Glycolytic potential and activity of adenosine monophosphate kinase (AMPK), glycogen phosphorylase (GP) and glycogen debranching enzyme (GDE) in steer carcasses with normal (<5.8) or high (>5.9) 24h pH determined in M. longissimus dorsi.

Muscle glycogen concentration (MGC) and lactate (LA), activity of glycogen debranching enzyme (GDE), glycogen phosphorylase (GP) and adenosine monophosphate kinase (AMPK) were determined at 0.5h (T0) and 24h (T24) post-mortem in Longissimus dorsi samples from 38 steers that produced high pH (>5.9) and normal pH (<5.8) carcasses at 24h postmortem. MGC, LA and glycolytic potential were higher (P<0.05) in normal pH carcasses. GDE activity was similar (P>0.05) in both pH categories. GP activity increased between T0 and T24 only in normal pH carcasses. AMPK activity was four times higher in normal pH v/s high pH carcasses, without changing its activity over time. Results reinforce the idea that differences in postmortem glycogenolytic/glycolytic flow in L. dorsi of steers showing normal v/s high muscle pH at 24h, could be explained not only by the higher initial MGC in normal pH carcasses, but also by a high and sustained activity of AMPK and an increased GP activity at 24h postmortem.

Prediction equations for Warner-Bratzler shear force using principal component regression analysis in Brahman-influenced Venezuelan cattle.

A database consisting of 331 beef animals (Brahman-crossbred) was used to determine the multivariate relationships between carcass and beef palatability traits of Venezuelan cattle and to develop prediction equations for Warner-Bratzler shear force (WBSF). The first three principal components (PC) explained 77.53% of the standardized variance. Equations were obtained for each sex class and the total variability observed in WBSF could be explained by its orthogonal regression with carcass weight (CW), fat cover (FC), fat thickness (FT), and skeletal maturity (SM). Prediction equations were: WBSF(steers)=3.566+0.003(CW)-0.033(FC)-0.015(FT)+0.0004(SM); WBSF(heifers)=4.824+0.002(CW)-0.229(FC)+0.096(FT)-0.064(SM); WBSF(bulls)=3.516+0.009(CW)+0.154(FC)-0.129(FT)-0.006(SM). A higher proportion of the variation was explained by the PC when variables of greater weight were selected to define each PC. The equation set presented herein could become an important tool to improve the Venezuelan carcass grading system.

Establishing tenderness thresholds of Venezuelan beef steaks using consumer and trained sensory panels.

The tenderness thresholds for ribeye steaks at 2d postmortem were found by using sensory trained (n=734 steaks) and consumers panel data (55 ribeye steaks and 296 consumers). Also, consumers' perceptions of sensory attributes of beef steaks were assessed to establish their relationships and to determine acceptability levels. The tenderness threshold obtained by regression analysis from trained panelists was 37.98N (3.87kg). Customer satisfaction of 81% was obtained when beef steaks had Warner-Bratzler shear force values (WBSF) less than 40.13N (4.09kg), suggesting that 40.13N could be considered as a tenderness threshold to segregate tough from tender steaks, for Venezuelan beef consumers. According to correlation and regression analyses, consumers focused on flavor to assign their overall liking score. Results suggest that consumers are able to detect changes in tenderness of steaks with different WBSF and that flavor drives customer satisfaction when the beef tenderness is acceptable.

Predicción del rendimiento en cortes de carniceríade bovinos venezolanos / Predicting beef carcass cutability in venezuelan cattle

Datos de cortes obtenidos de ganado bovino (hasta 1197 observaciones) fueron utilizados para desarrollar ecuaciones de predicción del rendimiento en cortes de valor (RCD), Porcentaje de hueso (PHUESO) y recortes de grasa (PGRASA). La condición sexual (CONSEXUAL) explicó el 43 por ciento y 30 por ciento de la variación en RCD y PGRASA, respectivamente. La mayor parte de la variación (>50 por ciento) en RCD, PHUESO y PGRASA no pudo ser explicada por su regresión lineal simple sobre cualquiera de los 13 rasgos de la canal considerados. Las variables incluidas para el análisis de regresión fueron CONSEXUAL, peso en canal (PCANAL), espesor de grasa dorsal (ESPEGRASA), área del ojo del lomo (AOL), porcentaje de grasa interna (GPR), acabado y conformacion. Las mejores ecuaciones fueron: RCD por ciento: 47,564 +2,281(CONSEXUAL) +0,003(PCANAL) -0,302(ESPEGRASA) +0,211(AOL) -1,237(GPR) +0,219(ACABADO) –0,659(CONFORMACION) (R2: +0,629; Cp-Mallows:8); PHUESO: por ciento 17,077 –0,749(CONSEXUAL) –0,005(PCANAL) -0,097(ESPEGRASA) -0,064(AOL) -0,402(GPR) +0,2(ACABADO) +0,272 (CONFORMACION) (R2: 0,387; Cp-Mallows: 8); PGRASA por ciento: 9,628 +0,345(ESPEGRASA) -0,162(AOL) +1,733(GPR) -0,725(ACABADO) –0,134(CONFORMACIÓN) (R2: 0,80; Cp-Mallows: 5,74). Es necesario, en futuras experiencias validar las ecuaciones obtenidas antes de su recomendación y uso comercial.

Carcass fabrication yield (%) data (up to 1197) of Venezuelan cattle were collected to develop prediction equations of boneless, closely trimmed cuts (high plus medium-valued) (YCV), bone percentage (PBONE), and fat trimmings (PFAT). The sex condition (SEXCON) explained 43% and 30% of the variation on YCV and PFAT, respectively. The majority of the variation (50% or more) on YCV, PBONE, and PFAT could not be explained by its simple linear regression over any of the 13 carcass traits considered. The variates included for the regression analysis were SEXCON, Carcass Weight (CWEIGHT), Back Fat Thickness (BACKFAT), Loineye Area (LEA), Internal Fat Percentage (IFP), FINISH and CONFORMATION. The best equations were: YCV%: 47.564 +2.281(SEXCON) +0.003 (CWEIGHT) -0.302( BACKFAT) +0.211(LEA) -1.237(IFP) +0.219 (FINISH) -0.659 (CONFORMATION) (R2: 0.629; Mallow´s-Cp: 8); PBONE: %17.077 -0.749(SEXCON) -0.005 (CWEIGHT) -0.097(BACKFAT) -0.064(LEA) -0.402(IFP) +0.2 (FINISH) +0.272(CONFORMATION) (R2: 0.387; Mallow´s-Cp: 8); PFAT%: 9.628 +0.345(BACKFAT) -0.162(LEA) +1.733(IFP) -0.725(FINISH) -0.134(CONFORMATION) (R2: 0.80; Mallow´s-Cp: 5.74). The equation set presented here in must be subjected to practical and statistical validation.

[Moisture, total lipids and fatty acids in raw longissimus muscle from Venezuelan cattle]. / Contenido de humedad, lípidos totales y ácidos grasos del músculo longissimus crudo de bovinos en Venezuela.

Randomly selected groups of slaughter cattle, crossbreds of dairy (n = 14) and zebu (n = 131) types were classified by age (2.5, 3.0, 3.5 and 4.0 yr., estimated by dentition), and carcass fatness (as described by different criterion, including marbling levels) to study variation in moisture (M), lipid (L), and fatty acid (FA) contents (g/100 g of fresh tissue) of longissimus muscle trimmed to zero fat cover. Overall means +/- standard deviations per 100 g of raw product for M and L were 73.9 +/- 1.36 and 2.9 +/- 1.04, respectively. Analyses of variance by the least squares (LS) method showed age, breed type, marbling, backfat thickness and carcass finish affected (p < 0.05) fatty acid (FA) profiles. The oldest cattle group (4 yr. or older) trended to present a lower intramuscular lipid content (2.72 g/100 g) and showed the highest (2.04) unsaturation (unsaturated/saturated FA) index (p < 0.05). Breed type had little effect on the FA profile. Comparison of LS means showed intramuscular concentrations of myristic and linolenic acids were slightly higher in samples from dairy types (p < 0.05). Carcasses with poor, "patch-like" fat distribution, showed muscles with the highest (0.16) polyunsaturated/saturated FA index (p < 0.05). Unsaturation indexes for trimmed beef samples with the prevailing marbling levels (1.76 for "Traces" to 1.92 for "Devoid") show a clear predominance of unsaturates, relatively larger than that estimated from compositional FA data reported for the same cut in the United States.

[Cholesterol content in longissimus muscle beef from slaughter cattle in Venezuela]. / Contenido de colesterol en el músculo longissimus de bovinos venezolanos.

An observational study was conducted with 149 cattle, raised under tropical conditions of Venezuela (mostly grassfed), to study the relationships of sex class (62 bulls, 67 steers, 20 heifers), age by dentition (2.5; 3.0; 3.5 and 4.0 yr), physiological maturity (A or B), cattle type (17 Dairy or 132 Zebu type crossbreds), Venezuelan carcass grade (Optima, Excelente, Selecta or Superior), marbling level (four levels from "None" to "Small quantity"), carcass fat cover (four level: "Even", "Uneven", "patch-like" and "Devoid") and subcutaneous fat thickness (SFT) over the ribeye (1 = 0.1-0.2 cm; 2 = 0.3-0.4 cm; 3 = 0.5-0.9 cm and 4 = > 1.0 cm) on cholesterol content (mg/ 100 g wet weight) of longissimus muscle. Cholesterol content, as determined colormetrically, did not vary in response to the differences in sex class, age, maturity level, carcass grade, marbling level or SFT represented in the present survey. However, cattle type affected (P = 0.08) cholesterol content. Least square means analysis showed that dairy type contained 12.2 mg more of cholesterol/100 g of muscle than Zebu type. The overall mean (+/- SD) muscle cholesterol for the kind of cattle sampled herein (66.6 +/- 16 mg/100 g) was not considered to be different from those of cattle fed in other latitudes.

[Factors affecting the cooking of longissimus muscle beef from Venezuela cattle]. / Factores que afectan la culinaria de bistés del músculo Longissimus de bovinos venezolanos.

A survey was conducted to study variation in cookery traits of beef longissimus in Venezuela. Cattle originated from the main beef producing regions of the country (n = 274) provided steaks to study the effects of cattle type (Zebu-dairy, Zebu), Sex (bull, steer, heifer), age by dentition (estimated chronological age of 2, 3 and 4 yr), maturity levels (A, B,C) and marbling scores (none, traces, slight). Cookery traits were affected (P > .05) by marbling and maturity. Steaks with "traces" of marbling cooked faster and had more cooking losses (P < 0.05) than steaks with marbling amounts described as "slight" or "none". Steaks derived from the more mature, "C" cattle, required lesser time (i.e., 14 min) and retained 3 g/100 g more weight during cooking than those from younger ("A" and "B") maturity groups. Beef from bulls and steers typified as Zebu-dairy, lasted more in reaching the cooking endpoint (70 degrees C) than that from Zebu counterparts Regardless of age or cattle type, steaks from heifers cooked more rapidly than those from bulls and steers. These results call attention to some of the important sources of variation of cookery traits of beef and afford guidelines for meal planning.

[Experiences during training of a group for tasting bovine meat at an industrial refrigerated abattoir in Venezuela]. / Experiencias en el entrenamiento de un panel de degustación de carne vacuna a nivel de un matadero frigorífico industrial venezolano.

During three months, a group of people (meat consumers and active personnel) of a Venezuelan packing house were asked to assign discretionary scores to a sample of 103 beef longissimus steaks in order to familiarize them with the score sheet and to their future job as panelists. Scores assigned to 37 steaks by seven candidates that assisted regularly to these preliminary sessions (out of 12 attendants), were subjected to Analysis of Variance (ANOVA) to determine variability among judges before training. The whole group (n = 12) potential candidates from both sexes, and ranging between 25 and 45 years, were interviewed and pre selected for formal training. Triangle tests were used as selection tool and allowed for dismissing two of them. Training reinforced acquaintance with test procedures and improved natural abilities, sensitivity and memory for test attributes by using an 8-point descriptive scale to describe samples differing in fiber tenderness, amount of connective tissue, overall tenderness, juiciness, and flavor intensity. After 2 mo. of training (5 h weekly) the first panel performance evaluation (PPE) was conducted over 4 days with 3 sessions per day and 3 samples per session with 9 different samples. Data for each candidate were subjected to one-way ANOVA and F-ratio served as criteria to rank candidates' ability for describing each attribute. Panelist 7 and 8 rated last and were excused to conform an 8-member panel. The panel evaluated 300 samples during a 6-mo period and a second PPE was conducted. The second PPE revealed changes in relative ranking positions. Data from the first 40 (out of 300) samples were subjected to ANOVA for testing score (panelist) variability after training. A significant effect of panelist was detected before (P < .05) and after (P < .001) training, but a much greater variability became apparent in untrained candidates. Mean separation for trained panelist only differed in decimal units within the same points or adjacent points of the scale. Results validated methodologies used for panel training and the panel capability for sensorial evaluation of non-processed beef.