Y. ALPARSLAN et l.: Qulity of Rinow Trout Stored in Geltin Film, Food Tehnol. Biotehnol. () () ISSN -9 (FTB-7) originl sientifi pper Effets of Geltin-Bsed Edile Films Enrihed with Lurel Essentil Oil on the Qulity of Rinow Trout (Onorhynhus mykiss) Fillets During Refrigerted Storge Yunus Alprsln*, Tu Bygr, Tçnur Bygr, Htie Hsnhooglu nd Cnsu Metin Mugl Sitki Komn University, Fulty of Fisheries, Kotekli, TR- Mugl, Turkey Reeived: June, Aepted: Ferury, Summry The effets of geltin films enrihed with lurel lef essentil oil on the qulity of rinow trout (Onorhynhus mykiss) during refrigerted storge t ( ) C were exmined over period of dys. Fish fillets were wrpped with % geltin films ontining,. nd % (y volume per mss) of lurel essentil oil nd vuum pkged. Sensory (rw nd ooked fish), miroiologil (totl vile ounts, psyhrotrophi teri ounts, Enteroteriee nd lti id teri) nd hemil (proximte omposition, ph, totl voltile se nitrogen (TVB-N), thiorituri id (TBA), free ftty id (FFA) nd peroxide vlue (PV)) nlysis, nd olour mesurement were rried out during the storge period nd shelf-life ws determined periodilly. The otined results showed tht the geltin film enrihed with lurel essentil oil ws suitle for the preservtion of rinow trout fillet nd the ility of lurel essentil oil to preserve the film depended on its rtio. Comined effets of geltin film nd lurel essentil oil ( % y volume per mss) ws effiient in mintining the qulity hrteristis t n eptle level up to dys of storge, while the nd geltin film without the essentil oil rehed n uneptle level t nd dys, respetively. Key words: geltin films, lurel essentil oil, rinow trout, Onorhynhus mykiss, shelf-life Introdution Fish nd fishery produts hve een reognized s nutrition soure due to their high protein ontent. Moreover, they ontin onsiderle mounts of unsturted ftty ids, espeilly ù- ftty ids, whih re regrded s helth-promoting ompounds. However, the shelf-life of sefood is limited due to iohemil nd miroiologil hnges (). Rinow trout is ftty frmed fish, nd it is highly demnded mong onsumers. Qulity deteriortion of ftty fish speies is primrily used y miroorgnisms nd lipid oxidtion during storge (). Food sfety nd qulity re the mjor onerns in food industry euse of the diret effet of food on humn helth nd qulity of life. Edile films nd otings mde from polyshrides, proteins nd lipids n extend the shelf-life of foods y ting s moisture, oxygen, ron dioxide or vpour rriers nd s enhners of mehnil properties (). Edile films nd otings hve rnge of dvntges, suh s ediility, iodegrdility, ioomptiility nd rrier properties, s well s eing nontoxi nd non-polluting (). In ddition, films nd/or otings my t s rriers of ntimiroil gents, ntioxidnts nd other food dditives nd hve een prtiulrly onsidered in food preservtion euse of their ility to extend the shelf-life (). The inorportion of essentil oils (EOs) into polymeri mtries gives them interesting ntimiroil/ntioxidnt properties. Although the use of iotive otings enrihed with EOs ppers to e promising tehnology in fish nd met preservtion, few *Corresponding uthor: Phone: +9 9; Fx: +9 7; E-mil: yunuslprsln@mu.edu.tr
Y. ALPARSLAN et l.: Qulity of Rinow Trout Stored in Geltin Film, Food Tehnol. Biotehnol. () () studies hve een pulished to dte (). Geltin is protein otined y physil, hemil or iohemil denturtion nd hydrolysis of ollgen. Geltin-sed edile film otings hve lredy een proposed to extend the shelf-life of vrious met produts. Lurus noilis L. (Luree) is n romti plnt used s spie in sefood ooking nd s trditionl mediine for the tretment of some infetious diseses due to its skin re properties. Its dried leves nd essentil oil re used in Itly, Frne, Turkey, Algeri, Moroo, Spin, Portugl nd Mexio s vlule spie in the ulinry nd food industry (7). Nevertheless, there is no informtion on the development of geltin films enrihed with lurel lef essentil oil. The im of this work is thus to determine whether the shelf-life of refrigerted rinow trout fresh fillets n e extended y the use of geltin film enrihed with lurel essentil oil s n ntioxidnt nd ntimiroil gent. Mterils nd Methods Plnt mterils Fresh y lurel leves were olleted from Mugl (Turkey) in My. Leves were seprted from their stem prts nd ir-dried until use. Extrtion nd nlysis of essentil oil The essentil oil (EO) ws otined y hydrodistilltion, using Clevenger pprtus (Edutek Instrumenttion, Hryn, Indi) with g of dry plnt mteril nd ml of wter. The oil ws otined fter h of distilltion t oiling temperture nd stored t ( ) C in irtight glss vils overed with luminium foil. The gs hromtogrphy-mss spetrophotometry (GC-MS) nlysis of the otined essentil oil ws onduted t the ARGEFAR-ÇEG Lortory of Aegen University (Ýzmir, Turkey), using n Agilent gs hromtogrph model 9 equipped with n Agilent mss seletive detetor (MSD) model 97 (Agilent Tehnologies, Snt Clr, CA, USA). Identifition of omponents in the essentil oil ws rried out with the Wiley 7 mss spetrl lirry (NIST, Wiley, New York, NY, USA). Preprtion of fish smples Fresh quultured rinow trout (Onorynhus mykiss, verge mss nd length: ( ) g nd ( ) mm, respetively) were otined from lol fish frm. The smples were pled in polystyrene fom oxes with flke ie nd trnsferred to the Fish Proessing Lortory t the Fulty of Fisheries t Mugl Sitki Komn University (Mugl, Turkey) within h, depitted, filleted y hnd nd wshed in tp wter. Two fillets were otined from eh fish. In totl, rinow trout fillets (verge mss: ( ) g) were prepred for nlysis. Preprtion of film-forming solution nd tretment of fish fillets Preprtion of edile films ws slightly modified from Gómez-Est et l. (). Food grde geltin powder ( g; Dog Drug nd Rw Mteril Co. Ltd., Ankr, Turkey) ws dissolved in ml of distilled wter (t room temperture) nd the mixture ws stirred until the geltin ompletely dissolved (pprox. min). Glyerol (. ml per g of geltin) nd D-soritol (. g per g of geltin) were then dded to the geltin solution, whih ws kept t C for dditionl min. Lurel essentil oil (LEO) in rtio of. nd % (y volume per mss of geltin) ws then dded to the film-forming solution. To stilize the emulsion, Tween- ws lso dded t % (y volume), depending on the LEO ontent. One of the geltin groups ws prepred without the ddition of lurel essentil oil ( % LEO). The film-forming solution with the dded LEO ws homogenized with n Ultrturrx T si lender ( rpm, position, for min; IKA-Werke GMBH & Co. KG, Stufen, Germny). The films were otined y sting ml of film-forming solution into squre polystyrene fom dishes (inner dimension of the fom dish ws. 9 m) nd drying t room temperture for ht(7 ) % reltive humidity (RH). Film thikness ws mesured using digitl mirometer (model MDC-M, Mitutoyo, Kngw, Jpn), verging nine different lotions ( m (p<.)). Three different types of films were then otined: geltin film with % LEO, nd geltin films with. nd % LEO. Wrpping method ws slightly modified from Ahmd et l. (9). Dried film smples were peeled off septilly from the fom dish. Prior to nlysis, oth sides of the films were sujeted to UV for min to e sterilized. To wrp the fillets, one piee of film ws put into sterile fom dish, the rinow trout fillet ws put onto the film nd nother sterile film ws put onto the fillet. Thus, eh fillet ws oted ompletely on oth sides. The group ws not wrpped in ny kind of geltin film. Then, eh smple (inluding the group) ws vuum pkged (Culinry, ATM Mhinery BV, Hksergen, The Netherlnds) nd stored t ( ) C. Sensory evlution Sensory evlution of the nd geltin-wrpped groups (,. nd % LEO) ws onduted y six trined persons. Pnellists gve sores for sensory hrteristis, suh s pperne, olour, odour, texture nd generl eptility using 9-point desriptive sle. On this sle, sores etween 7. nd 9. indited extremely like; sores etween. nd.9 indited like, nd.9 ws the limit of eptility (). Miroiologil nlysis of fish smples The following groups of miroflor were monitored: totl vile ount (TVC), psyhrotrophi teri ount, Enteroteriee nd lti id teri (LAB). A smple of g ws removed septilly from the fillet using slpel nd foreps, trnsferred to stomher g ontining 9 ml of sterile peptone wter (PW) solution (. %), nd homogenized t room temperture. For eh smple, further seril deiml dilutions were prepred in PW solution (. %). The pproprite dilutions were susequently used for enumertion nd differentition of
Y. ALPARSLAN et l.: Qulity of Rinow Trout Stored in Geltin Film, Food Tehnol. Biotehnol. () () 7 miroorgnisms. TVC ws determined using plte ount gr (PCA, Merk ode., Merk, Drmstdt, Germny) fter inution for dys t 7 C, nd psyhrotrophi teri ounts were determined fter inution t 7 C for dys with the sme medium (). Enteroteriee were determined using doule lyer Violet Red Bile Agr (VRB Agr, Merk ode.) fter inution for dys t 7 C (). Lti id teri were determined using doule lyer de Mn-Rogos- -Shrpe gr (MRS, Merk ode.) fter inution for dys t 7 C (). Chemil nlysis of fish smples The fish smples were nlysed in triplite for proximte omposition: lipid ontent of fish y the Bligh nd Dyer method (), moisture nd sh ontent y AOAC method () nd totl rude protein y Kjeldhl method (). The ph vlues were reorded y digitl ph meter (InoL, WTW, Weilheim, Germny) fter homogeniztion of eh g of fish musle smple in ml of distilled wter (7). Determintion of totl voltile se nitrogen (TVB-N) ws rried out s desried y Antonopoulos (). Homogenized fish smples were stem-distilled nd the TVB-N vlue (in mg of nitrogen per g of fish) ws determined ording to the onsumption of. M HCl. Thiorituri id (TBA) retive sustnes were determined ording to Trldgis et l. (9) to evlute the oxidtion stility during hilled storge nd the results were expressed s TBA vlue in mg of mlondildehyde per kg of fish met. Free ftty id (FFA) ontent, expressed in perentge of olei id, ws determined y idometri titrtion of extrts ording to Bligh nd Dyer (), fter the ddition of ethnol nd with phenolphthlein s n inditor, following the AOCS method (). Peroxide vlue (PV), expressed in millimole of peroxide per kilogrm of ft, ws determined ording to AOAC (). Colour mesurement The olour of smples ws mesured y l olour meter (Pen Color Art L model, Artoksi MSM, Istnul, Turkey) nd ws in ordne with the reommendtions of the Interntionl Commission on Illumintion (). The mesured L *, * nd * olour prmeters indited lightness/rightness, redness/greenness nd yellowness/ lueness, respetively. The olourimeter ws lirted with white stndrd nd the olour mesurement ws repeted times on different prts of the surfe. Sttistil nlysis Experiments were performed in triplite (N=) for three independent smples nd ompletely rndomized design (CRD) ws used. Dt were presented s men vlues stndrd devitions nd proility vlue of p>. ws onsidered signifint. Anlysis of vrine (ANOVA) ws performed nd the men omprisons were done y Dunn's multiple rnge tests. Sttistil nlysis ws performed using the Sttistil Pkge for Soil Sienes (SPSS for Windows, SPSS In., Chigo, IL, USA). Results nd Disussion Sensoril hrteristis of fish smples The results of the sensory ssessment of smples re given in Tle. The fish smples were onsidered to e eptle for humn onsumption until the sensory sore rehed (,). Texture, odour, olour nd overll eptility of smples reeived uneptle sores y the th dy ording to the pnellists' evlution, smples wrpped in geltin films with nd. % LEO reeived uneptle sores y the th dy, wheres tht with % LEO ws evluted s uneptle fter dys. The sensory evlution results ppered to e orrelted with miroil nd hemil vlue nlysis. Chnges in the sensory hrteristis of group were oserved s off-odour nd softening of the flesh tht were proly used y fish enzyme tivtion. The ntioxidnt, ntimiroil nd gs rrier effets of the oting were shown to minimise the oxidtive effets, prolonging the produt shelf-life while mintining qulity. Adding lurel oil to geltin oting enhned signifintly (p<.) the enefiil effets on the olour nd overll eptility of the fish in finl dys. Miroil flor of rinow trout fillets Miroil flor hnges of rinow trout fillets fter the tretment with geltin film ontining LEO re shown in Figs. d. The initil totl vile ount (TVC) of the fish fillets (Fig. ) ws log CFU/g. TVC rehed 7.9 log CFU/g fter dys of storge in ll other groups exept for the one ontining % LEO (. log CFU/g). Initil TVC lod of the fresh trout smples my e ssoited with ontmintion of smples during filleting. Considering the miroiologil upper limit of totl vile ount of CFU/g in fresh fish proposed y ICSMF (), our result indites good fish qulity. Chytiri et l. () reported tht the totl initil mesophili lod of the rinow trout fillets ws. log CFU/m. Higher initil ounts of. log CFU/g in se ss slies were reported y Ahmd et l. (9). During storge, the TVC oservly inresed in, nd the groups without or ontining. % LEO. The differenes etween the ltter two groups were not sttistilly signifint (p>.). The omintion of oth the geltin film nd the lurel essentil oil showed n dditive inhiitory effet on the miroflor of rinow trout fillets. Bteril spoilge in fish nd fish produts stored under hilled nd eroi onditions is used y Grm- -negtive psyhrotrophi teri suh s Pseudomons, Alteromon, Shewnell nd Flvoterium spp. (). Chnges in totl psyhrotrophi teri of rinow trout fillets re shown in Fig.. During storge, smples wrpped in geltin film ontining % LEO hd the lowest psyhrotrophi teri ount when ompred to the nd smples wrpped in geltin film with (p<.). Enteroteriee, regrded s hygiene inditor, re lso one of the spoilge miroorgnisms of fresh rinow trout (7). Enteroteriee ounts in fresh smples were pprox.. log CFU/g t the eginning the storge (Fig. ). By dy of storge, Enteroteriee ounts inresed to 7. log CFU/g in group,
Y. ALPARSLAN et l.: Qulity of Rinow Trout Stored in Geltin Film, Food Tehnol. Biotehnol. () () Tle. Chnges in ttriute sores of rw rinow trout fillets wrpped in geltin films ontining LEO during refrigerted storge Sensory V(LEO) t(storge)/dy /% ttriutes m(geltin) Apperne (..) (..) (..) (..) (..) (.7.) (..) (..) d (.9.) d (..) (7..) (7..9) (..) (..7) (..9) (.9.) (..) (.7.). (..) (7.7.) (7..) (..) (..) (..9) (..) (..) (..) (..) (7..) (7..) (..7) (.7.) (..) (..) (..) (..) Colour (.7.) (..) (.7.) (..7) (..) (..) (.7.) (.7.) (.9.) (.7.) (7.7.) (7..7) (..) (.9.) (..) (..) (..) (.7.7). (.7.) (7..) (7..) (..) (..) (..) (.9.) (.9.) (.7.) (.7.) (7..) (7..) (..9) (..7) (.9.) (.7.) (..) (.9.) Odour (.7.) (7..) (..9) (..) (.7.) (..) (..) (.9.) d (..) (.7.) (7..7) (..) (.9.) (..) (..7) (.9.) (..) (..7). (.7.) (..) (.9.) (..9) (..) (.9.) (..) (.9.) (..) (.7.) (7.9.) (7..7) (..) (.9.) (..7) (..) (..) (..7) Texture (..) (.9.) (.7.) (..) (.9.) (..9) (..) (..) (.9.) Generl eptility (..) (..) (..) (..7) (..7) (.7.) (..) (..) (..9). (..) (..) (..) (..) (..) (..) (.9.) (..) (..) (..) (7.9.) (7..7) (..) (..7) (..) (..9) (.9.9) (..9) (.7.) (..) (..) (..9) (.9.) (..9) (..) (..) (..) (.7.) (..) (.7.) (..) (..) (..) (.7.) (..) (..7). (.7.) (..) (.9.7) (..7) (..) (.7.) (..7) (..) (..) (.7.) (..) (7..) (..) (..) (..) (..) (..7) (.9.) while they were. log CFU/g in the group ontining % LEO (p<.). Geltin film without LEO ( % LEO) did not show n inhiitory effet on Enteroteriee ounts nd 7. log CFU/g were otined y the end of the th dy. The ontriution of Enteroteriee to the miroflor of fish nd its spoilge potentil must e tken into onsidertion (). Lti id teri (LAB) re fulttive neroi teri tht n grow under oth neroi nd eroi onditions (9). The initil LAB ount in the group ws pprox.. log CFU/g (on dy ) nd rehed. log CFU/g on dy of storge (Fig. d). On the sme dy, the use of geltin film with % lurel essentil oil resulted in redution of LAB ounts y.9 log CFU/g (p<.). Our findings re in greement with the results of Mexis et l. (7), who reported redution of LAB y. log CFU/g in Greek od roe pste fter the ddition of oregno oil t. % (y volume per mss). Rmos et l. () lso reported tht y lurel essentil oil nd its ethnoli extrt n e used s nturl lterntives to syntheti food preservtives, in order to enhne food sfety nd inrese food shelf-life. In their study, the EO exhiited strong ntiteril tivity ginst ll tested foodorne spoilge nd pthogeni teri. There re some other effetive studies deling with the ntimiroil properties of films sed on proteins, hitosn or lgintes inorported with vrious essentil oils suh s oregno, rosemry, grli, pimento or innmon (). Not only re the intrinsi properties of the food (ft/ protein/wter ontent, ntioxidnts, preservtives, ph, slt nd other dditives) relevnt in this respet; the extrinsi determinnts (temperture, pkging in vuum/ gs/ir, hrteristis of miroorgnisms) n lso influene teril sensitivity. Generlly, the suseptiility of teri to the ntimiroil effet of essentil oils lso ppers to inrese with derese in the ph of the food, the storge temperture nd the mount of oxygen within the pkging (). Thus, ftors suh s low ph, storge temperture, deresed O onentrtions nd high slt ontent enhne the ntimiroil effet of the essentil oil, while ftors like high levels of protein nd ft nd low wter tivity seem to protet the teri (). Proximte omposition of rw fish mteril Proximte nlysis results of rw mteril were: rude protein (..) %, moisture (7.97.) %, rude ft (..) % nd sh (..) %. The proximte omposition of the rinow trout fillet reported in different studies () showed some differenes, espeilly in the lipid ontent. Suh vritions in the hemil omposition of fish re strongly relted to the nutrition, thing seson, sexul vrition, fish size, living re, s well s other environmentl onditions (). The omposition of
Y. ALPARSLAN et l.: Qulity of Rinow Trout Stored in Geltin Film, Food Tehnol. Biotehnol. () () 9 ) N/(log CFU/g) ) N/(log CFU/g) ) N/(log CFU/g) d) N/(log CFU/g) Totl vile ount 9 7 t(storge)/dy 9 7 9 7 7 Psyhrotrophi ount t(storge)/dy Enteroteriee t(storge)/dy Lti id teri t(storge)/dy Fig.. Effet of geltin film enrihed with lurel essentil oil (LEO) on: ) totl vile ount, ) psyhrotrophi ount, ) Enteroteriee popultion, nd d) lti id teri popultion in rinow trout fillets during refrigerted storge. Letters show signifint differenes mong the groups t p<. fish n ffet the sensory hrteristis, suh s olour, texture, odour, tste nd surfe pperne, whih strongly influene the eptility of fish s food (,,), s it my lso ffet the miroil growth (). The results of hemil nlysis Chemil omposition of the essentil oil By lurel essentil oil ws found to ontin,-ineole (9.7 %), -terpinene ette (. %), linlool (.97 %), sinene (.9 %), -pinene (. %) nd -pinene (. %) s mjor onstituents. It ws reported tht y lurel leves ontined mostly,-ineole ( %), eugenol, etyl eugenol, methyl eugenol nd terpineol (). In our study,,-ineole ws lso found s the most undnt onstituent. Most of -terpinene ette (. %) ws thought to e prtiulr to the lotion or used y sesonl hnges of the y lurel tree. Different y lurel essentil oil ompositions found in previous studies re generlly relted to severl ftors suh s geneti, limti, sesonl nd geogrphi (7). The ility of prolonging the shelf-life of rinow trouts my e ffeted y the synergisti effets with the onstituents of lurel essentil oil. ph vlue of fresh fish smples The ph vlue of fresh fish flesh is often etween nd. (). The eptle upper limit for the ph of fish met is. 7. (9). The initil ph vlue of rinow trout smples in this study ws... During storge, ph ws found to e low in geltin film-wrpped smples ontining LEO nd there ws sttistilly signifint differene mong the groups (p<.). At the end of the storge (y dy ), ph inresed nd rehed the level of... The ph vlues of ll fish smples used in the study did not exeed the eptle limit. As reported in literture, the inrese of ph vlue during storge is ttriuted to the prodution of si ompounds suh s mmoni, trimethylmine nd other iogeni mines y fish spoilge teri (). Totl voltile se nitrogen ontent Totl voltile se nitrogen (TVB-N) ws used s the inditor of the qulity of fresh trout fillets. The TVB-N vlues of the smples during storge re presented in Fig.. The initil vlue of TVB-N ontent in fillets ws 7. mg of N per g of fish. The TVB-N vlues of oth nd the oted smples inresed signifintly (p<.) with storge time. Its inrese is relted to the tivity of spoilge teri nd endogenous enzymes (). There were no sttistilly signifint differenes etween groups with. % nd without ny LEO dded to the film (p>.). TVB-N ontent in freshly ught fish is typilly etween nd mg of N per g, nd TVB-N ontent of mg of N per g is usully regrded s the limit of eptility for fish (). The limit TVB-N level of mg per g, whih ws speified y the Europen Commission (EC) guidelines (), ws exeeded in the nd the group ontining % LEO in the film fter nd dys, respetively. In the groups without or with. % LEO in the film oting, the limit vlues were rehed y dy of storge (Fig. ). Tsi et l. () found tht pretretment of fish (Onorhynhus nerk) fillets with % ofhitosn
Y. ALPARSLAN et l.: Qulity of Rinow Trout Stored in Geltin Film, Food Tehnol. Biotehnol. () () w(tvb-n)/(mg/ g) t(storge)/dy w(tba s MA)/(mg/kg)..9..7....... t(storge)/dy d Fig.. Chnges in totl voltile se nitrogen (TVB-N) vlues of rinow trout fillets wrpped in geltin films ontining lurel essentil oil (LEO) during refrigerted storge. Letters show signifint differenes mong the groups t p<. Fig.. Chnges in thiorituri id (TBA) vlues of rinow trout fillets wrpped in geltin films ontining lurel essentil oil (LEO) during refrigerted storge. Letters show signifint differenes mong the groups t p<.. MA=mlondildehyde solutionforhretrdedtheinrese in the TVB-N. Also, López-Cllero et l. () found tht the protetive hitosn-geltin oting lowered TVB-N vlues distintly nd hene slowed down the spoilge. Ahmd et l. (9) reported tht the inhiitory effet of geltin film ontining lemongrss essentil oil ginst miroil growth ould retrd or lower the prodution of miroil degrdtion produts. The results of thiorituri id ssy During storge, signifint inrese in thiorituri id (TBA) ontent ws oserved in smples s ompred to the smples wrpped in geltin film only or in geltin film ontining different mounts of LEO (p<.) (Fig. ). The initil TBA vlue ws. mg of mlondildehyde per kg of tissue. Sthivel () reported tht the initil TBA vlue for the rw nonoted pink slmon fillets ws. mg of mlondildehyde per kg of fish. In our study, TBA vlues of the group nd the smples with geltin oting without LEO were higher thn of the geltin otings with LEO (p<.). TBA is widely used inditor of the degree of lipid oxidtion (,). It hs een proposed tht the mximum level of TBA vlue inditing good qulity of fish (frozen, hilled or stored in ie) is mg of mlondildehyde equivlents per kg of tissue, while the fish my e onsumed with up to the level of mg of mlondildehyde equivlents per kg of tissue (). In our study, TBA vlues in nd oted trout fillet smples were muh lower thn the reommended limits throughout the - -dy storge period (Fig. ). TBA vlue ws found to e lower in the smples ontining % LEO in omprison with nd other groups (p<.). As the LEO rtio inresed, lower oxidtion rte ws otined. In our study, ll wrppings with or without LEO ould inhiit the lipid oxidtion of trout fillets, nd geltin film enrihed with LEO hd etter effet thn the group nd geltin lone. Our results suggested tht lipid oxidtion in rinow trout fillets ould e retrded y geltin film enrihed with LEO. This is proly due to the ntioxidnt hrteristis of LEO s well s the low oxygen permeility of geltin film (9). Antoniewski et l. (7) found tht geltin oting hd no effet on lipid oxidtion in slmon fillet stored t C for dys. Adding different rtios of lurel essentil oil to the geltin film, therefore, proly hd synergisti effet. In the se of most herl extrts, their ntioxidnt tivity ws ttriuted to their ility to rek the free rdil hin y donting hydrogen tom (). Free ftty id ontent of fish smples The presene of free ftty ids (FFA) is used y the hydrolysis of lipids. Therefore, quntifying the FFA perentge n e profitly used s n index of the degree of lipolysis, whih in turn is n inditor of the fish freshness. The initil hydrolyti rnidity s evluted y FFA vlue of the trout fillets ws. (expressed s perent of olei id) on dy. During storge, the FFA vlues inresed signifintly (p<.) in ll smples. FFA vlues expressed s.,.,.7 nd. % of olei id were oserved in the, nd in smples wrpped in geltin without LEO, or with. or % LEO, respetively. Geltin wrpping with % LEO hd etter effet on mintining the qulity of fish fillet thn the one without LEO, while the qulity of fish smples wrpped with geltin with. % LEO ws etter thn of the group. Gomez-Guillén et l. (9) investigted the effet of geltin-sed films with inorported queous extrts of either oregno or rosemry on old-smoked srdine under high pressure, nd reorded signifint derese in FFA y dy. The results of peroxide vlue determintion Primry (peroxide vlue, PV) nd seondry (TBA) oxidtion produts were determined s inditors of the degree of lipid oxidtion, similr to Mexis et l. (7). The effet of film on the hnges of PV of fish lipids is shown in Fig.. The initil PV in the nlyzed fish fillets ws (..) mmol per kg of fish smple. The PV of the s nd treted smples inresed signifintly (p<.) onurrent with storge time. When ompred to smples treted solely with geltin film, PV inrese of the LEO-ontining groups ws found to e slower (p<.). In the group, PV vlue exhiited rpid inrese y dy nd rehed. mmol/kg y dy. During storge, PV vlue of. (on the th dy),. (on the th dy) nd.7 mmol/kg (on the th dy) ws o-
Y. ALPARSLAN et l.: Qulity of Rinow Trout Stored in Geltin Film, Food Tehnol. Biotehnol. () () PV/(mmol of O per kg) t(storge)/dy Fig.. Chnges in peroxide vlue (PV) of rinow trout fillets wrpped in geltin films ontining lurel essentil oil (LEO) during refrigerted storge. Letters show signifint differenes mong the groups t p<. ) L* ) * ) * t(storge)/dy - - - - - - - - - - t(storge)/dy t(storge)/dy Fig.. Chnges in the mesured instrumentl olour prmeters of fish smples: ) lightness (L*), ) redness (*) nd ) yellowness (*). Letters show signifint differenes mong the groups t p<. d served in smples without nd with. or % LEO, respetively. Aording to the literture, PV vlue of pprox. mmol/kg ( meq) is onsidered s the upper limit for foodstuffs (). Similr results for PV were otined y Mohn et l. () in tfish. The mjor protetive effet is proly due to the use of geltin s n oxygen sorer nd the ntioxidnt effet of lurel essentil oil. The results of olour determintion The results of olour mesurement of the rinow trout fillets re shown in Fig.. At the eginning of storge, lightness (L*), redness (*) nd yellowness (*) vlues of smples were determined t..9,.. nd.., respetively. The L* vlue of the group inresed throughout the storge, while no signifint differenes (p>.) were determined in geltin-wrpped smples without LEO, nd with. or % LEO (Fig. ). The * vlues deresed from red to green, while those of * inresed from yellow to lue throughout the entire storge period (Figs. nd ). Ahmd et l. (9) reported tht se ss slies wrpped in geltin film ontining lemongrss essentil oil showed fewer hnges in olour vlues, proly due to the ntioxidnt nd ntimiroil properties of lemongrss essentil oil. Conlusions Bsed on the sensory evlution, it n e onluded tht the omintion of geltin film nd lurel essentil oil ws effetive in extending the shelf-life of fresh rinow trout fillets to dys, wheres smples pkged without geltin film hd shelf-life of dys. Therefore, the ddition of lurel essentil oil to geltin films extended the shelf-life of rinow trout fillets for 7 dys more when ompred to the nonoted group. Geltin films with. nd % lurel essentil oil improved the qulity of fish during storge in terms of hemil indies (ph, TVB-N, TBA, FFA, PV). Fish fillets wrpped in geltin film ontining % LEO hd the est qulity sores ording to the sensoril, hemil nd miroiologil dt. As the rtio of essentil oil inresed, the shelf-life prmeters were enefiilly ffeted throughout the nlysis period. It is suggested tht geltin film tretment with lurel essentil oil my e profitle for slted, dryed nd smoked sefood, whih hs lower moisture ontent. In onlusion, geltin film enrihed with lurel essentil oil provides n effetive oting tht prolongs the shelf-life nd mintins the qulity ttriutes of the pkged food. Aknowledgements The uthors wish to thnk Bulent Olmez for the ontriution to the essentil oil nlysis, Mustf His from Mugl Sitki Komn University, Fulty of Fisheries, nd Sener Kof from Reis Alli ki li k Turizm Co. Ltd. Şti. for providing the fish smples. Referenes. P. Msniyom, Deteriortion nd shelf-life extension of fish nd fishery produts y modified tmosphere pkging, Songklnkrin J. Si. Tehnol. () 9.
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