EFFECT OF NATURAL ANTIOXIDANTS ON OXIDATIVE STABILITY OF FROZEN, VACUUM-PACKAGED BEEF AND PORK ABSTRACT

Transcription

1 EFFECT OF NATURAL ANTIOXIDANTS ON OXIDATIVE STABILITY OF FROZEN, VACUUM-PACKAGED BEEF AND PORK MARTHA C. ROJAS nd M. SUSAN BREWER 1 Deprtment of Food Science nd Humn Nutrition University of Illinois 202 Agriculturl Bioprocessing Lortory, 1302 W. Pennsylvni Ave. Urn, IL Accepted for Puliction July 24, 2007 ABSTRACT The effect of grpe seed extrct (GS; 0.01 nd 0.02%), oleoresin rosemry (0.02%) nd wter-solule oregno extrct (0.02%) on the oxidtive nd color stility of rw eef nd pork ptties, vcuum pckged nd stored frozen for 4 months, ws determined. Fresh eef or pork len nd trim were ground, then mixed individully with ft (30%) from their respective species. Antioxidnts, mixed with slt, were dded. The ptties were formed, vcuum pckged nd stored t -18C. Lipid oxidtion ws ssessed using thiorituric cid rective sustnces (TBARS) nd descriptive sensory evlution. Color chnges (instrumentl nd visul) nd ph were determined immeditely (time 0) nd fter 1, 2, 3 nd 4 months. Bsed on the TBARS vlues, GS provided smll degrees of protection ginst oxidtion in oth met species. It did not lter (P < 0.05) the sensory perception of oxidtion, redness, yellowness or color intensity. PRACTICAL APPLICATIONS Consumer interest in food formultions contining nturl ingredients hs motivted the food industry to evlute the effectiveness of nturlly occurring components of food for functionl purposes other thn their commonly recognized ones. A vriety of ntioxidnt compounds, mostly phenolic in nture, exist in plnt mterils. Grpe seed extrct ( %), rosemry nd oregno cn provide limited protection ginst lipid oxidtion in higher ft met products. However, higher levels my prove to e more efficcious thn those used in this study. 1 Corresponding uthor. TEL: ; FAX: ; msrewer@uiuc.edu Journl of Food Qulity 31 (2008) All Rights Reserved. 2008, The Author(s) Journl compiltion 2008, Blckwell Pulishing 173

2 174 M.C. ROJAS nd M.S. BREWER INTRODUCTION Of the more thn 45 million pounds of eef nd pork produced nnully in the U.S.A., 42% re consumed s ground met (Hley 2006). Ground met is more susceptile to microiologic nd color deteriortion thn re its whole muscle counterprts. Color stility is very importnt to retil shelf life ecuse consumers will not uy drk or discolored met (Glitsch 2000). Fewer pulls, discounts nd discrds ecuse of discolortion could e chieved y improving color stility. Oxidtive processes result in lipid nd protein (including pigment) degrdtion nd re one of the primry mechnisms y which qulity deteriortion limits shelf life in met nd met products (Knner 1994; Rnken 1994). In rw met products, the primry fctors tht influence lipid oxidtion include ftty cid composition, endogenous prooxidtive nd ntioxidtive constituents, nd nonmet dditives (prooxidtive nd ntioxidtive). Polyunsturted ftty cids in met memrne lipids, especilly those with four or more doule onds, re prticulrly susceptile to oxidtion (Gry nd Person 1987; Allen nd Hmilton 1994). This process cn produce vriety of voltile off-odors nd flvors usully descried s rncid (Gry nd Person 1994). In ddition, the reltionship etween lipid nd pigment oxidtion is significnt (Knner nd Hrel 1985). Free rdicls produced y lipid oxidtion cn ccelerte oxymyogloin oxidtion to metmyogloin (O Grdy et l. 2001). Similrly, hydrogen peroxide ctivtes metmyogloin to form ferrylmyogloin rdicls, which re lipid oxidtion ctlysts in muscle foods (Knner et l. 1987). Oxidtion requires tht n oxidizing gent hs ccess to the sustrte (lipid). The most common oxidizing gent is oxygen from the ir. Comminution of met increses the exposure of the lipids to ir, promoting lipid oxidtion (Rnken 1994). Processes tht exclude oxygen, such s vcuum pckging, or reduce its concentrtion, such s modified tmosphere pckging, cn prevent or reduce lipid oxidtion. Endogenous ntioxidnt enzymes, especilly ctlse nd glutthione peroxidse (GSH-Px), cn potentilly dely the onset of oxidtive rncidity in stored met (Mei et l. 1994; Rhee et l. 1996; Prdhn et l. 2000). However, met processing opertions reduce their ctivity (Decker nd Mei 1996) nd some commonly used nonmet dditives, such s slt, cn compromise their ntioxidtive potentil (Hernández et l. 2002). Slt is lipid prooxidnt t the concentrtions ( %) commonly used in met products; it lso ccelertes metmyogloin formtion nd discolortion in rw mets (Rhee nd Ziprin 2001). For more thn 50 yers, synthetic ntioxidnts, such s utylted hydroxynisole, utylted hydroxytoluene (BHT) nd propyl gllte, hve een

3 ANTIOXIDANT EFFECTS ON BEEF AND PORK 175 used to control lipid oxidtion. However, toxicologic effects (Brlow 1990; Bermond 1990) nd consumer preference for nturl products hve incresed interest in nturl ntioxidnts (Decker nd Mei 1996; Formnek et l. 2001). Rosemry, oregno nd their extrcts, which contin polyphenolic compounds, exhiit ntioxidnt ctivity in cooked mets (Rojs nd Brewer 2007) nd in rw mets (Chen et l. 1999; Formnek et l. 2001; McCrthy et l. 2001; Djenne et l. 2003; Sánchez-Esclnte et l. 2003,; Hn nd Rhee 2005; Lee et l. 2005; Blentine et l. 2006; Georgntelis et l. 2007). Previous studies hve indicted tht the concentrtions (>0.1%) re required to chieve mximum ntioxidnt ctivity (Lu nd King 2003; Ahn et l. 2004). Oregno (0.02 1%) lso exhiits ntioxidnt ctivity in rw mets (Sánchez-Esclnte et l. 2003,). Grpe seed extrct (GS), sold commercilly s dietry supplement, hs the potentil to reduce lipid oxidtion nd wrmed over flvor (WOF) in cooked ground eef when dded t 1% (d Silv 1991; Shhidi et l. 1992; Lu nd King 2003; Ahn et l. 2007). This ntioxidnt ctivity ppers to e concentrtion dependent etween 0.02 nd 0.1% (Ahn et l. 2002). The ojective of this reserch ws to compre the effectiveness of severl nturl ntioxidnts including GS, oregno extrct nd oleoresin rosemry extrct (OR) in delying lipid oxidtion in frozen rw ground eef nd pork. MATERIALS AND METHODS Nturl Antioxidnts nd Chemicls The GS (Grvinol Super, Kikkomn, Tokyo, Jpn) contined 98% totl flvnols (89% pronthocynidins). The wter-solule oregno extrct (WS) (Orignox WS, RAD Nturl Technologies Ltd., Brrington Chemicl Corportion, New York, NY) contined t lest 22% totl phenolics (7% rosmrinic cid nd other hydroxycinnmic compounds). Rosemry ws OR (Herlox Sesoning HT-25, Klsec Inc., Klmzoo, MI). Food grde slt (NCl) ws procured from US Slt (Wtkins Glen, NY). A finl concentrtion of 0.02% of the finished product ws chosen sed on previous studies (d Silv 1991; Shhidi et l. 1992; Lu nd King 2003; Ahn et l. 2004, 2007). Smple Mnufcture For ech repliction (n = 2), one mster tch (45 kg) of ground eef nd ground pork ws mnufctured seprtely to finl trget ft content of 30%. Fresh eef nd pork len nd trim were otined from the University of Illinois t Urn-Chmpign Met Science Lortory. Len nd trim were corse ground through 1.3-cm plte (4152 Series Met Grinder, Hort Corportion, Troy, OH), then reground through 0.32-cm plte (4346 Series

4 176 M.C. ROJAS nd M.S. BREWER Mixer/Grinder, Hort Corportion). Ech tch ws divided into five 9 kg portions to which nturl ntioxidnts were dded dispersed in slt (2% w/w sed on finished product weight) s crrier. The met mixtures were homogenized for 5 min in twin shft pddle mixer (Keeler Engineering Co., Chicgo, IL). Ech tch ws stuffed (Hndtmnn Vcuum Filler, VF 80, FoodMc, Int., Ltd., Lncshire, U.K.) into 5 50-cm firous csings nd lst frozen t -29C. After peeling, cm ptties were cut on nd sw (Model 5801, Hort Corportion), vcuum pckged (Multivc C500, Knss City, MO) in cm (3 mil) vcuum gs (Bush Brothers, Urn, IL), seven ptties per g, nd held t -18C for up to 4 months. On ech evlution dy, the smples were prepred for sensory, thiorituric cid rective sustnces (TBARS), color nd ph nlyses. Sensory Anlyses The 10-memer descriptive pnel, recruited from the University of Illinois t Urn-Chmpign grdute students nd stff, were experienced in met product evlution y virtue of hving prticipted in t lest three sensory evlution studies on met products over the pst yer. The pnelists were trined during four 2-h sessions to evlute the odor nd visul color of the ptties. During trining, the pnel leder fcilitted the discussions of the product chrcteristics. Using rw ptties, frozen for vrious time periods, descriptive odor terms were selected y group consensus (Tle 1). A 15-cm semistructured line scle (0 = none, 15 = extreme) ws used to chrcterize the odors using n nchor vlue for ech respective stndrd. For visul color evlution, 15-cm semistructured line scle ws used to score the intensity of rown, green-rown nd green color of the smples. Color stndrds were developed using pint chips comprle to the colors of eef or pork evluted during trining (Tle 2). The pnelists prcticed on eef nd pork ptties y TABLE 1. DESCRIPTIVE ODOR TERMS AND STANDARDS Descriptive odor term Stndrd Loction on the 15-cm line Rw met Fresh ground met* + 2% NCl 10 Grssy Hexnl (0.5 ppm) 10 Herl Orignox WS (400 ppm) 9 Acid Pririe Frms Sour Crem 8 Swety Science Diet Ct food (0.25% w/v) 13 * Beef nd pork ptties prepred efore the pnel s descried previously. Hexnl (Sigm, Sigm-Aldrich, St. Louis, MO). Science Diet Ct food (Hill s Pet Nutrition, Inc., Topek, KS).

5 ANTIOXIDANT EFFECTS ON BEEF AND PORK 177 TABLE 2. VISUAL COLOR STANDARDS FOR BEEF AND PORK PATTIES Pint chip Loction on the 15-cm line Instrumentl color mesurement L* * * Hue ngle Sturtion index Beef Red S-G-140 D Cherry Coler* Lte Tomto River Rouge Brown Buckeye F-7 D Brown Thrush* F-5 P Artifct* Green 280F-7 D Brekfst Blend* Molsses EB Rffi EB Pork Pink Duchess Rose Corl Rose Itlin Dusk Brown Stone Rose Velveteen Crush Kngroo Pw Crem Ivory Smpler 30YY 58/ Perl White 44YY 70/ Cshmere White J2** * BEHR Premium Plus (Snt An, CA). Color Plce (Wl-Mrt, Bentonville, AR). Signture Colors (Snt An, CA). PPG (Wl-Mrt, Bentonville, AR). Glidden (Huron, OH). ** Kilz (Wl-Mrt, Bentonville, AR). individully scoring the smples for intensities of ech ttriute using the respective scles, then compring their scores. Two sensory evlution sessions were conducted per dy. Five smples of the sme species (one smple of ech ntioxidnt tretment), leled with three-digit rndom numers, were evluted during ech session. The second session, replictes of the first session, ws conducted 30 min fter the first. The smples were prepred nd presented to the pnelists s descried y the Americn Met Science Assocition (AMSA) (1995). The ptties were

6 178 M.C. ROJAS nd M.S. BREWER thwed overnight t 4C. For the odor evlution, rw ptties were uniformly cut into four pie-shped wedges. The smples were plced in 5-cm lidded plstic cups nd held t 4C for 30 min prior to presenttion. The cups were plced on white pper pltes. References were prepred dily. Rosted coffee ens were presented for the pnelists to cler the plte etween smples. Visul color evlutions were conducted on rw smples fter the odor nlyses under wrm white fluorescent light (~1200 lux) ginst white ckground. TBARS TBARS were determined using the extrction method descried y Miller (1998) sed on tht developed y Witte et l. (1970). Met smple (5 g) ws extrcted with BHT (0.2 mg/ml) nd 45.5 ml nd 10% trichlorocetic cid in 0.02 M phosphoric cid (TCA/H 3 PO 4 ), then filtered (Whtmn No. 1). A stndrd curve ws prepred y spiking smples with 1,1,3,3- tetrethoxypropne (TEP). The smples were held in the drk for 20 h t room temperture. Asornce ws determined spectrophotometriclly (Beckmn Coulter DU 640, Inc., Fullerton, CA) t 530 nm. The sornce of lnks ws sutrcted from those of the test smples. A stndrd curve ws prepred using TEP (0 10 nm mlondildehyde [MDA]/mL). The concentrtion of MDA ws clculted using the stndrd curve (y = x 0.004; R 2 = ). TBARS re expressed s milligrm MDA per kilogrm smple. Regent grde chemicls were purchsed from Fisher Scientific (Pittsurgh, PA); phosphoric cid nd TCA were from Sigm-Aldrich (St. Louis, MO). Instrumentl Color Instrumentl color ws determined t three different loctions on the smple surfce, using HunterL spectrocolorimeter (LScn II, Hunter Assocites Lortory Inc., Reston, VA), clirted to white nd lck stndrds. The spectrl curve ws determined over the 400- to 700-nm rnge, nd CIE L*, * nd * vlues were clculted using Illuminnt A nd the 2 stndrd oserver. Chrom [(* 2 + * 2 ) 1/2 ] nd hue ngle [rctn (*/*)] were lso clculted (CIE 1978). The ph ws determined using stndrdized MPI ph meter (Met Proes Inc., Topek, KS). Sttisticl Anlyses This experiment ws designed s rndomized complete lock with five ntioxidnt tretments nd five storge times. Two complete replictions were conducted. All nlyses were conducted in duplicte on ech replicte tch (n = 2).

7 ANTIOXIDANT EFFECTS ON BEEF AND PORK 179 Dt were nlyzed s five (tretment) y five (storge times) fctoril design using the PROC MIXED procedure (SAS 2002). TBARS, instrumentl color nd ph min effects nd interctions were treted s fixed effects nd considered significnt t P < For the sensory dt nlyses, the pnelists were considered repeted mesures. The seprtion of lest squre mens ws chieved using proility of difference, djusted with the Bonferroni procedure for multiple comprisons. TBARS vlues were compred with the controls (percent reduction) sed on the TBARS vlue of the smple on dy 0. RESULTS AND DISCUSSION Effect of Nturl Antioxidnts nd Storge Time on TBARS of Beef nd Pork In eef ptties, no significnt (P < 0.05) interction occurred etween the ntioxidnt nd storge time for TBARS. TBARS, regrdless of the ntioxidnt used, decresed from out mg MDA/kg smple during the first month of storge, then remined similr during the reminder of the storge time (dt not shown) indicting tht storge time hd little effect. The TBARS vlues of rw eef ptties pooled over storge re shown in Fig. 1. The TBARS of the ptties contining GS 0.02% nd WS were lower (P < 0.05) thn the controls. Both tretments reduced the TBARS y out 12% compred with the control. The ntioxidnt ctivity of GS is ecuse primrily of phenolic compounds, especilly polyphenols, such s pronthocynidins. In ground eef ptties, WS hd similr ntioxidnt ctivity to tht of GS 0.02%, lthough the totl phenolic content of oregno ws lower thn tht of the GS. The WS contined t lest 22% totl phenolics, including 5 10% rosmrinic cid nd other hydroxycinnmic compounds (Orignox, RAD Interntionl Ltd, Kiryt-Ono, Isrel). Generlly, higher concentrtions of polyphenols result in higher ntioxidtive effects. As with eef, no significnt (P < 0.05) interction occurred etween the ntioxidnt nd storge time for TBARS of pork ptties. When dt were pooled over storge time, the TBARS were ffected y the ntioxidnt (Fig. 1). In pork, OR nd GS t oth concentrtions (0.01 nd 0.02%) resulted in lower (P < 0.05) TBARS vlues thn the control. GS t higher concentrtion resulted in the gretest reduction (24.7%); GS t lower concentrtion nd OR resulted in ~20% reduction in TBARS. WS resulted in n intermedite TBARS reduction. The OR results gree with those oserved y Chen et l. (1999) who found reduction in TBARS in irrdited rw pork ptties fter 3 dys of refrigerted storge (4C). Studies with GS nd WS hve een conducted in met systems under vrying conditions. Lu nd King (2003) showed tht type of GS contining

8 180 M.C. ROJAS nd M.S. BREWER TBARS C GS 0.01% GS 0.02% OR 0.02% WS 0.02% TBARS C GS 0.01% GS 0.02% OR 0.02% WS 0.02% FIG. 1. EFFECT OF ANTIOXIDANTS ON THE THIOBARBITURIC ACID REACTIVE SUBSTANCES (TBARS) OF FROZEN BEEF (TOP) AND PORK (BOTTOM) PATTIES Lest squre mens (LSM) of the TBARS (mg mlondildehyde/kg smple) pooled over storge (-18C) time. LSM with the sme superscript re not different (P < 0.05). Stndrd error of the men = C, control (no ntioxidnt); GS, grpe seed extrct; OR, oleoresin rosemry extrct; WS, wter-solule oregno extrct. 84% polyphenols reduced TBARS only when used t concentrtions >0.10% in unslted turkey ptties. Sánchez-Esclnte et l. (2003) reported similr results. The discrepncy in these results implies tht, in ddition to the qulity of the ntioxidnt, the conditions of the experiments influence the results.

9 ANTIOXIDANT EFFECTS ON BEEF AND PORK 181 Georgntelis et l. (2007) demonstrted tht OR reduced TBARS compred with the controls. Although they did evlute frozen, slted eef ptties, their smples were pckged in oxygen-permele polypropylene gs, while the smples in this experiment were vcuum pckged. In ddition, the differences in the type of rosemry extrct could ffect the results. The GS used in this study contined 89% pronthocynidins (Ymkoshi et l. 2002). The ntioxidnt properties of phenolic compounds re well documented. They re direct scvengers of rective oxygen species nd hve the ility to chelte metls, such s iron, with their o-diphenol groups. Dixon et l. (2005) reported tht pronthocynidins re potent free rdicl scvengers, which reduce free rdicl concentrtion nd lock their propgtion. However, the ntioxidtive ctivity of plnt extrcts is not simply correlted to the totl phenolic components determined in n extrct. Škerget et l. (2005) suggested tht other fctors must e tken into ccount including the method y which the phenols re mesured. The phenolic content in plnt extrcts re usully determined y hydrolysis; therefore, free glycones re ctully mesured. Flvonoid glycones re more potent in their ntiperoxidtive ctivity thn their corresponding glycosides In ddition to the totl phenolics in the extrct, the rtio of free to esterified phenolics/glycosides is importnt. Effect of Nturl Antioxidnts nd Storge Time on Odor of Beef nd Pork No significnt (P < 0.05) interction occurred etween ntioxidnt nd storge time for odor. Fresh ground eef odor decresed (26%) over the storge period (Fig. 2). No significnt differences (P < 0.05) occurred in the intensities of the off-odor chrcteristics ecuse of the ntioxidnt. In generl, off-odors were lower thn the nchor vlues (fresh ground eef = 7.4, grssy = 2.4, cid = 2.9, swety = 4.1 nd her = 1.2) nd decresed during frozen storge, except for cid odor, which remined similr (Fig. 2). The differences in the oxidtion, expressed in TBARS vlues, mong the ntioxidnt tretments were so low (Fig. 1) in eef, tht the pnelists were unle to detect differences. The pnel rted off-odors of ground pork ptties slightly lower thn the nchor vlues (fresh ground pork = 7.4, grssy = 2.9, cid = 2.9, swety = 4.0 nd herl = 1.4) nd ssigned vlue 26% lower vlue to the desirle fresh rw met odor of fresh pork (Fig. 2). Effect of Nturl Antioxidnts nd Storge Time on Color of Beef nd Pork Except for the * vlues, the instrumentl color prmeters of eef ptties chnged (P < 0.05) over storge time (Fig. 3). The * vlues decresed (out 18%) from 13 to 14 to 11.5 (4 months). The L* vlues incresed (7.8%) from

10 182 M.C. ROJAS nd M.S. BREWER 10 8 Sensory Score c c c c c c Storge Time (months) Grssy Acid Swety Her Fresh ground eef 10 8 Sensory Score Storge Time (months) Grssy Acid Swety Her Fresh ground pork FIG. 2. EFFECT OF STORAGE TIME ON THE ODOR OF FROZEN BEEF (TOP) AND PORK (BOTTOM) PATTIES Lest squre mens (LSM) of the sensory score pooled over tretment. c LSM with the sme superscript re not different (P < 0.05).

11 ANTIOXIDANT EFFECTS ON BEEF AND PORK L* vlue - Hue ngle vlue c c *vlue - * vlue - St. Index Storge Time (months) L* vlue Hue ngle *vlue *vlue Sturtion index 0 FIG. 3. EFFECT OF STORAGE TIME ON THE INSTRUMENTAL COLOR VALUES OF FROZEN BEEF PATTIES Lest squre mens (LSM) of the sensory score pooled over tretment. c LSM with the sme superscript re not different (P < 0.05). 36 (initilly) to 38.8 (2 months), then remined similr through the end of the study (4 months). Hue ngles were similr, except for slight increse fter 2 months (out 6%, from 66 to 70). The sturtion index decresed (out 13%) from 15 to 12.6 (4 months). These sme trends in * nd L* vlues, hue ngle nd sturtion index were reported y Georgntelis et l. (2007). They did, however, oserve reduction in the * vlue throughout the frozen storge time, regrdless of the tretment used, while in the present study, the * vlues remined similr over time. In ddition to differences in met qulity, the dissimilrities in the len-to-ft rtio nd pckging systems could explin these differences. The ptties used y Georgntelis et l. (2007) contined more len (85%) thn tht used in this experiment (70%). Therefore, the former hd more myogloin, which supports the modertely higher initil * vlues (18 22) thn those in this study (5 6). Georgntelis et l. (2007) pck-

12 184 M.C. ROJAS nd M.S. BREWER 8 6 Sensory Score Storge Time (months) Red Brown Green FIG. 4. EFFECT OF STORAGE TIME ON THE VISUAL COLOR OF FROZEN BEEF PATTIES Lest squre mens (LSM) of the sensory score pooled over tretment. c LSM with the sme superscript re not different (P < 0.05). ged the smples in ir-permele polypropylene gs; therefore, the myogloin ws exposed to oxygen, which fvors the formtion of oxymyogloin, rther thn deoxymyogloin, with the consequent increse of red color. No significnt (P < 0.05) interction occurred etween the ntioxidnt nd storge time for the visul color of frozen eef ptties. No differences occurred in the visul color mong the ntioxidnt tretments nd the control (dt not shown); however, visul colors decresed during frozen (-18C) storge, with red color eing the most ffected (Fig. 4). Instrumentl color mesures of the ntioxidnt-treted, frozen rw pork ptties were similr to the control; however, they chnged over storge time. In generl, the mjor chnges occurred during the first 2 months of storge (Fig. 3). The * nd * vlues, nd sturtion index decresed during the first month y 37, 12.2 nd 15.8%, respectively. However, the L* vlue nd hue ngle incresed with the mximum vlues (lightest nd lest true red) oserved fter 2 months of storge (6.8 nd 12.2%, respectively). These chnges indicte loss of red color purity nd intensity. Pork ptties did discolor over storge time, regrdless of the ntioxidnt tretment pplied. Visul pink, crem nd rown colors decresed from out

13 ANTIOXIDANT EFFECTS ON BEEF AND PORK to out 4 (on 15-point scle) over the 4 months, which supports the instrumentl color dt (dt not shown). Bsed on these results, ll of the nturl ntioxidnts, even GS which hs nturl red color, could e used in either eef or pork ptties without ffecting the initil color. CONCLUSIONS Lipid oxidtion of high-ft ground met products compromises qulity. Using TBARS vlues nd sensory odor s indictors of oxidtion, GS, WS nd OR differed little in their ntioxidnt ctivity in frozen rw eef nd pork. This my e ecuse miniml oxidtion occurred. The product hd not een precooked so little, if ny, lipid oxidtion should hve een initited, nd the product ws vcuum pckged, which excluded oxygen, limiting the progress of ny oxidtive rncidity tht my hve een initited. It my e tht the concentrtions of polyphenolics in these products vried sustntilly from those used in other studies. In ddition, the dominnt odor present ws tht of fresh eef or pork rther thn those indictive of lipid oxidtion. Becuse of the initil color of the GS, the ltertion of product color s result of GS ddition ws concern. GS did not lter the initil color of either eef or pork rw ptties. GS, OS nd WS my hve some potentil s ntioxidnts in frozen rw products. Future work might include evlution comintions of nturl ntioxidnts, inclusion of dditionl nturl nd synthetic ntioxidnts, nd/or incresed concentrtions of those evluted here. REFERENCES AHN, J., GRÜN, I.U. nd FERNANDO, L.N Antioxidnt properties of nturl plnt extrcts contining polyphenolic compounds in cooked ground eef. J. Food Sci. 67(4), AHN, J., GRÜN, I.U. nd MUSTAPHA, A Antimicroil nd ntioxidnt ctivities of nturl extrcts in vitro nd in ground eef. J. Food Prot. 67(1), AHN, J., GRÜN, I.U. nd MUSTAPHA, A Effects of plnt extrcts on microil growth, color chnge, nd lipid oxidtion in cooked eef. Food Microiol. 24, ALLEN, J.C. nd HAMILTON, R.J Rncidity in Foods, pp , Blckie Acdemic nd Professionl, Glsgow, U.K. AMERICAN MEAT SCIENCE ASSOCIATION (AMSA) Reserch guidelines for cookery, sensory evlution nd instrumentl tenderness

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