by conventional methods and by ultrasound-assisted treatment were compared. Three desserts, that is, chocolate Genoise, basic sponge cake, and chocolate mousse, were evaluated by using the sensory and physicochemical analyses. The chocolate Genoise produced by ultrasound treatment had lower scores for hardness and cohesion, and higher elasticity and adhesion values compared to the traditional one. There was a significant difference in the color of the product and in the more spongy structure (more air bubbles), since ultrasound treatment promotes a better homogenization and distribution of the bubble size. The sensory profile improved in the case of sonicated product, with a better assessment of the attributes of sweetness, softness, flavor, crispness, and cocoa. The basic sponge cake cooked by conventional methods had higher scores for hardness and lower scores for elasticity, cohesiveness, and adhesiveness, compared to the samples made by ultrasound treatment. A significant difference from a sensory point of view was also reported. The chocolate mousse, on the contrary, was harder, less elastic, less cohesive, and more adhesive when prepared by the ultrasound treatment. It was also smoother, with higher porosity, and had a darker color. Ultrasound treatment also caused a lowering in the viscosity value, while conventionally treated samples had more intense creamy and cocoa flavor, persistence, and sweet notes. A short ultrasonic treatment in the chocolate mousse is sufficient to generate significant off-flavor, especially metallic, fish, rancid, and tallow (Pingret et al., 2011). Several researchers have reported that off-flavors could appear in food prepared by using ultrasound treatment (Chemat et al., 2004; Patrick et al., 2004; Schneider et al., 2006). Based on this research, ultrasound treatment can be regarded as risky treatment for the potential development of off-flavors, which might be attributed to faster lipid oxidation phenomena. Therefore cooks should put more attention on these aspects, in addition to changes in the color and viscosity, when they prepare foods at home or at the restaurant kitchen by using ultrasound-assisted