Aroma profiles and sensory evaluation of yogurt during storage*

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1 M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 roma profiles and sensory ealuation of yogurt during storage* Mirjana Hruškar, ada Vahčić i Milana itz Original scientific paper - Izorni znansteni rad DC: ummary It is known that more than chemical compounds hae been isolated from yogurt and related milk products but only a few (acetaldehyde, ethanol, aceton, diacetyl and butanon-2) hae a high impact on the desired product flaour. he concentration of these typical flaour compounds changed during storage depending on duration and temperature in depot. In this article six commercial brands of plain yogurt were stored within days on two different temperatures and eery two days changes in acetaldehyde, diacetyl and ethanol were established. t the same time sensory ealuation was carried out as well. cetaldehyde and ethanol concentration was determined using aldehyde dehydrogenase and alcohol dehydrogenase method. Diacetyl was measured according to Hill's modification of colorimetric method. fie member panel, performed sensory analysis using scoring system with weighted factors in the 2- points' scale. xpert panel's ratings were regressed against concentrations of aroma compounds for both temperature leels and linear relationship among them were determined. he most pronounced relationship expressed as correlation coefficients (r) between expert panel's ratings and concentrations of indiidual compounds was obsered with ethanol (r=.996) in yogurt sample stored at +4 C. Coefficients of correlation were generally high (from.24 to -.996) and consequently ery accurately predicting equations were obtained using regression analysis. Key words: aroma compounds, acetaldehyde, diacetyl, ethanol, sensory ealuation, correlation Introduction Fermented milks are accepted by the consumer because of their characteristic properties: flaour, aroma, appearance and texture. ll these sensoric qualities are consequences of multiple fermentations and it is accepted that selection of the multi-strain or more often multi-species inoculum is necessary to obtain a good fermented product. herefore, the last twenty years considerable adances hae been made towards an understanding of cultured product flaours and the role of micro-organisms in the formation and degradation of these flaours. *Paper contributed ^' loenian International Congress "Milk and Dairy products", Portorož, 9-2/

2 M. Hruškar and ali: roma profiles. Mljekarsto 45 (3) 75-9 It is known that more than chemical compounds hae been isolated from yogurt but only a few (acetaldehyde, ethanol, aceton, diacetyl and butanon-2) hae a high impact on the desired product flaour. lthough acetaldehyde, diacetyl, acetoin, acetone and butanon-2 are all present in yogurt acetaldehyde is recognized as the main flaour component (lberth and Kneifel, 992; Kneifel and lberth, 992; lberth, 99.). Metabolic routes to flaour production are presented on following figures. Figurel Pathways of lactose catabolism (Daies and aw, 94.) lika. Putei razgradnje laktoze lactose lactose-p ^ I i glucose i galactose-6-p glucose-6-p tagatose-6-p fructose-6-p I dihydroxyacetone-p < fructose-l,6,di-p lgo PHW - put I ribose5-p [ galactose i glucose--p glyceraldehyde-3-pt^_^-^ xylulose 5-P I sedoheptulose 7-P I phosphogluconate ribulose 5-P OI PHW, put I pyruate MBD-MHOF PHW-put acetyl-p HXO MOOPHOPH H PHW- put Figure shows many of the releant catabolic pathways relatie to lactose breakdown, but it is important to realize that not all of the pathways are common to all of the micro-organisms fermenting milk. hus, Xr. thermophilus appears to use only the mbden-meyerhof pathway (Fig. ). he pathways describing the fates of pyruate are shown in Figure 2 (Daies and aw, 94.). cetaldehyde has been considered to hae central role in metabolism. he treptococcus may form acetaldehyde from lactose ia pyruate (Fig. 2), but only trace amounts are formed ia this route by b. bulgaricus. 76

3 Fig. 2)t Metabolism of pyruate lika 2. Metabolizam piruata. pyraate (2) pyruate DH "actie aldehyde" D -»- lactate *- acetyl Co + COj (3) acetyl Co + "actie aldehyde"-»-diacetyl 4. acetyl Co»- acetaldehyde 5. acetate + P -acetyl phosphate 6. acetyl phosphate + Co acetyl Co D -fc- acetoin. citrate -»- oxaloacetate + acetate 9. oxaloacetate. threonine - (() acetaldehyde 2. acetaldehyde ^3) acetaldehyde DH D DH - - pyruate + COj glycine + acetaldehyde - - ethanol D DH - acetate D - - ethanol Q4) pyruate + "actie aldehyde" acetolactate 5. acetolactate 6. acetoin ^7) threonine DH acetoin + COj D glycine + acetaldehyde 2,3,butylene glycol. pyruate ^- acetaldehyde + CO2 DH D 9. acetaldehyde '"-"^' ^- ethanol 2. acetaldehyde + "actie aldehyde" -*- acetoin 77

4 M. Hruskar and ali: roma profiles... Mljekarsto 45 (3) 75-9 hreonine metabolism is responsible for the acetaldehyde accumulation. (Fig. 2, reaction 7). b. bulgaricus is species largely responsible for the formation of acetaldehyde in yogurt although both are able to conert threonine to glycine as they possess enzyme threonine aldolase. Diacetyl and acetoin result from methabolic actiity of tr. thermophilus and are ery low, only.5 ppm. (Fig. 2, reaction 2,3,7). he presence of diacetyl contributes to the delicate, full flaour and aroma of yogurt and is especially important if acetaldehyde is low because it can enhance yogurt flaour. Pyruate also may be metabolised ia "actie aldehyde" to acetoin (Fig. 2, reactions 4,5). Many starter organisms metabolise acetaldehyde to ethanol (fig. 2, reaction ). he lack of alcohol dehydrogenase, the enzyme catalysing this reaction, in both tr. thermophilus and b. bulgaricus makes these starters incapable of metabolizing acetaldehyde to ethanol, which means that acetaldehyde is the end metabolite. Optimum flaour and aroma is obtained between 23 and 4 ppm acetaldehyde (Daies and aw, 94). he concentration of these typical flaour compounds changed during storage depending on duration and temperature in depot. he aim of this study was to show changes in content of flaour compounds and sensory ealuation occuring during storage as a function of duration and temperature. he aim was also to establish correlations between them. Material and methods In this article six commercial brands of plain yogurt were stored within a days period at two different temperatures (+4 C; + 2 C) and eery two days changes in acetaldehyde, diacetyl and ethanol were established. t the same time sensory ealuation was carried out. cetaldehyde and ethanol concentration was determined by aldehyde dehydrogenase and alcohol dehydrogenase method (Boehringer, 99). Diaceyl was measured by Hill's modification of the colorimetric method (Hill et al, 954). Fie members' panel performed sensory analysis using scoring system based on weighted factors in the 2-polnts scale (IO, 95), and data analysed applying correlation and regression analysis (/, 99). esults and discussion Inestigation results are summarized in tables -4. he results in table show decrease in concentration of acetaldehyde during storage at both temperature leels in all yogurt samples. he storage temperature leel significantly influence the decrease of acetaldehyde content. he results in table 2 show the increase in concentration of diacetyl during storage at both temperature leels that do not influence the increase in concentration significantly. 7

M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 able Concentration of acetaldehyde (ppm) in yogurt samples during storage at two temperature leels ablica.

5 M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 able Concentration of acetaldehyde (ppm) in yogurt samples during storage at two temperature leels ablica. dio acetaldehida (ppm) u uzorcima jogurta tijekom skladištenja pri dije temperature amples zorci ( C) torage duration (days) rajanje sl<ladištenja (dani) O O 7.O OO O.OO 9.2O 9.2O O O OO O O 9.O O O OO able 2 Concentration of diacetyl (ppm) in yogurt samples during storage at two temperture leels ablica 2. dio diacetila (ppm) u uzorcima jogurta tijekom skladištenja pri dije temperature amples torage duration (days) rajanje skladištenja (dani) zorci ( C) O OO

6 M. Hruškar and ali: roma profiles. Mljekarsto 45 (3) 75-9 able 3 Concentration of ethanol (ppm) in yogurt samples during storage at two temperture leels ablica 3. dio etanola (ppm) u uzorcima jogurta tijel<om skladištenja pri dije temperature amples zorci ( C) torage duration (days) rajanje sl<ladištenja (dani) O O6 6.OO O O able 4 ensory ealuation (scores) of yogurt samples during storage at two temperture leels ablica 4. eniorska procjena (bodoi) uzoraka jogurta tijekom skladištenja pri dije temperature amples zorci ( C) torage duration (days) rajanje skladištenja (dani) O O

7 " ' ' * " ' ' ' ' ' " ' ' ' '. ' " ' \ ', " ; ', ', ' " ' ' ' ' - M. Hruškar and ali.: roma profiles... Mljekarsto 45 (3) 75-9 able 3. shows the increase in concentration of ethanol in yogurt samples during storage at both temperature leels which significantly influence ethanol increase. ppm 4 - " ^ y\ y ^ y ^ -..-^:^^^^^'''^^ /^'^^^-^^^'^^ ^^^^>i^^^^\y'''^ ^--^"""^"^ 6 ^^^ y^y-^^ m ^,,,.----'''"'^^''^^ ^.^^:^^^^-^^'^^ ^^^^;_ :>^^^ 4 2 ^.^"^^^^^ - ^ - - " ' " ^ ^ V ^^ I I I I I «li bodoi 2 scores -2 ampk ample 2 amplt ample 4 amples ample 6 njg_l njaeg_2 injieg_3 njieg_4 inji^_5 wij?«g_6 Figure 3 Correlation between sensory ealuation and acetaldetiyde content in yogurt samples during days storage at +4 C lika 3. Korelacija između seniorske ocjene i udjela acetaldehida u uzorcima jogurta tijekom desetodnenog skladištenja pri +4 C

8 M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 ensory scoring (table 4) pointed out significant changes in yogurt quality during storage at both temperature leels those changes were pronounced on higher temperature leels. ppm I 6 7 bodoi 9 2 scores ample in.«gj ample 2 ljn.eg_2 ample 3 nji«g_3 ample 4 ittjieg_4 ample 5 ljhjlđg_5 ample 6 injlegjß Figure 4 Correlation between sensory ealuation and acetaldehyde content in yogurt samples during days storage at +2PC lika 4. Korelacija između senzorske ocjene i udjela acetaldehida u uzorcima Jogurta tijekom desetodnenog skladištenja pri +2CPC 2

9 M. Hruškar and ali: roma profiles. Mljekarsto 45 (3) 75-9 ensory ealuations were regressed against the concentrations of aroma compounds at both temperature leels. Indiidual data points were plotted as well as the least squares fitted lines of all data (Figures 3-). ppm 45 J H 9 boinfi 2 scores ampiš m ampk2 amp3 amp4 amp m ampkö ihjt«g_l iii^_2 IJHJt*g_3 iiutgji lil»ij5 ihjltg_6 Figure 5 Correlation between sensory ealuation and diacetyl content in yogurt samples during days storage at +4 C lika 5. Korelacija između senzorske procjene i udjela diacetila u uzorcima jogurta tijekom desetodnenog skladištenja pri +4 C 3

10 M. Hruškar and ali: roma profiles. Mljekarsto 45 (3) 75-9 Figure 3 and 4 show relationship between sonsory ealuation and acetaldehyde content. tatistical analysis was performed and high alues of correlation coefficients obtained. egression lines were used as a measure of the linear relationship for both temperature leels. ppm bodtrd 9 2 scores ampj m ampl 2 m amp ampl*4 m ampk m ampk6 njitgj HJl*g_2 jhjig_3 nji*g_4 njt^j njgj Figure 6 Correlation between sensory ealuation and diacetyl content in yogurt samples during days storage at +2PC lika 6. Korelacija između seniorske ocjene i udjela diacetila u uzorcima jogurta tijekom desetodnenog skladištenja pri +2PC 4

11 M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 ensory ealuation were correlated to diacetyl contents. High correlation coefficients alues characterized linear relationship presented in figures 5 and 6 at both temperature leels. ppm ' - 6- ^^^"".^ ^--^V""^"^--^ ^"\^ ' \. 4- ^^^^ \,^^ 2- ^ "-O^^ - h h bodoi 2 scores ampkl m amp2 amp 3 amplt4 amp m ampkć njitg_l njt«g_2 ljnjl»g_3 inji9g_4 njitgj lh.tgj6 Figure 7 Correlation between sensory ealuation and ethanol content in yogurt samples during days storage at +4 C lika 7. Korelacija između seniorske procjene i udjela etanola u uzorcima jogurta tijekom desetodnenog skladištenja pri +4 C 5

12 M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 he data of sensory ealuation and ethanol content were plotted as shown in figures 7 and for all temperature leels, regression equations determined again showing ery high linear correlation coefficients. ppm bodtm 9 2 scores ample ampl*2 -- njttgj njttg_2 ample 3 n.tgj ample 4 injieg_4 ample 5 njieg_5 ample 6 njieg_6 Figure Correlation between sensory ealuation and ethanol content in yogurt samples during days storage at +2PC lika. Korelacija između seniorske procjene i udjela etanola u uzorcima jogurta tijekom desetodnenog skladištenja pri +2CPC 6

M. Hruškar and ali: roma profiles.. Mljekarsto 45 (3) 75-9 tatistical parameters of regression analysis were summarized and presented in tables 5 and 6.

13 M. Hruškar and ali: roma profiles.. Mljekarsto 45 (3) 75-9 tatistical parameters of regression analysis were summarized and presented in tables 5 and 6. ensoric ealuation changes are highly correlated to changes in acetaldehyde.diacetyl and ethanol contents respectiely. he best correlation was between sensory ealuation and ethanol content at both temperature leels (from to.996), followed by correlation coefficients for sensory ealuation and diacetyl content also at both temperature leels (from-.49 to ). Other coefficients of correlation were high as well. he recorded alues for this statistic parameter were generally between.24 and.996. able 5 Correlation coefficients and coefficients of determination between sensory ealuation and concentration of acetaldehyde, diacetyl and ethanol, respectiely ablica 5. Koeficijenti korelacije i koeficijenti determinacije između seniorske procjene i udjela acetaldehida, diacetila i etanola samples uzorci ( C) roma compounds (ppm) Komponente arome (ppm) samples uzorci ( C) acetaldehyde acetaldehid diacetyl diacetil ethanol etanol samples uzorci ( C) r 2 r 2 r O.93O O.65 -O.963 O.92 -O.972 O O.944 O.9 -O.934 O.7 -O.963 O O.9O5 O.9 -O.932 O.6 -O.956 O O.97 O.O4 -O.992 O.94 -O.9 O O.72 O.76 -O.9 O.963 -O.969 O O.924 O.54 -O.996 O.992 -O.95 O O.996 O O.5 -O.97O O.94O O.947 O.97 -O.93 O.O -O.957 O O.99 O O.929 -O.994 O O.24 O.679 -O.949 O.9OO -O.96 O O.95 O.9 -O.49 O.72 -O.96 O O.952 O.9O6 -O.67 O.752 -O.996 O.992 7

14 M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 able 6 egression equations for relationstiip between sensory ealuation and concentration of acetaldehyde, diacetyl and ethanol, respectiely ablica 6. Jednadžbe regresije za poezanost između senzorske ocjene i udjela acetaldehida, diacetila i etanola s ^ J B ^ ^ samples uzorci ( C) acetaldehyde acetaldehid roma compounds (ppm) Komponente arome (ppm) diacetyl diacetil ethanol etanol - +4 =-9.57+O.6x = =9.7-O.3x +2 =-5.O3+O.64x =37.3-.x =.2O-O.32x =-2O.22+.5Ox = X = x +2 =-4.57+O.66x = x =.4-O.67x =-O.OO+O.9x = x = Ox +2 =-7.5+O.6x = O9x =7.93-O.5x = x =7.5O-4.O7x =5.49-O.77x +2 =-.2+.O2x = x =2.52-O.62x =-5.7+O.56x = O3x =2O.9-O.97x +2 =-2.O+O.35x =5.9-O.62x =2.-O.5x = Ox = x =3.O2-.x +2 =-.O9+O.73x = x =25.4O-.x Conclusion Concentration of acetaldehyde decreased, while concentrations of diacetyl and ethanol increased in all yogurt samples during storage at both temperature leels. emperature leel in depot significantly influenced the decrease of acetaldehyde content and the increase of concentration of ethanol but not significantly the increase of diacetyl content during storage. ensory scoring pointed out significant changes In quality of all yogurt samples at both temperature leels. Changes were pronounced during storage at higher temperature leel. egression analysis determined linear relationship between sensory ealuation and concentrations of all inestigated aroma compounds. Coefficients of correlation were generally high and consequently ery accurately predicting equations obtained by regression analysis.

15 M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 OJCI OM I IOK OCJ JOG IJKOM KDIŠJ ažetak Poznato je da od stotinjak kemijskih spojea izoliranih iz jogurta i sličnih fermentiranih proizoda samo neki od njih (acetaldehid, etanol, diacetil i 2- butanon) znatno utječu na željeni okus proizoda. Koncentracija tih tipičnih sastojaka arome mijenja se tijekom skladištenja oisno o temperaturi i trajanju. oom radu šest uzoraka jogurta čuano je pri dije različite temperature tijekom dana i saka da dana uzimani su uzorci za određianje acetaldehida, diacetila i etanola. Istoremeno je jogurt senzorski ocjenjen. dio acetaldehida i etanola određen je enzimnom metodom a udio diacetila modificiranom Hill-oom kolorimetrijskom metodom. enzorski je jogurt ocijenila skupina od 5 članoa koristeći sistem 2 ponderiranih bodoa. trđena je kantitatina oisnost senzorske ocjene sake pojedine komponente arome za obje razine temperature i izražena linearnim Jednadžbama. ajbolja poezanost, izražena koeficijentom korelacije, utrđena Je između senzorske procjene i etanola (r =.996) u Jednom od uzoraka čuanom pri +4 C. Općenito si su koeficijenti korelacije bili isoki (od,24 do -,996). Ključne riječi: komponente arome, acetaldehid, diacetil, etanol, senzorska procjena, korelacija. eferences dances in the nnicrobiology and biochemistry of cheese and fermented milk, (94) d. F. yndon Daies and Barry. aw, lseier pplied cience Publishers td., ondon and ew ork, 94. HI,. C, WZ, F. W. i BO. (954): Colorimetric method for detection of microbiological spoilage in citrus juices. Food echnology, March 6-7. IO (C 34) C 2 (ecretariat - 39) "ensory analysis" DC, KIF, W. et al. (992): roma profiles and sensory properties of yogurt and yogurt - related products. I. creening of commercially aailable starter cultures, Milchwissenschaft

16 M. Hruškar and ali: roma profiles... Mljekarsto 45 (3) 75-9 Methods of Biochemical nalysis and Food nalysis, Boehringer Mannheim GmbH, Mannheim, 99. Institute Inc. 99. / ser's Guide. Version 6,4^'^ ed. Gary, C. BH, F. (99): Headspace gas chromatographic estimation of some yogurt olatiles, J. ssoc. Off. nal. Chem BH, F. i KIF, W. (992): roma profiles and sensory properties of yogurt and yogurt - related products. II. Classification of starter cultures by means of cluster analysis, Milchwissenschaft 47, uthors'adresses - drese autora: eceied-prispjelo: Dip). Ing. Mirjana Hruškar Mr. ada Vahčić Prof. dr. Milana itz Prehrambeno-biotehnološki fakultet Zagreb, Plerottijea 6. 9

Analytical Report. Volatile Organic Compounds Profile by GC-MS in Clove E-liquid Flavor Concentrate. PO Box 2624 Woodinville, WA 98072

Analytical Report. Volatile Organic Compounds Profile by GC-MS in Clove E-liquid Flavor Concentrate. PO Box 2624 Woodinville, WA 98072 Millis Scientific, Inc 6400 Baltimore National Pike #201 Baltimore MD 21228 Telephone: 877-844-2635 Email: info@millisscientific.com Title Report No. Analytical Report Volatile Organic Compounds Profile