Wender L.P. Bredie

Molecular Gastronomy: A New Emerging Scientific Discipline

The science of domestic and restaurant cooking has recently moved from the playground of a few interested amateurs into the realm of serious scientific endeavor. A number of restaurants around the world have started to adopt a more scientific approach in their kitchens,1–3 and perhaps partly as a result, several of these have become acclaimed as being among the best in the world.4,5 Today, many food writers and chefs, as well as most gourmets, agree that chemistry lies at the heart of the very finest food available in some of the world’s finest restaurants. At least in the world of gourmet food, chemistry has managed to replace its often tarnished image with a growing respect as the application of basic chemistry in the kitchen has provided the starting point for a whole new cuisine. The application of chemistry and other sciences to restaurant and domestic cooking is thus making a positive impact in a very public arena which inevitably gives credence to the subject as a whole. As yet, however, this activity has been largely in the form of small collaborations between scientists and chefs. To date, little “new science” has emerged, but many novel applications of existing science have been made, assisting chefs to produce new dishes and extend the range of techniques available in their kitchens. Little of this work has appeared in the scientific literature,2,3,6–9 but the work has received an enormous amount of media attention. A quick Google search will reveal thousands of news articles over the past few years; a very few recent examples can be found in China,(10) the United States,11,12 and Australia.(13) In this review we bring together the many strands of chemistry that have been and are increasingly being used in the kitchen to provide a sound basis for further developments in the area. We also attempt throughout to show using relevant illustrative examples how knowledge and understanding of chemistry can be applied to good effect in the domestic and restaurant kitchen. Our basic premise is that the application of chemical and physical techniques in some restaurant kitchens to produce novel textures and flavor combinations has not only revolutionized the restaurant experience but also led to new enjoyment and appreciation of food. Examples include El Bulli (in Spain) and the Fat Duck (in the United Kingdom), two restaurants that since adopting a scientific approach to cooking have become widely regarded as among the finest in the world. All this begs the fundamental question: why should these novel textures and flavors provide so much real pleasure for the diners? Such questions are at the heart of the new science of Molecular Gastronomy. The term Molecular Gastronomy has gained a lot of publicity over the past few years, largely because some chefs have started to label their cooking style as Molecular Gastronomy (MG) and claimed to be bringing the use of scientific principles into the kitchen. However, we should note that three of the first chefs whose food was “labeled” as MG have recently written a new manifesto protesting against this label.(14) They rightly contend that what is important is the finest food prepared using the best available ingredients and using the most appropriate methods (which naturally includes the use of “new” ingredients, for example, gelling agents such as gellan or carageenan, and processes, such as vacuum distillation, etc.). We take a broad view of Molecular Gastronomy and argue it should be considered as the scientific study of why some food tastes terrible, some is mediocre, some good, and occasionally some absolutely delicious. We want to understand what it is that makes one dish delicious and another not, whether it be the choice of ingredients and how they were grown, the manner in which the food was cooked and presented, or the environment in which it was served. All will play their own roles, and there are valid scientific enquiries to be made to elucidate the extent to which they each affect the final result, but chemistry lies at the heart of all these diverse disciplines. The judgment of the quality of a dish is a highly personal matter as is the extent to which a particular meal is enjoyed or not. Nevertheless, we hypothesize that there are a number of conditions that must be met before food becomes truly enjoyable. These include many aspects of the flavor. Clearly, the food should have flavor; but what conditions are truly important? Does it matter, for example, how much flavor a dish has; is the concentration of the flavor molecules important? How important is the order in which the flavor molecules are released? How does the texture affect the flavor? The long-term aims of the science of MG are not only to provide chefs with tools to assist them in producing the finest dishes but also to elucidate the minimum set of conditions that are required for a dish to be described by a representative group of individuals as enjoyable or delicious, to find ways in which these conditions can be met (through the production of raw materials, in the cooking process, and in the way in which the food is presented), and hence to be able to predict reasonably well whether a particular dish or meal would be delicious. It may even become possible to give some quantitative measure of just how delicious a particular dish will be to a particular individual. Clearly, this is an immense task involving many different aspects of the chemical sciences: from the way in which food is produced through the harvesting, packaging, and transport to market via the processing and cooking to the presentation on the plate and how the body and brain react to the various stimuli presented. MG is distinct from traditional Food Science as it is concerned principally with the science behind any conceivable food preparation technique that may be used in a restaurant environment or even in domestic cooking from readily available ingredients to produce the best possible result. Conversely, Food Science is concerned, in large measure, with food production on an industrial scale and nutrition and food safety. A further distinction is that although Molecular Gastronomy includes the science behind gastronomic food, to understand gastronomy it is sometimes also necessary to appreciate its wider background. Thus, investigations of food history and culture may be subjects for investigation within the overall umbrella of Molecular Gastronomy. Further, gastronomy is characterized by the fact that strong, even passionate feelings can be involved. Leading chefs express their own emotions and visions through the dishes they produce. Some chefs stick closely to tradition, while others can be highly innovative and even provocative. In this sense gastronomy can be considered as an art form similar to painting and music. In this review we begin with a short description of our senses of taste and aroma and how we use these and other senses to provide the sensation of flavor. We will show that flavor is not simply the sum of the individual stimuli from the receptors in the tongue and nose but far more complex. In fact, the best we can say is that flavor is constructed in the mind using cues taken from all the senses including, but not limited to, the chemical senses of taste and smell. It is necessary to bear this background in mind throughout the whole review so we do not forget that even if we fully understand the complete chemical composition, physical state, and morphological complexity of a dish, this alone will not tell us whether it will provide an enjoyable eating experience. In subsequent sections we will take a walk through the preparation of a meal, starting with the raw ingredients to see how the chemical make up of even the apparently simplest ingredients such as carrots or tomatoes is greatly affected by all the different agricultural processes they may be subjected to before arriving in the kitchen. Once we have ingredients in the kitchen and start to cut, mix, and cook them, a vast range of chemical reactions come into play, destroying some and creating new flavor compounds. We devote a considerable portion of the review to the summary of some of these reactions. However, we must note that complete textbooks have failed to capture the complexity of many of these, so all we can do here is to provide a general overview of some important aspects that commonly affect flavor in domestic and restaurant kitchens. In nearly all cooking, the texture of the food is as important as its flavor: the flavor of roast chicken is pretty constant, but the texture varies from the wonderfully tender meat that melts in the mouth to the awful rubber chicken of so many conference dinners. Understanding and controlling texture not only of meats but also of sauces, souffles, breads, cakes, and pastries, etc., will take us on a tour through a range of chemical and physical disciplines as we look, for example, at the spinning of glassy sugars to produce candy-floss. Finally, after a discussion of those factors in our food that seem to contribute to making it delicious, we enter the world of brain chemistry, and much of that is speculative. We will end up with a list of areas of potential new research offering all chemists the opportunity to join us in the exciting new adventures of Molecular Gastronomy and the possibility of collaborating with chefs to create new and better food in their own local neighborhoods. Who ever said there is no such thing as a free lunch?

Differential transfer of dietary flavour compounds into human breast milk

Transfer of dietary flavour compounds into human milk is believed to constitute the infants early flavour experiences. This study reports on the time-dependent transfer of flavour compounds from the mothers diet to her breast milk using a within-subject design. Eighteen lactating mothers completed three test days on which they provided a baseline milk sample prior to ingestion of capsules containing 100 mg d-carvone, l-menthol, 3-methylbutyl acetate and trans-anethole. Milk samples were collected 2, 4, 6 and 8 h post-ingestion and analysed by a dynamic headspace method and gas chromatography-mass spectroscopy. The recovery quantities were adjusted for variations in milk fat content. Concentration-time profiles for d-carvone and trans-anethole revealed a maximum around 2 h post-ingestion, whereas the profile for l-menthol showed a plateau pattern. The ester 3-methylbutyl acetate could not be detected in the milk, but a single determination showed traces (<0.4 ppb) in a 1 h milk collection. Flavour compounds appeared to be transmitted differentially from the mothers diet to her milk. The results imply that human milk provides a reservoir for time-dependent chemosensory experiences to the infant; however, volatiles from the diet are transferred selectively and in relatively low amounts.

Sensory panel consistency during development of a vocabulary for warmed-over flavour

Abstract A sensory vocabulary of 20 terms each with a corresponding reference material was developed over 7 sessions using pork patties derived from the meat of carriers and non-carriers of the RN − gene. Patties were oven-cooked at 150 and 170°C and chill-stored for up to 5 days to facilitate warmed-over flavour development. Generalised Procrustes Analysis (GPA) was used to investigate sensory terms and their individual use by panellists over the sessions. GPA explained variance indicated that the final vocabulary displayed a similar amount of information to that of the initial vocabulary of 42 terms. Individual panellists scale use was found to converge over the sessions. Panel agreement on many odour and flavour terms appeared to be enhanced as term synonyms were removed in vocabulary development. Sample discriminability decreased from sessions 1–4, where term concepts were verbally communicated to the panel. Term reference introduction in session 5 caused a levelling in sample discriminability and a reduction in agreement, most likely related to perceptual confusion. Subsequently, references enhanced both discriminability and agreement. Thus, it may be more useful to introduce reference materials earlier, if not in the first session, of the vocabulary development process.

Release of peppermint flavour compounds from chewing gum: effect of oral functions

During chewing, the oral cavity functions like a bellow, forcing volatile flavour compounds into the exhaling air to the nasal compartment. Accordingly, we hypothesised that flavour release from chewing gum is predominantly governed by chewing frequency (CF), although other oral functions, like masseter muscle activity (MMA), chewing force (CFO), and saliva flow rate (SFR), may also play a role. In 10 healthy young males, the retronasal expired air of menthol and menthone from peppermint-flavoured (2%) chewing gum was determined as functions of CF, SFR, MMA, and CFO. The experimental setup comprised three separate series of a 4-min chewing period. These series differed only with respect to CF, i.e., habitual frequency, and 60 and 88 strokes/min. Results showed that more than 50% of the released menthol and menthone could be retrieved in the expired air and saliva. After 2-min of chewing, the concentration of flavour compounds in the expired air depended primarily on MMA and CF, becoming higher with increased MMA and CF. The concentration of flavour compounds in saliva depended primarily on SFR and the duration of the chewing task, becoming lower with high SFR and prolonged chewing duration. An increased volume of saliva in the mouth seemed to keep more flavour compounds in the aqueous phase, thereby diminishing the release via the retronasal route. In conclusion, flavour release to the retronasal compartment was dependent on MMA and CF and influenced by the volume of saliva present in the mouth.

Sensory profiling data studied by partial least squares regression

Abstract The statistical analysis of a descriptive sensory profiling data set distributed at the sensometrics meeting is presented. The data set is analysed with focus on the sensory differences between products (cooked potatoes). The data analytical strategy involves a descriptive statistical analysis to obtain an overview of the distribution and standard deviations of the scores for each sensory attribute. Subsequently, three-way analysis of variance (AVOVA) of the data gives a statistical measure of the reliability of the sensory attributes supplemented by principal component analysis, which visualise the main tendencies of systematic variation. Discriminant and ANOVA partial least squares regressions are used to relate the sensory structure to product design structure and vice versa. Statistical reliability and predictive validity of the product differences are obtained by ANOVA and cross-validation. Similar data structures are observed in the various multivariate models. Texture, taste and flavour attributes differentiated the potato samples, with the texture attributes being most reliable. It is emphasised that an appropriate interpretation of the profiling data should also include knowledge of the experimental background.

Gender and handedness effects on hedonicity of laterally presented odours

The effect of lateral presentation of odours on the hedonic evaluation is reported using a range of different substances. The hypothesis that hedonic evaluation of odours depends on stimulated nostril and on gender and handedness is tested using psychophysical methodology. A total of 51 untrained subjects evaluated 16 substances with different hedonic valences. Each odour substance was presented to the subjects four times, twice at each nostril using a balanced experimental design. Effects of gender and handedness, and interactions, are observed. Some parallels with the perception of visual emotional stimuli are suggested. Hedonic processing of odour stimuli is concluded to be an emotional, rather than an analytical task.

Instrumental and sensory characterisation of Solaris white wines in Denmark

This study aimed to investigate the volatile and non-volatile compositions as well as sensory properties of the most common monovarietal white wine (var. Solaris) in Denmark. Using dynamic headspace sampling (DHS) coupled to gas chromatography-mass spectrometry (GC-MS), 79 volatile compounds were identified. Among the major non-volatile components glycerol, sulphite, sugars and organic acids were analysed. A primary sensory difference was observed among wine samples, half of which were characterised by floral and fruity flavours (peach/apricot, Muscat, melon, banana and strawberry) while the remainder were described by less pleasant flavours, such as chemical, wood and rooibos/smoke. Partial least squares regression (PLS) showed that acetates and ethyl esters of straight-chain fatty acids were associated with floral and fruity odours while ethyl esters of branched-chain fatty acids were less associated with them. The study also suggested that differences in vintage were less characteristic than differences caused due to sulphite management by producers.

A comparative study of beef quality after ageing longissimus muscle using a dry ageing bag, traditional dry ageing or vacuum package ageing

The objective of this study was to investigate beef quality of longissimus muscle after ageing in dry ageing bags, traditional dry ageing or vacuum for 8 or 19 days. Lower ageing weight loss, odour score and microbial growth were found in meat aged in dry ageing bags than after traditional dry ageing. The sensory panel detected no differences for most of the sensory attributes between samples using the two dry ageing methods, except for the odour of the cutting surface. The dry-aged steaks had more umami and butter fried meat taste compared with vacuum-aged steaks. Ageing time affected most of the sensory traits in this study, which improved as ageing time increased from 8 to 19 days. In a consumer test, meat aged for 21 days in dry ageing bags was preferred than the samples aged in vacuum. This may be due to the higher tenderness and juiciness obtained during storage in dry ageing bags than meat aged in vacuum.

A Comparative Study on Facially Expressed Emotions in Response to Basic Tastes

Facially expressed emotions play a role in communication between individuals. They form another means of expressing oneself besides verbal expressions or self-reporting of feelings and perceptions on psychometric scales and are implicit in nature. This study aimed to evaluate the extent and specificity of evoking facial expressed emotions by basic tastes and to evaluate if facially expressed emotions provide additional information to explicit measures. The emotions were characterised upon tasting the five basic tastes in aqueous solutions at three different concentrations levels. The sensory and emotional responses reported were obtained from a 21-membered taste panel. Facial reactions and facially expressed emotions depended on the taste quality and taste intensity. However, the facially expressed emotions were generally weak even for the relatively strong taste intensities. Bitter (caffeine), sour (citric acid) and salty (sodium chloride) lead to clear disgust and surprise responses, whereas, sweet (sucrose) and umami (glutamic acid monosodium salt) taste gave weakly noticeable facially expressed emotions. Although correlations between the expressed emotions and hedonic responses were observed, the affective experience had a limited predictive ability for the facially expressed emotion at the individual level. In conclusion, psychometric rating of the hedonic response is easier to assess than facially expressed emotions although it may not completely represent the dimensions of the emotional experience.

Quinine sensitivity influences the acceptance of sea-buckthorn and grapefruit juices in 9- to 11-year-old children ☆

The acceptance of novel foods by children is related to a number of factors, and differences in taste sensitivity may form some specific challenges. High sensitivity might be a barrier to the acceptance of sour/bitter products by children. This study investigated the effect of sensitivity to bitter, sour, sweet, and salty tastes on the acceptance of Nordic juices in 9- to 11-year-old children. A total of 328 children were subjected to two taste sensitivity tests for quinine, citric acid, sucrose, and NaCl. Their acceptance of six juices (carrot, rosehip, sea-buckthorn, lingonberry, grapefruit, and aronia) was measured. Bitter sensitivity was found to be significantly correlated to the intake of the sweet sea-buckthorn and lingonberry juices; the most bitter-sensitive children exhibited the highest intake of these juices. The opposite relationship was found for bitter sensitivity and the intake of the bitter grapefruit juice. Sour, sweet, and salt sensitivities did not affect the intake of any of the juices. Liking scores were not affected by sensitivity. In conclusion, bitter sensitivity appears to influence food intake in children to a greater extent than sour, sweet, or salt sensitivity. Bitter-sensitive children exhibited a reduced intake of grapefruit juice and a higher intake of sucrose-sweetened juices. Thus, bitter sensitivity might be a challenge in the acceptance of certain bitter foods.