M. J. Marchello

Soft tissue composition of pigs measured with dual x-ray absorptiometry: comparison with chemical analyses and effects of carcass thicknesses.

Evidence of the validity and accuracy of dual x-ray absorptiometry (DXA) to measure in vivo body composition is limited. We compared DXA estimates made in prone and side positions with measurements of chemical composition of 20 pigs (10 barrows and 10 gilts) weighing 52-113 kg. DXA yielded similar estimates of body composition in prone and side positions. DXA estimates of body composition were significantly correlated with reference compositional values (r2 = 0.927-0.998). No significant differences were found for determinations of body weight, fat mass (FM), fat free mass (FFM), bone-free, and fat-free mass (BFFFM) between DXA and chemical determinations. DXA significantly underpredicted percent fat (% fat); it underestimated FM (20%, P > 0.05), and overestimated FFM and BFFFM (6 and 9%, respectively, P > 0.05). Differences between individual determinations of FM and % fat by chemical analyses and DXA were significantly correlated with mean values. No significant correlations were found between the differences for weight, FM, % fat, FFM and BFFFM and measurements of carcass breadth (19-28 cm) and width (15-25 cm). Total errors in determination of DXA body composition variables were similar with body thicknesses less than and greater than 24 cm. These findings indicate that DXA is a valid and accurate method for determination of soft tissue composition. Initial problems with DXA determinations of % fat apparently have been reconciled partially with revisions in soft tissue analytic software.

SPOILAGE IDENTIFICATION OF BEEF USING AN ELECTRONIC NOSE SYSTEM

A commercially available Cyranose-320. conducting polymer-based electronic nose system was used to analyze the volatile organic compounds emanating from fresh beef strip loins (M. Longisimmus lumborum) stored at 4°C and 10°C. Two statistical techniques, i.e., linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA), were used to develop classification models from the collected sensor signals. The performances of the developed models were validated by two different methods: leave-1-out cross-validation, and bootstrapping. The developed models classified meat samples based on the microbial population into “unspoiled” (microbial counts 6.0 log10 cfu/g). Overall, quadratic discriminant-based classification models performed better than linear discriminant analysis based models. For the meat samples stored at 10°C, the highest classification accuracies obtained by the LDA method with leave-1-out and bootstrapping validations were 87.10% and 85.87%, respectively. On the other hand, classification by QDA and subsequent validation by leave-1-out and bootstrapping provided highest accuracies of 87.5% and 97.38%, respectively. For samples stored at 4°C, the LDA method provided highest classification accuracies of 79.17% and 85.64% using leave-1-out and bootstrapping validation, respectively. When the QDA method was used, the highest classification accuracies obtained for the samples stored at 4°C were 87.50% and 98.48%, respectively, with leave-1-out and bootstrapping validations.

Validation of dual x-ray absorptiometry for body-composition assessment of rats exposed to dietary stressors.

Evidence of the validity and accuracy of dual x-ray absorptiometry (DXA) to measure soft-tissue composition of laboratory rats with altered body composition associated with nutritional perturbations is lacking. We compared DXA determinations made in prone and supine positions with measurements of chemical composition of 49 male, weanling Sprague-Dawley rats that were fed the basal AIN-93 growth diet, were fed the basal diet modified to contain 30% fat, were fasted for 2 d, were limit fed 6 g of the basal diet daily for 1 wk, or were treated with furosemide (10 mg/kg intraperitoneally 2 h before DXA). DXA produced similar estimates of body mass and soft-tissue composition in the prone and supine positions. DXA estimates of body composition were significantly correlated with reference composition values (R(2) = 0.371-0.999). DXA discriminated treatment effects on body mass, fat-free and bone-free mass, fat mass, and body fatness; it significantly underestimated body mass (1% to 2%) and fat-free and bone-free mass (3%) and significantly overestimated fat mass and body fatness (3% to 25%). The greatest errors occurred in treatment groups in which body mass was diminished and body hydration was decreased. These findings suggest that DXA can determine small changes in fat-free, bone-free mass in response to obesity and weight loss. Errors in DXA determination of fat mass and body fatness associated with extra corporeal fluid and dehydration indicate the need for revision of calculation algorithms for soft-tissue determination.

Nutrient composition of raw and cooked Bison bison

Abstract Longissimus muscle from 30 bison were lyophilized and analyzed for various nutrients including moisture, protein, fat, cholesterol, gross energy, minerals, and fatty acids. In addition nine shoulder roasts and three round steaks were also collected. The relative amounts of nutrients to total calories make bison a highly nutrient-dense food, similar to domesticated meats such as beef, pork, and chicken. The lean tissue was low in fat (

STUDY OF HEADSPACE GASES ASSOCIATED WITH SALMONELLA CONTAMINATION OF STERILE BEEF IN VIALS USING HS-SPME/GC-MS

Sterile beef (fresh strip loins) samples were inoculated with Salmonella typhimurium, and both control and inoculated samples were stored at 20°C in 20 mL headspace vials covered with food-grade cling film. An array of volatile compounds was detected in the headspace of the control and inoculated samples. The study was conducted for four days, and the volatiles in the headspace were analyzed each day using manual headspace solid-phase microextraction (HS-SPME) in combination with gas chromatography-mass spectrometry (GC-MS). Acetic acid, ethanol, carbon dioxide, and 3-hydroxy-2-butanone were the most prominent compounds detected in the study. The F-tests (Fishers variance ratio) for the main effect of the sample source established acetic acid and ethanol as compounds of interest for monitoring the status of Salmonella in raw fresh beef. Good linear correlations were found between the logarithms of the peak area responses of these compounds with Salmonella count.

Lean beef spoilage and contamination analysis using a mixed metal oxide sensor based electronic nose

Foodborne illness is a significant problem of current focus. Electronic nose, or artificial nose, technology is a promising non-destructive evaluation tool for food quality assessment. Mixed metal oxide detector-based electronic nose system was developed and fabricated. Customized electronics were developed to operate detectors at different operating temperatures. Experiments were conducted to evaluate the performance of the electronic nose system for classifying spoiled and Salmonella contaminated samples. Meat samples were stored at two storage temperatures of 3oC and 10oC under simulated real world packaging conditions. Data analyses from the experiments utilized linear and quadratic discrimination method with bootstrapping techniques. A maximum accuracy of 90% and 89% were obtained for spoilage and Salmonella classification, respectively.