Biogeneration of Aromas - ACS Publications - American Chemical

1 Downloaded by SUNY DOWNSTATE MEDICAL CTR on May 5, 2016 | http://pubs.acs.org Publication Date: August 25, 1986 | doi: 10.1021/bk-1986-0317.ch001

Legislative and Consumer Perception of Biologically Generated Aroma Chemicals Jan Stofberg PFW Division, Hercules Incorporated, Middletown, NY 10940 Many of the approximately 5000 known volatile flavoring substances are generated in biogenetic processes in natural foods, or during the subsequest processing of these foods. In both cases, they are perceived as natural flavorings by both consumer and legislator. Many of these same flavoring substances can be produced by chemical processes, in pure form. In that case they are perceived as artificial flavoring substances, both by consumer and legislator in the United States. It is, however, in many cases, also possible to manufacture exactly these same flavoring substances by biogenetic processes, at a usually much higher cost. We will review how the origin of flavoring materials influences their regulatory and safety status, and how it determines consumer perception of flavorful foods. Consumers and regulators all over the world, but particularly in the more developed countries, are becoming increasingly involved in and concerned about the source and composition of the flavorings in food. In many cases, especially on the side of consumers, there is an increased preference for what are called: "natural flavors". The consumer concept of natural flavors What consumers in general mean by "natural flavors" appears to be rather a vague concept. It is based on the archetype of the apple on the tree, with all its connotations of the Garden of Eden, perfection, purity and safety. More exactly, the concept certainly covers all flavoring materials biologically generated during the growing and ripening of vegetables and fruits. Indeed, many flavoring materials are being generated that way in the living cells. They are derived, as a kind of by-product, from amino acids and fatty acids, particularly in flowers, vegetables and fruits, at the time of ripening. Examples are: 0097-6156/ 86/ 0317-0002506.00/ 0 © 1986 American Chemical Society Parliment and Croteau; Biogeneration of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

1.

STOFBERG

Legislative and Consumer Perception

Downloaded by SUNY DOWNSTATE MEDICAL CTR on May 5, 2016 | http://pubs.acs.org Publication Date: August 25, 1986 | doi: 10.1021/bk-1986-0317.ch001

1.

the esters i n many f r u i t s , formed from alcohols and acids which are i n turn derived from common amino acids such as v a l i n e , leucine, cysteine and methionine; 2. the saturated, as well as the mono- and di-unsaturated aldehydes, formed from unsaturated f a t t y acids, i n particular linoleic and linolenic acid, i n many vegetables; 3. the terpene hydrocarbons, alcohols and aldehydes formed i n conjunction with the carotenoids and their oxidative breakdown products, p a r t i c u l a r l y i n c i t r u s fruits. I t seems, however, that the i l l - d e f i n e d consumer concept of natural flavorings extends far beyond t h i s limited area of biologically formed flavorings. Certainly the flavoring substances generated as a r e s u l t of minimal processing, such as the cutting or chewing of f r u i t s and vegetables are being considered natural. In these cases, the flavor formation takes place when enzymes i n one part of the vegetable material come i n contact with flavor precursors i n other tissues after the c e l l s have been ruptured. Cucumbers and tomatoes have very l i t t l e aroma which has been developed i n the course of the normal metabolism of the plant. Their "natural f l a v o r " that consumers are familiar with i s developed by enzymatic processes after cutting or chewing. Another p a r t i c u l a r l y well known example of t h i s type of flavor formation i s the flavor of onions which i s generated by cutting. S a l k y l cysteine sulfoxides are broken down to d i a l k y l d i s u l f i d e s , p a r t i c u l a r l y dipropyl d i s u l f i d e , under the influence of alliinase. Simultaneously, the lachrymator thiopropanal sulfoxide i s formed. (1) In many cases, even more natural flavoring materials are being formed by continued action of the plant's own enzymes on i t s flavor precursors, during further processing. Fermentation of tea, cocoa beans and v a n i l l a pods generates the desired flavoring materials c h a r a c t e r i s t i c for those products by various stages of further enzymatic reactions during withering, rolling and fermenting processes. For many t r a d i t i o n a l foods, further processing with added enzyme systems i s needed. The flavoring materials c h a r a c t e r i s t i c of bread and wine as well as of yogurt and cheese, are developed in b i o l o g i c a l processes under the influence of the enzymes in yeast, starters and rennet respectively. A l l such processes, which often take place during aging and ripening, are considered as p e r f e c t l y natural by the average consumer. More surprising, however, i s that the consumer w i l l also include in h i s everyday concept of natural f l a v o r , food preparation by physical processes such as heating. During various degrees of thermal processing of food, flavor generation by chemical reactions takes place. Mild heat treatment, such as parboiling of r i c e and conching of chocolate w i l l generate aldehydes by Strecker degradation of amino acids. At higher temperatures, the amino ketones formed during the Strecker degradation recombine to the very important pyrazine c l a s s of flavoring materials i n baked bread, roasted peanuts and roasted

Parliment and Croteau; Biogeneration of Aromas ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

3

BIOGENERATION OF A R O M A S


4

meat. S t i l l higher temperatures cause the decomposition of sugars to furan and pyrone d e r i v a t i v e s . In addition the combined reaction of sugars and amino acid degradation products, v i a the Amadori rearrangement, leads to dozens of furan and pyrazine derivatives. Introduction of low molecular sulfur and nitrogen compounds, resulting from the breakdown of sulfur containing amino acids, leads to large numbers of thiophenes, pyrroles and thiazoles. Since coffee, cocoa, baked bread and roasted meat are usually included i n the average consumer's concept of natural foods, their c h a r a c t e r i s t i c flavoring ingredients are considered to be natural also. (2) Over 5000 flavoring materials have been identified in t r a d i t i o n a l food so f a r . Many of those are not present i n the true natural state of the food. They are generated by the processing of the food by enzymatic or thermal processes. Often, the flavoring materials generated t h i s way are more dependent on the type of processing than on the s p e c i f i c food which has been processed. I t i s the r a t i o at which these d i f f e r e n t flavoring substances are present that determines the c h a r a c t e r i s t i c flavor of the food. The l e g a l status of natural f l a v o r s Legislators i n a l l countries have recognized that many forms of enzymatic and thermal processing are needed to develop the f l a v o r s perceived to be natural by consumers, i n t r a d i t i o n a l food. In the United States, the Code of Federal Regulations defines natural flavor in great d e t a i l . I t defines as natural flavor the essential o i l , oleoresin, essence or extractive, protein hydrolysate, d i s t i l l a t e or any product of roasting, heating or enzymolysis, which contains the flavoring constituents derived from a spice, f r u i t juice, vegetable or vegetable j u i c e , edible yeast, herb, bark, bud, root, leaf or similar plant material, meat, seafood, poultry, eggs, dairy products, or fermentation products thereof, whose s i g n i f i c a n t function i n food i s flavoring rather than n u t r i t i o n . (3) Some of the words used i n t h i s d e f i n i t i o n deserve a l i t t l e closer attention. I t i s commonly understood among experts on enzymes that the word "enzymolysis" covers not only hydrolysis but a l l enzymatic processes with no c e l l p r o l i f e r a t i o n . The words "protein hydrolysate" have been d e l i b e r a t e l y substituted in the f i n a l d r a f t of the flavor regulations, for the generic word "hydrolysate" which was present in an e a r l i e r d r a f t . (£) Even though the acid hydrolysis of proteins i s a chemical reaction, the natural amino acids present i n the hydrolysate have maintained the structure which they had as building blocks i n the b i o l o g i c a l l y formed protein molecules. This fact has obviously been the decisive factor i n including the acid hydrolyzed proteins i n the regulatory d e f i n i t i o n of natural flavors. Nature-identity and Consumption Ratio I t should be noted that l e g i s l a t i o n i n the U.S. recognizes only two kinds of flavorings: natural and artificial. There i s no



1.

STOFBERG


5

category "nature- i d e n t i c a l " , as i s the case i n most other developed countries. That term i s used to designate f l a v o r i n g substances that have undergone chemical processing, but which are identical i n a l l chemical aspects to f l a v o r i n g materials i d e n t i f i e d i n natural foods, either raw or processed for human consumption. In those countries where i t i s recognized, nature i d e n t i t y i s by regulation equivalent to recognition of safety. The basis for t h i s assumption i s that occurrence i n t r a d i t i o n a l food means that their consumption has been accepted as safe for humans. From a t o x i c o l o g i c a l viewpoint, t h i s may be questionable. The f a c t that traces of a l l y l caproate have been i d e n t i f i e d i n pineapple (5) does not necessarily mean that i t s use i n large quantities as a predominant ingredient i n pineapple f l a v o r s i s safe. Whether i t i s safe or not can only be determined by a proper safety evaluation, as has been c a r r i e d out i n the U.S. for c e r t a i n applications and use l e v e l s . This has been done for a l l f l a v o r i n g materials that have been Generally Recognized as Safe. (6) We should not, however, ignore the importance of the consumption of large quantities of b i o l o g i c a l l y formed f l a v o r i n g materials, large compared to the quantities consumed of the same materials produced by chemical processes. The r a t i o of the t o t a l annual poundage of a f l a v o r i n g material, unavoidably consumed as a component of t r a d i t i o n a l foods, and the annual poundage of the same f l a v o r i n g material used and consumed as a food a d d i t i v e , has been c a l l e d Consumption Ratio. (2) If t h i s r a t i o i s greater than 1, the average consumption v i a the traditional diet i s larger than the quantity of added synthetic f l a v o r i n g material. Such a flavoring material has been c a l l e d "Food Predominant", since i t i s consumed predominantly as a natural component of food. To i l l u s t r a t e the meaning of Consumption Ratio values: i f the Consumption Ratio of a f l a v o r i n g material i s greater than 10, then the consumption of that material as a food additive adds no more than 10% to the unavoidable consumption v i a food; c e r t a i n l y an i n s i g n i f i c a n t increase. So far the Consumption Ratio has been calculated for close to 350 f l a v o r i n g substances. 80% of them have a Consumption Ratio of more than 1, and are therefore Food Predominant. 60% even have a Consumption Ratio of over 10, which means that their intake as artificial flavoring materials i s i n s i g n i f i c a n t compared to that as ingredients of t r a d i t i o n a l food. (0) The consumption of f l a v o r i n g materials with a high Consumption Ratio cannot be managed by c o n t r o l l i n g their use as additives by regulations since their uncontrolled use would be much larger than the c o n t r o l l e d use. This should have s i g n i f i c a n t impact on the p r i o r i t y to be set for the safety evaluation of t h e i r use as a flavoring material. Even though nature-identical does not have a regulatory status in the U.S., the FDA i s f u l l y aware of the s i g n i f i c a n c e of the Consumption Ratio, and i s taking the data into consideration i n setting i t s p r i o r i t i e s .


6



The consumer "chemical"

perception

of

"natural"

versus

"artificial"

and

It has been explained e a r l i e r that many flavorings are generally accepted as "natural" both by consumer and l e g i s l a t o r because they are c h a r a c t e r i s t i c for the flavor of t r a d i t i o n a l foods. Even though many are formed as a r e s u l t of complicated chemical reactions that take place during food processing, these f l a v o r s s t i l l maintain, i n the consumers mind, the image of pure and safe associated with the apple on the tree. The consumer does not see them as a completely d i f f e r e n t and i n f e r i o r c l a s s of materials: chemicals 1 The Consumer Research Department of the Good Housekeeping Institute (9) conducted a study on, among other aspects, the consumer attitude toward food flavorings. From the tabulated r e s u l t s of a consumer survey i t appears that, with the exception of fresh fruits, the most desirable food flavors - the mouthwatering type - are processed foods, with meat, chocolate and baked goods ranking very high. "Natural" flavorings are, according to t h i s survey, considered very important for many foods and are considered better q u a l i t y than artificial flavorings. Many consumers, again according to t h i s survey, admit that they sometimes buy a r t i f i c i a l l y flavored foods, but a large majority i s of the opinion that artificial f l a v o r s consist of chemicals, whereas only 40% of them are aware that there are chemicals i n natural f l a v o r i n g s . A r t i f i c i a l f l a v o r s are thought to leave an a f t e r t a s t e and to be b i t t e r . They are perceived to have been made of chemicals, i n a laboratory, and that they are not found i n nature. In the background i s also the thought that they are harmful with, of course, the fear of cancer leading the list. This consumer opinion l a r g e l y disregards the protection provided by the FDA regulations, and the publication of l i s t s of flavoring materials that are permitted food additives, or are Generally Recognized as Safe by FDA. (10-11) This attitude of the consumer i n favor of natural flavorings i s , i n p a r t i c u l a r , promoted by the marketing strategy for newly developed food products: the natural status of the food and i t s f l a v o r i n g i s stressed and stretched as far as possible. The creation and production

of natural flavorings

This consumer preference for natural flavor has created a demand for natural (biologically rather than chemically produced) flavorings which s t i l l have a l l the desirable properties of flavorings containing both "natural" and " a r t i f i c i a l " f l a v o r i n g substances. Such desirable properties are, depending on the type of flavor and application: strength, heat stability, microbiological stability, uniform quality and unlimited availability. Therefore, part of the research e f f o r t i n the flavor industry has been directed towards the natural formation of f l a v o r i n g substances, using thermal processes. This approach has been f a c i l i t a t e d by the fact that FDA has recognized that processing of natural ingredients under endothermic conditions, by d i s t i l l a t i o n



1.

STOFBERG


and f r a c t i o n a t i o n , leads to f l a v o r i n g materials which s t i l l can be considered natural. Another way of obtaining natural f l a v o r i n g materials i s by recovery of volatiles, even i f they occur only in small quantities, from the processing of large quantities of f l a v o r f u l foods such as orange j u i c e and other f r u i t j u i c e s . The search for the presence and possible i s o l a t i o n of natural f l a v o r i n g materials from the processing of natural raw materials i s r e s u l t i n g i n the a v a i l a b i l i t y of many more f l a v o r i n g materials of b i o l o g i c a l o r i g i n . Another part of the research e f f o r t of the flavor industry i s being directed towards the generation of natural f l a v o r i n g substances from natural ingredients by enzymatic processes. In addition to the t r a d i t i o n a l enzymatic hydrolysis, s p e c i f i c enzymes such as esterases, oxidases and isomerases provide p o s s i b i l i t i e s for modification of natural s t a r t i n g materials to f l a v o r i n g substances without using chemical methods. The economic aspect of natural flavorings A l l f l a v o r i n g materials obtained i n the ways described above are t r u l y natural chemicals, chemically i d e n t i c a l to, and of the same food grade quality as many t r a d i t i o n a l l y known artificial flavoring materials. Because of the considerably higher cost of manufacturing involved, their cost w i l l be many times higher than that of their synthetic counterparts. This i s i n l i n e with the opinion expressed by a previous Commissioner of Food and Drugs, A.M. Schmidt that artificial flavor i s no l e s s safe, no l e s s n u t r i t i o u s and not inherently less desirable than the natural flavor; that the sole purpose for distinguishing between natural and artificial f l a v o r s i s for economic reasons. (12) D i s t i n c t i o n of synthetic and natural chemicals Pure flavoring substances, single chemicals, cannot be distinguished, as regards their synthetic or natural o r i g i n , by t r a d i t i o n a l chemical methods. There i s , however, one aspect i n which the artificial and natural versions of the same f l a v o r i n g substance may be d i f f e r e n t . I f the artificial material has been synthesized exclusively from chemicals of petrochemical o r i g i n , no radioactive carbon-14 isotope w i l l be present. Carbon from recent a g r i c u l t u r a l sources i s in equilibrium with carbon-14 present i n the atmosphere. A widely accepted interlaboratory standard for natural carbon-14 s p e c i f i c r a d i o a c t i v i t y i s o x a l i c acid from the National Bureau of Standards. 95% of the 1950 s p e c i f i c a c t i v i t y of NBS o x a l i c acid (13.56 disintegrations per minute per gram of carbon, dpm/g) has been defined as the "modern a c t i v i t y " of the carbon i n atmospheric CO2. Ever since 1960, due to nuclear weapons t e s t i n g , atmospheric ^ C a c t i v i t y has gone up, but i t started declining again a few years l a t e r after the l i m i t e d t e s t ban treaty went into e f f e c t . Even i f only part of the raw materials for the synthesis were from petrochemical o r i g i n , the content of carbon-14 i n the artificial f l a v o r i n g material w i l l be s i g n i f i c a n t l y lower than that of the naturally-derived materials which should give values close to 100% of "modern a c t i v i t y " .


1


8


Carbon 14 analysis has been successfully used in the d i s t i n c t i o n between natural wine- or cider vinegars and less expensive white vinegar made from acetic acid. (13) I t i s to be expected that t h i s a n a l y t i c a l technique, though far from generally available, w i l l have an impact on enforcing the economically j u s t i f i e d d i s t i n c t i o n between natural and artificial flavoring materials. The method can only prove absence of materials from recent a g r i c u l t u r a l sources. I t cannot distinguish between a natural flavoring and a material from natural o r i g i n which has been chemically modified without addition of carbon atoms from petrochemical sources. In such cases, determination of the r a t i o between the stable isotopes carbon-12 and carbon-13 may be a way to d i f f e r e n t i a t e between different sources of botanical origin, reflecting differences in the C0 assimilation pathways. This procedure has only been used with some degree of accuracy in a limited number of cases such as the d i s t i n c t i o n between v a n i l l i n from v a n i l l a beans and v a n i l l i n from wood l i g n i n . (14) I would l i k e to stress that, as far as the f u n c t i o n a l i t y in food i s concerned, there i s no difference between the flavoring materials from natural or synthetic o r i g i n . I t i s up to the marketing policy of the food industry, and the educated choice of the f i n a l consumer, which class of flavoring materials w i l l be chosen for a certain application. 2

Enzymatic flavorings and Process

flavorings

In addition to enzymatic processes aimed at the production of pure, single chemicals, there i s a growing interest i n enzymatic processes which duplicate, i n more concentrated and faster form, the entire flavor complex which i s being formed during aging, ripening and fermentation of t r a d i t i o n a l foods. Since their natural flavor has been formed t h i s way, dairy products obviously present themselves as candidates for t h i s approach, which may well lead to the most cost e f f e c t i v e way of developing natural f l a v o r s . Butter acids, butter esters, modified cheeses are by now well established, highly e f f e c t i v e natural flavorings. The flavorings that are b i o l o g i c a l l y prepared t h i s way are aiming for the reproduction of the entire flavor formation occurring during traditional food preparation, rather than duplicating them by i d e n t i f y i n g the individual components of the natural food flavor and combining the i d e n t i f i e d individual aroma chemicals. By t h i s procedure of developing the entire flavor complex in one process, i t i s sometimes possible to obtain a much closer match of the o r i g i n a l f l a v o r , since i d e n t i f i c a t i o n of many flavoring ingredients i n the parts per t r i l l i o n area i s s t i l l a problem. Such trace ingredients are important for obtaining the characteristic natural flavor, in particular the highly odoriferous s u l f u r - and nitrogen-containing substances. A similar procedure, aiming for a t o t a l flavor complex, has been followed in duplicating the flavor of many kinds of baked and roasted products, such as nuts and meats. Combinations of natural ingredients, analogous to those expected to play a role in the flavor formation of roasted foods, in p a r t i c u l a r amino nitrogen



1.

STOFBERG


9

sources, sugars and f a t s , are subjected to thermal processes of similar temperature and duration as kitchen cooking procedures. The procedure to create t h i s type of f l a v o r s , usually c a l l e d Process Flavors, reproduces i n concentrated form the processes that take place during the cooking, baking and roasting of food. If only natural ingredients are used i n such a process f l a v o r , i t r i g h t f u l l y enjoys the same status of natural flavor as t r a d i t i o n a l foods, even though complex chemical reactions are taking place i n the preparation of both foods and process f l a v o r s . To make sure that the reactions taking place remain within the range acceptable for food, the International Organization of the Flavour Industry (IOFI) has included i n i t s Code of Practice for the Flavor Industry a set of Guidelines for Process Flavors, l i m i t i n g the kind of ingredients used, and i n p a r t i c u l a r the main processing conditions, time and temperature. (15) The

future:

natural or functional?

The d i s t i n c t i o n between n a t u r a l l y and a r t i f i c i a l l y flavored food used to be as simple as the difference between raspberries and hard candies flavored with amyl acetate. In the future the choice i s more l i k e l y to be between g e n e t i c a l l y engineered botanical material, physically and enzymatically processed, and a manufactured food with added natural f l a v o r i n g complexes, prepared by thermal and enzymatic processes, or their precursors. The consumers w i l l have to be educated about the true meaning of "natural". I t does not j u s t stand for "the i d e a l source of n u t r i t i o n for humans", i n contrast to other products made with so-called "chemicals". Many natural foods contain ingredients that are useless, or even harmful, such as o x a l i c acid i n spinach and solanin i n potatoes. The consumer has to understand that a l l substances are chemicals, that l i f e i s a chemical process, and that many new processes w i l l have to be developed to provide s u f f i c i e n t food with high n u t r i t i o n a l value per d o l l a r for a hungry world. This i s not going to be achieved by stretching the word "natural" to f i t i n e a s i l y with preconceived consumer ideas on that subject, but by creating understanding for the need for functional flavorings as safe and normal food ingredients, either t r a d i t i o n a l l y present, or d e l i b e r a t e l y added. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9.

Buttery, R.G. In "Flavor Research", Teranishi, R. et. al. Ed.; Marcel Dekker, Inc.: New York, 1981; pp 175-216 Stofberg, J . Perf. Flav., 1985, 10, 1. Code of Federal Regulations 21, 101.22.a.3. Federal Register 38, August 2, 1973, p 20718. N i t z , N.; Drawert, F. Chem. Mikrobiol. Techn. Lebensm. 1982, 7, 148. H a l l , R.L.; Oser Β., Food Tech., 1965, 19, 253. Stofberg, J . Perf. Flav. 1981, 6, 69. Stofberg, J . ; Grundschober, F. Perf. Flav. 1984, 9, 53. "Food Attitude Study", the Consumer Research Department, Good Housekeeping I n s t i t u t e , A p r i l 1985.



10 10. 11. 12. 13. 14. 15.

Code of Federal Regulations 21, 172.515. Code of Federal Regulations 21, 182.60. Federal Register 38, December 3, 1973, p 33284 Krueger, D.A.; Krueger, H.W. J . Ass. O f f . Am. Chem., i n press. Krueger, D.A.; Krueger, H.W. J . Agr. Food Chem. 1985, 33, 323. "Code of Practice for the Flavour Industry", IOFI, 2nd ed., Geneva, Switzerland, 1984. January 3, 1986


RECEIVED


Biogeneration of Aromas - ACS Publications - American Chemical

Recommend Documents