T.E. Lawrence

Utilizing infrared thermography to predict pork quality.

Three experiments using 63 pigs were conducted to determine if infrared thermography could segregate pigs based on subsequent pork quality. Pigs were subjectively classified as either “hot” or “normal” based on infrared surface temperature of the loin region prior to slaughter. In the first experiment 18 market weight pigs were transported, imaged by infrared thermography and slaughtered immediately after 1 to 4 h of lairage. Differences in meat quality were detected; hot pigs had lower a* (less red) and chroma (less intense red color) values, and higher hue angle (less red/more yellow) values, all of which indicate paler muscle color. In the second experiment, 27 market weight pigs were transported, held in lairage for 12 to 16 h, imaged by infrared thermography, and then slaughtered. In the third experiment, 18 market weight pigs were transported, imaged by infrared thermography, held in lairage for 12 to 16 h, and then slaughtered. Regardless of the time infrared images were taken, no meat quality differences between hot and normal pigs were detected when pigs were held in lairage for 12 to 16 h. These data suggest that measurement of live animal surface temperature by infrared thermography may allow for detection of poor meat quality if pigs are slaughtered without extended lairage.

Supplementing feedlot steers and heifers withZilmax increases proportions of strip loin,chuck clod, and top sirloin steaks exceedingWarner-Bratzler shear force thresholds,whereas aging moderates this effect

Introduction Ractopamine hydrochloride (Elanco, Greenfield, IN) and Zilmax (zilpaterol hydrochloride; Intervet/Schering-Plough, Millsboro, DE) are β-adrenergic agonists approved in the United States and several other countries to increase growth rate, improve efficiency of feed utilization, and increase carcass meat yield. Zilmax has been shown to improve feed efficiency by 26% and increase hot carcass weight, longissimus muscle area, and meat yield. However, a few studies have shown that Zilmax significantly increased Warner-Bratzler shear force values (decreased tenderness).

Evaluation of mechanical probes used on uncooked steaks to classify beef longissimus tenderness

We pooled the mechanical probe data from two experiments to develop regression equations to predict beef longissimus tenderness. Fifty-three USDA Select strip loins were evaluated at 2 days postmortem with three mechanical probes to predict trained sensory panel (TSP) tenderness and WarnerBratzler shear force (WBSF) of cooked steaks aged 14 days. The sharp needle, sharp blade, and plumb bob probes were correlated to TSP tenderness (r=-0.51, -0.45, and -0.35, respectively) and WBSF (r=0.56, 0.53, and 0.36, respectively). Regression equations developed from sharp needle, sharp blade, and plumb bob probe measurements and L* (lightness) values accounted for 49, 50, and 47% of the variation in TSP tenderness. The predicted values of equations were also used to classify the strips as tough or tender, and this classification was compared to the actual TSP tenderness classification. Of the steaks predicted to be tender by the equations using the sharp needle, sharp blade, and plumb bob probes and WBSF 88, 88, 84, and 87%, respectively, were actually tender according to TSP. The sharp needle, sharp blade, and plumb bob probe prediction equations were comparable to WBSF in classifying carcasses into sensory panel determined tenderness groups, and they were superior to WBSF in simplicity and cost. Introduction

Mechanical Probes Used on Uncooked Steaks Can Predict Cooked Beef Longissimus Tenderness

We investigated five mechanical probes, used on uncooked strip loin steaks at 2 days postmortem, to predict trained sensory panel (TSP) tenderness and Warner-Bratzler shear force (WBSF) of steaks aged 14 days. Twenty-nine USDA Select strip loins were evaluated with sharp needle, blunt needle, sharp blade, and blunt blade probes in parallel and perpendicular orientations to the length of the strip loin. A steak from each loin was also measured with a plumb bob probe in a parallel orientation and with a Miniscan for instrumental color. None of the perpendicular orientation measurements were correlated (P>0.05) to TSP tenderness. The sharp blade and sharp needle probe values from the perpendicular orientation were correlated to WBSF (r=0.49 and 0.37, respectively). Parallel measurements by the sharp needle, blunt needle, sharp blade, blunt blade, and plumb bob probes were correlated with TSP tenderness (r=-0.77, 0.40, -0.52, -0.57, and -0.53, respectively) and WBSF (r=0.74, 0.38, 0.60, 0.41, and 0.46). Instrumental color variables were not correlated (P>0.05) with TSP tenderness or WBSF. A regression equation for predicting TSP tenderness using the sharp needle probe resulted in R2 of 0.74, while the equation predicting TSP tenderness from WBSF had an R2 of 0.69. Equations using the sharp blade and plumb bob probe values in addition to L* values resulted in R2 values of 0.45 and 0.56, respectively. The sharp needle, sharp blade, and plumb bob probes were successful in predicting trained sensory panel tenderness. However, the sharp needle probe was superior to the other mechanical probes.

Investigation of tenderness mechanisms in calcium-enhanced muscle

We explored the mechanism(s) of calcium-induced tenderization in calciumenhanced beef muscle. At 72 hours postmortem, we injected (9% by weight) beef strip loins (n=15) with 0, 0.05, 0.1, 0.2, or 0.4 M calcium chloride (CaCl2) with and without 0.05 M zinc chloride (ZnCl2), and they were then aged until 15 days postmortem. WarnerBratzler shear force peak values indicated that addition of ZnCl2 drastically inhibited tenderization; however, enhancement with CaCl2 still tended to reduce shear values (P=0.07; 0.55 kg) when ZnCl2 was present. In the absence of ZnCl2, the 0.2 and 0.4 M CaCl2 treatments were 18.9 and 32.1% more (P<0.05) tender than the no CaCl2 treatment. These results suggest that both calciumactivated enzymatic activity and a nonenzymatic salting-in effect contributed to tenderization of calcium-enhanced muscle. However, the enzymatic mechanism reduced toughness 2.9 to 7.5 fold more than the nonenzymatic mechanism. Calcium-activated enzymatic degradation appears to be the major tenderization mechanism, and non-enzymatic salting-in of calcium ions appears to be a minor tenderization mechanism, even at high calcium concentrations.

Mechanical force measures on uncooked beef longissimus muscle can predict tenderness of strip loin steaks

We investigated mechanical force measurements on uncooked longissimus muscle as a means to predict WarnerBratzler shear force (WBSF) and trained sensory panel tenderness (SPT) of cooked strip loin steaks. Uncooked steaks from 24 USDA Select strip loins (IMPS 180) were evaluated at 2 and 14 days postmortem using plumb bob and needle probe devices attached to an Instron Universal Testing Machine. Cooked steaks aged 14 days were then evaluated for WBSF and SPT. Regression models to predict SPT from needle probe and plumb bob measurements individually taken at 2 days postmortem had R of 0.54 and 0.51, respectively. Combining needle probe and plumb bob measurements resulted in an R of 0.76; however, when quadratic terms for both variables were in the model, R was 0.80. Regressing needle probe and plumb bob measurements at 2 days postmortem with WBSF produced R of 0.51 and 0.45, respectively. When linear terms of both probes were combined, R improved to 0.77. An equation to predict WBSF including both the linear and quadratic terms of needle probe and plumb bob measurements resulted in R of 0.84. Using plumb bob and needle probe combined on uncooked longissimus muscle at 2 days postmortem can predict cooked WBSF and SPT of strip loin steaks aged for 14 days. (

Surface roughening during slicing reduces iridescence

We evaluated surface roughening during slicing as a way to decrease iridescence of pre-cooked cured beef bottom round, inside round, and eye of round roasts. Using a textured slicing blade surface decreased iridescence intensity and the area of iridescence compared to the control (smooth surface). Iridescence intensity and percentage of iridescent area was greatest in the eye of round, followed by the inside bottom round. Iridescence (both intensity and percentage of area) in sliced meat products can be reduced by using a meat-slicing blade with a textured face.

Effects of injection marination with variouscalcium sources and molar concentrations ondisplay color life, tenderness, and microbialinhibition of beef loin steaks

Beef strip loins were assigned to one of 11 treatments that included injection marination (10% by weight) with three calcium salts at three molar concentrations, a distilled water control, and a nonmarinated control. The effects of calcium salt and concentration were tested for retail display color life, tenderness and sensory traits, and microbial growth. Calcium lactate marinated steaks had longer color life and less microbial growth than those treated with calcium chloride or calcium ascorbate. Increasing molar concentration (.1M to .2M to .3M) caused faster color deterioration, and did not significantly improve microbial inhibition. All calcium treatments improved tenderness; however, calcium chloride treatments induced off-flavors. Considering a whole system approach that accounts for color life, microbial inhibition, shear force, and sensory traits, we recommend injecting beef longissimus with 10% of a .1M solution of calcium lactate, and do not recommend other calcium salts or concentrations.

Tenderness and cooking characteristics of beef cooked by electric belt grill, forced-air convection oven, or electric broiler

We used an electric belt grill, a forced-air convection oven, and an electric broiler to cook 170 bottom round, 142 brisket, 177 top sirloin, 176 strip loin, and 136 eye of round steaks from USDA Select carcasses to determine the effects of cooking method and muscle on shear force values, cooking traits, and repeatability of duplicate measurements. All cooking treatments allowed differences to be detected (P<0.05) in Warner-Bratzler shear force, although the differences were inconsistent. Shear force values of strip steaks and eye of round steaks were similar across cooking treatments; however, shear force values of bottom round, brisket, and top sirloin steaks were different (P<0.05) among cooking treatments. Based on poor repeatability, shear force values for top sirloin steaks appear unreliable. Poor repeatability for shear force values from steaks cooked by the forced-air convection oven are a result of drastic temperature changes that occur when the doors are opened to remove steaks. We do not recommend using a forced-air convection oven to test treatment effects on shear force values when cooking multiple steaks simultaneously. Belt grill cooking resulted in the highest shear force repeatability R = 0.07 to 0.89) of strip steaks. Electric broiling resulted in acceptable R = 0.60) repeatability of shear force measurements for all classes of steaks. The electric broiler and electric belt grill are both satisfactory cooking methods when measuring shear force of bottom round, brisket, strip loin, and eye of round steaks.

Heat penetration patterns of outside round, loin strip and eye round muscles cooked by electric broiler, electric belt grill, or forced-air convection oven

We used an electric belt grill, a forced air convection oven, and an electric broiler to cook steaks from three beef muscles; outside round (biceps femoris), loin strip (longissimus lumborum) and eye round (semitendinosus). Belt grill cookery gave the fastest heat penetration into steaks regardless of temperature interval. Eye round had the slowest heat transfer rate for each cooking method perhaps partially explained by its fiber orientation. Heat penetration rate into outside round and loin strip was not different (P>0.05) for cooking method within a given temperature range. Heat penetration into muscles between 140 and 158°F was slowest because energy-expensive reactions (collagen and protein denaturation) occur in that temperature and temperature differential between the heat source and meat is less. Heat penetration also was slow between 122 and 140°F due to the denaturation of contractile proteins.