Journl of the Siene of Food nd Agriulture J Si Food Agri 85:1909 1913 (2005) DOI: 10.1002/jsf.2190 The development of got s milk yogurt Norerto C Poseion, Nny L Crowe, A Roin Roinson nd Smuel K Asiedu Nov Soti Agriulturl College, PO Box 550, Truro, Nov Soti B2N 5E3, Cnd Astrt: This study sought to estlish onditions suitle for smll-sle yogurt proess using got s milk nd to exmine the physiohemil properties (ph, titrtle idity, solids-not-ft (SNF), visosity, texture) nd orgnolepti eptility (preferene y Filipino pnellists) of the resultnt produt. Got s milk ws onentrted y heting (80 C, 1 h), whih resulted in n inrese in SNF from 85 to 110 g kg 1. To further improve the urd of got s milk yogurt, two hydroolloids were used: rrgeenn (1.5 nd 3gl 1 ) nd petin (50 g l 1 ). The ddition of dehydrted pinepple nd nn ues (50 nd 100 g l 1 )in sunde-style formultion inresed the SNF y n dditionl 2.5% nd produed urd tht ws firmer thn the ontrol, plin set yogurt. The use of rrgeenn ppered to e onvenient wy of ontrolling produt visosity. In terms of produt preferene nd firmness the fruit-flvoured sunde-style yogurts were rnked higher y sensory pnellists. 2005 Soiety of Chemil Industry Keywords: got milk; got yogurt; visosity; firmness; solids-not-ft (SNF) INTRODUCTION In the lst dede there hs een inresing interest in the funtionl properties of foods. Yogurt, potentilly ontining enefiil miroflor from lti id fermenttion, offers the onsumer more thn just the onventionl nutrients of diry produt. In ddition, yogurt hs oth redued ltose levels nd tive ltse enzymes whih my llow ltose-intolernt individuls to onsume moderte mounts of this diry produt. 1 Although yogurt mde from ow s milk is onventionl, yogurt produts hve een prepred with vrying suess from ovine nd prine milk. Yogurt gels re prtiulte strutures omposed minly of sein, nd in generl these ontinuously onneted strnds of protein produe heterogeneous three-dimensionl gel network tht holds wter. 2 The totl solids-not-ft (SNF) ontent of the originl milk plys ruil role in filitting the development of this physil network. Methods to inrese milk solids inlude the ddition of powdered milk solids, wterinding stilisers suh s petin 3 nd rrgeenn, 4 dehydrted pples nd pehes, 5,6 nd evportion of the milk. 2 Got s milk differs from ovine milk in numer of wys. It hs more free mino ids 2 nd its unique sein preipittes more redily nd into finer prtiles 7 thn ow s milk. The ft gloules nd mielles re smller in got s milk thn in ow s milk. 8 The higher mounts of short-hin ftty ids (proi, pryli nd pri ids) present re prtilly responsile for the distint flvour of got s milk. 9 Got s milk redily piks up slightly rnid nd musky flvour nd rom, 10 whih is hllenge in using got s milk fresh or in proessed form. Previous reserhers 11 14 hve investigted vrious spets of got s milk yogurt with vrying degrees of suess. The present study extends the previous work nd omines oth proessing tehniques (evportion) nd produt reformultion (hydroolloids, dehydrted fruit) in ttempts to hieve got s milk yogurt tht ws typil of yogurt produt nd, t the sme time, ws epted y memers of Filipino origin. Eight yogurt formultions were tested: () plin set yogurt (ontrol), () plin set yogurt with 1.5 nd 3 g l 1 rrgeenn, () sunde-style yogurt with 50 nd 100 g l 1 dehydrted pinepple ues, (d) sunde-style yogurt with 50 nd 100 g l 1 dehydrted nn ues nd (e) stirred yogurt with 50 g l 1 ommeril petin. The qulity of the yogurt produts ws evluted sed on their physiohemil hrteristis (ph, titrtle idity, SNF, pprent visosity, firmness) nd orgnolepti eptility. EXPERIMENTAL Rw mterils Rw got s milk ws otined from n inspeted got diry in Cnd (Fox Hollow Diry Limited, Middle Musqoudooit, Nov Soti, Cnd). The milk ws omposite from got herd whih hd 425 nimls of Correspondene to: Nny L Crowe, Nov Soti Agriulturl College, PO Box 550, Truro, Nov Soti B2N 5E3, Cnd E-mil: nrowe@ns.ns. Current ddress: Deprtment of Peditris, Hutzel Hospitl, Detroit Medil Center, Wyne Stte University, 4707 St St Antoine, Detroit, MI 48201, USA Contrt/grnt sponsor: Cndin Interntionl Development Ageny (CIDA) Islnd Sustinility Livelihood nd Equity Progrm (ISLE) (Reeived 30 June 2003; revised version reeived 30 Novemer 2004; epted 27 Jnury 2005) Pulished online 4 My 2005 2005 Soiety of Chemil Industry. J Si Food Agri 0022 5142/2005/$30.00 1909
NC Poseion et l mixed Alpine, Nuin, Snen nd Lmnhe reeds. Rw milk tht ws not immeditely proessed into yogurt ws psteurised t 72 C for 15 s nd stored t 1 2 C until yogurt preprtion for no more thn 24 h. This ws neessry s filities did not permit simultneous preprtion of ll yogurt formultions. Fresh pinepples (Del Monte rnd) in the rre-ripe stge were ued (1.3m 3 ), lnhed (100 C, 3 min) nd drined. Osmoti dehydrtion ws performed using 1:1 (w/w) ues/sugr rtio nd llowing ontt for 24 h. Exess surfe sugr ws lightly rinsed off with spry of wter nd the ues were dehydrted (Berron Food Dehydrtor Model 60; Vnouver, Cnd) for 14 h t dry ul temperture of 65 C. Fresh green mini-nns (Eudorin Chiquit nns) were peeled, ut into 1.3 m slies nd dipped in sori id solution (10 g l 1 ) to minimise enzymti rowning. The nn slies were then omined in 1:1 (w/w) rtio with sugr nd osmoti dehydrtion ws performed s ove, exept tht the time required in the dehydrtor ws only 8 10 h for this fruit. The stilisers used in the study were omposed of rrgeenn (FMC diry grde) nd ommeril fruit petin (Bernrdin rnd). Commeril mixed strter ulture of Ltoillus ulgrius nd Streptoous thermophilus in freezedried form (Yoghourmet rnd, Lyo-Sn Industries, Lhute, Cnd) ws used to ferment the got s milk. Six replites of eh yogurt formultion were prepred from one pooled th of got s milk nd sujeted to physiohemil nd orgnolepti nlyses. A rndomised omplete lok design ws employed where the loking ftor ws the th of got s milk used (n = 2). Chemil nlysis of rw mterils Eh ontiner of rw got s milk ws nlysed for ph nd titrtle idity efore psteuristion. The SNF ontent of the got s milk ws nlysed t severl stges in the yogurt proess (rw, fter psteuristion nd fter psteuriztion/evportion) s mens of following the onentrtion of the milk. The phosphtse test ws used to onfirm the dequy of psteuristion. All nlyses were performed in triplite. Generl proessing method (plin set yogurt) Preprtion of milk se To psteurise nd onentrte the milk, 2 l of got s milk ws pled in n open stinless steel stokpot nd heted t 80 C for 1 h. The milk ws stirred ontinuously to distriute the het uniformly nd enhne evportion. The milk ws then ooled to the inution temperture (43 C) y immersing the stokpot in old wter. Fermenttion A 5 g liquot of strter ulture ws dded to ferment 1 l of psteurised/evported milk. The inoulted milk (0.1 l) ws then filled into individul plsti trnsprent ups. A modified rosting pn with wter ws used s wter th inutor. The ups were pled on top of grill lid t the ottom of the pn, nd the fermenttion ws onduted (4 h, 43 C). To hlt the tivity of the strter miro-orgnisms, the yogurt ws trnsferred into refrigertor set t 1 2 C. Yogurt produt formultions For the plin set yogurt with rrgeenn the hydroolloid (1.5 nd 3 g l 1 ) ws dded to the psteurised/evported milk nd stirred to dissolve efore the strter ulture ws dded. In the se of the pinepple- nd nn-flvoured sunde-style yogurts the onentrted milk se ws sweetened with surose (50 g l 1 ) efore dding the strter ulture. The dried fruit ues were weighed into the ontiners prior to the ddition of the sweetened inoulted milk (50 nd 100 g l 1 ). To prepre the stirred-type yogurt, the ogulum of plin set yogurt ws stirred nd petin slurry omposed of 5 g of powdered fruit petin, 0.1 g of itri id nd 20 ml of wter ws mixed into 100 ml of the yogurt. Physiohemil nlysis The ph, titrtle idity nd SNF ontent (Mojonnier infrred method) of the yogurt produts were determined fter 24 h of refrigerted storge. The firmness of the yogurt produts ws mesured. 11 A Lloyd (Mississug, Cnd) tensile testing mhine fitted with Mgnus Tylor (Mississug, Cnd) proe modified with plsti dis (2.5 m dimeter, 1.3 m thikness) t the end ws used. The ompression ws done with fore of 5 N, moving t speed of 10 mm s 1 until the proe penetrted the yogurt to depth of 5 mm. The pprent visosity of the yogurt produts ws mesured with Fisher MMihel (Toronto, Cnd) rottionl visometer. Refrigerted smples were tested with ertified No 22 wire using 3 m smple depth. All nlyses were performed in minimum of three replites. A mss lne on the dehydrted fruit ues used in the sunde-formultions ws performed. Twenty-four hours fter preprtion the fruit piees were seprted from the yogurt se y striner, lightly rinsed nd shken to remove rinse wter. By determining the moisture ontent of the resultnt fruit piees, the wter tken up from eh yogurt formultion ws lulted. Orgnolepti nlysis Preferene testing ws onduted with 15-memer sensory pnel. To meet the ojetives of developing yogurt-like produt tht met Filipino food nd ulturl norms, pnellists were drwn from somewht limited pool of Filipino immigrnts residing in Nov Soti; this onstrint ounted for the unhrteristilly smll numer of pnellists. The smples were given to the pnellists following lned, rndomised order of presenttion. Sttistil nlysis The dt were nlysed sttistilly using the Sttistil Anlysis System (SAS Institute, Cry, NC, 1910 J Si Food Agri 85:1909 1913 (2005)
Got s milk yogurt USA). Speifilly, the generl liner model (GLM) ws employed t signifine level of α = 0.05. Where signifint differenes were deteted etween mens, Tukey s men test ws used to identify signifint differenes etween individul mens. RESULTS AND DISCUSSION Proess development Averged over nine thes, the psteuristion/evportion proess resulted in 35.7gkg 1 inrese in the totl solids ontent of the milk se, whih represented 3.57% inrese in totl solids (Tle 1). This followed the reommendtion tht n inrese in totl solids ontent of more thn 2.5% is required if got s milk yogurt is to hve visosity omprle to tht of ow s milk yogurt. 15 The men level of milk solids (155 g kg 1 ) otined y the psteuristion/evportion proess employed for nine thes of milk in this study ws in ft higher thn the vlues otined y Arhmsen nd Holmen 15 for milk onentrted y vuum evportion (141 g kg 1 ), ultrfiltrtion (142 g kg 1 ), reverse osmosis (139 g kg 1 ) nd ddition of milk powder (142 g kg 1 ). Under the milk evportion onditions desried, the onentrtion of the milk se did not inhiit the strter tivity t these levels, nor did the use of vrious hygrosopi ingredients (sugr, petin, rrgeenn, dried fruit ues). As the gol ws to produe n eptle yogurt produt, there ws no ttempt in the present study to seprte or understnd the effets of the hnge in milk solids ontent from the effets of dded ingredients. Chemil hrteristis of yogurt formultions The ph of the ontrol yogurt (4.25; Tle 2) ws lower thn the rnge of 4.44 4.49 found for the only other got s milk yogurt formultion reported in the known literture. 16 In the present study the got s milk ws onentrted efore fermenttion, while Olvido 16 did not employ this proessing tehnique; the resultnt onentrtion of the nturl ids in the milk nd/or the nture nd tivity of the strter ulture used in this study my ount for the differene in ph. The ph of the nn-sed yogurts (4.44 4.53) ws signifintly higher (α = 0.05) thn tht of the ontrol got s milk yogurt. The ddition of the higher level of dehydrted fruit piees resulted in signifintly higher SNF ontent in the nn yogurt produt ut ws not ompnied y ny signifint inrese in ph (Tle 2). This my indite tht there ws no mesurle suppression of the strter tivity y the higher quntity of milk solids present in these formultions. The nturl idity of pinepple produts my ount for the 0.2 0.3 ph unit redution reorded for the two yogurt formultions prepred using dehydrted pinepple (1PA nd 2PA). The sunde-style yogurts prepred using the dehydrted fruit piees hd finl ph levels in the rnge of 3.92 4.53; the ph of the plin yogurt produt ws 4.25. Only the got s milk yogurts prepred with the hydroolloids exhiited produt ph elow 3.9, whih my e result of greter strter tivity under the onditions of these formultions. In the se of the petin formultion the itri id used s prt of the petin suspension nd ph djustment would hve ontriuted to the higher idity. Interestingly, using level of rrgeenn tht ws fourfold higher, the other Filipino study 16 did not demonstrte similr low ph. The titrtle idity vlues (Tle 2) showed trends similr to those reported for produt ph. The SNF ontent of the heted milk ws 109.3 ± 1.9gkg 1. After fermenttion the yogurt ses prepred with the dehydrted nn nd pinepple Tle 1. Totl solids of nine thes (1 9) of psteurised nd psteurised/evported got s milk nd % inrese resulting from evportion Totl milk solids (g kg 1 ) 1 2 3 4 5 6 7 8 9 Psteurised 123.7 123.2 123.3 118.6 119.2 118.2 118.0 117.8 117.3 Psteurised/evported 162.7 160.7 162.4 154.6 154.0 154.0 149.4 151.3 151.7 % inrese in totl solids 3.90 3.75 3.91 3.60 3.48 3.58 3.14 3.35 3.44 Mens within row with the sme letter re not signifintly different t α = 0.05. Tle 2. ph, titrtle idity nd solids-non-ft (SNF) ontent of yogurt produts Formultion Plin 1PA 2PA 1BA 2BA PE 1CA 2CA ph 4.25 3.92 4.06 4.44 4.53 3.74 3.76 3.75 Titrtle idity (g l 1 ) 0.118 0.123 0.112 0.085 0.092 0.136 0.124 0.122 SNF (g kg 1 ) 110.2 d 165.7 169.0 174.4 189.6 114.8 d 112.1 d 111.1 d 1PA = 50 g l 1 pinepple; 2PA = 100 g l 1 pinepple; 1BA = 50 g l 1 nn; 2BA = 100 g l 1 nn; PE = 50 g l 1 petin; 1CA = 1.5gl 1 rrgeenn; 2CA = 3gl 1 rrgeenn. Titrtle idity expressed s lti id. d Mens with the sme letter re not signifintly different t α = 0.05. J Si Food Agri 85:1909 1913 (2005) 1911
NC Poseion et l ll hd signifintly higher SNF levels thn the originl milk (Tle 2). Previous reserhers 5,6 ttriuted similr effet of dried pples nd pehes to rehydrtion of the fruit piees. The dehydrted nn nd pinepple ues were found to prtilly regin their originl size nd shpe nd sored, on verge, their own dehydrted weight from the sunde-style formultions. For instne, the higher level of dehydrted nn ues, dded t rte of 100 g l 1, inresed to 201.9gl 1 fter eing in ontt with the sunde-style formultion for 24 h. A similr inrese in mss of the fruit piees ws oserved with the pinepple. This fruit rehydrtion ws presumly responsile for the reltive inrese in the SNF of the diry portion of the produt. The plin set (ontrol) yogurt s well s the yogurt prepred with the three hydroolloid tretments hd SNF ontents rnging from 110.2 to 114.8gkg 1 ; this ws not sustntilly inresed from the 109.3gkg 1 SNF ontent of the originl milk. Physil ttriutes of yogurt formultions If visous produt is the primry desired ttriute, use of the rrgeenn hydroolloid would result in the formultion of hoie (Fig 1). While there ws no disernile visosity differene etween the 1.5 nd 3 g l 1 rrgeenn formultions, the higher level of hydroolloid ws ompnied y the prodution of firmer yogurt produt (α 0.05) without n ppreily higher idity (Tle 2). Bsed on these physil ttriutes, the rrgeenn tretment shows promise. In spite of the referenes in the literture to the importnt reltionship etween SNF nd gel strength, 2 the rrgeenn formultion my hve resulted in the formtion of visous network in spite of the low SNF ontent, whih ws lower thn tht of the ontrol (Fig 1, Tle 2). The higher visosity of the rrgeenn tretments ws, however, not diretly trnslted into mximum produt firmness (Fig 2). A lower quntity of rrgeenn thn reported previously 16 ws needed to inrese the visosity of plin set yogurt when onentrted got s milk ws used. A level of 1.5gl 1 rrgeenn, s ompred with 6.8gl 1, 16 ws suffiient to produe thik yogurt omprle to tht of onventionl yogurt produt. In ft, the fruit-sed sunde-style yogurts were found to hve firmer textures on the surfe of the diry phse of the produt thn the other formultions exmined in this study. The firmness of the yogurts prepred with dehydrted fruit ues ws superior (Fig 2) nd did exhiit the expeted reltionship with the higher SNF ontent. 2 Testing only the firmness of the produt s diry omponent (to depth of 1.3 m) removed ny potentil interferene from the presene of the fruit t the ottom of the ontiner. These tretments did not sore s high with respet to pprent visosity s the rrgeenn formultions did. The low visosity of the petin (PE) tretment would suggest tht, sed on the onvention tht yogurt should normlly e visous, the petin stirred-style yogurt ws not overly promising. This low visosity ws more likely result of the stirring during the finl stges of preprtion thn of the inility of petin to form visous system in got s milk, s petin is used suessfully in onventionl yogurt. Alterntively, the preliminry studies on the petin slurry my not hve dequtely optimised the ph (itri id) nd sugr to llow the high methoxy petin ontent to reh its gelling potentil. Of ourse, if the ojetive is to develop semi-liquid yogurt everge produt, the petin formultion my show promise. Produt preferene sores The sensory preferene sores indited tht the pinepple-sed yogurts were most preferred (α 0.05) followed y the nn-flvoured produts. 2CA 1CA Yogurt Formultions PE 2BA 1BA 2PA d d 1PA Plin 0 50 100 150 200 250 300 350 Apprent Visosity (entipoise) Figure 1. Apprent visosity of yogurt produts. 1PA = 50 g l 1 pinepple; 2PA = 100 g l 1 pinepple; 1BA = 50 g l 1 nn; 2BA = 100 g l 1 nn; PE = 50 g l 1 petin; 1CA = 1.5gl 1 rrgeenn; 2CA = 3gl 1 rrgeenn. d Mens with the sme letter re not signifintly different t α = 0.05. 1912 J Si Food Agri 85:1909 1913 (2005)
Got s milk yogurt 2CA 1CA d Yogurt Formultions PE 2BA 1BA 2PA f 1PA Plin e 0 0.2 0.4 0.6 0.8 1 Mximum Fore (N) Figure 2. Firmness of yogurt produts. 1PA = 50 g l 1 pinepple; 2PA = 100 g l 1 pinepple; 1BA = 50 g l 1 nn; 2BA = 100 g l 1 nn; PE = 50 g l 1 petin; 1CA = 1.5gl 1 rrgeenn; 2CA = 3gl 1 rrgeenn. f Mens with the sme letter re not signifintly different t α = 0.05. The petin formultion (PE) nd the plin yogurt did not find fvour mongst the Filipino pnellists used in this study. The yogurt produts formulted with the two levels of rrgeenn (CA) were modertely eptle sed on the results of the preferene test rnking sores. CONCLUSION This work hs shown tht there is possiility for the development of simple proess for mking yogurt using got s milk. The therml proess used ws suitle for onentrting the milk SNF to 110 g kg 1, whih still llowed growth of the strter ulture nd permitted the development of visous yogurt produt. The sunde-style yogurt inorporting osmotilly dehydrted fruit ws suessful in further enhning the physil properties of the finished produt nd ws preferred y the sensory pnellists. ACKNOWLEDGEMENT The uthors re very grteful to the Cndin Interntionl Development Ageny (CIDA) Islnd Sustinility Livelihood nd Equity Progrm (ISLE) for funding this reserh. REFERENCES 1 Rosdo JL, Solomons NW nd Allen LH, Ltose digestion from unmodified, low ft, nd ltose hydrolyzed yogurt in dult ltose mldigesters. Eur J Clin Nutr 46:61 67 (1992). 2 Tmine AY nd Roinson RK, Yogurt Siene nd Tehnology, 2nd edn. Woodhed Pul, Cmridge (1999). 3 Bsk S nd Rmswmy HS, Simultneous evlution of sher rte nd time dependeny of stirred yogurt rheology s influened y dded petin nd strwerry onentrte. J Food Eng 21:385 393 (1994). 4 Gon S, Kili S nd Uysl HR, Investigtion of the properties of yogurt mde y dding different quntities of yogum. Diry Si Astr 56:16 (1994). 5 Mstrool D, Nioli MC, Mnzoo L nd Corrdini C, Dehydrted fruit piees s funtionl ingredients in yogurt. Si Teh Ltt Cs 47:441 454 (1996). 6 Gingiomo R, Torregini D, Er ML nd Messin G, Use of osmodehydrofrozen fruit ues in yogurt. Itl J Food Si 6:345 350 (1994). 7 Henlien GFW nd Cesse R, Got milk versus ow milk [Online]. (1992). Aville: http://www.inform.umd. edu/edres/topi/agren.../got Milk Versus Cow Milk. htm [10 Ferury 2000]. 8 Dvis JG, Qulity Control in the Food Industry, 2nd edn. Ademi Press, London (1984). 9 Henlien GFW, Did you know: diry got fts, in Amerin Diry Got Assoition. Extension Got Hndook USDA [Online]. (2000). Aville: http://www.dg.org/fts. htm [3 Ferury 2000]. 10 Dvide CL, Mnlo CS nd Perlt CN, Mnufture nd qulity of spied soft heese from got s milk. Philippine Agri 7:39 45 (1983). 11 Duistshver CL, Yogurt from got s milk. Cult Diry Prod J 13:20 23 (1978). 12 Arhmsen RK nd Rysstd G, Fermenttion of got s milk with yogurt strter teri: review. Cult Diry Prod J 26:20 22, 26, 42 (1991). 13 Kurmnn JA, Yogurt from ewe s nd got s milk. Int Diry Fed J 202:153 156 (1986). 14 Flngn JF nd Holsinger RH, Proedure for mking yogurt ndheese fromgot s milk. Cult Diry Prod J 20:6 7 (1985). 15 Arhmsen RK nd Holmen TB, Got milk yogurt mde from non-homogenized nd homogenized milk, onentrted y different methods. JDiryRes48:457 463 (1981). 16 Olvido MT, Aeptility of yogurt from got s milk. Thesis, University of the Philippines in the Visys (1996). J Si Food Agri 85:1909 1913 (2005) 1913