Volatiles from Red Pepper - American Chemical Society

12 Volatiles from Red Pepper (Capsicum spp.) URS KELLER

Downloaded by UNIV OF CALIFORNIA SANTA CRUZ on October 28, 2014 | http://pubs.acs.org Publication Date: November 11, 1981 | doi: 10.1021/bk-1981-0170.ch012

Firmenich SA, Geneva, Switzerland ROBERT A. FLATH, THOMAS R. MON, and ROY TERANISHI Western Regional Research Center, SEA-AR, U.S. Department of Agriculture, Berkeley, CA 94710

Fruit of the genus Capsicum has been included in the diet of Western Hemisphere peoples since long before the European discovery of the Americas (1,2). After European contact with the New World was made, Capsicum plants were dispersed through much of the remaining world, especially to sub-tropical and tropical regions. The fruits, both fresh and dried, are used as spices and as staples in the diet. An obvious characteristic of the fruits is their "hotness" or "bite" when eaten. This character is quite variable among the members of the genus, with some varieties exhibiting such hotness that they can only be added in small quantities as a spice to food dishes, whereas others exhibit no discernable bite at all. In addition, the fruits have rather distinctive flavor characters, making them very popular components of certain ethnic diets, especially when the hotness is not overpowering. Botanical classification of Capsicum members is rather confused (2,3,4), but recent sources include at least two major species, C. annuum and C. frutescens. As a rough generalization, the larger peppers tend to be C. annuum. These frequently are somewhat lower i n hotness, and this characteri s t i c may be entirely lacking in certain varieties. C. frutescens tends to include the smaller, hotter peppers. Certain botanical characteristics are also considered when classifying Capsicum plants into one or another species. Superimposed on the botanical classifications are the assortment of trivial names for individual varieties. The Hot Chilis, Jalapenos, and Tabasco peppers are usually considered to be C. frutescens, while Sweet Chilis, Bell Peppers, Paprika, and Cayenne are included among the C. annuum varieties. The term "red pepper" refers to the typical color that most presentday pepper varieties attain when permitted to ripen thoroughly, although yellow colorations are not unknown, and some early references to violet and white fruits may be found (1). The hotness of peppers (unrelated to black pepper [Piper nigrum L.]) is due to various capsaicinoids in the fruit. 0097-6156/81/0170-0137$05.00/0 © 1981 American Chemical Society In Quality of Selected Fruits and Vegetables of North America; Teranishi, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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C a p s a i c i n , the major c a p s a i c i n o i d , i s the N - v a n i l l y l amide of 8-methyl-6-nonenoic a c i d . Related dihydro-, homo-, and dihydrohomo- isomers have a l s o been r e p o r t e d . Most research e f f o r t s on r e d pepper have been concerned w i t h determining the c a p s a i c i n o i d makeup and c o n c e n t r a t i o n i n v a r i o u s r e d pepper v a r i e t i e s and products (5-8)· Several groups of workers have examined the v o l a t i l e s makeup of c e r t a i n pepper v a r i e t i e s . The f i r s t of these were Buttery e t a l . (9) who i s o l a t e d and i d e n t i f i e d 2-methoxy-3i s o b u t y l p y r a z i n e from f r e s h b e l l peppers. They determined i t s odor t h r e s h o l d i n water t o be 2 p a r t s i n 10 p a r t s of water. Haymond and Aurand (10) i d e n t i f i e d twenty-four components of f r e s h Tabasco peppers, i n c l u d i n g a number of e s t e r s , and decided t h a t a l l c o n t r i b u t e to Tabasco aroma. Murray and W h i t f i e l d ( 11 ), i n t h e i r extensive survey of 3alkyl-2-methoxypyrazines i n raw vegetables, reported f i n d i n g 3i s o b u t y l - , 3 - i s o p r o p y l - , and 3-(sec-butyl)-2-methoxypyrazines i n red, o r c h i l i peppers. Combining gc e f f l u e n t s n i f f i n g and gc-ms s e l e c t e d i o n m o n i t o r i n g , Huffman et_ a l . (12) detected 3-isobutyl-2-methoxypyrazine i n both f r e s h and processed Jalapeno pepper v o l a t i l e s . They a t t r i b u t e d most of the f r e s h Jalapeno aroma t o the presence of the b e l l pepper p y r a z i n e . In a recent communication on Capsicum v o l a t i l e s c o n c e n t r a t i o n , T e r a n i s h i e_t a l . (13) reported i s o l a t i n g from the o l e o r e s i n the methyl e s t e r s of l a u r i c , p a l m i t i c , and s t e a r i c a c i d , as w e l l as f r e e a c e t i c a c i d , along w i t h t r a c e s of s e v e r a l C^-C^ acids.


y

Experimental M a t e r i a l s . O l e o r e s i n of Capsicum, A f r i c a n type, was purchased i n s e v e r a l l o t s from K a l s e c , I n c . , Kalamazoo, MI. This m a t e r i a l i s a v i s c o u s deep orange-red l i q u i d / s e m i s o l i d residue obtained by hexane e x t r a c t i o n of ground, d r i e d r i p e £. frutescens peppers. Commercially, i t i s p r i m a r i l y used as a n a t u r a l source of "hotness" and f l a v o r f o r foods and f o r animal r e p e l l e n t f o r m u l a t i o n s . This m a t e r i a l was used i n the i n i t i a l analytical studies. Sweet c h i l i m i s c e l l a ( s o l u t i o n of e x t r a c t e d m a t e r i a l ) was a l s o obtained from K a l s e c , I n c . This m a t e r i a l i s a l s o hexanee x t r a c t e d , but from sweet c h i l i s (£. annuum [14]). I t i s much l e s s "hot" than i s the o l e o r e s i n Capsicum, and i s mostly used for f l a v o r i n g and c o l o r i n g foods. Normally the e x t r a c t i n g s o l v e n t i s s t r i p p e d from the e x t r a c t by the s u p p l i e r before shipment. In order t o minimize v o l a t i l e s l o s s during t h i s s t e p , the hexane content of the e x t r a c t was only reduced t o ca 20% of the t o t a l volume before shipment. Fresh Jalapeno peppers (C. f r u t e s c e n s ) were obtained from a l o c a l market. The c u l t i v a r i s unknown.

In Quality of Selected Fruits and Vegetables of North America; Teranishi, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

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D i s t i l l e d water was used i n a l l v o l a t i l e s c o n c e n t r a t i o n procedures. A l l s o l v e n t s were d i s t i l l e d i n g l a s s equipment immediately before use. An a n t i o x i d a n t ( 1 , 3 , 5 - t r i m e t h y 1 - 2 , 4 , 6 - t r i s [ 3 , 5 - d i - t e r t butyl-4-hydroxybenzyl]benzene; A n t i o x i d a n t 330, E t h y l Corporation) was added t o a l l f r a c t i o n s and concentrates which were t o be s t o r e d f o r any l e n g t h of time. Concentrates P r e p a r a t i o n . V o l a t i l e s concentrates were prepared from s t a r t i n g m a t e r i a l s w i t h a modified Likens and Nickerson steam d i s t i l l a t i o n - e x t r a c t i o n head ( J J ^ ) operated e i t h e r a t 1 atm. (ether s o l v e n t ) o r a t reduced pressure (5055mm; heptane s o l v e n t ) . O l e o r e s i n Capsicum - I n a t y p i c a l atmospheric pressure run, a q u a n t i t y (1.48 kg) of o l e o r e s i n was combined i n a 12 1 round-bottomed f l a s k w i t h d i s t i l l e d water (6 1). Ether (200 ml) was used as e x t r a c t i o n s o l v e n t . The steam d i s t i l l a t i o n e x t r a c t i o n process was r u n f o r 4 h r . The r e s u l t i n g ether s o l u t i o n was d r i e d (anhyd. sodium s u l f a t e ) and the ether d i s t i l l e d , l e a v i n g 2.49 g of pepper components ( c o n t a i n i n g 10% e t h e r ) ; 0.15% y i e l d a f t e r c o r r e c t i n g f o r r e s i d u a l s o l v e n t . In a t y p i c a l reduced pressure r u n (55 mm), o l e o r e s i n (1.92 kg) and d i s t i l l e d water (6 1) y i e l d e d 3.38 g (0.176% y i e l d ) of concentrate when heptane was used as the e x t r a c t i o n s o l v e n t . Two 4-hr e x t r a c t i o n periods were used i n each run f o r concent r a t e p r e p a r a t i o n a t reduced pressure. Sweet C h i l i M i s c e l l a - Concentrates were prepared a t reduced pressure o n l y . I n i t i a l attempts t o use the m i s c e l l a as obtained from the s u p p l i e r were u n s u c c e s s f u l . When the m i s c e l l a was combined w i t h d i s t i l l e d water and the mixture was heated w i t h s t i r r i n g , an i n t r a c t a b l e g e l formed. Subsequently, a hexane f r a c t i o n was f i r s t d i s t i l l e d from the s t a r t i n g m a t e r i a l a t reduced p r e s s u r e . Pepper v o l a t i l e s e n t r a i n e d i n t h i s d i s t i l l a t e were l a t e r reclaimed by c a r e f u l f r a c t i o n a l r e d i s t i l l a t i o n of the hexane f r a c t i o n . The residue from t h i s f r a c t i o n a l d i s t i l l a t i o n was combined w i t h the heptane-extracted m a t e r i a l obtained w i t h the steam d i s t i l l a t i o n - e x t r a c t i o n head. In a t y p i c a l run, 5.28 kg of m i s c e l l a y i e l d e d 1.8 1 of hexane d i s t i l l a t e . The m i s c e l l a residue was combined w i t h 12 1 of d i s t i l l e d water, and three 4-hr e x t r a c t i o n runs were made a t 50 mm pressure. On r e d i s t i l l a t i o n of the 1.8 1 hexane d i s t i l l a t e , 0.55 g of residue was obtained. The combined y i e l d from the e n t i r e process was 1.05 g (0.0257%). Fresh Jalapeno Peppers - I n a t y p i c a l run, the peppers were quartered (5 kg) and added t o b o i l i n g d i s t i l l e d water (5 1 ) . The d i s t i l l a t i o n - e x t r a c t i o n process was r u n f o r f o u r 2-hr p e r i o d s , u s i n g f r e s h l y - d i s t i l l e d e t h e r . A t o t a l y i e l d of 0.143 g (0.0029%) was obtained a f t e r removal of s o l v e n t .



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Concentrates F r a c t i o n a t i o n . O l e o r e s i n Capsicum - Conv e n t i o n a l vacuum f r a c t i o n a l d i s t i l l a t i o n , aluminum oxide a d s o r p t i o n chromatography, and p r e p a r a t i v e gas chromatography were a p p l i e d i n p r e l i m i n a r y e f f o r t s to f r a c t i o n a t e o l e o r e s i n Capsicum v o l a t i l e s . Sweet C h i l i M i s c e l l a V o l a t i l e s - A p o r t i o n (5.00 g) of sweet c h i l i v o l a t i l e s i n a 40-ml pentane s o l u t i o n was separated i n t o n e u t r a l , a c i d , base f r a c t i o n s by successive e x t r a c t i o n w i t h s a t u r a t e d sodium bicarbonate s o l u t i o n and 6N h y d r o c h l o r i c a c i d s o l u t i o n . The n e u t r a l organic l a y e r , a f t e r d r y i n g and s o l v e n t removal, y i e l d e d 4.00 g of o r g a n i c residue (80% y i e l d ) . The bicarbonate e x t r a c t , a f t e r a c i d i f i c a t i o n and s o l v e n t ext r a c t i o n , a f f o r d e d 0.110 g (2.2%) of f r e e a c i d s . The hydroc h l o r i c a c i d s o l u t i o n , on b a s i f i c a t i o n w i t h 5N sodium hydroxide s o l u t i o n and s o l v e n t e x t r a c t i o n , y i e l d e d 0.080 g (1.6%) of organic m a t e r i a l . Component Separation and I d e n t i f i c a t i o n . Hewlett Packard 5830A and 5840A gas chromatographs f i t t e d w i t h g l a s s , fused s i l i c a , or s t a i n l e s s s t e e l c a p i l l a r y columns of v a r i o u s i n s i d e diameters were used f o r s e p a r a t i o n of the v o l a t i l e s f r a c t i o n s . E f f l u e n t s p l i t t e r s were used on occasion to permit gc e f f l u e n t s n i f f i n g . Methyl s i l i c o n e o i l was the s t a t i o n a r y phase of choice f o r most of the work, although Tween 20 and Carbowax 20M were used o c c a s i o n a l l y . A quadrupole-type gc-ms (16) was used f o r component i d e n t i f i c a t i o n i n n e a r l y a l l i n s t a n c e s . A few components were i s o l a t e d by p r e p a r a t i v e gc f o r i n f r a r e d and nuclear magnetic resonance s p e c t r o m e t r i c examination. The r e t e n t i o n behaviors of a l l t e n t a t i v e l y - i d e n t i f i e d c o n s t i t u e n t s were checked, u s i n g a u t h e n t i c samples, i n order to v e r i f y the ms i n t e r p r e t a t i o n s . Sensory E v a l u a t i o n . Odor t h r e s h o l d s were determined as p r e v i o u s l y d e s c r i b e d , using T e f l o n squeeze b o t t l e s f o r panel t e s t i n g (17). R e s u l t s and D i s c u s s i o n A summary of the compounds i d e n t i f i e d i n v a r i o u s pepper samples i s provided i n Table I . Many of the i d e n t i f i c a t i o n s were obtained w i t h v o l a t i l e s f r a c t i o n s from o l e o r e s i n Capsicum. The three major compounds i n the c a p s a i c i n o i d f r a c t i o n of most "hot" Capsicum f r u i t s are c a p s i a c i n , d i h y d r o c a p s a i c i n , and n o r d i h y d r o c a p s a i c i n (6^,_7,8^). These compounds are the Nv a n i l l y l amides of 8-methy1-6-nonenoic a c i d , 8-methylnonanoic a c i d , and 7-methyloctanoic a c i d , r e s p e c t i v e l y . I n s p e c t i o n of Table I r e v e a l s that these three a c i d s were found i n the o l e o -


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Table I . Compounds I d e n t i f i e d i n Pepper V o l a t i l e s by Gc-Ms.

Alcohols cyclopentanol a_ 2-methylbutan-l-ol b 2- methylbutan-2-ol b^ 3- methylbutan-l-ol a 1- pentanol a_ 2,3-butanediol _b trans-2-hexen-l-ol a_ c i s - 3 - h e x e n - l - o l a_, e_ 2- methylpentan-2-ol t) 3-methylpentan-3-ol _b 4- methylpentan-l-ol a_, c_ 1- hexanol a_, I), e^ 2- hexanol a_, b_ 3-hexanol b l i n a l o o l a_, b^, c_ t e r p i n e n - 4 - o l a., Jb a l p h a - t e r p i n e o l _b, £ Aldehydes and Ketones 2-butanone b^ 2- methylbutanal a_, b 3- methylbutanal a_, b^ cyclohexanone b 4- methyl-3-penten-2-one a_, _b ri-hexanal a., 1), e_ 2-hexanone b^ benzaldehyde a_, e_ 2 - a c e t y l f u r a n b^ 5- m e t h y l - 2 - f u r f u r a l a, b 2-heptanone a_ 2-octanone a_ para-methylacetophenone a_ carvone a^ camphor a_ thujone a_ i s o - t h u jone a_ 2-undecanone a_ beta-ionone c_ geranylacetone a C a r b o x y l i c Acids a c e t i c a_ 2-methylpropionic _b 2- m e t h y l b u t y r i c a_, b 3- m e t h y l b u t y r i c _b pentanoic a_ 4- methylpentanoic a_, b^ hexanoic a_, b heptanoic a


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Table I . Compounds I d e n t i f i e d i n Pepper V o l a t i l e s by Gc-Ms. Continued

2-octenoic a_ o c t a n o i c a^ ]p_ 7- methyloctanoic a_ nonanoic 01 2-decenoic a_ 8- methylnonanoic a_ Esters methyl pentanoate a_ methyl hexanoate a_ e t h y l 3-methylbutyrate t) methyl heptanoate a. methyl phenylacetate a_ methyl octanoate a_ b e t a - p h e n y l e t h y l a c e t a t e a_ methyl beta-phenylpropionate a_ e t h y l octanoate a_ methyl nonanoate a_ methyl 8-methy1-6-nonenoate a_ 4-methylpentyl 2-methylbutyrate a, c, e 4-methylpentyl 3-methylbutyrate a, ç methyl 8-methylnonanoate £ methyl decanoate a_ methyl dodecanoate a_ e t h y l dodecanoate a_ methyl tetradecanoate a_, h e t h y l tetradecanoate a_ methyl hexadecanoate a_, h methyl octadecanoate a_, h_

Terpene Hydrocarbons para-cyme ne t) camphene t) delta-3-carene a_, t>_ limonene a_, t> myrcene a_, t)_ alpha-phe 1 landrene a, t> alpha-pinene 1) beta-pinene a_, _b sabinene b^ gamma-terpinene b_ t e r p i n o l e n e ID alpha-thu je ne t) caryophyllene a_, t> alpha-copaene ]D_ Miscellaneous toluene b_ e_ para-xylene a., _b octane t) 2-penty l f u r a n a_, ID 2 - p e n t y l p y r i d i n e b> 1,8-cineole a^ eugenol Jp_ pentadecane a_ hexadecane a. heptadecane a_ y

Pyrazines 2,3-dimethy l p y r a z i n e t)_ 2 , 3 , 5 - t r i m e t h y l p y r a z i n e _b 2-methy1-5-ethylpyrazine ]D_ 2,3-dimethyl-5-ethylpyrazine b t e t r a m e t h y l p y r a z i n e ID 2-methoxy-3-i sobutylpy raz ine a, b, d, f_, ^

a. - O l e o r e s i n , Capsicum f r u t e s c e n s ; _b - Sweet c h i l i , C. annuum; c_ - Fresh Jalapenos, C. f rutescens; d - B u t t e r y et_ _a_l., 1969; e - Haymond and Aurand, 1971; f_ - Murray and W h i t f i e l d , 1975; £ - Huffman e t a l . , 1978; h - T e r a n i s h i et_ a l . , 1980.



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r e s i n Capsicum v o l a t i l e s , as f r e e a c i d s and/or as t h e i r methyl esters. D i f f e r e n t l o t s of o l e o r e s i n Capsicum obtained at d i f f e r e n t times v a r i e d considerably i n aroma c h a r a c t e r and i n t e n s i t y . This was p r i m a r i l y due to v a r i a t i o n s i n the sources of s t a r t i n g m a t e r i a l f o r p r e p a r a t i o n of the o l e o r e s i n , and was one of the major reasons f o r s e l e c t i n g the sweet c h i l i m a t e r i a l f o r subsequent research e f f o r t s . The sweet c h i l i s are grown i n New Mexico. Numerous attempts were made to f r a c t i o n a t e the o l e o r e s i n Capsicum v o l a t i l e s i n such a manner t h a t a peppery aroma would be concentrated i n one f r a c t i o n . Vacuum f r a c t i o n a l d i s t i l l a t i o n y i e l d e d f o u r f r a c t i o n s p l u s a r e s i d u e , none of which e x h i b i t e d a peppery aroma. The f i r s t f r a c t i o n e l u t e d w i t h pentane from a d e a c t i v a t e d (15% water by weight) alumina a d s o r p t i o n column had a peppery aroma, but on rechromatographing the f r a c t i o n on more a c t i v e alumina, the pepper aroma was l o s t . The aroma was a l s o mostly l o s t when p r e p a r a t i v e gas chromatography was a p p l i e d i n an attempt to separate the peppery alumina column f r a c t i o n . Gc f r a c t i o n s which r e t a i n e d some p e p p e r - l i k e aroma l o s t t h i s aroma a f t e r a few hours, even at low temperatures. Some success was achieved w i t h l a r g e r bore g l a s s c a p i l l a r y columns; components w i t h odors reminiscent of the pepper aroma p a r t l y s u r v i v e d s e p a r a t i o n i n such columns, p e r m i t t i n g gc s n i f f i n g of the e f f l u e n t . However, attempts to c o l l e c t s e v e r a l components were u n s u c c e s s f u l . The n e u t r a l , a c i d i c , and b a s i c f r a c t i o n s of the sweet c h i l i v o l a t i l e s concentrate were examined i n some d e t a i l , and e f f o r t s were made to c o r r e l a t e the v a r i o u s f r a c t i o n s odor t h r e s h o l d s and odor character w i t h the components found i n each. The n e u t r a l m a t e r i a l , r e p r e s e n t i n g 80% of the o r i g i n a l sweet c h i l i v o l a t i l e s , c o n s i s t l a r g e l y of monoterpene hydrocarbons. Sabinene (15.0%), delta-3-carene (13.4%), alpha-pinene (9.7%), limonene (9.2%), beta-pinene (7.3%), and s e v e r a l other minor monoterpenes comprise 63% of the n e u t r a l f r a c t i o n . A number of a l i p h a t i c hydrocarbon s o l v e n t components were detected, along w i t h c o n s i d e r a b l e r e s i d u a l heptane (13%). Only two sesquiterpenes, alpha-copaene and caryophyllene were i d e n t i f i e d . Both are present at low c o n c e n t r a t i o n s . A v a r i e t y of lower molecular weight a l i p h a t i c aldehydes, ketones, and a l c o h o l s were a l s o present i n s m a l l amounts. Approximately 92% of the n e u t r a l m a t e r i a l gc peak area has been i d e n t i f i e d . Assuming the odor u n i t concept to be v a l i d above t h r e s h o l d l e v e l s (18), alpha-pinene and limonene together provide about o n e - t h i r d of the t o t a l n e u t r a l f r a c t i o n ' s aroma. The odor t h r e s h o l d of the t o t a l f r a c t i o n i n water i s 11 p a r t s per billion. The a c i d i c f r a c t i o n i s 2.2% of the t o t a l v o l a t i l e s by weight. While s e v e r a l of the a c i d s were i d e n t i f i e d by d i r e c t gc-ms of the f r e e a c i d f r a c t i o n , most i d e n t i f i c a t i o n s as w e l l 1



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as q u a n t i t a t i v e data were obtained a f t e r conversion to the methyl e s t e r s . Three lower a l i p h a t i c a c i d s , 2-methylbutyric (42.8%), 3-methylbutyric (25.3%), and 2-methylpropionic (4.8%) make up 78% of the a c i d f r a c t i o n . In a d d i t i o n , t r a c e s of 4methylpentanoic, n-hexanoic, and n-octanoic a c i d s were detected. S e v e r a l non-acid c o n s t i t u e n t s were a l s o found i n the methyl e s t e r f r a c t i o n , i n c l u d i n g t r i m e t h y l p y r a z i n e (1.1%), tetramethylpyrazine (1.7%), t r a c e s of s e v e r a l ketones and 3-methyl-3-pentanol. Eighty-two percent of the t o t a l chro matographic peak area has been i d e n t i f i e d . A major c o n t r i b u t o r to the aroma of the f r e e a c i d m a t e r i a l i s 2-methylpropionic a c i d (odor t h r e s h o l d = 50 ppb [_19] ) . On an odor u n i t b a s i s , t h i s a c i d may be shown to provide approximately one-half of the t o t a l odor u n i t s of the f r a c t i o n . The measured t h r e s h o l d of t h i s f r a c t i o n ( f r e e a c i d ) i s 255 ppb. Considering t h a t t h i s i s roughly 20 times the t h r e s h o l d of the n e u t r a l f r a c t i o n , and t a k i n g i n t o account the s m a l l amount of a c i d i c m a t e r i a l i n the t o t a l v o l a t i l e s , the a c i d s are not thought to be s i g n i f i c a n t c o n t r i b u t o r s to the aroma of the t o t a l sweet chili volatiles. The b a s i c f r a c t i o n comprises only 1.6% of the t o t a l sweet c h i l i v o l a t i l e s . Tetramethylpyrazine makes up 68% of the f r a c t i o n ; i n a d d i t i o n , l e s s e r amounts of s e v e r a l other pyrazines were i d e n t i f i e d , i n c l u d i n g 2,3-dimethyl-5-ethyl-, 2-methyl-5e t h y l - , 2,3,5-trimethyl-, 2,3-dimethyl- and 2-methoxy-3i s o b u t y l p y r a z i n e , l i s t e d i n descending order of c o n c e n t r a t i o n . Greater than 75% of the b a s i c m a t e r i a l c o n s i s t s of p y r a z i n e s , some of which have not been f u l l y c h a r a c t e r i z e d . A r a t h e r low t h r e s h o l d of 1.4 ppb was determined f o r t h i s f r a c t i o n . Considering that the b e l l pepper p y r a z i n e s measured concen t r a t i o n i n t h i s b a s i c f r a c t i o n i s 0.23% and i t s odor t h r e s h o l d i s 2 parts per t r i l l i o n (10 ), t h i s pyrazine might be expected to be the major source of the b a s i c f r a c t i o n ' s aroma ( t e t r a m e t h y l p y r a z i n e s odor t h r e s h o l d i s reported to be 10 ppm [2Ό] ). However, s i n c e a considerable margin of e r r o r e x i s t s i n q u a n t i t a t i n g such s m a l l gas-chromatographic peaks, and s i n c e t h r e s h o l d determination i s not without i t s sources of e r r o r , such a c o n c l u s i o n i s not n e c e s s a r i l y v a l i d . Indeed, the aroma of the t o t a l sweet c h i l i m i s c e l l a v o l a t i l e s f r a c t i o n , and for that matter, of the sweet c h i l i m i s c e l l a i t s e l f , i s q u i t e d i f f e r e n t from that of the b e l l pepper pyrazine alone. A d r i e d cooked vegetable t i s s u e odor reminiscent of ground p a p r i k a p r e dominates at f u l l s t r e n g t h on a b l o t t e r s t r i p , but when a d i l u t e (ca 1:100) pentane s o l u t i o n of the sweet c h i l i m i s c e l l a i s sampled i n s i m i l a r f a s h i o n , the cooked odor becomes subdued, and a d i s t i n c t f l o r a l note i s detected, along w i t h an under l y i n g b e l l pepper aroma. 1

1



12.

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145

Some 16% of the o r i g i n a l sweet c h i l i v o l a t i l e s m a t e r i a l i s not accounted f o r by the sum of the n e u t r a l , a c i d , and b a s i c f r a c t i o n s . This i s thought t o be p r i m a r i l y due t o the presence of considerable 2,3-butanediol i n the s t a r t i n g v o l a t i l e s con c e n t r a t e . This m a t e r i a l i s q u i t e water s o l u b l e , and would be r e t a i n e d i n the aqueous phases during s e p a r a t i o n i n t o three f r a c t i o n s . The d i o l was detected by gc-ms i n the o r i g i n a l v o l a t i l e s m a t e r i a l , but was not found i n any of the three f r a c tions . Numerous minor c o n s t i t u e n t s remain u n i d e n t i f i e d , espe c i a l l y i n the n e u t r a l and b a s i c f r a c t i o n s . S n i f f i n g runs have i n d i c a t e d that q u a n t i t a t i v e l y - m i n o r components may s t i l l pro v i d e considerable aroma c h a r a c t e r , so these minor c o n s t i t u e n t s cannot n e c e s s a r i l y be ignored. The f r e s h Jalapeno pepper v o l a t i l e s concentrate has a pleasant f l o r a l aroma, along w i t h an a p p r e c i a b l e b e l l pepper c h a r a c t e r . The concentrate was not examined i n d e t a i l , but gc-ms data i n d i c a t e s the presence of numerous higher a l i p h a t i c e s t e r s , i n c l u d i n g the two which were synthesized and i d e n t i f i e d - the 4-methylpentyl e s t e r s of 2-methylbutyric (5.1%) and 3-methylbutyric (2.2%) a c i d . Attempts t o i d e n t i f y 2methoxy-3-isobutylpyrazine were f r u s t r a t e d by c o n s i d e r a b l e component overlap i n the gc-ms r u n . Summary V o l a t i l e s from r e d pepper or c h i l i s (Capsicum annuum and C^. f r u t e s c e n s ) were i s o l a t e d by steam d i s t i l l a t i o n - s o l v e n t ex t r a c t i o n methods. Compounds i d e n t i f i e d by gas chromatographymass spectrometry a r e : 17 a l c o h o l s , 20 carbonyl compounds, 14 c a r b o x y l i c a c i d s , 21 e s t e r s , 6 p y r a z i n e s , 14 terpene hydro carbons, and 10 miscellaneous compounds. Only t e n of these components have been reported p r e v i o u s l y i n v o l a t i l e s from peppers. Although the odor t h r e s h o l d method was a p p l i e d , the c h a r a c t e r i s t i c r e d pepper odor was not f u l l y c o r r e l a t e d w i t h i d e n t i f i e d c o n s t i t u e n t s . The green b e l l pepper compound, 2-methoxy-3-isobutylpyrazine, was found i n both £. annuum and C. f r u t e s c e n s .

Literature Cited 1.

2. 3.

Hedrick, U. P., Ed. "Sturtevant's Notes on Edible Plants"; Twenty-Seventh Annual Report, Vol. 2, Part I I , State of New York - Department of Agriculture; J . B. Lyon Company, State Printers: Albany, NY, 1919; p 134-140. Bailey, L. H.; Bailey, Ε. Z. "Hortus Third"; Macmillan Publishing Co., Inc.: New York, 1976;p219. Bailey, L. H. "Manual of Cultivated Plants"; Macmillan Publishing Co., Inc.: New York, 1949;p873.


QUALITY OF SELECTED FRUITS AND VEGETABLES


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4. Arctander, S. "Perfumery and Flavoring Materials of Natural Origin"; S. Arctander, Publ.: Elizabeth, NJ, 1960; p 122-124. 5. Todd, P. H., Jr.; Bensinger, M. G.; Biftu, T. J. Food Sci. 1977, 42, 660-665, 680. 6. Sticher, O.; Soldati, F.; Joshi, R. K. J. Chromatogr. 1978, 166, 221-231. 7. Iwai, K.; Suzuki, T.; Fujiwake, H. Agric. Biol. Chem. (Japan) 1979, 43, 2493-2498. 8. Jurenitsch, J.; David, M.; Heresch, F.; Kubelka, W. Planta Medica 1979, 36, 61-67. 9. Buttery, R. G.; Seifert, R. M.; Lundin, R. E.; Guadagni, D. G.; Ling, L. C. Chem & Ind. (London) 1969, 490-491. 10. Hayman, L.W.;Aurand, L. W. J. Agric. Food Chem. 1971, 19, 1131-1134. 11. Murray, Κ. E.; Whitfield, F. B. J. Sci. Fd. Agric. 1975, 26, 973-986. 12. Huffman, V. L.; Schadle, E. R.; Villalon, B.; Burns, Ε. E. J. Food Sci. 1978, 43, 1809-1811. 13. Teranishi, R.; Keller, U.; Flath, R. Α.; Mon, T. R. J. Ag ric. Food Chem. 1980, 28, 156-157. 14. Cripps, H. D. Kalsec, Inc.; private communication 1979. 15. Schultz, T. H.; Flath, R. Α.; Mon, T. R.; Eggling, S. B.; Teranishi, R. J. Agric. Food Chem. 1977, 25, 446-449. 16. Flath, R. Α.; Forrey, R. R. J. Agric. Food Chem. 1977, 25, 103-109. 17. Buttery, R. G.; Seifert, R. M.; Guadagni, D. G.; Black, D. R.; Ling, L. C. J. Agric. Food Chem. 1968, 16, 1009-1015. 18. Guadagni, D. G.; Buttery, R. G.; Harris, J . J. Sci. Fd. Agric. 1966, 17, 142-144. 19. Holluta, J. Gas Wasserfach 1960, 101, 1018-1023. 20. Koehler, P. E.; Mason, M. E.; Odell, G. V. J. Food Sci. 1971, 36, 816-818. RECEIVED

April

3, 1981


Volatiles from Red Pepper - American Chemical Society

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