Objective Measurements of Flavor Quality: General Approaches

1 Objective Measurements of Flavor Quality: General Approaches, Problems, Pitfalls, and Accomplishments

Downloaded by 80.82.77.83 on October 10, 2017 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0051.ch001

WALTER G. JENNINGS Department of Food Science and Technology, University of California, Davis, CA 95616

After I had accepted the invitation to prepare an opening paper for this series, I was filled with a sense of foreboding, and for very good reasons. First, I can think of a number of individuals who beyond any doubt are better qualified to discuss this multi-disciplinary area than I am, and second, the title itself is enough to flash a warning light. While the complexity of this attribute we call "flavor" has been stressed by several workers (e.g. 1), Moncrief (2) argued that taste and odor are the major components. Certainly i t is generally agreed that flavor requires the participation of sensory receptors, which makes it an individual, and at least within certain limits, a variable characteristic. Because of this, flavor is necessarily a highly subjective trait. Rereading my title, I find that I'm committed to discussing objective measurements of a subjective characteristic and my first thought is, "I'm in trouble." But as long as we recognize this contradiction and are willing to accept a degree of compromise, hopefully we can make some progress. An early quest for an objective measurement of quality has been cited from the 13th and 14th centuries, when "ale conners" or "ale tasters" in England were assigned the task of setting the price on batches of brew based on their individual flavor judgments. In an effort to achieve a greater degree of objectivity, this was combined with a test of the ale strength: some of the ale was poured on a bench, and the ale Conner sat in i t . After a predetermined interval, "he made to stand up"; i f his leather breeches stuck to the bench, the ale was of the right quality (3). To most of us, an "objective measurement of flavor quality" means establishing a chemical or physical method for measuring the amount of a substance responsible for a particular flavor attribute. This requires first establishing which compound or compounds are responsible for a particular attribute, which has been done in relatively few instances, at least in complex mixtures. The problem is further complicated by the fact that synergism and antagonism can exist between compounds that elicit flavor responses. In many cases, flavor is due to an integrated 1 Scanlan; Flavor Quality: Objective Measurement ACS Symposium Series; American Chemical Society: Washington, DC, 1977.


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response to at l e a s t several compounds, and as we change the r e l a t i v e r a t i o s and/or absolute amounts of these compounds, the f l a v o r responses change i n a manner t h a t i s u s u a l l y u n p r e d i c t a b l e . Moskowitz (4) argued t h a t the a c t i v i t i e s of the f l a v o r chemist, who i s u s u a l l y concerned w i t h e s t a b l i s h i n g the c o n t r i b u t i o n of i n d i v i d u a l components to f l a v o r , diverge from but are complement a r y to psychometric e f f o r t s concerned w i t h the q u a l i t y of f l a v o r mixtures. Two general approaches have been u t i l i z e d i n attempts to o b t a i n o b j e c t i v e measurements of f l a v o r q u a l i t y . One has been concerned with the measurement or r e c o r d i n g of the minute e l e c t r i c a l response of o l f a c t o r y or t a s t e c e l l s e l i c i t e d by odor or t a s t e s t i m u l i (e.g. 5_, 6 ) , but a great deal of work remains to be done i n t h i s a r e a . Another widely used approach has involved s n i f f i n g the o u t l e t of a gas chromatograph (e.g. 7 ) . C e r t a i n problems are immediately obvious: f l a v o r i s an i n t e g r a t e d response to a mixture of compounds, and the gas chromatograph provides a d i f f e r e n t i a l r a t h e r than an i n t e g r a t e d response to those compounds. Secondly, i t can be most d i s t u r b i n g when the panel reports t h a t i n t e r e s t i n g odors e x i s t between the peaks (e.g. 8 , 9) which emphasizes the f a c t t h a t f o r some substances, the gas cïïromatograph has not y e t matched the s e n s i t i v i t y of the human nose. Even s o , useful r e s u l t s can be obtained by t h i s r o u t e . B a r y l k o - P i k i e l n a et a l . (10) s p l i t the e f f l u e n t from a gas c h r o matographic column to a s s i g n q u a l i t a t i v e odor assessments to the i n d i v i d u a l peaks of a sugar-amino a c i d r e a c t i o n m i x t u r e . McLeod and Coppock (TJJ used a s i m i l a r technique to a s s i g n odor e v a l u a t i o n s to f r a c t i o n s from b o i l i n g beef. A number of workers i n t e r ested i n c o r r e l a t i n g t h e i r a n a l y t i c a l r e s u l t s w i t h sensory response have a l s o used the odors of i n d i v i d u a l peaks, sometimes to good advantage (vide i n f r a ) . Tucknott and W i l l i a m s (12) pointed out t h a t s n i f f i n g the e f f l u e n t from a gas chromatograph s u f f e r s from a number of other shortcomings, and suggested t h a t the e f f l u e n t gas c o n t a i n i n g peaks of i n t e r e s t be trapped i n i n d i v i d u a l d i s p o s a b l e syringes f o r subsequent odor assessment. Clark and Cronin (13) u t i l i z e d a novel method; peaks were trapped i n short s e c t i o n s of support coated open t u b u l a r (SCOT) g l a s s columns, which were then crushed under water to produce a s o l u t i o n f o r sensory a n a l y s i s . Parliment (14) bubbled the gas chromatographic e f f l u e n t i n t o water to prepare s o l u t i o n s f o r t a s t e - t e s t i n g , which he reported was i n some cases more s a t i s f a c t o r y than s n i f f - t e s t i n g . When we r e s o r t to gas chromatography, we have of course r e s t r i c t e d our o b j e c t i v e measurements to v o l a t i l e compounds; i t i s a l l too easy to f o r g e t t h a t t a s t e i s a l s o a major c o n t r i b u t o r to f l a v o r (1). Weiss and S c h a l l e r (T5_, 16) s t u d i e d the i n f l u e n c e of several v a r i a b l e s - - e . g . t i t r a t a b l e a c i d i t y , pH, d i s s o l v e d gases-on the sensory p r o p e r t i e s of apple j u i c e ; a number of such s t u d i e s

Scanlan; Flavor Quality: Objective Measurement ACS Symposium Series; American Chemical Society: Washington, DC, 1977.


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on other products have been p u b l i s h e d . R e c e n t l y , Noble (17) used gel chromatography to f r a c t i o n a t e f l a v o r components of tomato. Another major problem i s o b t a i n i n g gas chromatographic r e s u l t s t h a t r e f l e c t with high q u a l i t a t i v e and q u a n t i t a t i v e f i d e l i t y the v o l a t i l e composition of the m a t e r i a l i n q u e s t i o n . Compositional changes are f r e q u e n t l y caused i n the p r e p a r a t i o n of a sample s u i t a b l e f o r gas chromatography, and a d d i t i o n a l e r r o r s may be introduced by the gas chromatographic a n a l y s i s i t s e l f . Many m a t e r i a l s r e q u i r e some type of treatment to f r e e the compounds of i n t e r e s t from m a t e r i a l s t h a t would otherwise i n t e r fere w i t h the a n a l y s i s (e.g. water and n o n - v o l a t i l e components) before the sample can be i n j e c t e d i n t o the gas chromatograph. A l s o , some type of c o n c e n t r a t i o n i s f r e q u e n t l y r e q u i r e d so t h a t the l i m i t e d amount of sample that can be i n j e c t e d contains d e t e c t able q u a n t i t i e s of the compounds to be s t u d i e d . Most o f the procedures t h a t are used to achieve these ends i n v o l v e d i s t i l l a t i o n , e x t r a c t i o n and/or e v a p o r a t i o n , or a d s o r p t i o n , a l l of which cause q u a n t i t a t i v e changes and some of which may engender q u a l i t a t i v e changes i n the concentrated sample, so that i t no longer r e f l e c t s the composition of the s t a r t i n g m a t e r i a l . In e f f o r t s to surmount these d i f f i c u l t i e s , many i n v e s t i g a t o r s p r e f e r to use d i r e c t i n j e c t i o n s of headspace gas f o r a n a l y s i s , but the chromatogram i s then r e s t r i c t e d to those components whose p a r t i a l pressures are r e l a t i v e l y h i g h . A great deal of a t t e n t i o n has been given to the use of porous polymers i n c o n c e n t r a t i n g headspace v o l a t i l e s by l e s s strenuous means ( e . g . 1J3, 19^, 20). Sample p r e p a r a t i o n remains a c r i t i c a l l y important a r e a , and forms the subject of another symposium at t h i s meeting. Another source of problems l i e s i n the gas chromatographic a n a l y s i s i t s e l f ; not a l l compounds are s t a b l e to the c o n d i t i o n s of the a n a l y s i s , and the chromatogram may not a c c u r a t e l y r e f l e c t the composition of the m a t e r i a l i n j e c t e d . A d d i t i o n a l l y , minor components t h a t are not w e l l resolved from l a r g e r c o n s t i t u e n t s may be of c r i t i c a l importance to a given f l a v o r a t t r i b u t e , but unless these are unambiguously separated from the other compon e n t s , we are f r e q u e n t l y not even aware of t h e i r e x i s t e n c e i n the sample. Recent developments i n w a l l - c o a t e d open t u b u l a r g l a s s c a p i l l a r y columns (WCOT: 21^, 22, 23) make i t p o s s i b l e to r e s o l v e many of these p r e v i o u s l y poorly separated components. A d d i t i o n a l l y , the more i n e r t c h a r a c t e r of the g l a s s columns has permitted a n a l y s i s of some c o n s t i t u e n t s (notably s u l f u r - c o n t a i n i n g compounds) t h a t are almost s u r e l y of great importance to some f l a v o r s and which have r e s i s t e d packed-column or m e t a l - c a p i l l a r y a n a l y s i s (e.g. 24, 25, 26). Glass i n l e t s p l i t t e r s of much higher l i n e a r i t y (27, 2 8 ) , when combined w i t h the open t u b u l a r g l a s s c a p i l l a r y column, are capable of producing chromatograms t h a t r e f l e c t much more a c c u r a t e l y the composition of the i n j e c t e d sample.



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U n f o r t u n a t e l y , column e f f i c i e n c y - - ! . e . the inherent power to separate the components of a m i x t u r e - - i s i n v e r s e l y p r o p o r t i o n a l to column c a p a c i t y . The maximum t h e o r e t i c a l e f f i c i e n c y of WCOT columns, expressed i n t h e o r e t i c a l p l a t e s per meter, i s a p p r o x i mately 1000/r, where r i s the inner column radius i n mm (29). A compromise i s a l s o u s u a l l y necessary i n the thickness of the f i l m of l i q u i d phase, as columns with t h i n n e r f i l m s have higher e f f i c i e n c i e s but impose severe l i m i t a t i o n s on sample c a p a c i t y , and columns w i t h t h i c k e r f i l m s possess higher c a p a c i t i e s at the expense of column e f f i c i e n c y (e.g. 2£, 30). While the lower c a p a c i t i e s of small diameter (e.g. 0.25 mm) WCOT columns are s t i l l s u f f i c i e n t f o r a p p l i c a t i o n s such as gas chromatographymass spectrometry, t h e i r use f o r the sensory a n a l y s i s of i n d i v i dual f r a c t i o n s poses very d i f f i c u l t problems. Some i n v e s t i g a t o r s have compromised on l a r g e r diameter WCOT columns (e.g. 31_, 3 2 ) , or columns whose roughened or extended inner surfaces (PLOT or SCOT columns) increase the surface area of the l i q u i d phase (e.g. 33, 34). Because of t h i s c a p a c i t y requirement, there remains a use and a need for packed columns. I t i s , however, c r i t i c a l l y important to d u p l i c a t e the a n a l y s i s on a high r e s o l u t i o n system, so the i n v e s t i g a t o r i s not misled by peaks that may play a c r u c i a l r o l e i n the sensory q u a l i t i e s and that are not w e l l resolved on the lower r e s o l u t i o n high c a p a c i t y system. The i n v e s t i g a t o r must a l s o f r e q u e n t l y compromise i n s e l e c t i n g gas chromatographic parameters, balancing the degree of separation d e s i r e d against the length of time required f o r the a n a l y s i s , and, f o r t h e r m a l l y l a b i l e m a t e r i a l s , the amount of heat to which the samples are exposed (35). A t t e n t i o n must a l s o be given to the s u i t a b i l i t y of the system f o r the separation of the components of a given m i x t u r e . Once the problems of sample preparation and sample a n a l y s i s are overcome, one has at best a w e l l - r e s o l v e d chromatogram, w i t h out overlapping or co-chromatographing components, which may q u a l i t a t i v e l y and q u a n t i t a t i v e l y r e f l e c t the composition of the o r i g i n a l m a t e r i a l . I t cannot be overemphasized t h a t even t h i s i s r a r e l y achieved. S t i l l to be reckoned w i t h are the myriad problems and sources of e r r o r inherent i n the sensory t e s t i n g procedures. Most of us would now agree that i t i s not s u f f i c i e n t f o r the chemist, untrained i n sensory a n a l y s i s , to c a s u a l l y s n i f f the o u t l e t of h i s gas chromatograph and record h i s impressions. Sensory a n a l y s i s , t o o , has come a long way, and a meaningful study should use s e l e c t e d panels of t r a i n e d personnel u t i l i z i n g q u a n t i t a t i v e procedures amenable to s t a t i s t i c a l e v a l u a t i o n . Martin (36) described procedures used i n the s e l e c t i o n and t r a i n i n g of p a n e l i s t s f o r various types of sensory e v a l u a t i o n s . Larmond (37) emphasized the importance of c o n t r o l l i n g p h y s i c a l s t i m u l i to which the p a n e l i s t s are subjected. Best (38) described the a n a l y s i s of t a s t e - t e s t d a t a , and H a r r i e s (39) reviewed the c o m p l e x i t i e s of sensory assessment. Stone et a l .



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(40) described a sensory e v a l u a t i o n technique termed " q u a n t i t a t i v e d e s c r i p t i v e a n a l y s i s " which uses an i n t e r v a l s c a l e and a panel of at l e a s t s i x t r a i n e d p a n e l i s t s , and Moskowitz (41_) has argued f o r a method he terms "magnitude e s t i m a t i o n " , i n which numbers are assigned to s t i m u l i so t h a t the r a t i o s of judgments r e f l e c t sensory r a t i o s . Taking a l l of these f a c t o r s i n t o account--changes engendered by sample p r e p a r a t i o n ; poor s e p a r a t i o n , a r t i f a c t s and e r r o r s i n the gas chromatographic a n a l y s i s ; s i n s of omission and s i n s of commission i n the sensory a n a l y s i s - - t h e i n v e s t i g a t o r may f i n a l l y be i n a p o s i t i o n to t r y and r e l a t e v a r i a t i o n s i n the sensory p r o p e r t i e s to v a r i a t i o n s i n the chromatographic p a t t e r n . Here a g a i n , however, r e s u l t s can be o v e r - i n t e r p r e t e d . Szczesniak (42) and Persson et a l . (43^, 44) both emphasize t h a t even a s i g n i f i c a n t c o r r e l a t i o n between a p h y s i c a l measurement and a sensory r a t i n g e s t a b l i s h e s only a p r e d i c t i v e r e l a t i o n s h i p , not a causal one. Two general approaches, which are not n e c e s s a r i l y mutually e x c l u s i v e , have been used i n attempts to c o r r e l a t e the a n a l y t i cal data with sensory a t t r i b u t e s . One has involved attempts to e s t a b l i s h the q u a l i t a t i v e and/or q u a n t i t a t i v e f l a v o r p r o p e r t i e s of i n d i v i d u a l compounds, sometimes with a t t e n t i o n to the synergism or antagonism t h a t they e x h i b i t i n mixtures w i t h other compounds, or i n one s o l v e n t as opposed to another. Meilgaard (45, 46) and Clapperton e t a l . (47) have accumulated a l a r g e amount of information on the f l a v o r c h a r a c t e r i s i t i c s and t h r e s h o l d values of aroma v o l a t i l e s i n beer. As emphasized by these workers, the odor p u r i t y of the compounds t e s t e d i s c r i t i c a l l y important to t h i s type of study. They p o i n t o u t , as one example, that Murahashi (48) reported l - o c t e n - 3 - o l as possessing a mushroom aroma, w h i l e Hoffmann (49) a s c r i b e d the odor to 1,3dioxalans formed on decomposition of the a l c o h o l . L a t e r Meilgaard (46) found t h a t the odor i n question was due to contamination by l - o c t e n - 3 - o n e , which had a m e t a l l i c aroma i n f a t s o l u t i o n s , and a mushroom aroma i n aqueous medium; the p u r i f i e d alcohol had an odor he reported as " s p i c y , perfumed and g r a s s l i k e . " S i m i l a r l y , Boelens et a l . (50), who i d e n t i f i e d a large number of compounds i n onion o i l , suggested t h a t 2 , 4 - d i m e t h y l thiophene and 3,4-dimenthythiophene possessed an odor of f r i e d onions. R e c e n t l y , G a l e t t o and Hoffman (5>1) synthesized these compounds, and reported t h a t alone or i n combination w i t h other compounds they d i d not make a s i g n i f i c a n t c o n t r i b u t i o n to the f r i e d onion aroma. The other major approach has involved attempts to c o r r e l a t e f l a v o r w i t h gas chromatographic p a t t e r n s . Guadagni et a l . worked on such c o r r e l a t i o n s f o r apple (7); these and other e f f o r t s have been reviewed by Powers (52), ASTM (53, 54) and von Sydow (55); a d d i t i o n a l e f f o r t s i n c l u d e those of Salo et a l . (56) and Salo (57).



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Bednarczyk and Kramer (58) reported that four gas chromato graphic peaks accounted f o r 85% of a sensory p a n e l ' s f l a v o r response to ginger e s s e n t i a l o i l . C i t e d as prime c o n t r i b u t o r s to the c h a r a c t e r i s t i c ginger a t t r i b u t e were 3-sesquiphellandrene and ar-curcumene; α t e r p i n e o l and c i t r a l s c o n t r i b u t e d a lemony a t t r i b u t e , and an undesirable woody or soapy note was caused by nerolidol. Using l i n e a r r e g r e s s i o n a n a l y s i s , Fore et a l . (59) found a high c o r r e l a t i o n between the f l a v o r score of stored peanut b u t t e r and the r a t i o between 2-methyl propanal and hexanal as d e t e r mined gas chromatographically. Dravnieks et a l . (60.) used stepwise d i s c r i m i n a t e a n a l y s i s to c l a s s i f y , by gas chromato graphic techniques, the odor of c o r n . G a l e t t o and Bednarczyk (61) used m u l t i p l e r e g r e s s i o n techniques i n e s t a b l i s h i n g t h a t the amount of methyl propyl d i s u l f i d e , methyl propyl t r i s u l f i d e and d i p r o p y l t r i s u l f i d e as determined gas chromatographically showed a high degree of c o r r e l a t i o n w i t h o v e r a l l onion f l a v o r . Tassan and R u s s e l l (62) used a micro olfactometer to evaluate the odors of i n d i v i d u a l cumin c o n s t i t u e n t s trapped from a gas chromato graph, and reported that v a r i a t i o n s i n four aldehydes i n f l u e n c e d the main odor c h a r a c t e r ; 3-p-menthen-7-al was shown to be necessary f o r the c h a r a c t e r i s t i c odor of heated cumin. Karlsson-Ekstrom and von Sydow (63) using a p s y c h o p h y s i c a l s t a t i s t i c a l approach, found t h a t the sensory changes that occur when black c u r r a n t s are heated could be w e l l c o r r e l a t e d w i t h a decrease i n monoterpene hydrocarbons and an increase i n dimethyl s u l f i d e and a l i p h a t i c aldehydes. Persson and von Sydow (640 examined the sum, d i f f e r e n c e s , r a t i o s , geometric means and v e c t o r i a l sums of peaks from gas chromatographic analyses for t h e i r c o r r e l a t i o n w i t h f l a v o r scores of frozen and r e f r i g e r a t e d cooked s l i c e d beef. A number of d i f f e r e n t models i n v o l v i n g both sensory response and gas chromatographic data e x h i b i t e d high c o e f f i c i e n t s of c o r r e l a t i o n . Studies on canned beef (43) e s t a b l i s h e d that a high degree of c o r r e l a t i o n e x i s t e d between 15 odor p r o p e r t i e s and four gas chromatographic peak combinations. In l a t e r work the methods were extended to a v a r i e t y of meat products and found to hold true (44). Akesson et a l . (65) used headspace sampling techniques and open t u b u l a r gas chromatography combined with a f l a v o r p r o f i l e technique to see i f sensory p r o p e r t i e s and preference values f o r a v a r i e t y of food m a t e r i a l s could be p r e d i c t e d by gas chromato graphic d a t a . T e s t i n g a large number of models t h a t used gas chromatographic peak areas i n various combinations and i n several types of f u n c t i o n s , they found that the assessment of sensory q u a l i t i e s was r e l a t e d monotonicly to gas chromatographic d a t a , w h i l e estimated preference values were i n most cases r e l a t e d i n a more complex non-mototonic way. Using the proper models, very accurate p r e d i c t i o n s could be made. Von Sydow (66)



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g e n e r a l i z e d t h a t a l l compounds present above t h r e s h o l d l e v e l s c o n t r i b u t e to the aroma of foods, and t h a t the number of important aroma c o n t r i b u t o r s i s v a r i a b l e , but i s u s u a l l y high i n t h e r m a l l y processed foods or foods of animal o r i g i n . He emphas i z e d t h a t the instrumental technique must be g e n t l e , so that the sample i n v e s t i g a t e d represents the true s i t u a t i o n i n the food, and that the sensory technique must be d e t a i l e d and s e n s i t i v e . The development of numerical and psychophysical models capable of r e l a t i n g the physicochemical data with the sensory data i s crucial. I t would appear t h a t we may f i n a l l y have a r r i v e d at a p o i n t where we have the opportunity to combine improved methods of sample p r e p a r a t i o n , gas chromatographic s e p a r a t i o n , sensory a n a l y s i s and computerized data a n a l y s i s to achieve some r e a l i s t i c r e s u l t s i n the search f o r o b j e c t i v e measurements of f l a v o r q u a l i t y i n at l e a s t some products. Success i n these e f f o r t s w i l l depend to a large degree on how w e l l we combine advances i n sample preparation w i t h high r e s o l u t i o n gas chromatography, v a l i d sensory procedures and advanced methods of data a n a l y s i s . This r e q u i r e s judgments and e v a l u a t i o n s on the part of the investigator. No s i n g l e sample preparation procedure can be accepted as uniformly s a t i s f a c t o r y ; one or another may be s u p e r i or depending on the sample composition and the compounds of interest. Gas chromatographic parameters must be s e l e c t e d c a r e f u l l y , w i t h a t t e n t i o n to the sample c o m p o s i t i o n , i t s s t a b i l i t y under the c o n d i t i o n s of a n a l y s i s and whether one's immediate goal i s r e s o l u t i o n or c a p a c i t y . Neither are a l l procedures f o r sensory or data a n a l y s i s — i n c l u d i n g those c i t e d i n t h i s p a p e r - - e q u a l l y v a l i d under a l l circumstances, nor are a l l of them acceptable to experts i n t h i s f i e l d (e.g. 4 0 , 41_, 5i8). And no degree of s o p h i s t i c a t e d computer a n a l y s i s can compensate f o r c a r e l e s s sensory procedures, or f o r an incompletely resolved chromatogram i n which peaks of sensory importance have f a i l e d to separate. But we do now have increased c a p a b i l i t y i n a l l of these a r e a s , and the next few years should see some e x c i t i n g results. I would l i k e to conclude by thanking several c l o s e f r i e n d s , e s p e c i a l l y E r i k von Sydow, Morten M e i l g a a r d , Rose Marie Pangborn and Gerry R u s s e l l f o r t h e i r help i n preparing t h i s i n f o r m a t i o n . There are of course many other i n v e s t i g a t i o n s which could and perhaps should have been included i n t h i s p r e s e n t a t i o n . I can only apologize f o r such o m i s s i o n s , but i n a very short time the data I have presented w i l l be l a r g e l y o b s o l e t e , as the papers that f o l l o w t h i s b r i e f i n t r o d u c t i o n extend our e f f o r t s and knowledge i n t h i s very important a r e a .



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flavor quality: objective measurement

Literature Cited 1. Amerine, Μ. Α., Pangborn, R. Μ., Roessler, Ε. B. "Principles of Sensory Evaluation of Food", page 3. Academic Press New York, London, 1965 2. Moncrief, R. W. in "The Chemistry and Physiology of Flavors", 3rd Edit., page 650. Avi Publishing, Westport, Conn. 1967 3. Corran, H. S. "A History of Brewing", page 40. Davis and Charles, London, 1975 4. Moskowitz, H. R. Lebensmittel Wissenshaft-Technologie (1975) 8, 237 5. Boeckh, J. in "Geruch und Geschmackstoffe", pages 1-18. Hans Karl, Nurenberg, Germany, 1975 6. Getchell, T. V. and Getchell, M. L. Ann. New York Acad. Sci. (1974) 237, 62 7. Guadagni, D. G., Okano, S., Buttery, R. G., Burr, Η. K. Food Technol., (1966) 20, 518 8. Jennings, W. G. Lebensmittel Wissenschaft-Technologie (1969) 2, 75 9. Jennings, W. G. Food Technol. (1972) 26, 25 10. Barylko-Pikielna, N., Daniewski, M. and Mielniczuk, Z. Die Nahrung (1974) 18, 125 11. MacLeod, G. and Coppock, B. M. J. Agr. Food Chem. (1976) 24, 835 12. Tucknott, O. G. and Williams, A. A. Chem. and Ind. (1974) No. 19, 784 13. Clark, R. G. and Cronin, D. A. J. Sci. Food Agric. (1975) 26, 1009 14. Parliment, T. H. Chem. and Ind. (1976) No. 9, 418 15. Weiss, J., Schaller, A. Confructa (1970 a) 15, 93 16. Weiss, J., Schaller, A. Confructa (1970 b) 15, 140 17. Noble, A. C. J. Agr. and Food Chem. (1976) 24, 321 18. Dravnieks, Α., Krotoszynski, Β. Κ., Whitfield, J., O'Donnell, A. and Burgwald, T. Environ. Sci. Technol. (1971) 5, 1220 19. Jennings, W. G., Wohleb, R. and Lewis, M. J. J. Food Sci. (1972) 37, 69 20. Jennings, W. G., Wohleb, R. H. and Lewis, M. J. M.B.A.A. Tech. Quarterly (1974) 11, 104 21. Jennings, W. G., Wohleb, R. H. Chemie, Mikrobiol. Tech. der Lebensmittel (1974) 3, 33 22. Jennings, W. G., Yabumoto, Κ., Wohleb, R. H. J. Chromatogr. Sci. (1974) 12, 344 23. Jennings, W. G. Chromatographia (1975) 8, 690 24. Whithycombe, D. Α., Walradt, J. P. Paper 13, 170th ACS National Meeting, Chicago, Ill. Aug. 25-29, 1975 25. Shibamoto, T. and Russell, G. F. J. Agr. Food Chem. (1976), 24, 843 26. Buttery, R. G., Guadagni, D. G., Ling, L. C., Seifert, R. M. and Lipton, W. J. Agr. Food Chem. (1976) 24, 829



1. jennings

Approaches, Problems, Pitfalh, and Accomplishments

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27. Jennings, W. G. J. Chromatog. S c i . (1975) 13, 185 28. Jennings, W. G. Food Chem. (1977) (in press) 29. Kaiser, R. "Chromatographie in der Gasphase", vol. 2, 3rd E d i t . : page 72. Bibliographisches Institut Mannheim, 1975 30. Ettre, L. S. "Open Tubular Columns in Gas Chromatography", page 15, Plenum Press, 1965 31. Verzele, Μ., Verstappe, Μ., Sandra, P . , van Luchene, E. and Vuye, A. J. Chromatogr. S c i . (1972) 10, 668 32. Roeraade, J. Chromatographia (1975) 8, 511 33. Cronin, D. A. J. Chromatog. (1970) 48, 406 34. Schieke, J. D . , Comins, N. R. and Pretorius, V. J. Chroma tog. (1975) 115, 373 35. Jennings, W. G. and Adam, S. Anal. Biochem. (1975) 69, 61 36. Martin, S. L. Food Technol. (1973) 27 (11), 22 37. Larmond, E. Food Technolol. (1973) 27 (11), 28 38. Best, D. J. Food Technol. in Australia (1974) 26, 20 39. Harries, J. M. J. S c i . Food Agr. (1973) 24, 1571 40. Stone, Η . , Sidel, J., Oliver, S . , Woolsey, A. and Singleton, R. C. Food Technol. (1974) 28 (11) 24 41. Moskowitz, H. R. Food Technol. (1974) 28 (11), 16 42. Szczesniak, A. S. Food Technol. (1968) 22, 981 43. Persson, T., von Sydow, E., Åkesson, C. J. Food S c i . (1973) 38, 682 44. Persson, T. and von Sydow, E. J. Food S c i . (1974) 39, 537 45. Meilgaard, M. C. M.B.A.A. Tech. Quarterly (1975) 12, 107 46. Meilgaard, M. C. M.B.A.A. Tech. Quarterly (1975) 12, 151 47. Clapperton, J. F., Dalgliesh, C. E. and Meilgaard, M. C. M.B.A.A. Tech. Quarterly (1976) (in press) 48. Murahashi, S. S c i . Papers Inst. Phys. Chem. Res. (Tokyo) (1938) 34, 155 cf. Chem. Abst. 32, 37556 49. Hoffmann, G. "Lipids and their Oxidation", page 224, Schultz, H. W. e d . , Avi Publishing, Westport, Conn. 1962 50. Boelens, M . , de Valois, P. J., Wobben, H. J., Van den Gen, A. J. Agr. Food Chem. (1971) 19, 984 51. Galetto, W. G. and Hoffman, P. G. J. Agr. Food Chem. (1976) 24, 852 52. Powers, J. J. Food Technol. (1968) 22, 383 53. ASTM. "Correlation of Subjective-Objective Methods in the Study of Odor and Taste". Spec. Tech. Pub. #440. 1968 54. ASTM. "Reviews of Correlations of Objective-Subjective Methods in the Study of Odor and Taste". Spec. Tech. Pub. #451. 1969 55. von Sydow, E. Food Technol. (1971 ) 25, 40 56. Salo, P. Lebensmittel Wissenschaft-Technologie (1973) 6, 52 57. Salo, P . , Nykanen, L., Soumalainen, H. J. Food S c i . (1972) 37, 394 58. Bednarczyk, A. A. and Kramer, A. Chem. Senses and Flavor (1975) 1, 377



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59. Fore, S. P . , Goldblatt, L. Α . , Dupuy, H. P. J . Amer. Peanut Res. Educ. Ass. (1972) 4, 177 60. Dravnieks, Α . , Reilich, H. G . , Whitfield, J. J . Food S c i . (1973) 38, 34 61. Galetto, W. G. and Bednarczyk, A. A. J . Food S c i . (1975) 40, 1165 62. Tassan, C. G. and Russell, G. F. J . Food S c i . (1975) 40, 1185 63. Karlsson-Ekström, G. and von Sydow, E. Lebensmittel Wissenschaf-Technologie (1973) 6, 86 64. Persson, T . , von Sydow, E. J . Food S c i . (1972) 37, 234 65. Åkesson, C . , Persson, T. and von Sydow, E. (1976). Personal communication. To be published. 66. von Sydow, E. (1976). Personal communication. To be published.


Objective Measurements of Flavor Quality: General Approaches

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