Meat Science 74 (2006)

Transcription

1 Met Science 74 (26) MEAT SCIENCE Effects of pre-rigor injection of sodium citrte or cette, or post-rigor injection of phosphte plus slt on post-mortem glycolysis, ph, nd pork qulity ttriutes q J.W. Stephens, M.E. Dikemn, *, J.A. Unruh, M.D. Hu, M.D. Tokch Deprtment of Animl Sciences nd Industry, 226 Weer Hll, Knss Stte University, Mnhttn, KS 6656, United Sttes Deprtment of Humn Nutrition, 127 Justin Hll, Knss Stte University, Mnhttn, KS 6656, United Sttes Received 13 Decemer 25; received in revised form 16 My 26; ccepted 16 My 26 Astrct Forty pork crcss sis were ssigned to one of four tretments: pre-rigor citrte (CIT) or cette injection (ACE); post-rigor phosphte nd slt injection (PHOS); nd non-injected control (CON). Loins in 2 sis were injected t 5 min post-mortem with 4% solutions of CIT or ACE to pproximtely 11% of projected loin weights, nd 1 loins were injected t 24 h post-mortem to 16.6% with solution of 4.4% PHOS nd 2.2% slt. Although CIT incresed ph (P <.5), neither CIT nor ACE ltered (P >.5) glycolytic metolite concentrtions. The ph increse in muscles from the CIT tretment ws most likely due to its uffering ility rther thn to its glycolytic inhiition. Pre-rigor CIT injection improved tenrness without the trimentl effects on color or flvor found with PHOS, ut neither CIT nor ACE ltered glycolytic metolites or improved firmness, wetness, or fresh visul color over CON. Poor flvor ttriutes of the ACE tretment will hinr its use s n ingredient for pork enhncement solutions. Ó 26 Pulished y Elsevier Ltd. Keywords: Pork; Pre-rigor injection; ; ; 1. Introduction Improving pork qulity trits, such s tenrness, juiciness, nd flvor, is common gol in the pork industry. Gret stris hve een m to improve hndling conditions nd to lter genetics to remove stress susceptiility, ut pork qulity fects cost the industry n verge of $2.13 per crcss (Stetzer & McKeith, 23). It is now common prctice to enhnce pork with solutions of phosphte, slt, nd vrious other ingredients. Although these solutions improve tenrness nd juiciness (Smith, Simmons, McKeith, Bechtel, & Brdy, 1984), they concomitntly induce some negtive consequences in flvor nd q Contriution No J from the Knss Agriculturl Experiment Sttion, Mnhttn, Knss, USA. * Corresponding uthor. Tel.: ; fx: E-mil ddress: mdikemn@ksu.edu (M.E. Dikemn). consumer cceptility (Brewer, Jensen, Prestt, & Zhu, 22). Pork qulity is highly pennt on the reltionship of ph nd temperture erly post-mortem (Syre & Briskey, 1963). Aneroic glycolysis is responsile for ph cline in post-mortem muscle. The lck of oxygen nd sence of circultory system from exsnguintion leds to post-mortem myocellulr ccumultion of lctte nd hydrogen ions. If glycolysis occurs t n ccelerted rte, ph clines too rpidly, nd muscle proteins nture due to the comintion of low ph nd high temperture. is recognized for its glycolysis-inhiiting properties y inhiiting the glycolytic enzyme, phosphofructokinse (PFK; Newsholme, Sugn, & Willims, 1977). This enzyme regultes the trnsfer of phosphte from nosine triphosphte (ATP) to fructose-6 phosphte (F6P), producing nosine diphosphte (ADP) nd fructose-1,6 isphosphte (F16BP). Phosphofructokinse hs een /$ - see front mtter Ó 26 Pulished y Elsevier Ltd. doi:1.116/j.metsci

2 728 J.W. Stephens et l. / Met Science 74 (26) intified s key regultory enzyme of glycolysis in postmortem muscle (Dlrymple & Hmm, 1975; Rhos et l., 25). inhiits PFK directly, ecuse it inds to the enzyme nd reduces its ffinity for its sustrte, F6P, nd its ctivtor, ADP (Kemp & Kres, 1967). inding lso increses the enzyme s ffinity for ATP, its second inhiitor (Kemp & Kres, 1967). The net product of the glycolysis rection is ATP; therefore, excess ATP in the cell indictes surplus of energy. Consequently, ATP inhiits PFK nd slows the glycolysis rection, in ddition to cting s the enzyme s source for phosphte. is converted to citrte in the ody y citrte synthse, resulting in similr effects (Fushimi et l., 21). Killefer (24) injected pork loins t 1 h post-mortem with solution of citrte, phosphte, nd slt. He reported incresed ultimte ph vlues, improved color, less cook loss, nd cresed sher force vlues compred with controls injected with phosphte nd slt. Sodium citrte hs een used s glycolytic inhiitor in eef muscle to improve tenrness (Streitel, Ockermn, & Chill, 1977; Perversi, Clkins, & Velzco, 23). They hypothesized tht the increse in ph due to glycolytic inhiition creted n environment in which the protein-nturing clpins would e more ctive. Perversi et l. (23) stted tht citrte ddition to eef muscle ws not trimentl to flvor ttriutes. injection ws originlly veloped to help lower the sodium content of processed mets, such s hm, ut hs een incorported into fresh mets to improve tenrness nd juiciness (Smith et l., 1984). enhncement is now commonly used in the pork industry to increse ph nd improve pork qulity ttriutes. Although phosphte injection my increse slty flvor nd crese disply life (Roins et l., 22), the routine use of this technology in industry mkes it impertive to inclu phosphte-injected tretment to compre to new technologies for improving pork qulity. The ojective of our study ws to termine the effectiveness of pre-rigor injection of pork crcsses with sodium citrte or cette, or post-rigor injection of phosphte plus slt on post-mortem glycolysis, ph cline, nd pork qulity ttriutes, including disply life nd sensory-pnel scores. 2. Mterils nd methods 2.1. Pigs nd tretments Two replictes of 1 pigs (n = 2) were fed finishing diets contining rctopmine for t lest 14 d efore hrvest. Pigs were weighed nd ssigned to pirs of similr weights. The four sis from ech pir of pigs were ssigned to one of four tretments s follows: pre-rigor citrte injection (CIT), pre-rigor cette injection (ACE), post-rigor phosphte plus slt injection (PHOS), nd non-injected control (CON) Hrvest Twenty hours efore hrvest, pigs were fsted nd trnsported to the Knss Stte University Mets Lortory. Pirs of pigs were hrvested in rndom orr. Pigs were stunned y using oth n electric stunning wnd nd cptive olt stunner. After stunning, pigs were exsnguinted nd hrvested ccording to norml procedures; the procedure ws pproved y the Institutionl Animl Cre nd Use Committee. After the crcsses were split nd wshed, ech si ws weighed Pre-rigor injection At pproximtely 5 min post-mortem, loins from sis ssigned to CIT nd ACE tretments were injected with 4% solution of sodium citrte or sodium cette in distilled wter. A hnd-held injector fitted with five 1-cm injection needles ws used to inject the solutions. Before injection, the skin ws sliced perpendiculr to the length of the loin t pproximtely 3-cm increments to llow the injection needles to penetrte the skin nd into the longissimus muscle. The loins were injected from point in the muscle opposite the lst lumr vertere to point immeditely posterior to the scpul. The solutions were injected t room temperture, nd injection-solution temperture ws record for ech si to ensure uniformity. Sis were weighed gin, nd pump percentge ws clculted. It ws ssumed tht the loin ws 2% of the totl si weight, nd tht only the loin sored the solution. The pproximted injection percentge of the loins injected pre-rigor ws clculted to e 1%. To monitor temperture cline, temperture logger (Hoo Ò XT, Onset Computer Corportion) ws plced in the longissimus muscle of ech si. A slice ws m t the sirloin-loin juncture, nd the temperture proe ws inserted into the muscle t lest 7 cm, t 45 ngle to the skin surfce. After injection (pproximtely 5 min post-mortem), muscle smple ws removed from the nterior portion of the injected longissimus muscle from oth sis of the crcsses. The muscle smples were cued, quick-frozen in liquid nitrogen, pckged, temporrily stored on dry ice, nd stored t 8 C for ph nd glycolytic-metolite nlysis. Additionl muscle smples were removed from the longissimus muscle of ech si t 3, 6, 12, nd 24 h post-mortem nd were frozen in liquid nitrogen s scried previously. At lest 3 cm of muscle ws mintined etween muscle smple loctions, to minimize the effects of chilling rte on the cut surfces Pre-24 h ph nlysis Frozen muscle smples were pulverized into powr with Wring Blenr nd stored t 8 C until nlysis for ph nd glycolytic metolites. Duplicte 5-g smples of powred muscle were mixed with 5 ml of solution of iodocette in 15 mm potssium chlori (Bendll,

3 J.W. Stephens et l. / Met Science 74 (26) ). The mixture ws covered with Prfilm nd llowed to cclimte to room temperture for no less thn 4 h. Then, the solution ws remixed, nd ech duplicte ws red twice y using two Accumet glss electro ph proes with portle meter (mol AP61; Fisher Scientific; Firlwn, NJ). The four redings were verged for sttisticl nlysis Glycolytic metolites Smples from 5 min, 3, nd 12 h were nlyzed for glucose-6 phosphte (G6P), fructose-6 phosphte (F6P), fructose-1,6 isphosphte (F16BP), comintion of glycerlhy-3 phosphte nd dihydroxycetone phosphte (GAPDAP), nd lctte ccording to the methods of Bergmeyer (1974) nd S. B. Smith (25, personl communiction). Approximtely 1 g of frozen, pulverized muscle tissue ws proteinted with perchloric cid prepred for glycolytic metolite nlysis s scried y Bergmeyer (1974), nd stored t 1 C for no more thn 4 weeks until nlysis. Determintion of G6P nd F6P ws crried out ccording to procedures scried y Bergmeyer (1974), with minor modifiction (Rhos et l., 25). Determintion of F16BP nd GAPDAP ws completed ccording to Bergmeyer (1974). Concentrtions of DAP re generlly quite low in muscle (Bergmeyer, 1974; S. B. Smith, personl communiction), so GAP nd DAP were mesured in concert. Lctte concentrtion ws termined ccording to the procedure of S. B. Smith (25, personl communiction). Buffer ws prepred with 3.8 g glycine, 4. ml 85% hydrzine hydrte, 76 mg EDTA, 8 ml 1 N sodium hydroxi, nd distilled, onized wter to mke out 9 ml of solution. The ph ws djusted to 9.4 with sodium hydroxi, nd the finl volume ws rought to 1 ml with wter. Cuvettes were prepred with 1.95 ml uffer, 2 mg NAD in.2 ml wter,.9 ml wter, nd.5 ml smple extrct. Asornce ws red t 34 nm, lctic hydrogense (1.55 U/cuvette) ws dd, nd the rection occurred for 9 min. A second sornce reding ws m to termine lctte concentrtions. Asornce incresed with incresing NADH production, nd one NADH ws produced for ech lctte molecule present Friction nd post-rigor injection At 24 h post-mortem, sis were fricted into loins (IMPS 41), nd the nterior section, from which the muscle smples were removed, ws discrd. Loins ssigned to CIT, ACE, nd CON tretments were vcuum pckged nd stored t 1 C. Loins ssigned to post-rigor PHOS tretment were injected with solution contining 4.4% sodium tripolyphosphte (Pryon, Inc.) nd 2.2% sodium chlori with the hnd-held injector used for the CIT nd ACE tretments. After two rounds of PHOS injection, the loins hd sored 6.6% of their pre-injected weight, nd were not injected gin to keep the tretments s uniform s possile. After injection, the loins ssigned to PHOS were vcuum pckged nd stored overnight t 1 C. The loins were re-weighed fter vcuum storge nd retined 14.6% of their pre-injected weight Chop removl, initil pork color, firmness, nd wetness At 2 d post-mortem, loin sections were -oned, nd three 2.54-cm chops were removed from the posterior section of the longissimus. One chop, for nlysis y trined sensory pnel, ws vcuum pckged nd stored t 1 C for 8 d efore freezing t 2 C. An dditionl chop ws vcuum pckged nd stored t 1 C overnight for ph nd expressile-moisture nlysis. The third chop ws llowed to loom for no less thn 3 min nd ws evluted y three-memer, trined visul pnel for color, firmness, nd wetness. Color ws evluted y using the officil NPPC color stndrd crds (1 = lightest nd 6 = drkest; NPPC, 1999). Firmness nd wetness were evluted seprtely y using three-point scles (1 = softest or wettest nd 3 = firmest or driest) Disply color Chops for visul evlution were pckged in white fom trys with sorent pds, over-wrpped with PVC film (MAP-PAC M 23,25 cc O 2 /m 2 /24 h guge), nd plced in n open-top disply cse unr continuous fluorescent lighting (1614 lux, 3 K). A trined visul pnel of no less thn six persons evluted color ech dy for 7 d of disply. Pnelists scored ech chop for color on six-point scle (1 = extremely right pink, 2 = right pink, 3 = dull pink, 4 = slightly drk pink or tn, 4.5 = orrline uncceptle, 5 = mortely drk pink or tn, 6 = drk pink or tn) nd discolortion on seven-point scle (1 = no discolortion (%), 2 = slight discolortion (1 19%), 3 = smll discolortion (2 39%), 4 = most discolortion (4 59%), 5 = morte discolortion (6 79%), 6 = extensive discolortion (8 99%), 7 = totl discolortion (1%)). The pnelists scores for ech dy were verged for nlysis Disply loss After disply, pckges were weighed nd chops were removed, ded with pper towel, llowed to dry for 5 min, nd weighed gin to clculte disply loss, clculted s follows: ((pre-disply weight post-disply weight)/pre-disply weight) Instrumentl color Ech dy of disply, HunterL Miniscn XE Plus spectrophotometer (Mol D/8-S, 1.4 cm perture, Hunter Assocites Lortory) ws used to otin L *, *, nd * vlues on the PVC over-wrpped chops. Ech chop ws mesured twice y using 3.2-cm perture, 1 oserver, nd illuminnt D 65. Redings were verged for nlysis.

4 73 J.W. Stephens et l. / Met Science 74 (26) Expressile moisture At 3 d post-mortem, chops ssigned to expressile-moisture evlution were removed from their vcuum gs. Expressile moisture ws termined using the methods of Dhnd, Pegg, Jnz, Alhus, nd Shnd (22). Duplicte smples (2 3 g) were removed from the interior of the chop, prllel to the muscle fier direction, with sclpel nd tweezers. The reminr of the chop ws vcuum pckged nd stored t 1 C until ph nlysis. Smples were weighed nd plced in 5-ml centrifuge tue fitted with one piece of Whtmn No. 3 filter pper fold round one piece of Whtmn No. 5 filter pper. The tues were cpped nd centrifuged t 21 rpm for 1 min t 75g. After centrifugtion, smples were weighed gin, nd expressile moisture ws clculted s: ((pre-centrifuge weight post-centrifuge weight)/pre-centrifuge weight) Ultimte ph nlysis Duplicte smples (1 g ech) were minced with sclpel. Smples were plced in filtered stomcher g with 1 ml of distilled wter nd were stomched for 2 min. After smples were stomched, ph ws mesured with portle Accumet proe nd meter (mol AP61; Fisher Scientific). Dt from duplicte smples were verged for nlysis Sensory pnel evlutions Chops for nlysis y the trined sensory pnel were stored frozen for 3 months nd thwed overnight t 4 C. Chops were cooked to 7 C in Blodgett dul-ir flow convection oven (mol DFG-21, G.S. Blodgett Co., Inc.), nd temperture ws monitored with 3-guge, type-t thermocouples inserted into the geometric centers of the chops nd ttched to Doric temperture recorr (mol 25, Vs Engineering). After cooking, the outer connective tissue ws removed, nd the chops were cut into cues (1.27 cm 1.27 cm chop thickness) nd held in preheted doule roilers. No fewer thn 6 trined pnelists were seted in n environmentlly controlled room, t pproximtely 21 C nd 55% reltive humidity, in individul ooths unr djustle red-plus-green lighting tht ws less thn 11 lumen comined. Ech pnelist ws given two wrm-up smples from non-injected chop to orient themselves efore ech pnel. A pnel ler discussed the wrm-up smples with the pnelists. Then, two cues from ech chop were served to pnelists in sttisticlly rndomized orr, nd score ws termined y using n eight-point scle to the nerest.5 (AMSA, 1995) Sttisticl nlysis Muscle temperture dt were nlyzed s n incomplete lock with the repeted mesure of time, with individul pig s the lock. Pre-rigor ph nd glycolytic-metolite dt were nlyzed in split-plot sign, with injection tretment s the whole plot nd time post-mortem s the su plot. Pig ws used s the lock in the whole plot. Visul color, firmness, wetness, expressile moisture, nd ultimte ph were nlyzed in n incomplete lock, with pig s the lock. Visul- nd instrumentl-disply dt were nlyzed in n incomplete-lock sign, with the repeted mesure of time, nd pig s the lock. Dt from the trined sensory pnel were nlyzed in n incomplete-lock sign, locking on pig nd pnelist. Injection tretment nd time post-mortem were treted s fixed effects, while pig nd pnelist were treted s rndom effects. Dt were nlyzed with PROC MIXED in the Sttisticl Anlysis System (Version 8., SAS Institute), nd lest squres mens were seprted y using the PDIFF test when P <.5. For repeted-mesures nlysis, the repeted-mesures commnd ws used with the utoregressive option. 3. Results nd discussion 3.1. Temperture All tretments followed n exponentil cline in temperture to 1 C. At 1 h post-mortem, longissimus muscles from CON nd PHOS tretments, which received no pre-rigor injections, were wrmer (P <.5) thn those from CIT nd ACE tretments, nd those from the ACE tretment were wrmer (P <.5) thn those from the CIT tretment. Nevertheless, muscle tempertures mong tretments were similr (P >.5) for mesurements tken in 1-h increments fterwrds. It is prole tht the temperture of the injection solution (pproximtely 17 C) lowered the temperture of the muscle in the first few minutes fter injection, ut did not ffect chill rte fter 1 h Pre-24 h ph There ws no time tretment interction (P >.5) for pre-24 h ph (Tle 1). Longissimus muscles from the CIT tretment hd the highest (P <.5) pre-24 h ph vlues, wheres those from the ACE tretment did not differ (P >.5) from CON nd PHOS tretments. Jerez, Clkins, nd Velzco (23) reported incresed ph vlues t 24- nd 72-h post mortem for eef muscles injected with CIT nd ACE, ut they did not report pre-rigor ph. In our study, ph ws highest (P <.5) t 5 min post-mortem, nd vlues t 3, 6, 12, nd 24 h were similr (P >.5), indicting tht the mjority of ph cline occurred during the first 3 h Glycolytic metolites A time injection tretment interction (P <.5) ws found for G6P concentrtion (Fig. 1). All four tretments resulted in similr (P >.5) G6P concentrtions t 5 min post-mortem. However, vlues for G6P in CON muscles incresed (P <.5) with post-mortem time, nd were higher (P <.5) thn for the CIT nd ACE tretments

5 J.W. Stephens et l. / Met Science 74 (26) Tle 1 Men vlues for pre-24 h ph of longissimus muscle from crcsses injected 5 min post-mortem with sodium citrte or sodium cette, non-injected control crcsses, nd crcsses injected with phosphte + slt t 24 h post-mortem Time Pre-rigor injection Non-injected control Post-rigor phosphte + slt Men A 5 min h h h h Men Mens for times nd tretments lcking common superscript letters differ (P <.5). A Stndrd error for ll mens =.2. Glucose-6 phosphte (umol/g) cf f ef f S.E. g =.47 5 min d ef 12 h t 3 nd 12 h post-mortem. In muscles from the CIT tretment, G6P concentrtions were lowest (P <.5) t 3 h, ut did not increse (P >.5) from 5 min to 12 h. Concentrtions of G6P in longissimus muscles from the ACE tretment incresed (P <.5) with time, ut were lwys similr to the CIT-treted muscles. Muscles from the CON nd PHOS tretments hd higher concentrtions (P <.5) of F6P thn those from the ACE nd CIT tretments (Fig. 2). Concentrtions of F6P were similr (P >.5) t 5 min nd 3 h, ut were higher (P <.5) t 12 h. No interction existed for F6P vlues (P >.5). Glucose-6 phosphte is the precursor to F6P, which is sustrte for PFK. Successful inhiition of PFK y CIT nd ACE tretments should hve resulted in elevted concentrtions of G6P nd F6P. Nevertheless, our G6P nd F6P concentrtions were highest (P <.5) for CON nd PHOS tretments, indicting tht CIT nd ACE ctivted PFK ctivity rther thn inhiited it. Kemp nd Kres (1967) stted tht, in comintion with low concentrtions f 3 h Time post mortem d Fig. 1. Men concentrtions of glucose-6 phosphte in longissimus muscle t 5 min, 3 h, nd 12 h post mortem from crcsses injected pre-rigor with cette or citrte, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt. f Mens lcking common superscript letters differ (P <.5). g Lrgest interction men stndrd error. Fructose-6 phosphte (umol/g) min 3 h 12 h Time post mortem Fig. 2. Men concentrtions of fructose-6 phosphte in longissimus muscle t 5 min, 3 h, nd 12 h post mortem from crcsses injected pre-rigor with cette or citrte, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt. Min effect mens lcking common superscript letters differ (P <.5), stndrd error for nte-mortem tretment min effects =.6, stndrd error for time min effects =.5. of ATP, CIT my ct s n ctivtor of PFK. increses the enzyme s ffinity for ATP t the sustrte site nd ctivtes the rection. Rections of rigor tke plce due to drop in ATP concentrtion (Hmm, 1977). Therefore, pre-rigor CIT injection, in comintion with low ATP levels ssocited with rigor, my hve ctully ctivted PFK. Although previous reserchers hve not experienced this phenomenon in post-mortem eef muscle (Jerez et l., 23; Perversi et l., 23; Streitel et l., 1977), pork is inherently more glycolytic thn eef is nd goes into the rigor stte erlier post-mortem. It is possile tht the pproximtely 1% ddition of wter diluted G6P nd F6P concentrtions in the ACE nd CIT longissimus muscles, ut this dilution effect ws not evinced in other metolites. Concentrtions of F16BP cresed with time for ll four tretments (Fig. 3). A time tretment interction (P <.5) ws found for F16BP vlues. For CON, PHOS, nd ACE tretments, the 5-min concentrtions were higher (P <.5) thn t 3 nd 12 h. However, for the CIT tretment, concentrtions t 5-min nd 3-h were similr (P >.5), nd were greter thn tht t 12 h (P <.5), indicting tht the rte of cline in F16BP in the CIT-treted muscles my hve een slower thn the other tretments. There ws time tretment interction (P <.5) for GAPDAP concentrtions (Fig. 4). Both CIT nd ACE were similr (P >.5) to CON. All tretments were similr t 3 nd 12 h post-mortem. The 5-min concentrtions were highest (P <.5), nd the 3 nd 12 h concentrtions were similr (P >.5) for ll tretments. The product of PFK is F16BP, nd inhiition of PFK should hve resulted in cresed concentrtions of F16BP for CIT nd ACE tretments. Mintennce of high levels of F16BP t 3 h for CIT could indicte tht F16BP levels were eing replenished y PFK s they were used,

6 732 J.W. Stephens et l. / Met Science 74 (26) Fructose-1,6 isphosphte (nmol/g) S.E. f = 9. cd e 5 min 3 h 12 h Time post mortem e e Lctte (umol/g) min c 3 h 12 h Time post mortem (h) Fig. 3. Men concentrtions of fructose-1,6 isphosphte in longissimus muscle t 5 min, 3 h, nd 12 h post mortem from crcsses injected prerigor with cette or citrte, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt. e Mens lcking common superscript letters differ (P <.5). f Lrgest stndrd error for interction mens. Fig. 5. Men concentrtions of lctte in longissimus muscle t 5 min, 3 h, nd 12 h post mortem from crcsses injected pre-rigor with cette or citrte, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt. c Min effect mens lcking common superscript letters differ (P <.5); stndrd error for nte-mortem tretment min effect =.3; stndrd error for time min effect =.26. Glycerlhy-3 phosphte nd Dicylglycerol phosphte (nmole/g) S.E. f = min 12 h Time post mortem Fig. 4. Men concentrtions for comintion of glycerlhy-3 phosphte nd dihydroxycetone phosphte in longissimus muscle t 5 min, 3 h, nd 12 h post mortem from crcsses injected pre-rigor with cette or citrte, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt. e Mens lcking common superscript letters differ (P <.5). f Lrgest stndrd error for interction mens. cd 3 h e nd tht PFK ws ctivted rther thn inhiited. The F16BP concentrtions in muscles from CON, PHOS, nd ACE tretments were not eing replenished. Aldolse, the enzyme tht cleves F16BP to form GAP nd DAP, opertes continuously in the presence of its sustrte, F16BP (Voet, Voet, & Prtt, 22). Therefore, GAPDAP concentrtions indicte PFK ctivity. Our dt indicte tht GAPDAP concentrtions were not eing replenished y PFK for ny tretment. Muscles from the CIT tretment hd lower (P <.5) lctte concentrtions thn those signted for 24-h PHOS injection (Fig. 5), ut those from CON nd ACE tretments were not different (P >.5) in lctte concentrtion thn those from CIT or PHOS tretments. There ws no interction (P >.5) for lctte concentrtions. Lctte concentrtions incresed (P <.5) s post-mortem time incresed, which ws expected ecuse lctte ccumultes with time (Hmm, 1977). Cross-over digrms represent rtios of glycolytic metolite concentrtions t different times post-mortem: 3 h/5 min (Fig. 6), 12 h/3 h (Fig. 7), nd 12 h/5 min (Fig. 8). These cross-over digrms represent chnges in metolites over time. The vlues on the y-xis re rtios of metolite levels t two times post-mortem multiplied y 1. The glycolytic metolites of G6P, F6P, F16BP, GAPDAP, nd lctte indicte rte-limiting enzymes in pthwys, nd re presented from left to right on the x-xis in the orr in which they occur in glycolysis. Rtios greter thn 1 indicte tht the metolite is ccumulting over time, wheres vlues less thn 1 indicte tht the metolite is cresing over time. If the line etween two Rtio of 3 hto 5 min vlues x G6P F6P F16P GAPDAP LAC Metolite Fig. 6. Cross-over digrm for glycolytic metolites of pork longissimus from crcsses injected pre-rigor with citrte or cette, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt. Dt points re rtios of [(men t 3 h)/(men t 5 min)] 1. Mens for rtios within metolites were not different (P >.5). Lrgest stndrd error for G6P = 12., F6P = 13.2, F16BP = 34.2, GAP- DAP = 16.2, lctte = 1.3.

7 J.W. Stephens et l. / Met Science 74 (26) h/3h x G6P F6P F16BP GAPDAP Lc Metolite Fig. 7. Cross-over digrm for glycolytic metolites of pork longissimus from crcsses injected pre-rigor with citrte or cette, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt. Dt points re rtios of [(men t 12 h)/(men t 3 h)] 1. Mens for rtios within metolites were not different (P >.5). Lrgest stndrd error for G6P = 42.3, F6P = 28.1, F16BP = 35.4, GAPDAP = 5., lctte = 6.3. Rtio of 12 h / 5 min vlues x c G6P d F6P F16BP GAPDAP Lc Metolite Fig. 8. Cross-over digrm for glycolytic metolites of pork longissimus from crcsses injected pre-rigor with citrte or cette, non-injected control crcsses, nd crcsses signted for injection post-rigor with phosphte + slt. Dt points re rtios of [(men t 12 h)/(men t 5 min)] 1. c Mens, within metolite, lcking common superscript letters differ (P<.5). d Lrgest stndrd error for G6P = 17.8, F6P = 2.2, F16BP = 4.9, GAPDAP = 8.1, lctte = metolites crosses over 1, then the enzyme etween them is rte-limiting. For 3 h/5 min (Fig. 6), rtios of PFK-sustrte compounds (G6P nd F6P) were greter thn 1 for smples from CON, PHOS, nd ACE tretments, wheres those from the CIT tretment were less thn 1. For the post- PFK compounds (F16BP nd GAPDAP), rtios were less thn 1 for CON, PHOS, nd ACE, ut rtios of F16BP for CIT were greter thn 1. This pttern of rtios indicted tht rte-limiting step existed for CON, PHOS, nd ACE tretments for the rection ctlyzing the chnge from F6P to F16BP, or PFK. But, the rte-limittion of PFK in the CIT tretment from 5 min to 3 h is questionle. For the CIT tretment, rtios of pre-pfk metolites were less thn 1, indicting tht these metolites did not ccumulte etween 5 min nd 3 h. If G6P nd F6P did not ccumulte, they were most likely eing used y PFK, so PFK ws not limiting glycolysis. The post-pfk metolite, F16BP, did not crese from 5 min to 3 h s ws expected, indicting tht the pool of F16BP ws eing replenished y n uninhiited-pfk enzyme. Rtios for lctte greter thn 1 indicte tht this compound ccumulted over time in ll tretments. Rtios of 12 h/3 h concentrtions of G6P nd F6P were greter thn 1 for ll tretments (Fig. 7), ut F16BP nd GAPDAP rtios were less thn 1 for CON, PHOS, nd CIT tretments, indicting tht PFK ws the rte-limiting fctor etween 3 nd 12 h. It is likely tht PFK hd ecome inctivted fter 3 h in the CIT-treted muscles. Muscles in the ACE tretment hd 12 h/3 h rtios greter thn 1 for the post-pfk compounds, indicting lck of rte limittion y PFK during this time period. From 3 h to 12 h, the pre-pfk metolites were incresing in ll tretments, nd the post-pfk metolites were cresing in the CON, CIT, nd PHOS-treted muscles. In the ACE-treted muscles, the F16BP nd GAPDAP concentrtions were not cresing during this time period, indicting tht the enzymes fter PFK in glycolysis hd lso ecome inctive. Lctte rtios were lso greter thn 1, ut were not s elevted s the 3 h/5 min rtios, indicting tht lctte levels did not increse s much etween 3 nd 12 h s they did etween 5 min nd 3 h. From 5 min to 12 h, ll four tretments exhiited pttern indictive of rte-limiting step t PFK (Fig. 8). Pre- PFK rtios were greter thn 1, nd post-pfk rtios were less thn 1. Lctte rtios indicted n ccumultion of tht compound. Glycolytic metolite dt nd cross-over digrms indicte tht CIT nd ACE were ineffective s glycolytic inhiitors when injected into pork muscle, even though muscles injected with CIT hd higher ph vlues. The CIT solution likely incresed muscle ph due to its uffering cpcity nd multiple negtive chrges on the citrte ion. Jerez et l. (23) found tht pre-rigor injection of eef muscles with CIT inhiited glycolysis, s evinced y incresed muscle ph nd glycogen levels. Glycogen levels were not mesured in our study. Allison, Btes, Booren, Johnson, nd Doumit (23) climed tht PFK ws inctivted within 2 min post-mortem nd, therefore, does not ffect pork qulity ttriutes. Nevertheless, Rhos et l. (25) nd Dlrymple nd Hmm (1975) stted tht PFK is the min rte-limiting enzyme in post-mortem muscle glycolysis. Cross-over digrms indicted tht PFK ws still ctive in the muscle fter 5 min post-mortem when the CIT nd ACE solutions were introduced into the muscle system, ecuse the glycolytic

8 734 J.W. Stephens et l. / Met Science 74 (26) metolites were still chnging fter 5 min post-mortem. Concentrtions of ATP my hve een t non-sturted stte erly post-mortem, nd PFK my hve een ctivted y CIT s discussed erlier. Killefer (24) lso found CIT to e inhiitory in pork, ut his injection solution includ phosphte nd slt, which would hve drsticlly ffected muscle ph. Enzyme ctivities re ltered t higher ph. Furthermore, the increse in ionic strength, due to the phosphte nd slt, my hve ffected the PFK ctivity in his study Pork qulity ttriutes Men vlues for visul color, firmness, nd wetness, s well s expressile moisture, ultimte ph, nd disply loss re presented in Tle 2. According to visul pnelists, chops from the ACE nd CIT tretments were less firm (P <.5) nd wetter (P <.5) thn those from CON nd PHOS. These inferiorities were not surprising insmuch s the CIT nd ACE tretments dd pproximtely 1% wter to the longissimus muscle. Chops from the PHOS tretment lso hd dd wter, ut the percentge ws lower thn for CIT nd ACE. The PHOS tretment lso gretly incresed (P <.5) muscle ph. Chops from the PHOS tretment hd the highest (P <.5) ultimte ph vlues, nd chops from the CIT tretment hd higher (P <.5) ultimte ph vlues thn those from CON or ACE tretments. Chops from the CIT nd ACE tretments hd greter (P <.5) disply losses thn those from PHOS nd CON tretments. Chops from the PHOS tretment hd the lest (P <.5) disply loss. Visul color nd expressile moisture were not ffected y injection tretment. Killefer (24) used CIT in conjunction with phosphte nd slt injection in pork nd found incresed ultimte ph compred to tht of controls injected with phosphte. He Tle 2 Visul evlutions, expressile moisture, ultimte ph, nd disply loss of longissimus chops from pork crcsses injected pre-rigor with sodium cette or sodium citrte, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt Item Pre-rigor injection Non-injected control Post-rigor phosphte + slt Color Firmness 1.95 y 2.14 y 2.36 z 2.49 z.15 Wetness 1.93 y 1.96 y 2.46 z 2.41 z.18 Expressile moisture Ultimte ph 5.51 x 5.63 y 5.48 x 5.99 z.3 Disply loss 9.36 z 9.71 z 7.45 y 4.73 x.58 xyz Mens, within row, lcking common superscript letters differ (P <.5). Color ws evluted on 6-point scle using officil color stndrds from the Ntionl Pork Producers Council (1 = lightest nd 6 = drkest). Firmness nd wetness were evluted seprtely on 3-point scles (1 = softest nd wettest nd 3 = firmest nd driest). c Stndrd error of the men. SE c lso reported incresed visul color, nd tenncy (P =.6) for incresed firmness in chops injected with CIT. Jerez et l. (23) reported incresed ph t 24 nd 72 h in eef muscles injected with CIT nd ACE Disply evlutions Visul color nd discolortion scores throughout disply re presented in Fig. 9. Visul color scores incresed (P <.5) throughout disply for ll four tretments, indicting teriortion of color during disply. Chops from the PHOS tretment hd the highest (drkest; P <.5) visul scores ech dy of disply compred with those of other tretments. Chops from the PHOS tretment were lso consired uncceptle (color scores greter thn 4.5) y the pnelists fter 5 d of disply, wheres no other tretment reched tht mrk. Chops from the ACE nd CIT tretments were similr (P >.5) to those from CON ech dy of disply. Chops from the PHOS tretment were more discolored (P <.5) thn those from other tretments throughout the disply period (Fig. 9). Discolortion scores of chops from the ACE tretment were similr (P >.5) to those from CON throughout disply. For the first 6 d of disply, chops from the CIT tretment were similr (P >.5) to those from CON, ut the Visul color score Discolortion score S.E. r =.11 gh op q q klm n nn no q jkl m n n d no no pq hij klm nlm mn eh lm mn no cd hij hij jkl c jk jkl kl gh hi ij f Dy of disply cd ghij ghij ijk ef ef Fig. 9. Visul color nd discolortion scores for longissimus chops from pre-rigor cette or citrte injection, non-injected control crcsses, nd crcsses injected post-rigor with phosphte nd slt, over 7 d of disply. q Mens lcking common superscript letters differ (P <.5). r Stndrd error of the interction mens. cd

9 J.W. Stephens et l. / Met Science 74 (26) discolortion scores were higher (P <.5) on the finl dy of disply for chops from the CIT tretment thn those from CON. Chops from PHOS loins were drkest (lowest L * ; P <.5) throughout disply (Fig. 1). Although chops from the ACE tretment were similr (P >.5) to those from CON for the first 2 d of disply, they were lighter (P <.5) thn those from CON for the lst 5 d of disply. Chops from the CIT tretment were similr (P >.5) to those from CON in L * vlue throughout the disply period. Chops from the CIT tretment did not chnge (P >.5) throughout disply, wheres L * vlues for chops from PHOS nd CON peked (P <.5) fter 1 d of disply. Jerez et l. (23) stted tht L * vlues for CIT-injected eef smples were similr to CON, ut ACE-injected smples were lighter thn CON. Killefer (24) reported lower L * vlues for CIT-injected pork loins thn for CON, oth initilly nd fter 14 d in modified tmosphere pckging, ut their CON nd CIT solutions oth contined phosphte nd slt. Chops from the PHOS tretment were less red (lower * ; P <.5) thn those from CON nd ACE ech dy of disply (Fig. 11). Chops from the CIT tretment were similr (P >.5) to those from PHOS on d nd on the finl 2 d of disply. Chops from the CON tretment were similr to those from the ACE tretment the first 2 d of disply, nd similr to chops from the CIT tretment fter 1 d, ut they hd the highest * vlues (P <.5) on the finl 5 d of disply. Chops from the ACE tretment were redr (P <.5) thn those from the CIT tretment on d nd 2, ut they were similr (P >.5) throughout the rest of disply. Killefer (24) found tht pork chops from CITinjected loins hd higher * vlues thn did controls injected with PHOS, ut his CIT tretment lso includ PHOS. Smples from the CIT nd ACE tretments were less red thn non-injected controls in eef (Jerez et l., 23). * vlue e c klmno o c c ghij klmn S.E. p =.36 d h lmno eh ghij Dy of disply ghi ijkl cf hijk klmn h jklm klmno Fig. 11. Vlues for * for longissimus chops from cette or citrte injection t 5 min post-mortem, non-injected control crcsses, nd crcsses signted for injection post-rigor with phosphte + slt, over 7 d of disply. o Mens lcking common superscript letters differ (P <.5). p Stndrd error of the interctions mens. * vlue mno lmno d f d d e cf cf d c g k h S.E. l =.27 ij j lmn no ij hi hi Dy of disply Fig. 12. Vlues for * for longissimus chops from cette or citrte prerigor injection t 5 min post-mortem, non-injected control crcsses, nd crcsses signted for injection post-rigor with phosphte + slt, over 7 d of disply. k Mens lcking common superscript letters differ (P <.5). l Stndrd error of the interction mens. L* vlue f e i cf f g S.E. j =.71 d f hi f hi Dy of disply h f e hi h Chops from the PHOS tretment hd the lowest * vlues (lest yellow; P <.5) throughout disply (Fig. 12), wheres chops from CIT nd ACE tretments were similr (P >.5) to those from CON throughout disply. Chops from the PHOS tretment hd the lowest * vlues on d, wheres vlues for * did not notly chnge (P >.5) over time for ny of the other tretments. Previous reserch in eef found tht smples injected with CIT were less yellow thn controls, wheres smples from the ACE tretment were similr to controls (Jerez et l., 23) Sensory ttriutes Fig. 1. Vlues for L * for chops from cette or citrte pre-rigor injection t 5 min post-mortem, non-injected control crcsses, nd crcsses signted for injection post-rigor with phosphte + slt over 7 d of disply. i Mens lcking common superscript letters differ (P <.5). j Stndrd error of the interction mens. Vlues for ttriutes evluted y the trined sensorypnel re displyed in Tle 3. chops were toughest (P <.5), chops from the PHOS tretment were most tenr (P <.5), nd the CIT nd ACE tretments, which

10 736 J.W. Stephens et l. / Met Science 74 (26) Tle 3 Men vlues nd stndrd errors for trits evluted y trined sensory pnel for longissimus chops from crcsses injected pre-rigor with sodium citrte or sodium cette, non-injected control crcsses, nd crcsses injected post-rigor with phosphte + slt Item Pre-rigor injection Non-injected control + slt Myofirillr 5.78 y 5.83 y 4.81 z 6.34 x.19 tenrness Juiciness 5.12 z 4.99 z 4.83 z 6.17 y.15 Pork flvor 4.56 z 5.22 y 5.19 y 4.83 z.22 intensity c Off flvor d 5.42 z 7.52 y 7.9 y 5.3 z.24 Connective tissue e 7.34 y 7.38 y 6.94 z 7.42 y.14 Overll tenrness 6.2 y 6.13 y 5.1 z 6.61 x.18 xyz Mens within row lcking common superscript letters differ (P <.5). Myofirillr tenrness nd overll tenrness were evluted on n 8- point scle (1 = extremely tough nd 8 = extremely tenr). Juiciness ws evluted on n 8-point scle (1 = extremely dry nd 8 = extremely juicy). c Pork flvor intensity ws evluted on n 8-point scle (1 = extremely lnd nd 8 = extremely intense pork flvor). d Off flvor ws evluted on n 8-point scle (1 = undnt nd 8 = none). e Connective tissue mount ws evluted on n 8-point scle (1 = undnt nd 8 = none). f Stndrd error of the men. were injected pre-rigor, were intermedite in oth myofirillr nd overll tenrness. chops lso hd the lowest (P <.5) connective tissue scores, indicting greter perception of tectle connective tissue. The increse in tenrness of chops from the PHOS tretment my hve een prtly due to the swelling of myofirils cused y phosphte nd slt nd to the dilution of the proteins y the injection solutions (Ptterson, Prrish, & Stromer, 1988). In pork, chops from loins injected with CIT hd lower sher force vlues thn controls (Killefer, 24). hs een injected into pre-rigor eef muscle to improve tenrness (Jerez et l., 23; Perversi et l., 23; Streitel et l., 1977). These reserchers theorized tht citrte inhiited post-mortem glycolysis, nd the muscletenrizing clpin enzymes were more ctive due to the incresed ph in muscles injected with CIT. Nevertheless, ACE ws not effective t improving eef tenrness, even though ph ws incresed compred with CON (Jerez et l., 23). Chops from the PHOS tretment were lso juiciest (P <.5), wheres chops from CIT nd ACE tretments were similr (P >.5) to those from CON. The increse in ultimte ph, resulting in improved wter-holding cpcity, y the PHOS injection likely ws responsile for the improved juiciness of tht tretment. Chops from CON nd CIT tretments hd higher (P <.5) pork flvor intensity scores nd less incince (P <.5) of off-flvors thn those from PHOS nd ACE tretments. It is likely tht the off-flvors ssocited with the PHOS nd ACE tretments msked the pork flvor SE f of the chops. The most common off-flvor scriptor for chops from the PHOS tretment ws slty. Other off-flvor scriptors of sopy, metllic, rncid, nd cidic were sometimes used to scrie the chops from the PHOS tretment. Chops from the ACE tretment were most commonly scried s sweet or sugry, s well s cidic, lemony, or vinegry. Other infrequent off-flvor scriptors includ chemicl, sopy, slty, metllic, clener fluid, nd Tsco. Although chops from the CIT nd CON tretments hd less incince (P <.5) of off-flvors thn those from ACE nd PHOS, some scriptors were provid. Chops from the CIT tretment were infrequently scried s cidic, metllic, slty, itter, nd rncid, wheres those from CON were scried s cidic, itter, slty, nd metllic. Our results re in greement with those of Perversi et l. (23), who stted tht eef injected with CIT ws similr to controls in eef sirility rtings. injection hs long een known to improve tenrness nd juiciness in pork (Smith et l., 1984), nd increse sltiness (Brewer et l., 24), nd PHOS is used wily in industry to improve yields nd consumer stisfction. Nevertheless, the PHOS tretment resulted in incresed off-flvors in our study. 4. Conclusions Glycolytic metolite dt indicted tht the increse in ph in muscle injected with CIT ws not due to n inhiition of glycolysis post-mortem. The ph increse in the muscle ws likely due to the reltively high ph of the citrte solution. The highly glycolytic conditions of pork muscle nd the low ATP concentrtions during rigor my hve overwhelmed CIT s ility to inhiit glycolysis. Glycolytic metolite dt reinforced the rtelimiting ffects of phosphofructokinse in post-mortem muscle. Although pre-rigor CIT injection incresed ph nd improved tenrness, compred with CON, visul firmness nd wetness were cresed with CIT injection. Chops from the CIT tretment were similr to those from CON in pork-flvor intensity, nd there were no excessive offflvors. Perhps using CIT in conjunction with phosphte nd slt solution would llow for improved muscle wterholding cpcity, nd the wter-solule CIT in the injection-solution would e more ccessile to rect with PFK. The ddition of the CIT my llow for lower concentrtion of phosphte to e dd to the product nd might llevite the off-flvors ssocited with the phosphte. Chops from the ACE tretment were superior to those from CON in tenrness, ut glycolytic metolite nd ph dt indicted tht ACE did not inhiit post-mortem glycolysis. Furthermore, the cresed pork-flvor intensity nd ojectionle off-flvors of ACE injection likely will discourge use of this compound t this concentrtion in the future in fresh met injection solutions.

11 J.W. Stephens et l. / Met Science 74 (26) Acknowledgement The uthors thnk Dr. Stephen Smith in the Deprtment of Animl Science t Texs A&M University, College Sttion, TX, for his dvice nd guidnce in conducting severl of the lortory procedures in our reserch. References AMSA (1995). Reserch guilines: Cookery, sensory evlution, nd instrumentl tenrness mesurements of fresh met. Centennil, CO: Americn Met Science Assocition in coopertion with the Ntionl Live Stock nd Met Bord (now the Ntionl Cttlemen s Beef Assocition). Allison, C. P., Btes, R. O., Booren, A. M., Johnson, R. C., & Doumit, M. E. (23). Pork qulity vrition is not explined y glycolytic enzyme cpcity. Met Science, 63(1), Bendll, J. R. (1973). Postmortem chnges in muscle. Structure nd function of muscle (2nd ed.). New York, NY: Acmic Press (pp ). Bergmeyer, H. U. (1974). Methods of enzymtic nlysis. New York, NY: Acmic Press (pp ). Brewer, M. S., Jensen, J., Prestt, C., & Zhu, L. G. (22). Visul cceptility nd consumer purchse intent of enhnced pork loin rosts. Journl of Muscle Foods, 13, Brewer, M. S., Sosnicki, A., Field, B., Hnkes, R., Ryn, K. J., Zhu, L. G., et l. (24). Enhncement effects on qulity chrcteristics of pork rived from pigs of vrious genetic kgrounds. Journl of Food Science, 69(9), SNQ5 SNQ1. Dlrymple, R. H., & Hmm, R. (1975). Postmortem glycolysis in prerigor ground ovine nd rit muscle. Journl of Food Science, 4(4), Dhnd, J. S., Pegg, R. B., Jnz, J. A. M., Alhus, J. L., & Shnd, P. J. (22). Pltility of ison semimemrnosus nd effects of mrintion. Met Science, 62(1), Fushimi, T., Tym, K., Fuky, M., Kitkohi, K., Nki, N., Tsukmoto, Y., et l. (21). Acetic cid feeding enhnces glycogen repletion in liver nd skeletl muscle of rts. Journl of Nutrition, 131, Hmm, R. (1977). Postmortem rekdown of ATP nd glycogen in ground muscle: review. Met Science, 1(1), Jerez, N. C., Clkins, C. R., & Velzco, J. (23). Prerigor injection using glycolytic inhiitors in low-qulity eef muscles. Journl of Animl Science, 81, Kemp, R. G., & Kres, E. G. (1967). Binding of metolites y phosphofructokinse. Biochemistry, 6(2), Killefer, J. (24). Effect of enhncement of pork nd eef on post mortem events. In Proceedings of the 59th reciprocl mets conference, June 2 23, Lexington, Kentucky. Newsholme, E. A., Sugn, P. H., & Willims, T. (1977). Effects of citrte on the ctivities of 6-phosphofructokinse from nervous nd muscle tissues from different nimls nd its reltionship to the regultion of glycolysis. Biochemistry Journl, 166, NPPC (1999). NPPC officil color nd mrling stndrds. Des Moines, IA: Ntionl Pork Producers Council. Ptterson, B. C., Prrish, F. C., Jr., & Stromer, M. H. (1988). Effects of slt nd pyrophosphte on the physicl nd chemicl properties of eef muscle. Journl of Food Science, 53(5), Perversi, C. D., Clkins, C. R., & Velzco, J. (23). Use of sodium citrte to enhnce tenrness nd pltility of pre-rigor eef muscles. Journl of Animl Science, 79(Suppl. 1). Astrct Rhos, R. D., King, D. A., Jenschke, B. E., Behrends, J. M., Hively, T. S., & Smith, S. B. (25). Postmortem regultion of glycolysis y 6- phosphofructokinse in ovine M. sternocephlcus prs mndiulris. Met Science, 7(4), Roins, K., Jensen, J., Ryn, K. J., Homco-Ryn, C., McKeith, F. K., & Brewer, M. S. (22). Enhncement effects on sensory nd retil disply chrcteristics of eef rounds. Journl of Muscle Foods, 13, Syre, R. N., & Briskey, E. J. (1963). Protein soluility s influenced y physiologicl conditions in the muscle. Journl of Food Science, 28, Smith, L. A., Simmons, S. L., McKeith, F. K., Bechtel, P. J., & Brdy, P. L. (1984). Effects of sodium tripolyphosphte on physicl nd sensory properties of eef nd pork rosts. Journl of Food Science, 49(6), , Stetzer, A. J., & McKeith, F. K. (23). Quntittive strtegies nd opportunities to improve qulity. In Benchmrking vlue in the pork supply chin (pp. 1 6). Svoy, IL: Americn Met Science Assocition. Streitel, R. H., Ockermn, H. W., & Chill, V. R. (1977). Mintennce of eef tenrness y inhiition of rigor mortis. Journl of Food Science, 42, Voet, D., Voet, J. G., & Prtt, C. W. (22). Fundmentls of iochemistry (Upgr ed.). New York, NY: Wiley.