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Bulletin of Environment, Pharmacology and Life Sciences Bull.Env.Pharmacol.LifeSci.,Vol4[11]October2015:146-159©2015AcademyforEnvironmentandLifeSciences,IndiaOnlineISSN2277-1808Journal’sURL:http://www.bepls.comCODEN:BEPLADGlobalImpactFactor0.533UniversalImpactFactor0.9804

ORIGINAL ARTICLE OPEN ACCESS

Evaluation of Rheological, Physicochemical, and Sensory properties of Gundelia tournefortii yogurt

Azam Ebrahimi1, Ali Mohamadi Sani2*, Mohamad Hojjat Islami3,

1DepartmentofFoodSciencesandTechnology,QuchanBranch,IslamicAzadUniversity,Quchan,Iran 2DepartmentofFoodSciencesandTechnology,QuchanBranch,IslamicAzadUniversity,Quchan,Iran

3DepartmentofFoodSciencesandTechnology,ShahrkordBranch,IslamicAzadUniversity,Shahrkord,Iran

ABSTRACT

The influence of Gundelia tournefortii puree percentages 0, 1, 3, 5, 10, 15 and 20% were added to the stirred yogurts on the Physicochemical properties include Acidity, pH, syneresis, sensory quality of yoghurt samples were determined during 1, 7, 14, and 21 days of storage. Rheological behavior include flow properties of the final product in order to follow n (flow behavior index) and K (consistency index), and the apparent viscosity (µe in mpa.s) by a means of Brookfield model rheometer and range of 0.136-0.323 1/s in a total time of 18 minutes of yoghurt samples were determined during21 days of storage. There were significantly differences between plain yogurt and Gundelia tournefortii yogurt in the pH and titratable acidity amounts 1 day of storage. The results showed that acid during storage was increased to fourteen days, but 21 days of storage decreased although Again Gundelia tournefortii yogurt samples were more acid than plain yogurt. lowest values for syneresis were belonged to Gundelia tournefortii yogurt with 15 % and 20% and 21 days storage. Plain yogurt and Gundelia tournefortii yogurt samples during21 days no coliform bacteria, E. coli, mold and yeast were not. All samples were treated sudoplastic. Sensory evaluation results showed that there were no significant differences about shelf life among the yoghurt samples but there were significant differences About concentration. The yoghurt containing Ggundelia tournefortii 20% had the highest overall acceptability scores as compare to other Gundelia tournefortii yogurt samples and also plain yogurt. The results of current study demonstrated that the addition of Gundelia tournefortii puree to the yogurt significantly improved the quality of yogurt. Key word:Gundelia tournefortiiyogurts,Rheologicalbehavior, Storagetime&concentration.Received12.09.2014 Revised23.10.2014 Accepted23.12.2014

INTRODUCTIONFoodrheologyisthestudyofthedeformationandflowoffoodmaterials[1].Yoghurtisadairyfoodwithcomplex rheology that depends on temperature, solids concentration and the physical state of fats andproteinspresent in themilk.Anunderstandingof the rheologicalproperties ofyoghurt is important totexture, stability, and process design [2]. Between all milk fermented products, yoghurt is more well-knownthanothersandhasmoreacceptabilityintheworld[32].Itiseasilydigested,hashighnutritionalvalue and is a rich source of carbohydrates, protein, fat, vitamins, calcium and phosphorus [3]. Thenaturalandusualyoghurt isproducedbyaddingthecertain lacticacidbacteria that increase the lacticacidcontentofyogurt[5].Stirredyogurtismadebyfermentingmilkandstirringthesetcurdtobreaktherigidgelstructuretoobtainaviscousliquid[33].Theproductisacceptedbyconsumerforitsflavorandaroma,(mainlyacetaldehyde)andpleasanttexture[3].Severalyogurt-basedproductsaremarketedwiththeadditionofeitherfruitorvegetablesrichinbioactivefoodingredientsorediblefibersclaimedtohavebeneficialeffectsonhumanhealthproduct[7].Therationalebehindtheseenrichmentsisthattheeaseofconsumptionofyogurtmay improve bodyhealthstatus bymaintaininga favorable intestinalmicrobialprofile,possiblyloweringcholesterolandbloodpressure,andatthesametimeprovideanoptimalintakeof bioactive components, often with beneficial antioxidant and free radical scavenging capacities. Thispolicymatchesthehighexpectationsofconsumersandinturnencouragestheconsumptionoffermenteddairyproducts[7].Larioetal.foundthattheadditionoffiberfromorangescausedaslightdecreaseinthepHofmilk;Thisdecreasedidnotaffectthefermentationprocessoftheyogurt;however,therheologicalpropertiesoftheyogurtweremodifiedbyadditionoffiberfromorangeanddependedonthedoseofthis

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fiber: 1% fiber addition reduced yogurt syneresis and improved textural properties, increasing gelfirmness[37].Salwaetal.,2004statedthattheuseofcarrotwithyoghurtwasadvantageousdueto itsantibacterial and antifungal properties as well as its inhibitory effect on aflatoxin M1[19]. Bachir RahoGhalem,andBenattoucheZouaoui,2013reportedthatadditionofR. officinalis essentialoilenhancedthequalitiesofyogurt[6].Thekindofflavoringsandtheirconcentrationisusuallyregulatedaccordingtotheinternational standard say by each country [5]. According to Iranian Standard (No. 4046) vegetablesyoghurtisaproductwhichismadebyaddingVarietyoffreshordriedvegetablessuchasmint,oregano,spinach,basil,tarragon,celery,carrots,cucumber,boiledbeets,shallots,etc.toyoghurt[8].Gundelia (Gundelia tournefortii) is a member of the Asteraceae (Compositae) family which grows in thesemi-desertareasofIran,Jordan,Palestine,Syria,Iraq,Syria,Anatoliaandothercountries.Traditionally,G. tournefortii is used for treatment of liver diseases, diabetes, chest pain, heart stroke, gastric pain,vitiligo, diarrhea and bronchitis. It is also reported to have hypoglycaemic, Laxative, sedative, anti-inflammatory,anti-parasite,antisepticandemeticeffects.Compoundsfoundingundeliaprovedtohaveseveral pharmacological effects, e.g. antibacterial, anti-inflammatory, hepatoprotective, antioxidant,antiplatelet and hypolipemic activities. The observed pharmacological properties indicated a closeassociationoftheseeffectswithinfectiousdiseases,digestivedisorders,highbloodpressureandcancer.In traditional medicine, this plant has been prescribed in many disorders [9]. Therefore, Gundelia tournefortiicanbeusedinyoghurtsproductionforimprovingtheirqualityproperties.Theobjectivesofthis study were to evaluate the physicochemical, microbiological, rheological properties and sensoryquality of yoghurts with different percentage of Gundelia tournefortii puree during storage period andcomparethemwithplainyogurt.MATERIALS AND METHODSMaterials Freshcow’smilk,Skimmilkpowder,salt(Nacl),yoghurtcultureincludingStreptococcus thermophilusandLactobacillus delbrueckii ssp. bulgaricus, and microbial media were obtained from the dairy factory ofGolriz, Iran. Gundelia tournefortii were obtained from the local market of Isfahan, Iran. Experimentalyoghurts with viscometer Brookfield Digital Rheometer model DV-III+ (Brookfield, Middleboro, USA),weredevelopedinthefoodslab,SugarFactoryofchaharMahal,Iran.Bacterial Starter Cultures: Yoghurt starter culture (YC-X11 DIP 50u) contains Streptococcus thermophilusandLactobacillus delbrueckii subsp.Bulgaricus markChr.Hansens,Denmark wasobtainedfrom factory of Golriz , Iran and activated at 42°C using 12% sterilized reconstituted skim milk. Afterincubationat42°Cfor4-5h,theobtained workingculturewasfreshlyused.Gundelia tournefortii puree production Rosaliaferracaneetal.demonstratedthatsomecommoncookingtreatmentscanbeusedtoenhancethenutritionalvalueofvegetables,increasingbioaccessibilityofhealth-promotingconstituents[10].Gundelia tournefortii were first cleaned, thorns and frills were taken, washed, and heat treated at 100 °C for 15min,then,itspulpwasobtainedfromthecrushedGundelia tournefortii,andfilledintothesterilejars.Thispulp was stored at freeze temperature until after thaw and at ambient temperature added to yogurt.TrailswerecarriedouttostandardizetheGundelia tournefortiiyoghurt.Yoghurt productionStirred Gundelia tournefortii yoghurt with different concentrations manufactured according to theprocedureofManjulaetal.,[11]withsomemodificationsasfollows:Cow’smilk(milkfat3%,totalsolids12.3%andacidity0.17%)wasusedforyoghurtproductionand2%Skimmedmilkpowderwasaddedtoincreasesolidsmilk.Themilkwasheatedto60oCandhomogenized.Themilkwaspasteurizedat85oCfor30 min, and then rapidly cooled to 45oC. Streptococcus thermophilus and Lactobacillus delbrueckiibulgaricusasstarterculturewereaddedattherateof2%(w/v)intothemilk.Theinoculatedmilkwasincubatedat42oCuntilpHwasreachedto4.5.Theyoghurtsampleswerecooledto25°Cbyrestinginatemperaturecontrolledroom(15°C)andthenstoredat3–5°Cforaperiodof12hours.Theyoghurtwasstirredtosmoothenandtoobtainsemisolidconsistency.1,3,5,10,15and20%ofgundelia tournefortiipulp with 0.7% of salt (Nacl) were added to the smoothened yoghurt. The samples were Mixed withelectric stirrer, packed into suitable packing material, then stored under refrigeration i.e., bellow 50C.Along with gundelia tournefortii yoghurt one control yoghurt was also prepared without addition ofgundelia tournefortiipulp.Theexperimentalyoghurtandcontrolyoghurtwerestoredintherefrigeratorfor21days.Theyoghurtsampleswereanalyzedintriplicateatduringat1,7,14,and21daysstorage.Analytical MethodsPhysicochemical Analysis Syneresis 2

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Onehundredgramsofeachsamplewasplacedonafilterpaperrestingonafunnel.After2hoursat7oC,theweightofwheycollectedwasusedassyneresis[5].Thesamplesanalysiswasperformedintriplicateatduring1,7,14,and21daysstorage.Determination of titratable acidity Titratableaciditywasdeterminedinmilkandyogurtsamplesatroomtemperature.Thetitratableacidityof the yoghurt samples was done according to the procedure of Zekai TARAKÇI., [12] with somemodificationsasfollows:Thetitratableacidityaftermixingyogurtsamples(10g)with10mLofdistilledwater was determined as lactic acid percentage (LA%) by titrating with 0.1 N NaOH, using0.5%phenolphthaleinasanindicator.Thesamplesanalysiswasperformedintriplicateatduring1,7,14,and21daysstorage.Determination of pH pHofthemilkandyogurtsampleswas determinedwithaMethrohmpHmeter691(Switzerland)atroomtemperature [13] . The samples analysis was performed in triplicate at during 1, 7, 14, and 21 daysstorage.Sensory evaluation Sensory analysis of the yoghurt samples was done according to the procedure of Zekai TARAKÇI., [12]withsomemodificationsasfollows:Theorderofpresentationofsampleswasrandomizedanddifferent3-digitnumbercodeswereusedforthesamplesetsindaylight,whowereaskedtoevaluateeachsampleinturncoveringalistofjudgedparameterattributesusinga7pointHedonicScalewith1beingtheworst(1, very poor; 7, very good). The score given by panellists for each sample was noted separately. Thequalitiesjudgedwere:exteriorappearance(bylookingtoyogurtsampleindaylightdirectly),consistencybyspoon(bygentlemixingyogurtwithaspoon),odorandtasteintensity.Todetermineodorandtasteintensity,aspoonofyogurtistakenandspreadedoutbytongue.Theoverallacceptabilitywascalculatedassumofthescoresoftheparametersjudged.Theyogurtswereevaluatedintriplicateatduring1,7,14,and21daysofstoringbysevenpanelistsfamiliarwithyogurt:4werefemaleand3weremaleandagesrangedfrom22to40y.Waterwasprovidedformouthwashingbetweensamples.Microbiological analysis Yoghurt samples were diluted according to the procedure of Okoye and Animalu [15] with somemodifications as follows: The samples (5 g) were weighed aseptically diluted with 45 mL of bufferedpeptonewater.Thus,thefirstdilutionof10–1wasobtained;theotherdilutionswerepreparedfromthisfirst 10–1 dilution to dilutions of 10–3[14] . Potato dextrose agar was used for fungal (yeast and mold)count at 280C for 4 days [15]. Procedure Coliform count of the yoghurt samples was determinedprocedure as follows:. One gram of each sample of yoghurt was serially diluted to 10-3. 0.1 millilitre ofeachdilutionwasplatedon[15]violetredbileagarplatesandincubatedat370Cfor24h[14].Thecolonyforming unit per millilitre sample (cfu/ml) was counted in each case with the aid of electronic colonycounter[15].AllmediawereprovidedbyMerck[14].TheaboveprocedurewasrepeatedforE.colicountexcept that luryl sulphat agar was used at 370C in place of violet red bile agar. The samples microbiologicalanalysiswasperformedintriplicateatduring1,7,14,and21daysstorage.Rheological Measurements Rheologicalpropertiesoftheyogurtsamplesafter24hofstorageat4°CwereDeterminedaccordingtothe procedure of Mircea-Adrian OROIAN, Gheorghe GUTT., [16] with some modifications as follows:apparent viscosity (η) measurements with different shear rates ranging from 0.136 to 0.323 s−1 werecarriedoutonthegundelia tournefortiiyogurtsamplesatambienttemperature(250C),withaBrookfieldDigitalRheometermodelDV-III+(Brookfield,Middleboro,USA).Thespindlewasusedinaccordancewiththesamplenaturetogetallreadingswithinthescale.Thesamples(accordingtotheBrookfieldrequests)werekeptinathermostaticallycontrolledwaterbathforabout10minbeforemeasurementsinordertoattaindesirabletemperatureof250C.Allmeasurementswerecarriedouton50gofeachsamplethatwaspreviously prepared by gently stirring in identical conditions in during every day of experiment. Thesampleswerestirredfor40secondsbeforemeasurement.Firstmeasurementsweretaken2minafterthespindlewasimmersedineachsample,soastoallowthermalequilibriuminthesample,andtoeliminatethe effect of immediate time dependence. All data were then taken after 50 s in each sample. Eachmeasurementwascarriedouttriplicateonthesampleinduring1,7,14and21daysstorage.The totalanalysis time was 18 min and collected 210 points in total. For each sample the shear stress (τ) wasrecordedforshearrates(γ)rangingfrom0.136to0.323s−1.TheshearrateversusshearstressdatawereinterpretedusingtheHersch-Bulkleyexpression[22];Viscosity:η=0/•+K•n-1

Shear stress:=0+K•n

Where: η= Viscosity(pa.s),(mpa.s)

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K= consistency index(pa.sn),(mpa.sn)n= behavior index(dim ensionless)= Shearstress(pa),(mpa)•=Shearrate(s-1)0=yieldstrengthStatistical analysis Allexperimentswerecarriedoutintriplicate,andtheanalysiscarriedoutforeachtreatmentbatchwasat least for three samples [18]. Data were analyzed for treatment effects, storage time effects, andtreatmentbystoragetimeinteractions[34].Alldataobtainedwereexpressedasmeanvalues±standarddeviation[18].Meansandstandarddeviations(SD)ofdatawerecalculatedwithSPSS(version20.0,IBMSPSS.). Statistical software SPSS was used to perform [10] two-way analysis of variance (ANOVA) [35],and least significant difference test (LSD) at a 95% confidence level (p < 0.05) to identify differencesamonggroups[10].CurvesdesignwascarriedoutusingthesoftwareMicrosoftExcel2007.RESULTS AND DISCUSSIONPhysicochemical CompositionThe data given in Table 3, fig.1, and fig.2 indicated that time storage and concentration had significanteffectontheresultingacidity,pH,andsynersisofthepreparedyoghurtsamples(p<0.05).ThepHvaluesdecreasedwhilethetitratableacidityincreasedgraduallybuthaveenhancedthepHandhavedecreasedthe titratable acidity, after14th day in all yogurt samples, during 21 days of storage. The decrease inacidity of gundelia tournefortii yogurt with increase of concentration might be due to the acidity ofgundelia tournefortii.MorvaridYousefetal.,[6]reportedthattheincreaseinacidityoffruityogurtmightbeduetotheacidityofapple,bananaandstrawberryfruits.ThismightbeduetothehigherTScontent(lowmoisture)infruityogurtwhichaffectstheactivityoflactic acid bacteria,while YanWenet al.,(2011)reportedthatComparedto theacidproductioninthecontrolyoghurt, treatmentofskimmedmilkwithhorseradish peroxidase (HRP)orthecombinationofHRPandFerulicacid(FA)didnotshowanyimpactontheacidproductionintheyoghurtsamples.Theseresultsmeanthatthetreatmentofskimmedmilkhadnoimpactonthefermentationormainchemicalcompositionoftheyoghurtsamples, i.e.thedifferentrheologicalpropertiesofthepreparedyoghurtsamplesarenottheresultoftheirdifferentcompositionoracidity.Salwaet al.,[39]reportedthat theacidityincreasedandthepHdecreasedduringthestorageperiod especially for samples with 15 and 20% carrot juice may be due to the excessive sugarfermentation and the presence of lactic acid producing organisms, or may be due to the presence ofphenols and polyphenols components which naturally present in carrot. Nafiseh Vahedi et al., [33]reported that pH value increased after14th day in strawberry and 21th day in apple yoghurt and statedthatassugarsourcesfinish,microorganismsbegintoconsumeproteinsandproducingsomeproductsbymicroorganisms,willresultinpHincrease.Okoyeetal .,[15]reportedthatthepHandthetitrableacidityoftheyoghurtsampleswassignificantlydifferentfromeachother(p<0.05).Thedifferencescouldbeduetovariationinthegrowthoflactic acid bacteria during fermentation [15]. Amna Mahmood et al. [12] reported that the variation in pH valuemightbeduetotheenvironmentaltemperature,humidityandexposuretothesun[12].Inbothofcontrolandgundelia tournefortii yogurtthehighestofpHrelatedtothefirstdayofproductionwithlimit(4.31-4.50) and the lowest of pH related to the 21th day with limit (4.24-4.38) while the lowest of titratableacidity belong to the first day of production with limit (85.33-98) and the highest of titratable acidityrelatedtothe14thdaywithlimit(93-116).MorvaridYousefetal.[14]reportedthatthisphenomenawasdue to the growth of lactic acid bacteria and produced the lactic acid, which was due to the especialsynergism between Lac. Spp and Strep. spp. L. delbrueckii subsp. bulgaricus and S. thermophilus areresponsible for the post acidification of yogurt during cold storage.The lactic acid produced as aconsequenceof themetabolicactivityof lactic acid bacteria causes the increase of milkacidityandthereductionofthepH[22].ParmjitandChetanShinde[39]statedthatdecreaseinpHmightbeattributedtothe utilization of residual carbohydrates by viable microorganisms and production of lactic acid, smallamountsofco2andformicacidfromlactose.Vahedietal.,(2008)reportedthatdecreaseinpHisduetothe microorganisms activity, whereas Kailasapathy [39] stated that post-acidification, during storage isduetoB-galactosidasewhichisstillactiveat0-5Ĉ.Inthiscase,pHmaybedecreasetolessthan4.2.SomeresearcherssuggestedthatthedropinpHduringstorageperiodisduetoresidualenzymesproducedbystartersduringfermentation.Reasons that pH is at limit (4.30-4.40) may be due to: ThepHvalueswereapproximatelyat limit(4.30-4.40)duringthestorageperiodespecially forsampleswith10,15and20%Gundelia tournefortiipulp.ThisphenomenamaybeduetothepresenceofphenoliccompoundspresentinGundelia tournefortii.KonstantinosB.Petrotos et al., (2012)reportedthatsampleA

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which was spiked with 1000 ppm of encapsulated Olive Fruit polyphenols exhibited a fast drop of pHvalue in the incubator and reached the critical pH value of 4.6 faster than the sample B withoutpolyphenols,thusimplyingabenefitinenergycostsandinproductiontimeforthepolyphenolenrichedyogurt.Atthesametime,inthelongterm,duringstorageoftheproductinchilledconditions(0-4oC)thepolyphenolsseemtoexertaprotectiveeffectagainstpost-acidificationoftheyogurtandstabilizethepHvalue approximately at 4.4 while the same value for non polyphenol-enriched yogurt (Sample B)approachesavalueof4.2at25day,whichisnotorganolepticallyacceptablebytheconsumer.Thismeansthat the presence of the polyphenols can extend the shelf life of the product by more than 10 days. R. officinalis oil as mentioned by Moreno et al. [6], contained high levels of phenolic compounds thatcontributedtothemaintenanceoflowerpHincheese(adairyproductlikeyoghurt).Syneresis The syneresis is a measure of the quantity of whey separated from the yogurt and is one of the mostimportantfactorsinfluencingconsumers’acceptance[22].Higherlevelofsyneresisshowsthatyogurtisof low quality. The syneresis of the prepared yoghurt samples were affected significantly (P<0.05) byboth Gundelia tournefortii concentration and storage time. In both of control and Gundelia tournefortiiyogurtthehighestofsyneresisrelatedtothefirstdayofproductionwithlimit(8-19.1)andthelowestofsyneresisrelatedtothe21thdaywithlimit(3.5-6.4).Reasons for decreasing syneresis in both control and Gundelia tournefortii yogurt might be: Yogurtwashomogenizedbeforefermentation;theintensityofsyneresisishigherinthecaseofyogurtswithlowlevelsoffat[22].PiyawanSupavititpatana(2010)reportedthatthehighersyneresisofthecowmilkyogurtpossiblyresultedfromthelessgelstrength.thecommercialyogurtwashomogenizedbeforefermentation.Homogenizationproducessmall-sizedfatglobules.Asaresult,moreproteinisabsorbedonthesurfaceofthefatglobules,leadingtoincreasedabilitytoimmobilizewaterbutthegelofthecowmilkyogurt had lower consistency. the consistency of the yogurt is related to the strength of the protein-proteininteractionsofthegelstructure.Pulpcontent inyogurt formulation,thepreparationofyogurtundercontrolledcondition;theexcessivewhey separation may be a consequence of overcoming the fermentation or storage temperature, ofinadequate cooling or of improper handling while in containers during storage and distribution. Thesyneresiscanbeusuallylimitedoreliminatedbyincreasingthemilksolidscontent.Anyway,certainfoodadditives used for yogurt stabilization can affect the sensory properties of the final product [22].Morvarid Yousef et al., (2013) reported that with increase to pulp content in yogurt formulation wasexpected water absorption will be increased and therefore syneresis decreased. Nafiseh Vahedi et al., (2008)reportedthatinappleyoghurtbyincreasingfruitamount,synersisdecreasedinbothconditions(before and after fermentation). Synersis was lower in samples which fruit cubes were added to themafter fermentation. Because of high acidity of strawberry, by increasing fruit amount, acidity increasedtooandstarter'sactivityhadaffectedandsynersisincreased.Synersisvalueinwholeperiodwaslowerthanfirstdayofproduction.Synersisreductioncanberelatingtoabsorptionofunboundwaterbyfruitcubes.AmnaMahmoodetal.,(2008)reportedthatadecreaseinthevalueofsyneresiswasrecordedoverthestorage,becausetheyogurtswerepreparedundercontrolledconditionsandstoredinscrewcappedbottles.Salwaetal(2004)reportedthatthesyneresisincreasedwiththeincreaseoftheconcentrationofaddedcarrotjuiceandwiththeincreaseofstorageperiod.AccordingtoTamime,lowpHvaluescanpromotesyneresisofyogurt,duetoexcessiverepulsioncharges[23].ThelevelsofsyneresisdecreasedasthefinalfermentationpHdecreased[12].Rheological properties of yoghurtFoodrheologyisthestudyofthedeformationandflowoffoodmaterials[1].Therheologicalpropertiesofstirred yogurt have been well studied; their flow properties are characteristic of a non-Newtonian andweakly viscoelastic fluid [25]. Lee and Lucey (2006) found that the rheological properties of stirredyogurts were greatly influenced by the physical properties of the original intact (set) yogurt gels.Rotational viscometers, such as the Brookfield viscometer, are often used to characterize the flowbehaviorofstirredyogurts.Itshouldbenotedthatthepowerlawmodeldoesnothaveayieldstresstermwhile all stirred yogurts have yield stress unless they have been sheared first and no recovery timeallowedtorebuildsomestructures[1].Theviscosityisanimportantparameterthatcanbesuccessfullyusedforcomparingthequalityoftheyogurtsamplespreparedindifferentconditions[22].The rheological tests showed that the products studied demonstrated non-Newtonian behavior (shearthinning),which couldbedescribedwithHerschell-Bulkleyrheologicalmodel [24].Thedecreaseof theapparentviscosityofallstudiedsampleswiththeincreaseoftheshearrateindicatesthepseudo-plasticbehavior, with time dependent structural viscosity [22]. All values of flow index (n) were less than1.Thiago Rocha dos Santos MATHIAS et al. [23] observed All values of flow index (n) were less than 1,confirming the pseudoplastic characteristic. According to Horne and Lucey [23] this can occur due to

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physicaldestructionofweakbondsbetweenthemoleculesoftheproductandduetodecreasedenergyofinteractionbetweenthem[23].Aproduet al.,[22]reportedthattheapparentviscosityreachesaplateauofconstantvalues,meaningthatthedestructionand thereformationrateoftheproteinaggregatesarecomparable.HojjatKarazhiyanet al. [26]reportedthatForallsamples,an increase inconcentrationortemperatureledtoanincreaseinpseudoplasticity.ThedatagiveninTables5,and6indicatedthatconcentration,andstoragetimehadsignificanteffectontheresultingapparentviscosity,andconsistencyindex(k)(p<0.05),buthadnosignificanteffectontheresultingflowbehaviorindex(n)ofthepreparedyoghurtsamples(p>0.05).WithincreasethecontentofGundelia tournefortiipulpintoyoghurttheconsistencyindex(k)andapparentviscosityincreased,exceptwhenPulpGundelia tournefortii20%wereadded.TypeofGundelia tournefortiifiber,increasinggundelia tournefortiipulprateinyogurts;DelloStaffoloetal., [25] observed that the type of fiber significantly affected the rheological properties of the yogurts.Apple fiber fortification decreased yogurt compression values, probably due to the formation of fiberaggregatesthatinterferedwithyogurtstructure.Wheatandbamboofiberfortificationincreasedyogurtcompressionforceandtexturesensoryscores;Consumer’spreferredfirmeryogurts,probably,resultingfrom the insoluble nature of these fibers. Zekai Tarkci [12] stated that increasing marmalade rate inyogurts increased the mean viscosity values and this was also found to be concentration-dependent(P<0.05).Therheologicalcharacteristicsofyogurtaregovernedbymilkcomposition,temperatureandtimeofmilkheat pre treatment, type and quantity of starter culture employed to inoculate the milk, fermentationtemperature and storage conditions of the final product. Several authors have studied the correlationamongyogurtrheologyandstructure,evaluatingtheeffectofmilkheattreatment,typeofstarterculture,incubationtemperature,storagetime,etc.[25].YanWenetal.,(2011),reportedthatSkimmedmilktreatedwithhorseradish peroxidase (HRP)andFerulicacid(FA)hadthehighestapparentviscosityandthecontrolmilkhadthelowestone,whichindicatesthatHRPtreatmentcouldenhancetheapparentviscosityofthetreatedskimmedmilk,especiallywhencross-linkingagentFAwasadded.Theseresults indicatedthatmodificationoftheserheologicalpropertiesofthe treated skimmed milk might be related to the modification of the main milk components, milkproteins.ApparentviscosityofthepreparedyoghurtsamplesfromtheskimmedmilktreatedwithHRPandFAhadthehighestvalue,butthatpreparedfromthecontrolmilkhadthelowestone.HRPtreatmentof skimmed milk had no significant influence on the resulting flow behavior indices (n) of the yoghurtsamples(p>0.05),butmighthaveenhancedtheconsistencycoefficient( K),especiallywhenFAwasadded(p<0.05). Different rheological properties among the prepared yoghurt samples arose from themodificationofmilkproteinscatalyzedbyHRP (especiallywhenFAwasadded),whichshows that thisapproachhaspotentialapplicationtoimproveproductqualityinyoghurtprocessing. Toobtainhighconsistencyandviscosityyoghurts, the industryusually followsoneoracombinationofthe followingapproaches: (1)milksupplementation withnonfat dairysolids; (2) milkhomogenization;and (3) heat treatments o denature serum proteins to allow a better interaction of these with caseins.Denatured serum proteins enhance firmness of yoghurt. Indeed this is the reason milk is heat treatedbefore starter addition [38]. Ana Lúcia Barretto Penna et al. [27] reported that with increase in thecontent of total solids (9.3–22.7 %) the consistency index and apparent viscosity increased and flowbehavior index decreased. Increasing the temperature of heat treatment (81.6–98.4 °C), an increase inconsistency index (K) and decrease in flow behavior index (n) were observed. Higher sampletemperatures (1.6–18.4°C) promoted a decrease in consistency index, and increased the flow behaviorindex.Rheologicalpropertiesofyogurtwerehighlydependentonthecontentoftotalsolidsofmilk.Thus,the choice of type and quantity of dry matter fortification of milk should be considered in improvingrheological properties of yogurt. Collet, L.S.F.C.A and Tadini, C.C. [28] stated that yogurt with highercaseinatecontent(2%)presentedhigherequilibriumshearstressthat isahigherequilibriumapparentviscosity[28].At during storage period: The apparent viscosity and the consistency index of the yogurt increasedduringthefirst7daysofstorage.Nosignificantdifferencewasobservedforlongerstorageperiods.Theflowbehaviorindexofyogurtdecreasedweakly,butresultswerenotsignificant,despiteagoodvariationcoefficientobtainedintheflowcurvemeasurements.TheourreasonsareinlinewithSamuelLubbersetal.[29]thatstatedthattheincreaseintheconsistencyindexandtheapparentviscositycouldbedue,ontheonehand,toanacidificationoftheproduct,whichreinforcestheproteinnetwork.Theyobserved,thepHofyogurtdecreased in28daysat100C.AccordingtoRawsonandMarshall[36],S. thermophilus arethe most germs incriminated in the production of exocellular texturizing agents calledexopolysaccharides that might interact with the protein content of milk and increase the viscosity andrheologialqualityofproducts.Duringthepost-acidificationperiod,theactivityofS. thermophilus isnot

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completely stopped, but it is less important compared to that of L. bulcaricus which not only produceslacticacid,butprobablyasmallamountoftexturizingagents.Ontheotherhand,theresidualmicrobialactivityinyogurtwouldgenerateexopolysaccharides(EPS)inthemedium,whichtakepartintheproteinnetworkandcouldreinforcethetexturalpropertiesofyogurt.Hessetal,MarshallandRawson,andLawsandMarshallobservedthatmodificationsmightbeduetoEPSproductionandpHdecreaseshowever;theauthors agreed that the highest EPS production generally occurred in the beginning of the lacticfermentation. Moreover, Shah et al. and Birollo et al. studied the viability of lactic microflora and pHduringstorageandfoundnotonlythatpHdecreasedbutalsothatthesurvivalactivityoflactic bacteriacandecreasedramaticallyaroundthe25thdayofstoragedependingonthebacteriastrain.However,nodataareavailableonthoseparametersforalongerperiodoffermentation.Themaineffectobservedonaplainyogurtisanincreaseofviscosityduetothebacterialactivity,whichdecreasesthepHduringaging.Indeed,thestrengthoftheproteinnetworkincreasesalongwithbytheincreaseoflacticacidamountandexopolysaccharidesproduction,fromlivebacteriainyogurt[29].Microbiological analysisTable4showedinbothplainandgundelia tournefortiiyoghurtdidn'thaveanymoldandyeast;ColiformsandE.coliatduring21daysofstorage.Thismaybeduetoreasonsofbelow:Theinhibitoryeffectofgundelia tournefortiiupon;Coliform,E.coliorganismsandthegrowthofmoldandyeast. This reasons were in agreement with salwa et al. (2004) that reported that mold and yeast ,Coliforms count markedly decreased with increase carrot juices concentration and completelydisappearedinyoghurtwith15and20%carrotjuicerespectively.InDukeshandbookofmedicinalBible,someofactivitiessuchasantiseptic,bactericideandemetichavebeenmentionedforG.tournefortii, It isalsoreportedtohavehypoglycaemic,Laxative,sedative,anti-inflammatory,andanti-parasite,effects. Itcould act as an inhibitor of multidrug resistance and a vulnerary agent. According to some studiesmethanol extracts of the whole plant material of G.tournefortii acted as antibacterial against multidrugresistant Escherichia coli and Pseudomonas aeruginosa. The antibacterial activity of gentamycin andchloramphenicol,whenmixedG.tournefortiimethanolextract,wassignificantlyimprovedagainststrainsofstaphylococcus aureus(Darwishetal.,2002).StudyofphytocompoundsandantibacterialeffectsoffourmedicinalplantsessenceinLorestan,IranshowedthatessenceofG.tournefortiileaveshasbacteriostaticeffect on staphylococcus epidermis. Essence of leaves has effect in concentration of 30 µml-1 indicatingbacteriostaticeffectonGram-positive cocci.However,theresultsofrecentstudiesdemonstratedthatonlyroot extracts of G.tournefortii rather than the whole plant parts, are responsible for antimicrobialproperties.Therefore,gundelia tournefortiiinagreementwithaboutcarrotisconsideredasantibacterialagentagainstpathogenicmicroorganismswhichmaygetaccessintoyoghurteitherbeforeorevenafterprocessingrenderingtheproductunsafeforhumanconsumption[29]. •Thepresenceofphenolsandpolyphenolscomponentswhichnaturallypresentingundelia tournefortii;plantphenolsandpolyphenolsareeffective inpreventingvariouspathologicalconditions.Accordingtosomereports,plantphenolscontributetoimportantactivitiesincludingantiviral,anti-tumoral,antibioticandantioxidantactivities[9].KonstantinosB.Petrotos et al., (2012)reportedthatthepresenceofplainorencapsulatedpolyphenolsinyogurtprovidesprotectionfortheproduct,initiallyduetoafasterpHdropand later by decelerating mould development in the product. This means that the presence of thepolyphenolscanextendtheshelflifeoftheproductbymorethan10days.Theourstudyresultsonbothplain and gundelia tournefortii yoghurt were in agreement with Bachir Raho Ghalem and BenattoucheZouaoui., [6] on both plain and yoghurt enriched with Rosmarinus officinalis oil who reported that thepresence of major components of R. officinalis which possess strong antibacterial and antimicrobialactivitiesonmicro-organismsosmophilesresponsible forthedeteriorationof themarketablequalityofthefoodproducts.The effect of acidity and high sanitation conditions during manufacture and storage in all yoghurtsamples; Coliforms prefer 7-44 ºC temperature and minimum initial pH 4.4-4.5. Both refrigeratorconditionswhichusedforyoghurtstorageandpHreductioncanmakeundesirableconditionforcoliforms tocontinuetheirgrowth[32].NafisehVahediet al.[33])statedthatCompetitionwithLABcausedifficultsituation for coliforms' activity so these microorganisms were inactive. Azza M. Farahat and O.I. El-Batawy., [3] reported that Coliform bacteria were not detected in either fresh control or experimentalsamples and during the refrigerated storage. This may be due to the efficient heat treatment of thedifferentyoghurtmilks(85ºCfor10min)andhighsanitationconditionsduringmanufactureandstorageofyoghurt.Inaddition,ithadbeenalsoreferredtotheeffectofacidityindifferentyoghurts,whichplaysanimportantroleinreductionofthegrowthrateofcoliform bacteria. Thehighyeastsandmouldscountcould be attributed to contamination from air incorporation during stirring the different yoghurttreatments.Inaddition,thepostcontaminationmaybeoccurredinyoghurtsamplesfromdifferentfruithomogenates and during filling the products [3]. Çon [30] found much higher yeast and mold count in

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theiryogurtsamples.Thehighyeastandmoldcountcouldbeattributedtocontaminationfromair, thefruitmarmalade,molassesandthe1dayoldcultureusedforyogurtmanufacture.Sensory evaluationsSensory properties of foods offer quality control criteria [19].Yogurt should firm, free from any wheyseparationandcreamylayer.Generallytheappearanceofyogurtshouldconveysmooth,homogeneous,moderately firm gel or custard like body and texture and uniform off white color [20]. Many factorscontributetotheorganolepticevaluationinmilkproducts.PohjanheimoandSandellnotedthatsubjectswhoconsiderednaturalcontent,ethicalconcernsandhealthasimportantfoodchoicemotivesperceivedsourer, thicker and more genuine yoghurt flavour as more pleasant, compared to subjects whoconsidered convenience, price, mood and familiarity more important, evaluated sweeter and smootheryoghurt as more pleasant. Addition of other uncommon additives also affects the acceptability of milkproducts[31].TheadditionofGandelia tourfonettiindifferentproportionssignificantlyaffected(P<0.05)thescoresforaroma,taste,appearance,bodyandtexture,andoverallacceptabilityyogurtsamples,whilethe storage time showed no significant difference (P>0.05) with addition of Gandelia tourfonetti forsensory parameters evaluated. The scores increased with increase in the percentage of Gandelia tourfonettipulpaddedtoyogurtinalmostallsensoryattributes.Yogurttextureisimportantforproductqualitycontrol,processdevelopment,andconsumeracceptability[5].Thischaracterizationcanbedoneusingeitherinstrumentalorsensorymeasurements[20].TheourreasonsabouttexturepropertiesInbothofcontrolandgundelia tournefortiiyogurt isagreementofAzzaM.FarahatandO.I.El-Batawy[3]thatstatedthattheuseoffruithomogenateformakingstirredyoghurtcausedanimprovementinbodyandtexturepropertiesofthefinalproduct.Thisimprovementcouldbeduetothehighercontentoffibersassociatedwithfruithomogenatesaddedandthismayleadtoincreasetheviscosityandconsequentlyimprovethebodyandtexture.In both of control and gundelia tournefortii yogurt the highest scores of almost all sensory attributesrelated to yoghurt with 15 and 20% Gandelia tourfonetti pulp during the storage period. The resultsobtainedare inaccordance to theresultsofSalwaet al., [19].Theadditionof20% Gandelia tourfonettipulp to yoghurt showed to be the best concentration as it got the highest evaluation marks during thestorage period. It implies no unpleasant aftertaste, a pleasant level of acidity and pleasing balance offlavorduring thestorageperiod[19]. The appearance, taste, texture, flavorandoverallacceptabilityoftheexperimentalsamplescoredmoremeansensoryscores than thecontrol [11]. ZekaiTARAKÇI., [31]reported that the overall acceptable scores of the yogurts containing 15% and 20% marmalade werefound to be generally higher than that the other types of flavored yogurts. Azza M. Farahat and O.I. El-Batawy about fruit yoghurt [3] reported that some fruit additives increased acceptability of stirredyoghurt.Thiswasduetocoordinationbetweenpineappleandpapayafruitflavoranddairyproducts[3].TheseresultsarenotinaccordancetotheresultsobtainedinthestudyofM.Rasdhariet al.,[20]whereSabdariffaaddedyogurtshowedahigherscoreinalmostallsensoryattributes[20].Allyoghurtsamplesreceivedsignificantlyhigher texture percentage.Essentialoilmass fractiondidnotsignificantlychangethetexturepercentageofthesamples.Thewild strainsgiveyoghurtswithstronglydifferentpropertiesofindustrialoneduetothemicroorganisms’mutation[2].At during storage period:Atthebeginningofstorage,allyogurtsweresuperior,mainlybecauseoftheirmore intense flavorand betterconsistency.However,after7days, theacidityof theyogurts increased,andthesensoryscoresofallsamplesbegantodecrease[14].WhenpHdecreased,aromaandacidictasteincreasedasaresultofdecreasedflavoringcharacteristics[12].Theoverallacceptabilityscoresofsamplesincreasedduringstorageforupto7daysandthendecreased.This could be attributed to the development of acidity [14]. Zekai TARAKÇI, Erdoğan [31] stated thatOverall, with prolonged storage the body and texture scores decreased. In contrast, Keating and Whitefound that prolonged storage led to an increase in the body and texture score. The aerobic mesophilic bacteriacountwassignificantlyaffectedbythetypeofflavoradditivesusedinyogurt.Aziza M. Farahat and O.I. El-Batawy [3]reported that decrease scores of all the samples may be due to the aciditydevelopment or the production of microbial metabolism which slightly harmed the rheological andsensorypropertiesoftheproduct.

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Table 1. Composition of milk and Gundelia tournefortii pulp used for yogurt making

Table2. Physicochemical composition of different types of fresh yogurt Syneresis(ml/2hour) Acidity(%) pH Dose of Gundelia tournefortii (%)

14.90.86 4.43 0 16.7 0.85 4.41 1 15.7 1.04 4.28 313.3 0.86 4.39 58.7 0.86 4.45 108.2 0.86 4.42 157.4 0.86 4.48 20

Fig. 2: pH value during storage Fig. 1: Acidity value during stora

Table3. Physicochemical composition of control and gundelia tournefortii yogurt in storage period Syneresis(ml/2hour) Acidity(%) pH Storagetime(days) Dose of Gundelia tournefortii (%)

16.9±3.30.86±0.056 4.44±0.0056 1th

0

8.4±2.60.98±0.056 4.30±0.0056 7th

6.3±0.61.05±0.056 4.22±0.0056 14th

5±0.91.04±0.056 4.24±0.0056 21th

9.1±5.1a 0.98±0.079a 4.30±0.089aYx̅

19.1±2.70.86±0 4.39±0.0056 1th

1

11.9±3.71.03±0.057 4.24±0 7th

7.6±0.31.05±0.056 4.22±0 14th

4.7±0.51.04±0.058 4.24±0 21th

10.8±6a 0.99±0.084a 4.27±0.074Yx̅

17.7±1.20.98±0

4.31±0 1th 3

10.3±1.61.12±0 4.150 7th

6.1±0.71.16±0 4.01±0.0057 14th

4.1±0.21.05±0 4.36±0.4630 21th

9.6±5.5a 1.07±0.071a 4.21±0.2449aYx̅

15.7±0.60.86±0.057 4.40±0.0056 1th

5

8.7±0.31.03±0.056 4.26±0.0057 7th

7.5±0.41.08±0 4.17±0 14th

6.4±11.02±0.056 4.28±0 21th

9.6±3.8a 1±0.086a 4.28±0.088a Yx̅

9.4±0.50.86±0.056 4.44±0.0056 1th 8.2±0.80.92±0.056 4.36±0.0056 7th

Acidity(%) pH Food 0.17 6.67Milk0.41 5.4 Gundelia tournefortiipulp

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6.4±0.40.98±0.056 4.30±0 14th 10 3.8±0.4 0.92±0 4.37±0.0057 21th

6.9±2.2a 0.92±0.044a 4.37±0.0544a Yx̅

9.9±0.3 0.86±0.057 4.45±0 1th 15

8.8±0.40.91±0 4.32±0.0057 7th

5.7±0.21.03±0.056 4.25±0.0058 14th

3.5±0.30.98±0.058 4.30±0 21th

7.1±2.6a 0.94±0.070a 4.33±0.0751aYx̅

8±0.1 0.85±0.057 4.50±0.0057 1th 20

7.7±0.9 0.92±0 4.37±0.0057 7th

4.4±0.50.93±0 4.33±0.0056 14th

3.5±0.50.91±0.057 4.35±0.0057 21th

5.9±2.1a0.90±0.031a4.39±0.0688aYx̅

13.8±4.5A0.87±0.042A4.42±0.057A1th Total

STx̅ 9.1±2.1A0.99±0.073A 4.28±0.074A7th Total

6.3±1.1A1.04±0.068A4.21±0.1000A Total14th

4.4±1.1A0.99±0.057A4.30±0.1559A21th Total

* abcd Lettersindicatesignificantdifferencesamongyogurts(Yx̅),P<0.05,

ABC Lettersindicatesignificantdifferences

amongstoragetimes(STx̅),P<0.05.

Table4. Microbiological evaluation of control and Gundelia tournefortii yogurt in storage period E.colicount

Storageperiod(days) Coliformscount

Storageperiod(days) Yeastandmoldcount

Storageperiod(days)

21th 14th 7th 1th 21th 14th 7th 1th 21th 14th 7th 1th Dose of Gundelia tournefortii (%) absabsabsabsabsabsabsabsabsabsabsabs0 absabsabsabsabsabsabsabsabsabsabsabs1 absabsabsabsabsabsabsabsabsabsabsabs3absabsabsabsabsabsabsabsabsabsabsabs5absabsabsabsabsabsabsabsabsabsabsabs10absabsabsabsabsabsabsabsabsabsabsabs15absabsabsabsabsabsabsabsabsabsabsabs20

Table 5 Apparent viscosity (mPa·s) of control and Gundelia tournefortii yogurt in storage period. Apparentviscosity(mPa·s)

Storageperiod(days)

Yx̅21th 14th 7th1thDose of Gundelia tournefortii (%)

14019.70±12863a10180.90±3825.613044.67±4630.6 21038.13±23265 11815.10±5424.20 23868.62±10660a 20295.93±8079.520857.63±750026054.93±11.74028266±12646.771 22018.36±10732a18235.53±6414.516815.07±7537.828078.3±12300.0824944.57±11535322432.34±11528a 18729.27±747.2419918.2±7892.933593.13±1356 1748.88±8423523056.28±100.96a 21755.43±8094.319425.23±7113.730765.53±1292820278.93±7165.41018190.78±14191a19037.20±742.6221397.40±1036018093.27±2446514235±6090.3941519543.98±8003.9 18100.70±7065.4 22920.60±815617100.07±6595.620054.57±9068.32018047.85±7759.1

A 19196.97±8243.5

A 24960.47±16955A 19583.28±1006.3ASTx̅

* abcd Lettersindicatesignificantdifferencesamongyogurts(Yx̅),P<0.05,

ABC Lettersindicatesignificant

differencesamongstoragetimes(STx̅),P<0.05.

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Fig 3: Apparent viscosity of the yoghurt samples (control) and gundelia tournefortii yogurts as a

function of shear rate Table6. Rheological parameters ( n , k, and R2) of control and Gundelia tournefortii yogurt in storage period.

R2 n(-) K(mPa・sn)Storageperiod(days) Dose of Gundelia tournefortii (%)

0.9850.66±0.288.12±8.741th

0

0.9910.36±0.1216.78±7.87 7th 0.9910.33±0.1013.35±4.5914th 0.9910.36±0.127.62±4.36 21th 0.43±0.19a11.47±6.94 Yx̅ 0.9850.46±0.1026.96±5.841th

1

0.9940.52±0.5110.36±9.137th 0.9910.36±0.9118.57±3.08 14th 0.9850.62±1.226.02±6.7321th

0.49±0.6915.48±11.61a Yx̅ 0.9820.50±0.0527.98±10.881th 30.9890.43±0.5016.86±16.897th 0.9820.60±0.289.27±3.9914th 0.9840.32±0.0513.93±17.7121th 0.46±0.2217.01±15.26aYx̅ 0.9950.41±030.15±3.491th

5

0.9860.79±0.4111.73±13.337th 0.9850.64±0.125.59±7.2314th 0.9980.36±0.0513.27±2.8221th

0.55±0.1415.19±11.67aYx̅ 0.9900.57±0.138.54±10.781th

10

0.9930.42±0.6836.66±16.267th 0.9890.49±0.3114.93±11.1314th 0.9920.70±0.5113.51±10.9821th

0.55±0.4118.41±16.62aYx̅ 0.9920.67±0.6511.68±11.931th 150.9940.37±0.0212.76±4.38 7th 0.9960.42±0.1622.46±7.4214th 0.9920.44±0.0315.59±1.4621th 0.47±0.31a15.62±7.68aYx̅ 0.9890.70±0.603.30±3.011th 200.9910.99±0.796.06±6.917th 0.9900.59±0.238.22±4.9914th 0.9920.65±0.288.59±9.9421th 0.73±0.47a 6.55±6.52aYx̅ 0.57±0.2616.67±13.75A 1th Total

ST x̅

0.55±0.4715.89±13.53A7th Total 0.49±0.3013.20±8.2114th Total 0.49±0.3311.22±8.97A21th Total

* abcd Lettersindicatesignificantdifferencesamongyogurts(Yx̅),P<0.05,

ABC Lettersindicatesignificantdifferences

among storage times (ST x̅), P<0.05. **Flow behavior indices (n). ***consistency coefficient (k). ****regressioncoefficient(R2).

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Table7. Sensory properties of control and Gundelia tournefortii yogurt in storage period SmellTasteTexture Appearance Storageperiod(days) Dose of Gundelia

tournefortii (%) 4.81±0.40 5.24±0.75.10±0.53 5.10±0.53 1th

0

5.52±0.51 5.48±0.515.7±0.57 5.19±0.40 7th 4.90±0.53 5±0.545.19±0.68 5.19±0.68 14th 4.95±0.21 5.05±0.594.90±0.3 4.86±0.35 21th

5.05±0.51a 5.19±0.61a 5.21±0.60a 5.08±0.52a Yx̅

4.86±0.47 4.95±0.594.90±0.43 4.90±0.62 1th

1

5.33±0.48 5±0.774.95±0.49 4.90±0.43 7th 5.14±0.57 4.86±0.354.86±0.35 5.33±0.48 14th 4.81±0.40 4.81±0.404.81±0.6 4.86±0.65 21th 5.04±0.52 4.90±0.55a 4.88±0.47a 5±0.58a Yx̅ 5.05±0.59 5±0.545.38±0.49 5.19±0.40 1th 35.52±0.51 5.43±0.505.33±0.48 5.33±0.48 7th 5.52±0.51 5.29±0.464.90.±0.3 4.95±0.21 14th 4.81±0.4 4.81±0.44.86±0.47 5.19±0.60 21th

5.23±0.58a 5.13±0.53a 5.12±0.50a 5.17±0.46a Yx̅ 5.29±0.46 5.24±0.435.52±0.51 5.33±0.48 1th

5

5.62±0.49 5.43±0.505.33±0.48 5.38±0.49 7th 5.48±0.51 5.43±0.505.19±0.40 5.24±0.43 14th

5±0.31 4.95±0.215.24±0.53 5.38±0.49 21th 5.35±0.50a 5.26±0.46a 5.32±0.49a 5.33±0.47a Yx̅ 5.33±0.48 5.29±0.465.76±0.7 5.48±0.51 1th

10

5.76±0.7 5.62±0.495.48±0.68 5.52±0.68 7th 5.57±0.50 5.43±0.55.24±0.53 5.29±0.56 14th 5.57±0.50 5±0 5.38±0.49 5.67±0.48 21th

5.56±0.56a 5.33±0.47a 5.46±0.63a 5.49±0.57a Yx̅ 5.52±0.60 6±0.83 6.43±0.5 5.57±0.50 1th 156.48±0.51 6.14±0.475.52±0.6 6.48±51 7th 6.38±0.49 6.10±0.765.48±0.68 5.52±0.68 14th 6.10±0.62 6.05±0.596.14±0.57 6.29±0.56 21th

6.12±0.66a 6.07±0.67a5.89±0.71a 5.96±0.70a Yx̅ 6.05±0.53 6.05±0.596.71±0.46 6.62±0.49 1th 206.14±0.49 6.14±0.656.05±0.59 6.10±0.62 7th 6.14±0.48 6.14±0.656.05±0.49 6.10±0.53 14th 6.10±0.65 6.10±0.626.38±0.66 6.48±0.51 21th 6.38±0.59a6.11±0.62a6.30±0.61a6.32±0.58aYx̅ 5.28±0.645.39±0.725.69±0.805.46±0.461th Total

STx̅ 5.84±0.77 5.61±0.67 5.48±0.635.56±0.567th Total 5.67±0.715.46±0.715.27±0.625.37±0.3714th Total 5.34±0.745.25±0.695.39±0.785.53±0.5321th Total

* abcd Lettersindicatesignificantdifferencesamongyogurts(Yx̅),P<0.05,

ABC Lettersindicatesignificantdifferences

amongstoragetimes(STx̅),P<0.05.

Table 8. OverallacceptablescorespropertiesofcontrolandGundelia tournefortiiyogurtinstorageperiod

Yx̅21th 14th 7th 1th DoseofGundelia tournefortii (%) 20.54±1.5a 19.76±0.5320.29±1.5521.86±1.38 20.24±1.510 19.82±1.36a19.29±1.4820.19±0.9220.19±1.4719.62±1.35120.64±1.35a19.67±1.1520.67±0.8521.62±1.1120.62±1.493 21.26±1.15a 20.57±0.4921.33±0.43 21.76±0.49 21.38±0.48521.85±1.33a 21.62±0.8721.52±1.1922.38±1.1721.86±1.071024.05±1.43a24.57±1.2423.48±1.4724.62±1.11 23.52±1.501525.11±1.33a25.10±1.72 24.95±1.1624.90±1.0925.48±1.282021.51±2.5121.78±2.0422.48±2.0321.82±2.33STx̅

* abcd Lettersindicatesignificantdifferencesamongyogurts(Yx̅),P<0.05,

ABC Lettersindicatesignificantdifferences

amongstoragetimes(STx̅),P<0.05.

CONCLUSION In the present investigation, there were significant differences in physicochemical and sensorycharacterization of gundelia tournefortii yogurt compare to control. Generally, gundelia tournefortii

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additiondecreasedpH(slightly),sineresisvalues;increasedtitratableacidity(slightly),induringstoragetime. yogurt samples during 21 days no coliform bacteria, E. coli, mold and yeast were not. All sampleswere treated pseuodoplastic. Generally, gundelia tournefortii pulp addition increased of apparentviscosityandconsistencyvaluesofthefinalproduct,excepttheyoghurtcontaininggundelia tournefortii20%.Sensory evaluation resultsshowedthat theyoghurtcontaining gundelia tournefortii20%hadthehighest overall acceptability scores as compare to other gundelia tournefortii yogurt samples and alsoplainyogurt.Theresultsofcurrentstudydemonstratedthattheadditionofgundelia tournefortiipureetotheyogurtimprovedthequalityofyogurt. ACKNOWLEDGEMENTS The authors would like to thank M.r V.Loghmani, Master Sciences, Department of Food Sciences andTechnologyShahrkordBranch,IslamicAzadUniversity,Shahrkord,Iran;forhishelptofindofsoftwaretoCurvedesign. REFERENCES 1. W. J. Lee and J. A. Lucey. (2010). Formation and Physical Properties of Yogurt. Asian-Aust. J. Anim. Sci.

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aspectsofyoghurtenrichedwithRosmarinus officinalisoil.AfricanJournalofBiotechnologyVol.12(2),pp.192-198,9January,2013.

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CITATION OF THIS ARTICLE Azam E, Ali Mohamadi S, Mohamad H I. Evaluation of Rheological, Physicochemical, and Sensory properties ofGundelia tournefortiiyogurt.Bull.Env.Pharmacol.LifeSci.,Vol4[11]October2015:146-159

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