Time-Varying Input and State Delay Compensation for Uncertain Nonlinear Systems

A robust controller is developed for uncertain, second-order nonlinear systems subject to simultaneous unknown, time-varying state delays and known, time-varying input delays in addition to additive, sufficiently smooth disturbances. An integral term composed of previous control values facilitates a delay-free open-loop error system and the development of the feedback control structure. A stability analysis based on Lyapunov-Krasovskii (LK) functionals guarantees uniformly ultimately bounded tracking under the assumption that the delays are bounded and slowly varying

Relationship of Warner-Bratzler shear force and trained sensory panel tenderness of strip loin steaks cooked to 131 and 158°F

In a previous study, eighteen strip loins from USDA Select and premium Choice carcasses were cooked on a Magikitch’n® belt grill to determine tenderness at nine different endpoint temperatures. That study revealed that optimum Warner-Bratzler shear force (WBSF) values occurred in strip loin steaks cooked to 131°F, but current WBSF protocol requires steaks to be cooked to 158°F. Therefore, trials employing trained sensory panels (TSP) were conducted to determine the relationship of WBSF with TSP tenderness from steaks cooked to 131 and 158°F on the belt grill. As expected, panelists found steaks cooked to 131°F more tender than those cooked to 158°F. The relationship of WBSF with TSP ratings for tenderness was not significant (P>0.05) when both steaks were cooked to 158°F. When both steaks were cooked to 131°F, however, there was a moderate relationship (r = -0.52) of WBSF with TSP tenderness. The relationship of WBSF from steaks cooked to 131°F with TSP ratings for tenderness from steaks cooked to 158°F was the strongest (r = -0.66). More research is needed to determine the feasibility of cooking steaks to 131°F, rather than 158°F, to improve WBSF determination

Endpoint temperature, cooking method, and marbling degree have different effects on Warner-Bratzler shear force of beef strip loin, bottom round, and brisket muscles

Our objective was to determine the effects of endpoint temperature, cooking method, and marbling on Warner-Bratzler shear force (WBSF; an objective method for determining tenderness) of three beef muscles. Eighteen subprimals of a muscle containing low content of connective tissue, longissimus lumborum (strip loin), and two muscles containing a high content of connective tissue, biceps femoris (bottom round) and deep pectoralis (brisket), were selected from USDA Select and Choice (Certified Angus Beef) carcasses. After 14 days of aging, subprimals were frozen, fabricated into steaks, and stored frozen until cooking. Steaks were assigned to one of two cooking methods, the Magikitch’n® electric belt grill (a rapid conduction method) or a water bath (a slower, convection method); and one of nine endpoint cooking temperatures, 104, 113, 122, 131, 140, 149, 158, 167, or 176°F. According to WBSF results, optimum tenderness for the strip loin occurred around 131°F. Higher marbling protected tenderness at higher endpoint temperatures. Tenderness increased in bottom round and brisket muscles as endpoint temperature increased from 104 to 140°F, then tenderness decreased as endpoint temperature rose from 149 to 176°F. Endpoint temperature was the only significant factor affecting bottom round tenderness. Steaks cooked in the water bath had higher WBSF and, therefore, were less tender than those cooked on the belt grill. This was true for both the strip loin and brisket. The effect of increasing endpoint temperature on WBSF of the strip loin was different than for the bottom round and brisket

Textural, chemical and sensory properties of döners produced from beef, chicken and ostrich meat

In this study, the chemical, textural and sensory properties of beef, chicken, or ostrich meat döners empirically produced were compared. Ostrich döner samples had lower (P<0.0001) cholesterol content than beef or chicken döners but higher calori values. It is observed that beef döners had higher (P<0.0001) Warner-Bratzler shear force (WBSF) than chicken and ostrich döners. According to the texture analyses results it is concluded that hardness measured by Texture Profile Analyzer was found to be a better predictor of sensory tenderness than WBSF. Panelists rated ostrich döner meat with highest point in terms of sensory properties. Ostrich döners had better overall acceptance than beef or chicken döners. Therefore it is concluded ostrich döner can be taken into consideration as an alternative protein source to beef or chicken döners

Effects of cooking beef muscles from frozen or thawed states on cooking traits and palatability

We used an electric belt grill to cook steaks from two muscles; outside round (biceps femoris), and loin strip (longissimus lumborum) from both frozen and thawed states. The color values L* and a*, Warner-Bratzler shear force (WBSF), juiciness, flavor, connective tissue amount, and overall tenderness did not differ (P>0.05) between steaks cooked from frozen and thawed states. Thawed steaks cooked faster and had less cooking loss. The biceps femoris had higher WBSF than longissimus and was rated less tender by trained panelists. Color values L*, a*, or b* did not differ (P>0.05) among the muscles. The biceps femoris needed more time to cook and had greater cooking loss than longissimus

Effects of end-point temperature, reheating, holding time, and holding temperature on beef tenderness

We cooked steaks from two muscles; outside round (biceps femoris), and strip loin (longissimus lumborum) with an electric belt grill. Biceps femoris steaks had higher Warner-Bratzler shear force (WBSF), connective tissue force (WB Cforce), and myofibrillar force (WB Mforce) values than longissimus lumborum steaks. Holding biceps femoris steaks at 144°F after cooking increased WB C-force (P<0.05) and WB M-force (P<0.01) as compared to holding them at 135°F. Holding biceps femoris steaks for 15 min decreased shear force by 12%, whereas the decrease was only 3% from holding for 30 min, likely because more moisture was lost with the longer holding time. Reheating had the only significant effect on longissimus lumborum steaks’ WB measures because low collagen content of this muscle is not affected by holding time or temperature

Will blade tenderization decrease iridescence in cooked beef semitendinosus muscle?

Ten beef semitendinosus muscles were divided into three sections, which were randomly assigned to one of three blade tenderization treatments (control-zero, one, or two times). Blade-tenderized muscles were cooked in a forced-air convection oven at 325° to 145°F and held for 1 min. Cooked muscles were chilled overnight at 38°F and sliced by a sharp knife. Panelists (n=19) evaluated iridescence intensity on a five-point scale (0=no iridescence, 5=very strong) and extent of iridescence (0=no iridescence, 5=81-100% affected area). Blade tenderization decreased (P<0.05) iridescence intensity from 2.37 to 2.02 and extent of iridescence from 2.18 to 1.83 (control zero vs. two passes). Cooking loss increased (P<0.05) with blade tenderization (30.4% control, 32.6% one pass, 33.7% two passes). Blade tenderization has a moderate effect on reducing iridescence