Effect of Organic Acids on Microbial Populations and Salmonella typhimurium in Pork Loins

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1 96 Effect of Orgnic cids on Microil Popultions nd Slmonell typhimurium in Pork Loins Seoknm Kng, er Jng, Sng Ok Lee, Joong Seok Min, Il Suk Kim nd Mooh Lee* Lortory of Muscle Food Science, School of griculturl iotechnology, Seoul Ntionl University Suwon -7, Kore STRT :The ojective of this study ws to evlute the effects of vrious orgnic cids on microil chrcteristics nd Slmonell typhimurium in pork loins. Fresh pork loins were spryed with vrious orgnic cids such s lctic cid, citric cid nd cetic cid t vrious concentrtions (.5,,.5 nd %). fter sprying, the smples were pckged y HDPE film under ir nd stored t for dys, nd nlyzed. Microil deteriortion of pork loins during the eroic cold storge ws delyed y orgnic cid spry. The ctericidl effect of cids incresed with the incresing concentrtion. However, the inhiitory ctivity of orgnic cids during the storge vried with the kinds nd concentrtions of the cids. s for totl plte counts, cetic cid ws found to hve the highest ctericidl ctivity, wheres citric cid ws found to e the most inhiitory for coliform nd S. typhimurium. (sin-ust. J. nim. Sci.. Vol 6, No. : 96-99) Key Words : Lctic cid, itric cid, cetic cid, Slmonell Typhimurium, Totl Plte ounts, oliforms INTRODUTION Spoilge microorgnisms nd pthogenic cteri such s Slmonell, mpyloctor, nd Listeri, re contminted during slughter nd susequent processing to produce retil cuts from live nimls. ppliction of orgnic cids to crcss surfces hs een reported to reduce popultions of spoilge cteri nd pthogens, nd thus hs potentil to extend shelf-life nd reduce food orne illness in pork (Fu et l., 99), eef nd lm (Osthold et l., 98) nd poultry (Tmlyn nd onner, 997). However, cids tretment of eef crcsses hd little or no effect on the microiologicl qulity of met cuts fter friction (Prsi et l., 99). In pork, Fu et l. (99) reported tht orgnic cids tretments were of reltively limited effectiveness for long term storge. On the other hnd, n cid spry immeditely prior to pckging cn reduce some species of cteri without dversely ffecting the physicl properties of eef (Goddrd et l., 996). Therefore, this study ws crried out to evlute the effects of vrious orgnic cids including lctic cid, citric cid nd cetic cid on microil chrcteristics nd Slmonell typhimurium in pork loins. MTERILS ND METHODS Vrious orgnic cids such s lctic cid (85%, fisher * ddress reprint request to Mooh Lee. Tel: , Fx: , E-mil: moohlee@snu.c.kr Deprtment of Interntionl Livestock Industry, Jinju Ntionl University, Jinju, , Kyongnm, Kore. Received pril, ; ccepted Octoer, science, Firlwn, NJ, US), citric cid (99.8%, nhydrous, Fisher scicence, St. Louis, Mo, US), nd cetic cid (glcil, food grde, J.T. ker chemicl o., Phillipsurg, NJ, US) were used. They were diluted to.5% (v/v), % (v/v),.5% (v/v), % (v/v) with distilled wter nd then spryed on fresh pork loins for 5sec t y hnd spryer. The control smples were spryed with sterilized distilled wter. fter sprying, the smples were pckged y HDPE film under ir nd stored t for dys, nd nlyzed for totl plte counts nd coliforms (n=9). In nother experiment, fresh pork loins were inoculted with Slmonell typhimurium T 8 (from Veterinry Microiology L, ollege of Veterinry Medicine, Seoul Ntionl University) nd then spryed with orgnic cids in the sme wy s in the first experiment. fter sprying, the smples were pckged nd stored t. For Slmonell typhimurium mesurements, g of ech smple ws stomched in ml of mient distilled wter for min. The stomched smple ws diluted serilly. However, for other microil mesurements, smple s surfce ws swed y using sterile cotton sws nd sterile metl templtes ( cm). The sws were septiclly roken into sterile ml.% peptone wter lnk. fter then seril dilutions were mde. eroic nd coliform cteri were enumerted on Petrifilm (Microiology Products M Helth re, US) for dys t 7, while SS gr (Difco L, ML, US), slmonell selective medium, ws used for enumertion of Smonell typhimurium on pltes. It ws evenly spred on the surfce of the pltes with sterile ent glss rod. (Frederick, 99) The ph vlues of smples were mesured in the homogenized met slurry y ph meter with glss

2 ORGNI IDS ON MIROIL POPULTIONS OF PORK 97 electrode (Model 5985 Digi-Sense ph meter, ole-prmer Instrument o., US). The ph vlues of % (v/v) lctic cid, citric cid, cetic cid were.9,.,.8, respectively. Duncn's multiple rnge test ws used to compre mong tretments using SS (995) progrm RESULTS ND DISUSSION Results showed tht orgnic cids tretments reduced the totl plte counts of pork in eroic pckge fter dy of storge t. The counts of tretment smples t.5% were.7-. log unit lower thn tht of the control. (Figure ). With ech orgnic cid, the ntimicroil effect incresed s the concentrtion incresed. The effect during the storge period vried with the kind of orgnic cid. Lctic nd citric cids showed decresing trends while cetic cid showed n incresing trend except t.5% level. (Figure ). The results of Figure on coliform cteri reveled similr pttern to those on totl plte counts. The ctericidl effect incresed with the concentrtion. itric cid ove % ws most effective in keeping the count low during the storge. Fu et l. (99) reported tht t.5%, oth cetic cid nd citric cid showed some initil effects on decresing eroic plte counts nd coliform count of pork loins, ut the effects did not continue eyond dys storge under vcuum pckging, while lctic cid hd no effect on inhiiting them t ny point of storge. Outtr et l. (997) suggested tht on weight sis, cetic cid ws found to e the most inhiitory, followed y lctic nd citric cid. ecuse cetic cid (pk vlues.8), under comprle conditions of the cid (sme medium nd sme cid concentrtion), ws considerly less dissocited thn lctic cid (pk.8) while citric cid (pk., pk.8, pk 6.) ws the most dissocited of ll. The numer of Slmonell typhimurium on the fresh pork loins which hs een spryed with orgnic cids ws lower thn tht of the control spryed with distilled wter (Figure ). The lctic cid spry reduced S. typhimurium y. to. log unit, citric cid.6 to.5 unit nd cetic cid.5 to.5 unit. The ctericidl ctivity ws the highest t % for ll cids. mong cids, citric cid ws found to hve most inhiitory effect t ll concentrtions nd cetic cid ws the second. In this experiment, the ctericidl effect of orgnic cids ppered to e not solely due to the ph lowering effect. The ph chnges of pork loins vried with the concentrtions nd types of orgnic cids (Figure ). During storge, ph kept decresing t vrying degrees with different concentrtions of orgnic cids until 7 dys. fter tht storge time, there ppered different pttern of ph chnges ccording to orgnic cids: ph incresed t ll Dys Dys Dys Figure. Totl plte counts on eroic-pckged pork loins spryed with lctic cid, cetic cid nd citric cid (from left to right) during storge t. Zero percentge smples were controls. Mens with the different letter in the sme dy re significntly different. (p<.5) ; Lctic cid, ; ctric cid, ; cetic cid levels of lctic cid, incresed only t.5% level of citric cid nd decresed t ll levels of cetic cid. Tmlyn nd onner (997) reported tht ctericidl ctivity of orgnic cids incresed linerly with incresing concentrtion nd the ctivity of orgnic cids depended on the concentrtion nd the method of ppliction. cetic cid ws found to

3 98 KNG ET L %.5% %.5% % c c c c c c c hve most inhiitory effect ginst slmonelle, wheres lctic cid exhiited intermedite ctivity, nd citric cid ws lest inhiitory (hung nd Goepfert, 97). Effective use of n cid depends upon the dissocition constnt (pk) or the ph t which 5% of the totl cid is dissocited (Doores, 99). In our results, the ph vlues of lctic cid, citric cid, cetic cid were slightly higher thn ech pk vlues on 7th storge dys. It cn e suggested tht ll these cids must hve een dissocited, even though the citric cid ove % showed cteriosttic effect. The lower cpcity of citric cids to enter cteril cells is c c %.5% %.5% % cc 7 Dys %.5% %.5% % ccc c c c %.5% %.5% % 7 Dys c c c 7 Dys ccc Figure. oliform counts of eroic-pckged pork loins spryed with lctic cid, cetic cid nd citric cid (from left to right) during storge t. Zero percentge smples were controls. Mens with the different letter in the sme dy re significntly different. (p<.5) ; Lctic cid, ; citric cid, ; cetic cid Log FU/g Slmonell typhimurium c Figure. Slmonell typhimurium of eroic-pcked pork loins spryed with orgnic cids fter h t. Zero percentge smples were controls. Mens with the different letter in the sme percentge of orgnic cids re significntly different (p<.5). compensted y their greter cpcity to dissocite inside the cell nd thus cidify the cell cytoplsm. Indeed, prtilly ionized citrte cn enter the cells of mny cteri (e.g., cillus sutilis, numerous memers of the fmily Entereoctericee, Lctococcus lctis, nd Leuconostoc spp.) through the ction of proton-or ction dependent citrte permese. (Quttr et l., 997) We ssume tht the reson why the citric cid showed high cteriosttic effects in spite of higher ph vlues thn pk vlues ws tht undissocited cid roke into S. typhimurium so tht it ws dissocited inside. ONLUSIONS c cetic cid c %.5% %.5% % Percentge of orgnic cids Lctic cid itric cid Microil deteriortion of pork loins during the eroic cold storge ws delyed y orgnic cid spry. The ctericidl effect of cids incresed with the incresing concentrtion. However, the inhiitory ctivity of orgnic cids during the storge vried with the kind nd the concentrtion of the cid. For totl plte counts, cetic cid ws found to hve the highest ctericidl ctivity, wheres citric cid ws the most inhiitory for coliform nd S. typhimurium. ecuse humn infectious dose of S. typhimurium is known to e round to, the decresed numer of S. typhimurium, y c. log cycle my help consumer e it sfe from the possile link from it. Therefore, it cn e concluded tht orgnic cid spry could e utilized to extend the shelf-life of pork loins nd ensure sfety.

4 ORGNI IDS ON MIROIL POPULTIONS OF PORK 99 ph vlue ph vlue ph vlue %.5% %.5% % 7 Dys %.5% %.5% % 7 Dys %.5% %.5% % 7 Dys REFERENES hung, K.. nd J. M. Goepfert. 97. Growth of Slmonell t low ph. J. Food. Sci. 5():6-8. Doores, S. 99. Orgnic cids. In: ntimicroils in Foods (Ed.. L. rnene nd P. M. Dvidson). Mrcel Dekker, Inc. pp Federic. T. L., M. F. Miller, L. D. Thomson nd.. Rmsey. 99. Microiologicl properties of pork cheek met s ffected y cetic cid nd temperture. J. Food. Sci. Vol. 59. No.. -. Fu,.-H., J. G. Sernek nd E.. Murno. 99. Microil nd qulity chrcteristics of pork cuts from crcsses treted with snitizing sprys. J. Food Sci. 59():6-9. Grutt, J Essentils of food microiology. The th Press, th, Gret ritin. pp Goddrd,. L., W.. Mikel, D. E. onner nd W. R. Jones Use of orgnic cids to improve the chemicl, physicl, nd microil ttriutes of eef strip loins stored t - for dys. J. Food Prot. 59(8): Osthold, W., H. K. Shin, J. Dresel nd L. Leistner. 98. Improving the storge life of crcsses y treting their surfces with n cid spry. Fleischwirtschft 6:88. Outtr,., R. E. Simrd, R.. Holley, G. J. -P. Piette nd. egin Inhiitory effect of orgnic cids upon met spoilge cteri. J. Food Prot. 6():6-5. Prsi, R. K., G. R. cuff, L. M. Luci, D. S. Hle, J. W. Svell nd J.. Morgn. 99. Microiologicl effects of cid decontmintion of eef crcsses t vrious loctions in processing. J. Food Prot. 5: SS SS User's Guide. SS Institute, Gry, N, US. Tmlyn, K.. nd D. E. onner ctericidl ctivity of orgnic cids ginst Slmonell typhimurium ttched to roiler chicken skin. J. Food Prot. 6(6):69-6. Figure. The ph chnges of pork loins during the storge t fter eing spryed with different levels of lctic cid, citric cid nd cetic cid (from left to right). rs t vlues show stndrd devitions of mesurements. ; Lctic cid, ; itric cid, ; cetic cid

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