馒头 品质 论文

Spontaneous sourdough processing of Chinese Northern-style steamed breads and their volatile compoundsYangsoo Kim a,*,Weining Huang a ,Huiyan Zhu a ,Patricia Rayas-Duarte baThe State Key Laboratory of Food Science and Technology,International Exchange and Cooperation Program,School of Food Science and Technology,Jiangnan University,1800Lihu Road,Wuxi,Jiangsu 214036,China bRobert M.Kerr Food &Agricultural Products Research Center,Oklahoma State University,Stillwater,OK 74078,USAa r t i c l e i n f o Article history:Received 2July 2008Received in revised form 27August 2008Accepted 7October 2008Keywords:Chinese steamed bread SourdoughSpecific volumeCrumb texture firmness Volatile compoundsa b s t r a c tThe effect of amount of flour in the pre-fermented form (10%,20%,and 30%flour in the pre-fermented form),fermentation time (12,24,and 36h),and amount of yeast (0.5%,1.0%,and 1.5%)on acidity,specific volume,and crumb texture of Chinese Northern-style sourdough steamed breads were studied.Volatile compounds of the sourdough and non-sourdough steamed breads were also determined.The prefer-ments were produced from spontaneous fermentation using all purpose (APF)and whole wheat flours (WWF).Specific volume was the highest at 20%preferment for APF sourdough steamed bread (ASSB)and 30%preferment for WWF sourdough steamed bread (WSSB).The softest texture was obtained with 20%preferment while at 30%preferment there was excessive gluten weakening due to high acidification.A total of 89volatile compounds were identified in steamed breads with ethanol and 3-methyl-1-butanol being the most abundant compounds.Ó2008Elsevier Ltd.All rights reserved.1.IntroductionChinese steamed bread is a widely consumed breakfast item,representing about 40%of the wheat consumption in China.Steamed bread is formulated with wheat flour,water,and yeast.Since the 1980s,studies on Chinese steamed bread have ex-plored the relationship of quality to different types of flour,formu-lation,and processing factors (Addo,Pomeranz,Haung,Ruventahler,&Jefferes,1991;He,Liu,Peña,&Rajaram,2003;Huang,Detker,Quail,&Moss,1993;Huang,Yun,Quail,&Moss,1996;Rubenthaler,Huang,&Pomeranz,1990;Rubenthaler,Pomeranz,&Huang,1992).Quality requirements of Chinese steamed bread are different from those of pan breads,including distinct attributes of elasticity,stickiness and smooth appearance associated with the traditional product (He et al.,2003).Conflicting reports on the effects of flour protein quantity and gluten quality on Chinese steamed bread quality include no effect (Zhang &Wang,1987),positive effect (Addo et al.,1991)and negative effect (Rubenthaler et al.,1992).These contrasting reports could be due in part to the use of different types of flour,laboratory processing,and evaluation procedures (Huang et al.,1996).Other flour attri-butes,i.e.,flour whiteness,rapid visco analyser peak viscosity,and ash content were also related to the quality of steamed bread (He et al.,2003;Huang et al.,1996).The types and amount of ingredients and processing conditions also contribute to the conflicting reports.Amount of water in steamed bread dough is considerably lower than that of the pan bread (45–50%,flour weight basis)(Rubenthaler et al.,1990).Huang et al.(1993)suggested that a number of studies do not ade-quately represent the traditional Chinese style steamed bread when salt,sugar,and fat were included in the formulation.Sourdough bread has been produced for thousands of years using natural or spontaneous fermentation,and it was the only bread leavening method available before the commercial produc-tion of yeast (Röcken &Voysey,1995).It is well established that sourdough bread has a unique flavour,longer shelf life,and larger volume compared to conventional bread (Katina,Heinio,Autio,&Poutanen,2006;Katina et al.,2005).Other positive nutritional implications such as increasing mineral bioavailability as well as the reduction of glucose and insulin responses in human subjects have been reported (Clarke,Schober,Angst,&Arendt,2003).The traditional formulation of sourdough steamed bread also utilized sourdough technology before yeast was commercially available (Huang et al.,1993).In some parts of China,the steamed bread is still produced with sourdough (Sun,2007).However,little information on quality of sourdough steamed bread has been reported.The objective of this study was to evaluate the effect of process-ing parameters such as amount of flour in sour,fermentation time of sour and amount of yeast on the quality of Chinese sourdough0308-8146/$-see front matter Ó2008Elsevier Ltd.All rights reserved.doi:10.1016/j.foodchem.2008.10.008*Corresponding author.Tel./fax:+8651085919139.E-mail addresses:yskksu@ ,yskksu@ (Y.Kim).Food Chemistry 114(2009)685–692Contents lists available at ScienceDirectFood Chemistryj o u r n a l h o m e p a g e :/locate/foodchemsteamed breads with spontaneous sours using all purpose and whole wheatflours.2.Materials and methods2.1.Ingredients andflour propertiesAll purposeflour(APF)and whole wheatflour(WWF)were pur-chased from New Cultural Starch Ltd.(Gaoyou,China)and active dry yeast(Heibei Mauri Food Co.,Zhangbei,China)from a local supermarket.Moisture,ash,and protein content offlour were determined using approved methods44–15A,08–01,and46–12, respectively(AACCI2000).Optimum water absorption and dough properties were determined with approved method54–22using a Farinograph(C.W.Brabender Instruments Inc.,Hackensack,NJ) (AACCI2000).Farinogram for sourdough was conducted following the method described by Clarke,Schober,and Arendt(2002)with a modification:the24h fermented material(20%flour in the pre-fermented form)and water were premixed and added to the rest offlour in the Farinograph.2.2.Preferment and steamed bread dough preparationPreferments,also known asflour brew or liquid sponge,were prepared using1:1.25w/w ratio wheatflour:water and mixed with a spoon until lumps offlour were minimized.Preferments were produced spontaneously at30°C and85%rh from12to36h.Northern-style sourdough steamed bread containingflour,pre-ferment,water,and yeast was prepared as described by Huang et al.(1993)with modifications.The amount of water was reduced to85%of Farinograph optimum water absorption(FOWA)and dough for steamed bread was mixed only once instead of twice. Water temperature was varied in order to yield afinal dough tem-perature20–21°C.Dough(500g)was mixed with the preferment,flour,water,and yeast using an A120T Hobart mixer(Troy,Ohio)for3min at low speed and1min at medium speed.Amount offlour in the dough was adjusted by replacing10%,20%,and30%offlour with an equivalent quantity offlour in the preferment.Three levels of3fac-tors,amount offlour in the preferment,fermentation time;and amount of yeast were assigned with a central composite face-cen-tered design(CCF).The levels were10%,20%,and30%for amount offlour in the pre-fermented form(flour weight basis(fwb));12, 24,and36h for fermentation time,and0.5%,1%,and1.5%for amount of yeast.In total,17experiments with3experiments at the central point(20%,24h,and1%for amount of the preferment, fermentation time,and amount of yeast,respectively)were de-signed using Design Expert software(Stat-Easy,Inc.,Minneapolis, MN)and conducted.After mixing,the dough was fermented at30°C and85%rh for 1h,divided into four100g pieces and sheeted at9and5.5mm for 5times each(TP413,Shanghai Zaomio Co.Ltd.,Shanghai,China). The dough was rounded and molded manually and proofed for 20min at30°C and85%rh.The proofed dough was steamed for 10min using a steam tray and boiling water(JYC-1851,Joyong, Jinan,China).Each dough treatment was processed in duplicate.2.3.pH and total titratable aciditypH and total titratable acidity(TTA)of preferment,sourdough after mixing,and steamed bread were determined according to Bastetti(2001).The samples(10g)were homogenized with 90ml of sterile distilled water.The pH value was recorded and the acidity was titrated with0.1N NaOH to afinal pH8.5.The TTA was expressed in ml of0.1N NaOH.pH and TTA of the prefer-ments were determined at0,5,10,15,20,25,30,and36h fermen-tation.All tests were performed at least in duplicate.2.4.Specific volume and crumb texture of sourdough steamed breadAfter a cooling period of15min,the volume(seed displace-ment)and weight of steamed breads were recorded.Within1h of steaming,the crumb texture was determined using a TA–XT2i Texture Analyser(Stable Micro Systems,Ltd.,Godalming,UK) equipped with a25mm diameter aluminium cylindrical probe. Steamed bread was sliced horizontally and a bottom piece, 25mm height,was compressed to50%of its height.The test con-ditions were:pre-test speed3mm/s,test speed1mm/s,post-test speed5mm/s,and trigger force5g.The peak force of the compres-sion curve was reported as crumbfirmness.The analysis was per-formed in duplicates with four sub-samples.2.5.Volatile compounds of sourdough steamed breadVolatile compounds of steamed breads with(20%offlour in the preferment)and without the preferment were determined for both flours.A solid phase micro extraction(SPME)isolation technique was used.Five grams of sample were heated to60°C in a vial and the headspace was sampled with a100l m polydimethylsilox-ane SPMEfibre(Supelco,Bellefonte,PA)for40min.The SPMEfibre was directly inserted in a Finnegan Trace MS for GC/MS(Thermo-Quest,Austin,TX)equipped with a DB-5MS capillary column (60mÂ0.32mmÂ1l m,lÂidÂed)(J&W Scientific Inc.,Fol-som,CA).The GC temperature was at40°C for1min,increased to160°C at a rate of6°C/min and then to250°C at a rate of 10°C/min.The carrier gas was helium with a columnflow of 1.2ml/min and split ratio12:1.Mass spectra were recorded by electronic impact(EI)at70eV using ion source temperatures at 200°C.The scan mode was used to detect all the compounds in the range m/z33–495atomic mass unit(amu).The identification of volatile compounds was verified by comparison of the mass spectral data obtained with those in the XCalibur database(Ver 1.1,ThermoQuest,Austin,TX).The contents of the volatile com-pounds were expressed as relative peak areas(peak area of each compound/total area)X l00.3.Results and discussion3.1.Flour propertiesMoisture,ash,and protein content were13.7%,0.65%,and10.6% (14%flour moisture basis,mb)for APF and11.4%,1.85%,and13.2% (14%mb)for WWF.Addition of the preferment(24h at20%offlour in the pre-fermented form,fwb)in farinograph decreased water absorption(56.4–56.1%and74.2–72.6%,for APF and WWF,respec-tively),development time(2.2–1.3min and5.5–4.3min,for APF and WWF,respectively)and stability(4.4–2.1min and 5.1–2.6min,for APF and WWF,respectively),while mixing tolerance index(MTI)increased for bothflours(82–141Brabender Unit (BU)and31–50BU,for APF and WWF,respectively).These results were similar to those reported by Clarke et al.(2002).In contrast, the dough development time in this study also decreased with the addition of20%preferment.The development time decreased by59and21.8%for the APF and WWF,respectively.These obser-vations agree with Arendt,Ryan,and Bello(2007)who reported that lower pH in dough reduced the development time.Sourdough is a dynamic and complex system in which changes,due to metab-olites produced from fermentation,affect the dough rheological properties considerably more than simply by decreasing the pH (Wood,Cardenas,Yong,&McNulty,1975).686Y.Kim et al./Food Chemistry114(2009)685–692Huang et al.(1993)suggested water amount for steamed bread to be70–75%,80%,and85%of FOWA for weak,medium,and strong glutenflours,respectively.Results from farinograph and protein content offlours indicated that bothflours had weak gluten strength in this study.However,for these samples the optimum water was85%of FOWA of bothflours,which was47.7%and 62.0%(flour weight basis)for APF and WWF,respectively.The water amount for APF was within the range of previous reports, 45–50%(fwb)(Rubenthaler et al.,1990;Lukow et al.,1990).3.2.pH and TTA of the preferment and sourdough steamed breadsThe acidification levels of the preferment for APF and WWF,pH and TTA,are shown in Fig.1.In thefirst8h of fermentation,the pH (6.25)of APF preferment(APFP)was lower than that(6.48)of WWF preferment(WWFP).After8h of fermentation,the pH of WWFP dropped rapidly until20h of fermentation.The acidificat-ion of APFP was slightly slower than that of WWFP.Around10h of fermentation of APFP,the pH started to drop.The values of TTA from WWFP were higher than those from APFP up to36h fer-mentation.The difference in the two acidity profiles might be due to the presence of different compounds with a range of buffering capacity in the dough system(Clark et al.,2003).The fermentation curves showed the well known four phases: lag,exponential,stationery,and lethal(Fig.1).These phases appear to be heavily dependent on the properties of the ingredients,fer-mentation conditions,and types of bacteria in the inoculums(Clark et al.,2003).In the early stage(<10h),due to the lag phase of inoculums,acidification was slow.The dough gradually became more acidic(pH<6.0)as the lactic acid bacteria dominated the sourdough microflora as suggested by Röcken and Voysey(1995).The pH(4.36)and TTA(7.25)values of APFP were lower than lit-erature values while WWFP reached similar literature values of pH around30h and before20h for TTA.pH and TTA values of the pre-ferment ranging from3.57to3.85and10.1to12.5,respectively, were reported by Röcken and Voysey(1995).Slightly higher values of3.9–4.1and14–19for pH and TTA,respectively,were reported by Bastetti(2001).Flour ash content influenced the acidification characteristics of sourdough(Arendt et al.,2007;Brummer&Lorenz,1991).Higher ashflour yielded higher acidity compared to a lower ashflour but the latter one acidified in shorter time to pH4(Brummer&Lor-enz,1991).A higher acidification in high ashflour was related to a higher buffering capacity which allowed longer fermentation by lactic acid bacteria(LAB)without suppression by low pH(Salova-ara&Valjakka,1987).The amount offlour in the preferment and fermentation time significantly(P60.01)affected the pH of Chinese steamed breads made with bothflour types,APF(ASB)and WWF(WSB)(Table1). The amount of yeast significantly(P60.01)influenced the pH of the WSB but not for ASB.The amount offlour in the preferment-by-fermentation time interaction was significant only for ASB (P60.05).Both quadratic models had high R2values(0.97and 0.98for ASB and WSB,respectively).As the amount offlour in the preferment,fermentation time,and amount of yeast increased the pH decreased for both ASB and WSB.Thesefindings were sim-ilar to Clarke et al.(2003).TTA values of steamed bread were significantly(P60.05)af-fected only by the amount of the preferment for ASB and fermen-tation time for WSB(Table1).The R2values of quadratic models (0.60and0.75for ASB and WSB,respectively)for the TTA were lower than those of pH from steamed breads.As the amount of flour in the preferment or fermentation time increased,the TTA also increased.But when yeast level was increased from1.0%to 1.5%,TTA appeared to reach a plateau and started to decrease (Fig.2a and b)at yeast concentrations of1.0%or higher and all the concentrations of the preferment tested for both sourdough steamed breads.This might be a saturation effect due to a synergis-tic effect between the yeast and lactic acid microflora as suggested by Clarke et al.(2003).Table1Coefficients of independent variables for the quadratic regression models from response surface analysis for pH,TTA,specific volume,and crumbfirmness of Chinese Northern-style sourdough steamed bread a.Terms pH TTA Specific volume Crumbfirmness ASB b WSB c ASB b WSB c ASB b WSB c ASB b WSB cIntercept 5.55 5.48 2.36 5.60 2.71 2.111152.11642.1 Flour(F)dÀ0.23**À0.21**0.34*0.980.12***À0.028À51.0À47.7 Time(T)eÀ0.39**À0.32**0.059 1.12*0.032À0.060À90.0**À713.5*** Yeast(Y)À0.040À0.13**0.170.740.0070.10*À68.8À143.3 FÃTÀ0.11*À0.037À0.110.66À0.089**À0.061À46.3À92.8 FÃYÀ0.030À0.055À0.0560.23À0.0170.05685.8À345.3** TÃY0.001À0.0580.0790.600.019À0.10*10.1**109.0 F20.091À0.040.18À0.2À0.24***0.22*133.1219.6 T2À0.0580.15**0.15À0.083À0.082**À0.27**58.3À688.0* Y20.007À0.04À0.19À2.34À0.0210.1122.9575.6* R20.970.980.600.750.960.860.520.91a Significant level at*P60.05;**P60.01;***P60.001.b ASB=sourdough steamed bread produced with all purposeflour,10%,20%,and30%of theflour was in the form of the preferment for12,24,and36h.c WSB=sourdough steamed bread produced with whole wheatflour,10%,20%,and30%of theflour was in the form of the preferment for12,24,and36h.d F=amount offlour in the form of preferment.e T=fermentation time.Y.Kim et al./Food Chemistry114(2009)685–6926873.3.Specific volume of sourdough steamed breadOverall,specific volume of WSB was lower than that of ASB. Reduction of specific volume in whole wheatflour products is well documented.Thefibre particles disrupt the gluten network and re-duce the extensibility of dough which restricts gas cells expansion and gas retention,resulting in reduced specific volume of bread (Gan,Galliard,Ellis,Angold,&Vaughan,1992).High R2values(0.96and0.86for ASB and WSB,respectively) were obtained from quadratic models describing specific volume of steamed breads(Table1,Fig.3a and b).The amount offlour in sour significantly affected the specific volume of ASB in the linear and quadratic terms,in addition to the interaction with fermenta-tion time(P60.001,P60.01,and P60.001,respectively).The amount offlour in the preferments and fermentation time had a greater effect on specific volume of ASB than yeast as sug-gested by the coefficients in Table1.However,the amount of yeast (linear term as well as interaction with fermentation time)signif-icantly(P60.05)affected the specific volume of WSB.The linear term of amount of sour and fermentation time did not significantly affect the specific volume.The quadratic term significantly affected the specific volume of WSB(P60.05and P60.01for amount of flour in sour and fermentation time,respectively)(Table1).For steam bread made with APF,as the amount offlour in the preferment increased from10to20%,the specific volume in-creased and then decreased as theflour in the preferment in-creased(>20%)(Fig.3a).These observations suggest that there was an optimum level for the amount offlour in the preferment for ASB to obtain maximum specific volume.For the WSB,the con-cave curve suggests the lowest values of specific volume around 20%flour in the preferment(Fig.3b).These results contrast to pre-vious reports of a significant improvement of specific volume when sourdough was used in a highfibre pan bread(wheat bread and wheat bread with20%bran)(Katina et al.,2006).The different re-sults are due in part to differences in formulation and processing, i.e.,pan bread vs.Chinese steamed bread.However,there has not been a consensus on the effect of sourdough on the specific volume of bread.Reports have included a negative effect(Armero&Collar 1996;Salovaara&Valjakka,1987),and a positive effect(Clarke et al.,2002;Hansen&Hansen,1996).The specific volume of bread was highly dependent on the type and level of acidification(Clarke et al.,2002;Katina et al.,2006).The positive effect of sourdough in bread volume has been linked to improved gas holding capacity of the dough(Gobbetti,Corsetti,&Rossi,1995).However,too much acidification of dough hydrolysed and depolymerized gluten pro-teins during the sourdough fermentation(Loponen,Mikola,Katina, Sontag-Strohm,&Salovaara,2003;Thiele,Grass,&Ganzle,2004) resulting in weakened gluten network in bread doughs and lower specific volume(Clarke,Schober,Dockery,O’Sullivan,&Arendt, 2004).Clarke et al.(2003)suggested that the acidity level of sour-dough and subsequent bread dough must be carefully controlled in order to attain increased bread volume.3.4.Crumb texture of sourdough steamed breadThe crumb texture of sourdough steam breads is an important quality characteristic and it was evaluated as crumbfirmness. ASB had lower crumbfirmness than that of WSB for all the levels of factors(Fig.4a and b).The decrease in crumbfirmness of WSB688Y.Kim et al./Food Chemistry114(2009)685–692was caused by the same factors affecting the specific volume, includingfibre content which negatively affected the gluten net-work by breaking the gluten strands and reducing the gas holding capacity of the dough.Relatively low R2(0.52)for crumbfirmness from ASB while high R2(0.91)from WSB were obtained from the response surface anal-ysis(Table1).The linear term of fermentation time of the prefer-ment significantly affected crumbfirmness of both steamed breads.As fermentation time increased,crumbfirmness decreased for both steamed breads(Fig.4a).Reduction of crumbfirmness in sourdough bread has been reported(Katina et al.,2005,2006).A soft crumb has been associated with the acidification of the dough which reduced its elasticity and resistance to extension(Arendt et al.,2007;Clarke,Schober,Dockery,O’Sullivan,&Arendt,2004). The softest crumb texture was obtained between20%and25%of flour in the preferment for both steamed breads(Fig.4a and b). This observation suggests that even though acidification improved the texture of steamed bread,there is an optimum acidification le-vel,beyond that level of acidity,a detrimental effect occurred by excessive gluten weakening(Loponen et al.,2003;Thiele et al., 2004).Loponen et al.(2003)suggested that during the fermenta-tion of the preferment,high molecular weight glutenin subunits (HMW–GS)were degraded thus changing the rheology of dough. It is generally accepted that HMW–GS are the main factors respon-sible for dough elasticity and provide the strength for adequate expansion of the dough(Thiele et al.,2004).When lower amount of HMW–GS were present,the dough strength failed and the bread collapsed during baking or steaming process.The amount of yeast,interaction with fermentation time for ASB and interaction with amount offlour in the preferment for WSB affected significantly(P60.01)the crumbfirmness of the steamed bread.As the amount of yeast increased,crumbfirmness was gradually reduced in the ASB,but for WSB,1%yeast produced the softest steamed bread(Fig.4b).Rubenthaler et al.(1990)re-ported that there might be an optimum yeast level for crumbfirm-ness of steamed bread.Thus,sourdough processing,fermentation conditions and ingredients need to be carefully controlled,to ob-tain a desirable crumb texture in bread(Katina et al.,2005;2006).3.5.Volatile compounds in sourdough steamed breadAnother desired characteristic of sourdough fermentation is the production of uniqueflavours that contribute to a pleasant aroma and taste.Sourdough bread has a higher content of volatile com-pounds compared to regular white pan bread(Hansen&Hansen, 1996).Among the compounds found in significant concentrations in sourdough bread are methylpropanol,ethyl acetate,and ethyl lactate(Hansen&Lund,1987).Sourdough bread also has been re-ported to contain high amounts of aldehydes,such as2-methyl-propanal,2-and3-methylbutanal,pentanal,hexanal,heptanal, octanal,and nonanal(Seitz,Chung,&Rengarajan,1998).Chang,Seitz,and Chambers(1995)identified74volatile com-pounds from white and whole wheat breads,while Meignen et al.(2001)reported more than150volatile compounds from sourdoughs before baking.Thus,during the baking process,many compounds appear to be evaporated and/or formed.In this study,a total of89compounds(including6unknown) were detected on non-sourdough steamed breads,non-sourdough all purpose steamed bread(NASB)and non-sourdough whole wheatflour steamed bread(NWSB),and sourdough steamed breads,ASB and WSB and an average of53compounds were iden-tified in the four types of steam breads(Table2).Among the89 compounds,30were detected in the four types of steamed breads.The most abundant compound in all four steamed breads,NASB, NWSB,ASB and WSB was ethanol(Compound No.4in Table2) followed by3-methyl-1-butanol(15),nonanal(31),hexanal(8), 1-hexanol(30),butanoic acid(54),heptanal(11),acetic acid(2), octane(1),1-(4-methoxyphenyl)-1-methoxypropane(67),and 1-heptanol(39)(Table2).These compounds represented over 70%of the total peak area.The relative abundance of ethanol(4) was higher in ASB compared to NASB.This result agrees with Seitz et al.(1998)who reported a slight increase in ethanol content in sourdough bread compared to non-sourdough bread.However, the relative abundance of ethanol appeared to be higher in NWSB compared to the other steamed breads in this study including WAB (Table2).Ethanol contents of bread were slightly increased from white pan bread to sourdough white pan bread(Seitz et al., 1998)and from white pan bread to whole wheat bread(Chang et al.,1995).The relative abundance of3-methyl-1-butanol(15)was the highest in NASB followed by those made with sourdough(Table 2).3-Methyl-1-butanol has been reported present in dough fer-mented with yeast and not in sourdough fermented with lactic acid bacteria(LAB)(Damiani et al.,1996).Gobbetti,Simonetti et al.(1995)suggested that the association of different LAB and yeast produced different amounts of3-methyl-1-butanol.The relative abundance of both acetic(2)and butanoic(54) acids were increased in sourdough steamed breads which was characteristic of the sourdough product.Kirchhoff and Schieberle (2002)reported that even though significant amounts of acetic acid were already present in theflour,its concentration increased with the fermentation.Butyric acid(5)was only detected from sourdough steamed breads(Table2),which was consistent with Seitz et al.(1998). However,Chang et al.(1995)also reported the presence of butyric acid in white pan and whole wheat breads from different sources offlour.This suggests that the presence of butyric acid might beY.Kim et al./Food Chemistry114(2009)685–692689690Y.Kim et al./Food Chemistry114(2009)685–692Table2Volatile compounds and their relative peak area of Chinese steamed breads Northern-style with and without sourdough from all purpose and whole wheatflours a.pounds Relative peak areaRT b NASB c NWSB d ASB e WSB f(min)(Â107)(Â107)(Â107)(Â107)1Octane 2.23 2.10 4.99 3.67 4.63 2Acetic acid(ethyl ester) 2.99 4.10 1.71 5.47 5.69 3 4.4-Dimethylcyclooctene 3.26– 1.88––4Ethanol 3.8326.9050.0931.4727.42 5Butyric acid(ethyl ester) 6.20––0.44 1.24 6Unknown 6.860.29–––7Acetic acid(butyl ester)7.27–0.26–0.40 8Hexanal7.4711.5910.6110.1110.21 92-Methyl-1-Propanol8.42 1.060.660.660.41 101-Butanol8.78–0.600.480.59 11Heptanal10.73 2.33 3.12 1.7813.35 12Cyclopentasiloxane11.00––0.26–132-PentylFuran11.82 2.46 2.64 3.05 3.94 14Hexanoic acid12.220.000.430.74–153-Methyl-1-butanol12.3514.179.4711.9610.44 16Styrene12.80 1.66 3.93 1.69 2.30 17 1.2.4-Trimethyl-benzene13.32–0.37––18Hexyl ester13.46 1.390.200.30–191-Pentanol13.79–0.920.77 1.72 20Octanal13.89 1.78 1.63 1.86 1.81 21Unknown14.17–––0.93 22Tridecane14.350.37–––232-Butanone14.47––0.59 1.55 24 1.6.6-Trimethyl-3-methylene-1.4-cyclohexadiene14.84–––0.28 252-Heptenal15.020.890.960.91 2.08 26 2.3-Octanedione15.170.54–––27Heptanoic acid15.270.500.380.350.26 285-Hepten-2-one15.47––0.32–291-Methyl-4-Benzene15.60–0.520.000.55 301-Hexanol16.207.65 6.647.387.23 31Nonanal16.7510.0111.348.4614.60 32Unknown17.13––0.000.59 33Butanoic acid(hexyl ester)17.34–0.510.470.64 34Benzene(Prehnitol)17.59–0.28––352-Octenal17.690.980.530.72 1.48 36Octanoic acid17.790.53 1.640.55 3.04 37Dodecane17.99––0.31–381-Octen-3-ol18.42 1.620.77 1.44 1.21 391-Heptanol18.580.73 1.17 3.33 5.61 40Indan19.13–0.29–0.43 41Decanal19.26 1.50 1.13 2.72 1.49 42Pentadecane19.430.65–––43Benzaldehyde19.82 1.090.920.980.79 44Nonenal20.08 1.14 1.520.80 5.16 45Unknown20.21––0.31–461-Nananol20.420.26–––47 2.3-Butanediol20.48–– 2.43–481-Octanol20.700.780.50 1.210.92 493-Methylpentadecane20.830.90–––50Propanoic acid20.99––0.39–51 2.3-Butanediol21.14–– 1.25 3.68 52Hexadecane21.27 1.150.45 1.110.35 532-Octen-1-ol21.740.37––0.24 54Butanoic acid21.910.600.328.7315.88 558-Benzoylocatanoic acid22.19––0.82–564-(Benzoyloxy)-2h-pyran-3-one22.30 1.900.70 1.89 1.78 571-Nonanol22.420.650.94 1.43 1.57 58Octadecane22.510.32–––593-(Hydroxymethyl)-1-phenyl-1-heptadecyn-3-ol22.54–0.22–0.23 603-Nonen-1-ol22.780.54 2.780.70 2.18 61Heptadecane22.980.71–0.340.25 62Naphthalene23.46–0.30––63Cyclohexanone23.48––0.38–64Tricyclo(4.3.2.0(1.4))undeca-2.4(5)8.10-Tetraen-7-one23.51––0.000.27 655-(t-Butyl)-4-methyl-4-(2’methylpropyl)thiophen-2-one23.530.59–––66 3.6-Nonadien-1-ol23.730.00––0.27 671-(4-Methoxyphenyl)-1-methoxypropane23.85 1.99 5.18 4.34 3.67 68Unknown24.01–0.27––694-Decen-1-ol24.32–0.85––70Ethyl-1,3-dithioisoindoline24.46–0.73––712,4Decadienal24.480.26–0.530.87 72Methylnaphthalene24.99––0.39–(continued on next page)。