Biomedical subjects

J C Forrest

Publications and source records attributed to J C Forrest.

36 records · Page 2Linked to original sources

PubMed1993

Palatability of prerigor cooked boar meat.

Cooking reduces odor intensity in boar meat but also may induce lipid oxidation unless the meat pH is above approximately 6.0. This research was designed to determine the feasibility of cooking boar meat in the prerigor state to overcome boar odor and lipid oxidation problems. Prerigor and postrigor triceps brachii muscle samples from 40 boars (20 Duroc and 20 Yorkshire) were cooked to 60 degrees C, frozen and stored at -20 degrees C, reheated in a 60 degrees C water bath for 1 h, and then subjected to pH, thiobarbituric acid (TBA), and sensory analyses. Boar odor intensity and skatole concentration in backfat samples were determined by olfactory test and HPLC, respectively. Cooked (initial cooking) prerigor meat was found to have higher (P < .05) pH and lower (P < .05) TBA values than comparable postrigor meat (6.44 vs 6.09 and 2.15 vs 3.23, respectively). Regression analysis indicated an inverse relationship between pH and TBA values (r = -.52; P < .01). No appreciable changes in TBA values were noted after frozen storage for 14 to 98 d, but reheating increased TBA values (P < .05) in both prerigor and postrigor samples (3.45 vs 4.32, respectively). Sensory evaluation scores indicated that prerigor cooked meat was less tender with more pronounced rancid flavor than postrigor cooked meat (P < .05), but panelists may have allowed the toughness of the prerigor samples to adversely affect their flavor scores. No difference in boar odor was detected between rigor states or breeds. Mean skatole concentration in backfat was .12 micrograms/g and no difference was detected between breeds.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1993

Effect of heating rate on palatability and associated properties of pre- and postrigor muscle.

Precooked, uncured meat is not widely available to consumers, partially because of associated palatability problems and lack of published information on heat uptake under different industrial conditions. The objectives of this study were to determine the tenderness, extent of lipid oxidation, and total cooking losses in pre- and posterior beef and pork roasts heated at different rates. The muscles were cooked in stainless-steel, perforated heating chambers at oven temperatures of 150, 200, or 250 degrees C and the temperature rise during and after heating was monitored with a digital temperature recorder. Samples were vacuum-packaged, frozen at -20 degrees C for 45 d, thawed at 4 degrees C for 24 h, and reheated in 60 degrees C water for 1 h. Cooking losses, Warner-Bratzler shear force values, thiobarbituric acid values, and pH were determined. The results provide heating curves for pre- and postrigor beef and pork roasts at three oven temperatures. Prerigor samples of both species were less tender than postrigor samples (P < .05). Cooking losses were generally low in prerigor samples of both species compared with postrigor samples (P < .05). All beef samples had relatively low thiobarbituric acid (TBA) values before and after storage, whereas pork samples had relatively high TBA values before and after storage. Results indicate that prerigor cooked roasts shrink less, are equivalent or better in oxidative stability, and are less tender than postrigor cooked roasts under the conditions of this experiment.

Animals↗

PubMed1992

Evaluation of alternative techniques to determine pork carcass value.

Three techniques for estimating the value of pork carcasses were evaluated: an optical probe, a real-time ultrasound scanner, and an electromagnetic scanner (EMSCAN). The ability of these techniques to predict carcass value was compared to the predictive ability of actual measures of backfat depth and longissimus muscle area taken with a ruler and a dot grid. Results indicated the EMSCAN model was the best predictor of carcass value. However, the optical probe, ultrasound, and the ruler/dot grid all provided information not contained in the EMSCAN model. The choice among ultrasound, the optical probe, and the ruler/dot grid depends on how the carcass will be used. There is no significant difference between ultrasound and the ruler/dot grid or the optical probe and the ruler/dot grid if the carcass is to be marketed in wholesale primal form, but the ruler/dot grid is superior if the ham and loin are to be sold as lean, boneless products. A model combining the EMSCAN and optical probe readings provided more accurate value predictions than either technique alone. A carcass value matrix for use in pricing pork carcasses was developed using readings from the optical probe. Carcass use has a substantial impact on value differences between fat and lean pigs.

Adipose Tissue↗

PubMed1992

Genotype and treatment biases in estimation of carcass lean of swine.

Carcasses of 181 barrows, representing five genotypes, 1) H x HD, 2) SYN, 3) HD x L[YD], 4) L x YD, and 5) Y x L (H = Hampshire, D = Duroc, SYN = synthetic terminal sire line, L = Landrace, and Y = Yorkshire), and two levels of ractopamine (RAC) treatment (0 and 20 ppm) were completely dissected and the data were used to examine genotype and treatment (RAC) biases in estimation of fat-standardized lean weight and to evaluate accuracies and precisions realized by use of equations based on variables derived from different technologies. Independent variables used to establish regression equations represented technologies of direct carcass measurements, optical probe data, TOBEC (total body electrical conductivity) readings, and dissected (DHMLN) and fat-standardized (FSHMLN) ham lean. Genotype bias existed when any equation from a single technology was used and was minimized by combining FSHMLN with one TOBEC reading, carcass length, and the probe measurement of 10th rib fat depth. Large RAC biases appeared when equations from direct carcass measurements or optical probe data were used and were minimized by an equation using either DHMLN or FSHMLN. A practical equation with relatively high R2 value and small genotype and RAC biases were developed by combining TOBEC readings with direct carcass measurements of 10th rib fat depth and warm carcass weight.

Adipose Tissue↗

PubMed1992

Preparation of muscle samples for comparative electron microscopy.

The interpretation of muscle structure by scanning electron microscopy (SEM) has not been consistent among various studies. Consequently, the literature is confusing with respect to the identity of T-tubules, transverse ridges, Z-disks, and intermyofibrillar connections. The objective of this research was to evaluate the effects of different methods of sample preparation and imaging on ultrastructural details of previously identified transverse structures and intermyofibrillar connections and to verify or disprove the commonality of these structures under different viewing conditions. Scanning electron microscopy coupled with a cold stage, SEM at room temperature, and transmission electron microscopy (TEM) of thin sections were most appropriate for exposing detail of inter- and intracellular structures and for measuring sarcomere length and spacing of intermyofibrillar connections. Scanning electron microscopy of samples mounted on a cold stage, fractured, and sublimed provided excellent images of meat and muscle ultrastructure and may be used in correlative microscopy. Sarcomere length and spacing between intermyofibrillar connections were similar among most specimen preparation techniques and were affected similarly by heat treatments. Results indicate that the regularly spaced transverse structures viewed by conventional SEM and the intermyofibrillar connections viewed by low-temperature SEM are Z-disks.

Animals↗

PubMed1991

Effects of ractopamine, genotype, and growth phase on finishing performance and carcass value in swine: I. Growth performance and carcass merit.

A replicated factorial experiment using 183 individually fed crossbred barrows was conducted. Pigs were fed an 18.5% CP (.95% lysine) diet with 3,594 kcal of ME/kg. The effects of five genotypes (GT): 1) Hampshire (H) x (H x Duroc [D]), 2) synthetic terminal sire line, 3) (H x D) x (Landrace [L] x [Yorkshire (Y) x D]), 4) L x (Y x D), and 5) Y x L; two levels of ractopamine (RAC) treatment: 0 and 20 ppm; and three treatment weight periods (WT): 1) 59 to 100, 2) 73 to 114, and 3) 86 to 127 kg live weight on growth performance and carcass traits were evaluated. Ractopamine increased (P less than .0001) amount (FSL) and percentage (PFSL) of carcass lean standardized to 10% fat content, loin eye area (LEA), and dressing percentage (PDRES) and reduced (P less than .01) amount (DF) and percentage (PDF) of dissected fat. Magnitudes of RAC effects were smaller than those reported by other researchers. Effects of GT and WT on all growth and carcass traits were highly significant (P less than .001) except for those of WT on ADG (P less than .05) and GT on average feed intake (AFI) and backfat thickness at the last rib (BFLR; P less than .05). Genotype 3 performed better for most economically important traits than did GT 1 and 4, suggesting that heterosis existed in GT 3, which essentially was obtained by crossing GT 1 and 4. Among the three treatment periods, WT 2 had the highest ADG. As BW increased from WT 1 to 3, AFI and AFI/ADG ratio (FCR) increased and lean percentage decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1991

Effects of ractopamine, genotype, and growth phase on finishing performance and carcass value in swine: II. Estimation of lean growth rate and lean feed efficiency.

A replicated factorial experiment using 183 individually fed crossbred barrows was conducted. The pigs were fed an 18.5% CP (.95% lysine) diet with 3.594 kcal of ME/kg. The effects of five genotypes (GT): 1) Hampshire (H) X (H X Duroc [D]), 2) synthetic terminal sire line, 3) (H X D) X (Landrace [L] X [Yorkshire (Y) X D]), 4) L X (Y X D), and 5) Y X L; two levels of ractopamine (RAC) treatment: 0 and 20 ppm; and three treatment weight periods (WT): 1) 59 to 100, 2) 73 to 114, and 3) 86 to 127 kg live weight on ADG of dissected lean (ADLG) and fat standardized lean adjusted to 10% fat content (ADSLG) and feed efficiency of ADLG (LFE) and ADSLG (SLFE) were evaluated. Initial carcass lean quantity of each individual animal was determined by a regression equation (R2 = .95) generated from 30 additional barrows (six per GT) slaughtered at 59 kg and 30 (six per GT) untreated pigs slaughtered at 100 kg average live weight. Logarithmic and reciprocal transformations of dependent variables were used to stabilize heterogeneous variances and to improve normality of the residuals. Ractopamine increased (P less than .0001) ADLG, ADSLG, LFE, and SLFE, respectively, by 19.5, 25.0, 19.6, and 25.5%. Differences (P less than .001) were observed among genotypes for all traits, showing that considerable variation existed in the data and indicating that genetic improvement can be realized through the identification and selection of superior genotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Practical means for estimating pork carcass composition.

Three hundred sixty-one market-weight barrow and gilt carcasses were physically dissected into bone, skin, fat and muscle. A three-variable multiple linear regression equation containing the same independent variables (warm carcass weight, 10th rib loin muscle area and 10th rib fat depth) used (U.S.) to determine pork carcass lean weight was found to be the most practical means for predicting weight of muscle standardized to 10% fat. Multiple linear regression equations containing more than three independent variables produced only slight improvements in R2 values; however, the standard deviation about the regression line was not greatly improved by the addition of more independent variables to this three-independent-variable regression model. A single multiple linear regression equation using the three independent variables above may not be adequate to describe variation over the entire live-weight range for all hogs marketed in the U.S. For most accurate muscle weight prediction, different equations should be used for weight subclasses with one equation for carcasses under 100 kg and another for those heavier than 100 kg. A single prediction equation for muscle weight was adequate for carcasses of both barrows and gilts.

Adipose Tissue↗

PubMed1984

Isolation of Yersinia enterocolitica and related species from porcine samples obtained from an abattoir.

Swabs of swine carcasses and samples of porcine tongue and trim obtained from an abattoir were examined for the presence of Yersinia enterocolitica and related species (Y. intermedia, Y. kristensenii and Y. frederiksenii). Three enrichment media (phosphate buffered saline, sorbitol-bile salts-phosphate buffered saline, and a modified Rappaport's broth) were compared at 4 degrees C for their efficiency of recovery of Y. enterocolitica and related species. Two secondary enrichment procedures (post-enrichment in modified Rappaport's broth for 2 d at 25 degrees C and treatment with 0.5% KOH in 0.5% NaC1) also were evaluated. The porcine isolates were characterized by biochemical and serological examination, speciation, and biotyping. Eight of 43 samples were positive for Y. enterocolitica and related species. The combination of incubation in sorbitol-bile salts-phosphate buffered saline for 21 d at 4 degrees C followed by post-enrichment in modified Rappaport's broth yielded maximum number of isolates. All isolates, except one, were avirulent as determined by autoagglutination, calcium dependence at 37 degrees C, and HeLa cell invasiveness tests.

Animals↗

PubMed1976