EFFECT OF ANTIOXIDANTS ADDITION IN COMBINATION WITH MILK RE PASTEURIZATION ON THE PHYSICAL, CHEMICAL AND SENSORY PROPERTIES OF CONDENSED YOGHURT

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1 EFFECT OF ANTIOXIDANTS ADDITION IN COMBINATION WITH MILK RE PASTEURIZATION ON THE PHYSICAL, CHEMICAL AND SENSORY PROPERTIES OF CONDENSED YOGHURT Mhmoud Abu-Ghoush* 1, Mutlg Al-Otibi 2, Abdulziz Al-Shthri 3, Suhd Abu-Mweis 4 1 Associte professor, Deprtment of Food nd Nutrition Sciences, King Fisl University University, Sudi- Arbi, Corresponding Author. e-mil: mbughoush@kfu.edu.s, Phone: Associte Professor, Deprtment Of Food And Nutrition Sciences, King Fisl University, The Kingdom Of Sudi Arbi, P.O.Box 420, Al-Ahs Assistnt Professor, Deprtment Of Food And Nutrition Sciences, King Fisl University, The Kingdom Of Sudi Arbi, P.O.Box 420, Al-Ahs Assistnt professor, Clinicl Nutrition nd Dietetics Dep., The Hshemite University, The Hshemite *Corresponding uthor: e-mil: mbughoush@kfu.edu.s Kingdom of Jordn, P.O.Box , Zrq ABSTRACT: Our min gol in this project is to study the cuses nd finding solutions for both the hydrolytic nd the oxidtive rncidity tht cn be produced during condensed yoghurt production. The re psteuriztion of the psteurized milk nd the ddition of different types of ntioxidnts (scorbic cid nd propyl gllte) were used to chieve this gol. Chemicl, physicl, microbil nd sensory tests were done to evlute the product. It ws found tht there were significnt differences between the different tretments nd the control regrding the peroxide vlue. This mens tht the ddition of both types of ntioxidnts hve positive effect in decresing the rncidity vlue. However, it ws found tht there were some smples hve hydrolytic rncidity flvour without ny type of oxidtive rncidity (low peroxide vlue). To overcome this problem the re psteuriztion step ws used to destroy ll the vegettive form of microbes. It ws found tht this tretment ws very useful in controlling the rncidity flvor ccording to the sensory evlution of the condensed yoghurt products for severl btches. The best condensed yoghurt which contins 0.25% scorbic cid exhibited the highest sensory properties vlues. Also, it hs the bility in lowering the oxidtive rncidity in the combintion with the re psteuriztion step of the psteurized milk. This suggests tht higher qulity nd stble condensed yoghurt cn be obtined upon using this combintion. These results my help producers in selecting the best tretment methods to overcome the rncidity flvor in this type of condensed yoghurt. Key words: Antioxidnt, Re psteuriztion, Condensed milk INTRODUCTION The diry industry is constntly trying to obtin competitive dvntge by improving their product qulity. The qulity of diry products is minly influenced by fetures such s texture, shpe, colour, flvour, nd nutritionl content. In condensed yoghurt production (Zbdi), one of the min problems tht rise is the production of rncid flvour due to the microbil nd chemicl chnges in the crem milk ft composition. Different studies were done to study the effect of vrious processing tretments on the diry products qulity. Kruse et l. (2008) studied the effect of refrigerted nd frozen storge on butter flvour nd texture. Emmons et l. (1986) studied the effect of storge time on butter flvour Grding nd peroxide vlue (PV) were used to evlute butter qulity. Gndy et l. (2008) studied the effect of psteuriztion temperture on the shelf-life of fluid milk nd its sensory cceptbility. Actully, fts in milk re subject to two types of deteriortion tht ffect the flvours of Zbdi: 1. Hydrolytic rncidity: In hydrolytic rncidity, ftty cids re broken off from the glycerol molecule by lipse enzymes produced by milk bcteri. The resulting free ftty cids re voltile nd contribute 1

2 significntly to the flvour of the yoghurt. 2. Oxidtive rncidity: Oxidtive rncidity occurs when ftty cids re oxidised. In milk products it cuses tllowy flvours. Oxidtive rncidity of dry butterft cuses off-flvours in recombined milk. For both kind of rncidity the detection nd the preventing cn be done. Hydrolytic rncidity (Lipolysis) cn be cused through the ction of milk lipoprotein lipse. One wy in which this enzyme is normlly prevented from hydrolyzing milk ft is by the physicl brrier of the milk ft globule membrne. Agittion tht results in disruption of this membrne cn result in lipolysis; this 'induced lipolysis' is problem tht cn be cused by pumping, processing nd trnsport of milk. Microbil contmintion cn lso cuse lipolysis nd, lthough psteuriztion kills psychrotrophic bcteri, proteinses nd lipses produced by them withstnd norml psteuriztion temp. Minly, the gittion tht hppens during the milk ft seprtion (in the production of crem milk (50% ft) cn cuse disruption of this membrne (Pennsylvni Stte University report, 1991). In the oxidtive rncidity the role of copper in the oxidtion were stressed, nd the role of scorbic cid nd propylgllte in preventing lipid oxidtion were studied. Csein lso hs protective effect by binding Cu2+ nd Fe3+ ions. Psteuriztion t 80 C cn reduce the prooxidtive effects of lctoperoxidse nd xnthine oxidse, but other forms of processing such s churning, encourge oxidtion. Reserchers hve concluded tht the development of objectionble flvours in psteurized milk is generlly result of bcteril growth (Simon nd Hnsen, 2001), nd unplesnt roms in fluid milk re chrcteristic of milk spoilge (Hyes et l., 2002). However, in this reserch different steps were done to chieve complete protection of Zbdi flvour. Our min gol in this project is to study the cuses nd finding solutions for the rncidity tht cn be produced during crem milk nd condensed yoghurt production (Zbdi). Different steps were done to chieve our gol. These steps re: 1. Controlling the psteuriztion conditions. 2. Using nturl nd synthetic ntioxidnts (such s Vit C. nd Propyl gllte) fter psteuriztion step. At the sme time, evlution Zbdi product fter selecting the best processing conditions ws done. This evlution step ws done by using different nlyticl nd sensory tools. MATERIAL AND METHODS Zbdi Formultion nd Production Severl steps re involved in the Zbdi (condensed yoghurt) production. These steps re: Milk Ft (3% ), Churning nd ft seprtion, Crem milk (50% ft) ddition, Psteuriztion (95 C/ 16 s), Reconstitutions nd mixing with 3% milk ft to obtin milk with 10% ft, Re psteuriztion (95 C/ 16 s), Cooling to 42 C, Inocultion with strter culture nd incubtion, nd finlly Condensed Zbdi Product (10% Ft). The following experimentl design ws chieved to help in solving ny type of oxidtive rncidity. The experimentl design consisted of 6 condensed crem formulted with ntioxidnts produced t stndrd processing conditions nd replicted three times s cn be shown in Figure 1. The min vribles which were investigted nd selected for further investigtions in this study re shown in Figure 1. As shown, the study ws subdivided into two stges. In ech stge, one tretment ws selected for further investigtion ccording to the best ntioxidnt properties. Yoghurt crems were immeditely pcked, seled, nd plced in storge t 4 C fter production. Antioxidnt Type 1. Ascorbic Acid A B C 2

3 Antioxidnt Concentrtion 0.25% 0.5% Control Antioxidnt Type 2. Propyl gllt Antioxidnt Concentrtion D 100 ppm 200 ppm E F Control Figure 1. The experimentl design consisted of 6 condensed crem formu-lted with ntioxidnts produced t stndrd processing conditions nd replicted three times. Antioxidnts Addition nd Ft Extrction The ntioxidnts t different concentrtion were dded directly to the psteurized yoghurt crem smples t room temperture. The fresh psteurized yoghurt crem (50% ft) ws selected to study the effect of the ntioxidnts ddition on the oxidtive rncidity becuse of the highest extrction rte of the ft which will help in keep monitoring the peroxide formtion. However, the ph nd the peroxide vlue of the extrcted crem ft were determined before nd fter the ntioxidnt ddition. Totl lipid extrction ws crried out ccording to Folch, Lees, nd Slon (1957): 15 g of yoghurt crem ws dded to 200ml of chloroform : Ethnol solution (1:1, v/v), homogenized for 30 s nd nother 100 ml of chloroform ws then dded to the mixture. The mixture ws gin homogenized for 1 min nd filtered. The filtrte ws dded to 100 ml of 1 mol/l KCI nd ws left overnight t 4 C. After phse seprtion, the chloroform phse ws evpo rted using rotry evportor nd the lipid frction ws stored t -20:t 1 C. Peroxide determintion ws done ccording to the following procedure: 1. Weigh 5 g of ft smple into 250ml stndrd Erlenmeyer flsk. 2. Add 30 ml of cetic cid-chloroform (60:40) nd shke vigorously. 3. Add 0.5 ml sturted Potssium iodide solution. Stopper nd shke thoroughly nd llow to stnd in drk for exctly 2 minutes. 4. Add 30 ml distilled wter nd severl drops of strch solution nd titrte liberted iodine with stndrdized 0.02 N sodium thiosulphte. The end point is the trnsition from drk blue to cler. 5. Peroxide vlue is equl to (meq.100g lipid)= (titrtion volume-blnk)*normility of thiosulphte*100/oil weight Microbiologicl properties Yoghurt crems were immeditely pcked, seled, nd plced in storge t 4 oc fter production. Totl erobic plte count ws determined ccording to stndrd pour plte method (Speck, 1979) on plte count gr (Stndrd Plte Count Agr, Cond Lbortories, S.A., Spin) incu bted t 37 C for 48 h. Bcillus sp. ws identified ccording to their shpes on the plte count gr. The min im behind doing the microbil exmintion is to find if there is reltion between the microbil growth contmintion nd the flvor defect on the finl product. Sensory Evlution of the Yoghurt Zbdi The best yoghurt crem which contins 0.25% scorbic cid ws selected for the sensory evlution tretment. The selection of this tretment for further study ws bsed on its efficiency in lowering the peroxide vlue. Also, it is nturl ntioxidnt which differs from the propyllgllte nd finlly it is formed the lest mount of ntioxidnt tht ws dded to the formul. It is expected tht using this ntioxidnt t this low level will not cuse ny chnging in the product qulity. However, to chieve 3

4 this purpose nd to find the effect of this ddition on the finl product the sensory evlution ws done. Addition of this ntioxidnt ws done t the industril level. Ascorbic cid t 0.25% ws dded to 25 L of Zbdi condensed crem finl product (E300) fter mixing the skim milk with yoghurt crem nd before the filling step of the finl product. The smples were collected stored t 4 C. The comprison ws done between E300 tretment nd the stndrd tretment (No ntioxidnt ws dded, E500) in terms of ll the qulity ttributes (overll cceptnce, flvour, mouthfeel, color nd ppernce). Sensory evlution ws conducted in the Lbortory t the Hshemite University. 6 sensory judges (3 mle nd 3 femle) with ges between 22 nd 40 were trined on descriptive nlysis of yoghurt properties. Descriptive nlysis pnelists were consumers of yoghurt nd trined for 2 hours (1-h session/dy) on qulity ttribute profiling (overll cceptnce, flvor, mouthfeel, color nd ppernce). The pnelists were trined for evlutions of reference smples, with nd without spiking with ingredients to lter smple sensory ttributes. Pnelists evluted smples in stndrd sensory pnel booths contining n ttribute definition sheet. During ech trining session the pnelists were fmilirized with yoghurt qulity ttribute profile to be evluted using 9 point scle for ech qulity ttribute using descriptive nlysis. Sensory evlution ws performed on ll different types of yoghurt products. These yoghurt smples were presented to the trined sensory pnel in yoghurt cns. Smples were presented to the trined pnels ccording to rndom, blnced design long with 2 unslted crckers, glss of room-temperture distilled wter for rinsing the plte between smples, npkin, nd score sheet. Pnelists evluted smples in stndrd sensory pnel booths contining n ttribute definition sheet nd pencil. The pnelists for ech session hd no prior informtion bout the coded test products. Sttisticl nlysis Dt were nlyzed by the Anlysis of Vrince procedure (ANOVA) by using SAS softwre (version 8.1, SAS Institute, Cry, NC). Comprison between tretments ws nlyzed using Fishers Lest Significnt Difference (LSD). In the nlysis of vrince, lph level of 5 % ws used to test the null hypothesis. RESULTS AND DISCUSSION Peroxide nd ph vlues The results of the peroxide vlues of the different tretments before nd fter ntioxidnts ddition cn be shown in Tble 1. As cn be shown tht there were significnt differences between the different tretments nd the control regrding the peroxide vlue. This mens tht the ddition of both types of ntioxidnts hve positive effect in decresing the rncidity vlue. However, s cn be shown tht this difference is so smll. It ws found tht during the study there were some smples hve rncidity flvour without ny type of oxidtive rncidity (low peroxide vlue). Thus, it ws expected tht the hydrolytic rncidity could be the min reson. It ws found tht the rw psteurized milk nd the finl Zbdi product contin uncountble Bcillus species which should not be present. This is good indictor bout the presence of the spores which re highly resisted the psteuriztion tretment. However, to overcome this problem re psteuriztion tretment of the milk is so useful. The re psteuriztion step hve the cpbility to destroy ll the vegettive form of Bcillus species tht were formed from the spores fter the first psteuriztion tretment. It ws found tht this tretment ws very useful in controlling the rncidity flvor ccording to the sensory evlution of the Zbdi products for severl btches. The results of the ph vlues of the different tretments before nd fter ntioxidnts ddition cn be shown in Tble 1. As cn be shown tht there were significnt differences between the different tretments nd the control regrding the ph vlues. Tble 1. Peroxide nd ph vlues of the different tretments before nd fter the ntioxidnts ddition. 4

5 Tretments Peroxide vlue ph vlues Control (without ntioxidnt) 1.0 A ± A ± % Ascorbic cid 0.5 B ± A ± % Ascorbic cid 0.4 B ± A ± ppm Propyl gllte 0.5 B ± A ± ppm Propyl gllte 0.4 B ± A ± Sensory evlution Yoghurt Crem in the presence of ntioxidnt The results of the pnel sensory evlution of the condensed yoghurt produced t different stges of productions re shown in Figures 2. All the tretments exhibited sensory properties vlues (overll, mouthfeel, flvor, ppernce nd color) tht were not significntly different between E300 (with ntioxidnt) nd E500 (without ntioxidnt). However, E500 hd higher flvor nd mouthfeel score thn tht of the E300, but the score ws not significntly. The E300 hd multiple consumer comments bout the cid/sour flvors. These results suggest tht the ddition of 0.25%scorbic cid s n ntioxidnt hs not ny dverse effect on the sensory properties on the other hnd it hs the bility in lowering the oxidtive rncidity effect in the combintion with the re psteuriztion step of the psteurized milk. This suggests tht higher qulity nd stble condensed yoghurt crem could be obtined upon using these combintions. Hedonic scle (score) Overll Color Appernce Flvor Mouthfeel Sensory property E300 E500 Figure 2. Sensory properties of two types of condensed yoghurt produced by using 0.25% Ascorbic cid (E300) nd without (E500, control)) The finl product of the condensed yoghurt crem produced by the two different tretments cn be shown in Figure 3. 5

6 Figure 3. The condensed Yoghurt (Zbdi) finl product produced by ddition of 0.25% scorbic cid (E300) nd without (E500). CONCLUSIONS 1. Our gols in this project were chieved by overcoming ny types of possible rncidity through the ddition of the suitble ntioxidnts nd the re psteuriztion of the milk without ny dverse effect on the finl product. 2. The Sensory evlution of the product before nd fter the ntioxidnts ddition of the Zbdi proves tht the ddition of scorbic cid t 0.25% to the finl product did not cuse ny significnt effect. 3. Determining the min fctors tht influence the rncidity were chieved which will help the producers to control these fctors during processing nd produce stble product. АCKNOWLEDGEMENTS Sincer thnks for the Jordnin-Dnish diry compny for their vluble help in ccomplishing this reserch. REFERENCES 1. Emmons, D. B., Froehlich, D. A., Pquette, G. J., Beckett, D. C., Modler, H. W., Butler G., Brckenridge P., nd Dniels G Flvor stbility of butter prints during frozen nd refrigerted storge. J. Diry Sci. 69, Gndy, A. L., Schilling, M. W., Coggins, P. C., White, C. H., Yoon, Y., nd Kmdi, V. V The Effect of Psteuriztion Temperture on Consumer Acceptbility, Sensory Chrcteristics, Voltile Compound Composition, nd Shelf-Life of Fluid Milk. J. Diry Sci. 91, Hyes, W., White, C. H., nd Drke, M. A Sensory rom chrcteristics of milk spoilge by Pseudomons species. J. Food Sci. 67, Kruse, J., Mircle, R. E., Snders, T. H., Den, L. L., nd Drke M. A. (2008). The Effect of Refrigerted nd Frozen Storge on Butter Flvor nd Texture. J. Diry Sci. 91, Pennsylvni Stte University report, Guidelines for Preventing Off-Flvors in Milk. The Diry Prctices Council. 6. Simon, M., nd Hnsen, A. P Effects of vrious diry pckging mterils on the shelf life nd flvor of psteurized milk. J. Diry Sci. 84,