Chemical and Microbiological Evaluation of Mozzarella Cheese During Storage

Transcription

1 Austrlin Journl of Bsi nd Applied Sienes, 4(3): , 20 ISSN Chemil nd Mirobiologil Evlution of Mozzrell Cheese During Storge Mohmed Osmn Mohmed Abdll nd Nisreen Nourein Mohmmed Ibrhim Deprtment of Diry Prodution, Fulty of Animl Prodution, University of Khrtoum, Shmbt P.O. Box 32, Postl Code 13314, Khrtoum Nor, Sudn Abstrt: This study ws rried out to evlute e hemil omposition nd mirobiologil qulity of trditionlly mde Mozzrell heese by two mnufturers in Khrtoum Stte, Sudn. Thirty six smples, eighteen from eh mnufturer, were olleted. The hemil omposition (ft, protein, totl solids, sh nd titrtle idity) nd mirobil qulity (totl teri ount, proteolyti teri ount, lipolyti teri nd psyhrotrophi teri ount) of e heese were evluted. The results showed t during e shelf life of 75 dys e ft ontent of heese grdully (P<0.01) inresed from dy one to mximum t dy 60, nd en deresed erefter. The protein ontent showed grdul derese from dy one to dy 60, nd en slightly inresed t e end of shelf life. The totl solids ontent slightly inresed t dy 30 nd deresed towrds e end. The sh ontent inresed to mximum t dy 30 nd en deresed t dy 45, followed by n inrese t dy 60 nd deresed t e end. The titrtle idity showed n irregulr pttern roughout e shelf life nd deresed t e end. The totl teri ount deresed to minimum t dy 60, en slightly inresed. The lipolyti nd psyhrotrophi teri ounts showed grdul inrese from dy one to e end. The proteolyti teri ount inresed from dy one to e end. Key words: Mozzrell heese, storge period, hemil omposition, mirobiologil qulity INTRODUCTION Mozzrell heese is Mediterrnen Pst filt heese originted in Itly. Its onsumption is inresed in Sudn due to its inorportion in pizz t is gining populrity. When kept in brine is heese hs short shelf life of 5-7 dys (Altieri et l., 2005; Conte et l., 2007). Owing to e vriety of miroorgnisms found in is produt, mozzrell hs rer short shelf life. The speifi hrters of mozzrell heese minly rise from e speifi rw mterils employed, e re of prodution, e environmentl onditions, e trditionl tools, nd mnufturer (Muriello et l., 2003). Extending shelf life of mozzrell heese is importnt issue to e diry industry due to e interest in extending e distribution of e produt beyond e mrket, nd to keep good qulity food produt depends on e improvement of rw mterils, proess innovtions, nd use of suitle storge filities (Frkye et l., 1991; Kindstedt nd Fox, 1993). Numerous studies hve hrterized e presene of spoilge miroorgnisms t limit e shelf life of Mozzrell heese. Miroorgnisms suh s Klebsiell, Enteroter, Esherihi oli, Enteroous, Pseudomons, yests nd moulds were isolted from Mozzrell heese (Mss et l., 1992; Romno et l., 2001; Dun et l., 2007). Mozzrell heese is spoiled by Pseudomons spp. oming from wter or diry mnufture, in ddition to e ft t oliforms limit e shelf life of Mozzrell heese (Altieri et l., 2005). The Sudnese stndrds sttes t e shelf life of Mozzrell heese should not exeed eight weeks from e dy of mnufture, provided heese is stored t temperture not more n C (SSMO, 2008) Due to inresing onsumption of Mozzrell heese for pizz nd oer purposes, e tehnology of mking is kind of heese is gining populrity lough ll mnufturers re produing it trditionlly, nd mny smll-sle mnufturers re involved in is industry. Therefore e objetives of is study were to evlute Mozzrell heese hemilly nd mirobiologilly during e shelf life nd to determine how e mnufturing onditions n ffet e qulity of e produt during its shelf life. Corresponding Auor: Mohmed Osmn Mohmed Abdll, Deprtment of Diry Prodution, Fulty of Animl Prodution, University of Khrtoum, Shmbt P.O. Box 32, Postl Code 13314, Khrtoum Nor, Sudn 532

2 MATERIALS AND METHODS Colletion of Smples: Thirty six smples of mozzrell heese were olleted from two ftories in Khrtoum nd Khrtoum Nor (18 smples from eh one) in e dy of mnufture (dy one). The smples were stored in e refrigertor t 4 C to determine e hemil omposition nd mirobiogil qulity. Chemil Anlyses: Ft ontent ws determined by Gerber meod ording to AOAC (1990). Protein ontent ws determined by Kjeldhl meod ording to e meod desribed in AOAC (2000). Totl solids ontent ws determined by oven drying meod ording to AOAC (2000). Ash ontent nd titrtle idity were determined ording to meods desribed in AOAC (2000). Mirobiologil Exmintion: The teri ount ws determined ording to Houghtby et l. (1992) using stndrd plte ount gr. The pltes were inubted t 32 C for 48 hrs nd olonies were ounted. Lipolyti teri ount ws determined s desribed by Zki (1988). Nutrient gr ws used nd e pltes were inubted t 37 C for 3 dys. The lipolyti olonies were identified using opper sulphte (20%) flooded fter inubtion. Psyhrotrophi teri ount ws determined ording to Frnk et l. (1992) using plte ount gr. The pltes were inubted t 7±1 C for dys. Proteolyti teri ount ws determined ording to Frnk et l. (1992) using plte ount gr plus % sterile skim milk. The pltes were inubted t 37 C for 3 dys Purifition ws done by sub-ulturing of well isolted typil olony on nutrient gr medium for 24 hrs nd e pltes were heked by Grm's stin, en e olonies were trnsferred to plte ontining fresh solidified orresponding medium (Brrow nd Felm, 1993). Identifition of Orgnisms: The purified isoltes were identified ording to e riteri desribed by Brrow nd Felm (1993). Sttistil Anlyses: Sttistil nlyses were performed using Sttistil Pkge for Soil Sienes (SPSS). The dt were nlyzed for ft, protein, sh, totl solids, titrtle idity, totl teri ount, lipolyti ount, proteolyti ount nd psyhrotrophi ount. Mens were seprted using Dunn Multiple Rnge Test wi P Results: Tle (1) shows e hemil omposition of heese from e two mnufturers during e storge period of 75 dys. The ft ontent grdully (P<0.01) inresed from dy one (22.17±2.93) to mximum t dy 60 (26.0±1.29), nd en deresed erefter (24.5±2.46). The protein ontent showed grdul (P<0.05) derese from 37.67±2.18 t dy one to 24.58±1.81 t dy 60, nd en slightly inresed to 25.2±1.35 t dy 75. However, e totl solids ontent slightly inresed to ±1.28 t dy 30 nd deresed towrds e end, lough e flutution ws not of signifint vlue (P >0.05). The sh ontent inresed to mximum of 3.13±0.89 t dy 30 nd deresed to 2.62± 2.84 t dy 45, followed by n inrese t dy 60 (3.73±2.72) nd deresed to 2.45± 2.87 t e end (P< 0.01). The titrtle idity showed n irregulr pttern roughout e storge period, wi e highest vlue being rehed t dys 30 (0.36±0.13) nd 45 (0.36±0.06), fter whih e idity deresed to 0.29±0.08 t e end (P<0.05). The ft ontent of heese from mnufturer1 (M1) showed grdul inrese till dy 60, e deresed erefter. The protein nd totl solids ontents deresed towrds e end. The sh ontent inresed to mximum t dy 60, nd en deresed. The titrtle idity inresed till dy 30, en deresed. The ft ontent of mnufturer2 (M2) inresed till dys 45 nd 60, nd en deresed. The protein nd totl solids ontents deresed till dy 60, nd en slightly inresed erefter. The sh ontent showed n irregulr pttern roughout e period, while e titrtle idity showed derese towrds e end (Tle 2). Tle (3) showed t e totl teri ount deresed to minimum of log 6.08 ±1.57 t dy 60, en slightly inresed to log 7.86±1.09 t dy 75 (P<0.05) 8. The lipolyti teri ount showed regulr inrese from log 4.48 ±1.57 t dy one to log 6.82±1.08 t e end (P<0.01). The proteolyti nd psyhrotrophi ounts inresed from log 5.88±2.45 nd log 4.07±0.82 respetively t dy one to log 7.44±1.37 nd log 6. ± 1.72 t e end. 533

3 Tle 1: Chemil omposition of mozzrell heese during storge period Storge Ft ontent (%) Protein Totl solids Ash ontent Titrtle idity (% period ontent (%) ontent (%) (%) lti id) (dys) b ± ± ± ± ± 0.15 b ± ± ± ± ± 0.04 b ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.08 Grnd men S.L ** 0 NS ** * Mens wiin eh olumn bering e sme supersripts re not signifintly different (P > 0.05). **=P 0.01 *=P 0.05 N.S= Not signifint (P 0.05) Tle 2: The hemil omposition of mozzrell heese during storge period from two mnufturers under study. Storge period (dys) Ft ontent (%) Protein ontent (%) Totl solids Ash ontent (%) Titrtle idity ontent (%) (% lti id) Mnufturer (M1) Mnufturer (M2) Tle 3: Mirobiologil qulity (Log fu gm) of mozzrell heese during storge period (dys): Count (Log fu gm) Storge period (dys) Grnd men S.L Totl teri 7.72 ± ± ± ± ± ± * Lipolyti teri d 4.48 ± 1.57 d 4.92 ± ± 0.42 b 5.85 ± 1.52 b 5.90 ± ± ** Porteolyti teri d 5.88 ± 2.45 d 6.56 ± ± ± ± ± * d Psyhrotrophi teri 4.07 ± ± ± ± ± ± ** Mens wiin eh row bering e sme supersripts re not signifintly different (P > 0.05). *= P<0.05 **=P<0.01 The totl teri ount of heese from M1 inresed till dy 30 nd en deresed t dy 45 nd en grdully inresed towrds e end, while e proteolyti teri ount inresed t dy 15, followed by derese t dy 30, nd en inresed t e end. The lipolyti teri ount stedily inresed towrds e end of storge period. The psyhrotrophi teri ount inresed till dy 60 en deresed erefter. Cheese from M2 showed t totl teri ount showed n irregulr pttern roughout e storge period. However e proteolyti, lipolytio nd psyhrotrophi teri ount grdully nd regulrly inresed wi inresing storge period (Tle 4). Disussion: This study ws rried out to evlute Mozzrell heese mnuftured by two mnufturers loted in two different ities in Khrtoum Stte. The mnufturing meod of heese from bo mnufturers ws trditionl, where M1 used vuum pkging under septi onditions wi shelf life of e produt being 75 dys s stted in e lel, while M2 used no pkging nd no leling erefore e shelf life of e produt ws not stted. It ws observed t bo mnufturers used no hygiene system of prodution nd e milk might hve ome from different soures of vrying hygieni onditions nd e milk ws not subjeted to het tretment. The hemil omposition of Mozzrell heese indited t ft ontent inresed t first nd en deresed t e end, nd is ws e trend for protein nd sh ontents. The milk used for heese mking 534

4 Tle 4: The mirobiologil qulity (Log fu gm) of mozzrell heese during storge period from two mnuftures under study Storge period totl teri Porteolyti teri Lipolyti teri Psyhrotrophi teri (dys) ount ount ount ount Mnufturer (M2) Mnufturer (M2) ws minly ow milk. These results re wiin e limits reported by Imm et l. (2003) nd Guinee et l. (2000). However, e results re higher n ose of Everett et l. (2004) nd de Cndi et l. (2007). During shelf life mjor omponents (ft, protein, totl solids, nd sh) showed grdul derese in heese from bo mnufturers, lough e ft ontent showed slight inrese t e end ompred to dy one. The protein ontent deresed, while e totl solids ontent showed no hnge. The titrtle idity slightly deresed towrds e end, nd is might be due to e trditionl meod of mnufture in whih no strter ultures were used. Generlly, e flutution in hemil omposition of heese smples my be due to different mnufturing onditions between mnufturers nd different soures of milk used, meod of mnufture in terms of temperture nd use of strter ultures. From mirobiologil point of view, heese from M2 ws more ontminted ompred to t from M1. All teri exmined were found to inrese during shelf life in regulr behviour inditing t bo mnufturing onditions nd rw mteril were responsible for e high number of teri nd onsequent inrese during storge period. Mss et l. (1992) isolted Klebsiell pneumonie, K. oxyto, nd Enteroter erogenes from Mozzrell heese s spoilge orgnisms, while Romno et l. (2001) isolted yests from trditionl wter bufflo Mozzrell. The shelf life of Mozzrell heese ws prolonged using different pkging systems where Pseudomons spp. were redued from Log 7.77 fu/g to Log fu/g nd erefore e shelf life ws prolonged from 1.58 dys to dys using ree different innovtive tive pkging systems (Conte et l., 2007). Dun et l. (2007) reported t hitosn-lysozyme films nd oting resulted in drsti redution in e popultion of Listeri monoytogenes, E. oli, Pseudomons fluoresens nd yests nd moulds in Mozzrell heese stored for 14 dys. In noer study it ws found no signifint vrition in lti id teri nd oliforms between heese treted wi hitosn nd hitosn-free heese (Altieri et l., 2005). The inrese in number of teri isolted wi dvnement of shelf life might in prt be due to sene of ommeril strter ultures whih if were present might hve resulted in deresing e number of teri during shelf life (Dun et l., 2007). Psyhrotrophi teri suh s Pseudomons fluoresens use bitter tste nd bd odour rough lipolyti nd proteolyti retions resulting in spoilge of heese (Sndrou nd Arvntitoynnis, 2000). Constle et l. (2007) reported t hnges in heese mking proess were insuffiient to produe signifint differene in proteolysis of heeses. Hsn et l. (2006) reported t psyhrotrophi teri use signifint spoilge problem in refrigerted diry produts due to seretion of hydrolyti enzymes espeilly lipses nd proteses. Conlusions: There ws signifint inrese in ft ontent, nd derese in protein nd totl solids ontents nd titrtle idity, while n irregulr pttern ws observed during shelf life. However, exept for ft ontent of heese from M1 whih inresed wi time, ll oer heese omponents studied showed deresing pttern roughoutt shelf life. Totl teri, lipolyti teri, proteolyti teri nd psyhrotrophi teri ounts inresed wi time in heese from bo mnufturers. 535

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