Problems with meat quality are usually caused by aberrations in the biochemistry and morphology of individual muscles, as well as by postmortem events. Poultry, l i b pigs, have been subjected to intense genetic selection for rapid lean muscle growth. The selection traits are most often associated with economic importance rather than biophysical significance. which often results in stress syndromes (e.g. porcine stress syndrome) and pale, soft, exudative (PSE) muscle conditions. The occurrence of PSE muscle and subsequent alterations in meat quality has been shown to be related to increases in muscle sue, stressful preslaughter handling conditions, and rate of onset of rigor mortis. Morphological studies have revealed significant increases in fiber size, in addition to structural irregularities in PSE muscle. These structural irregularities include decreased capillary density, hypercontracted (gianl) fibers, and myoplasmic calcium loading. The common theme between poultry and swine in the development of PSE muscle is predominately in anaerobic fast-twitch muscles with low energy lactate metabolism yet accelerated onset of rigor mortis.' Mention of specific equipment or trade names does not imply endorsement by USDA.

The organoleptic trait most affecting consumer acceptance of beef is tenderness. The Hydrodyne process uses a small amount of explosive to generate a shock wave in water. The shock wave passes through (in fractions of a millisecond) objects in the water that are an acoustic match with water. Four beef muscles (longissimus, semimembranosus, biceps femoris, and semitendinosus) exposed to either 50, 75, or 100 g of explosives were significantly tenderized compared with controls. As much as a 72% reduction in shear force was observed for the longissimus muscle using 100 g of explosives. Reductions in shear force with magnitudes of 30 to 59% improvements were observed for the other three muscle types. Results suggest that tenderizing beef with the Hydrodyne process presents a potentially novel opportunity in the way the meat industry can tenderize meat.

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This study evaluated the effects of hydrodynamic pressure (HDP) processing and aging on the tenderness and myofibrillar proteins of beef strip loins. Loins (n = 12) were halved at 48 h postmortem and assigned to HDP or control treatments. Following treatment, each half was divided into three portions for aging (0, 5 or 8 days). Samples were removed for Warner-Bratzler shear force (WBSF) determination and myofibrillar protein isolation. HDP decreased (P < 0.0001) WBSF values 23% at 0, 5 and 8 days of aging. Myofibrillar fragmentation and myofibrillar protein solubility increased (P < 0.01) with HDP and aging. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting analysis of myofibrillar proteins showed that HDP and aging decreased the intensity of the troponin T (TnT) band and enhanced the accumulation of the 30 kD TnT degradation product. These data suggest that HDP is more effective than aging tenderization, and that HDP tenderization is caused by both protein degradation and physical disruption of the myofibril apparatus. PRACTICAL APPLICATIONSHydrodynamic pressure (HDP) processing was shown to instantaneously tenderize tough cuts of beef to tenderness levels attained following 8 days of * Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the United States Department of Agriculture.

The effect of sex class on proximate composition and cholesterol, vitamin, mineral, and fatty acid content was determined for carcass composite samples of cooked goat meat. Soft tissues (fat and lean) from dissection of one side of seven carcasses each for female, castrate, and intact male Florida native or F1 crosses of Florida natives with Nubian or Spanish goats were ground, formed into patties, and then broiled. Also, a leg slice was removed from the side not used for dissection, broiled, and then sampled for fatty acid determination. Broiled samples from female goats had lower (P = .04) moisture and higher (P = .03) fat and total calories than did samples from castrates and intact males. Sex class had no effect on cholesterol, vitamin, or mineral content of cooked goat meat. Broiled goat leg slices from intact males were lower (P = .005) in percentage of total saturated fatty acids and had a higher (P = .01) unsaturated to saturated fatty acid ratio than samples of broiled leg slices from females or castrates. Broiled goat meat had higher values for calcium, potassium, thiamin, and cholesterol than that reported in USDA Handbook 8 for cooked composite samples of beef or chicken. Also, broiled goat meat had lower total lipid, phosphorus, and vitamin B12 than composite values reported for beef. Other nutrients were similar to those reported for cooked composite samples of beef and chicken.

The objective was to determine the meat quality effects of rapidly thawing beef steaks in a water bath. Frozen beef strip loins (n = 24) were cut into steaks sequentially from the rib end and identified by anatomical location (anterior, middle, posterior) within the loin. Within location, steaks were randomly assigned to conventional (C; 18 to 20 h, 4 °C) or rapid thawing methods. Rapid thawing methods, fast (20 min, 20 °C) or very fast (11 min, 39 °C), were conducted in a circulating water bath. The physical, thawing, cooking, color, and texture characteristics of each steak were recorded. Data were analyzed as a randomized complete block design with a 3 thawing treatments × 3 locations factorial analysis with loin as a block. No location by thawing method interaction was detected (P > 0.05) for the measured variables. Compared to C steaks, rapidly thawed steaks exhibited lower thaw drip loss (P < 0.001) and higher a* values (P < 0.001). Thawing treatment did not influence L*, b*, cook yield, or shear force. Steaks from the posterior end had higher (P < 0.001) surface to volume ratios that may have contributed to the higher thaw loss (P < 0.01), longer cooking time (P < 0.001), lower cooking yield (P < 0.001), and higher shear force (P < 0.02) compared to steaks from the anterior and middle portions of the loins. These data indicate that beef steaks taken from the entire length of the loin can be rapidly thawed in a water bath following food safety guidelines with minimal impact on meat quality. Practical Application:  Freezing rate and frozen storage effects on meat quality have been well documented; however, there is comparatively little information on the meat quality effects of rapid thawing within food safety guidelines. This study demonstrates that beef strip loin steaks can be rapidly thawed in as few as 11 min without affecting texture or cooking yield, while reducing thaw drip loss. Thus, rapid thawing may enhance the apparent juiciness of steaks for consumers and provide an effective method for maintaining consistent control of experimental conditions for researchers.

This research showed that the protein profiles of exudates that accumulate on the surface and in the packaging of beef change with meat aging and tenderness. These data suggest that muscle exudates may be a good source of protein markers that are useful in the development of rapid, noninvasive methodologies for predicting beef tenderness.

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