Leslie Thompson

Effects of conventional and grass feeding systems on the nutrient composition of beef

The objectives of this study were to determine the nutrient composition of grass-fed beef in the United States for inclusion in the USDA National Nutrient Database for Standard Reference, and to compare the fatty acid composition of grass-fed and conventionally fed (control) beef. Ground beef (GB) and strip steaks (SS) were collected on 3 separate occasions from 15 grass-fed beef producers that represented 13 different states, whereas control beef samples were collected from 3 regions (Ohio, South Dakota, and Texas) of the United States on 3 separate occasions. Concentrations of minerals, choline, vitamin B(12), and thiamine were determined for grass-fed beef samples. Grass-fed GB samples had less Mg, P, and K (P < 0.05), and more Na, Zn, and vitamin B(12) (P < 0.05) than SS samples. Fat color, marbling, and pH were assessed for grass-fed and control SS. Subjective evaluation of the SS indicated that grass-fed beef had fat that was more yellow in color than control beef. Percentages of total fat, total cholesterol, and fatty acids along with trans fatty acids and CLA were determined for grass-fed and control SS and GB. Grass-fed SS had less total fat than control SS (P = 0.001), but both grass-fed and control SS were considered lean, because their total fat content was 4.3% or less. For both GB and SS, grass-fed beef had significantly less (P = 0.001 and P = 0.023, respectively) content of MUFA and a greater content of SFA, n-3 fatty acids, CLA, and trans-vaccenic acid than did the control samples. Concentrations of PUFA, trans fatty acids, n-6 fatty acids, and cholesterol did not differ between grass-fed and control ground beef. Trans-vaccenic acid (trans-11 18:1) made up the greatest concentration of the total trans fats in grass-fed beef, whereas CLA accounted for approximately 15% of the total trans fats. Although the fatty acid composition of grass-fed and conventionally fed beef was different, conclusions on the possible effects of these differences on human health cannot be made without further investigation.

Demographics and beef preferences affect consumer motivation for purchasing fresh beef steaks and roasts

Surveys completed by 1370 consumers determined the motivational factors affecting consumer purchasing decisions for fresh beef steaks and roasts in three regions in the United States. Females placed greater importance on tenderness, ease of preparation, and nutritional value of steaks and roasts when compared to males. Age influenced tenderness, product consistency, and nutritional value of steaks, but influenced flavor, product consistency, and nutritional value of roasts. Consumers felt juiciness, nutritional value, and natural products were less important in determining their purchasing choices of steaks and roasts as their level of education increased. The preferred degree of doneness of steaks influenced the value placed on six of the nine purchasing motivators. Beef preferences and demographics influenced consumer purchasing decisions for fresh beef steaks and roasts. Results from this study can be used to help identify factors to positively influence purchasing decisions within targeted market segments.

Microbiology of pork carcasses from pigs with differing origins and feed withdrawal times

The effects of buying source (terminal market, buying station, outdoor farm, and indoor farm), feed withdrawal before slaughter (0, 2, 4, and 6 h), and the incidence of punctured gastrointestinal (GI) tracts during evisceration on the numbers of pathogenic and spoilage bacteria on pork carcasses were determined. Of the 932 samples tested, a 0% incidence of the pathogens Salmonella spp., Listeria monocytogenes , Campylobacter spp., Clostridium perfringens , and Yersinia enterocolitica was found.A significant (P < 0.05) location effect was found, with the belly-sternum region having higher total plate counts than the head, pelvic cavity, and diaphragm regions of the carcass. A significant (P < 0.05) buying-source effect indicated that pigs from buying stations had higher lactic acid bacteria counts than pigs from outdoor and indoor farms. A buying source by fasting time interaction (P < 0.05) was noted for GI tract weights, with the indoor farm pigs having the highest incidence of ruptured GI tracts. The removal of feed prior to slaughter resulted in lighter GI tract weights and a lowered incidence of vicera rupture resulting in a lowered risk of pathogen contamination of carcasses. The extent of punctured GI tracts during evisceration was influenced by fasting time and buying source and may be useful in a HACCP system for the pork-processing industry.

Intramuscular fat and fatty acid composition of longissimus muscle from divergent pure breeds of cattle

The objective of this study was to compare the fatty acid (FA) composition of intramuscular fat from the LM of 3 divergent breeds of cattle: Angus (AN, n = 9), Brahman (BR, n = 7), and Romosinuano (RM, n = 11). Cattle were blocked by breed and finished 129 d before slaughter in one year and 157 d in the next year. Longissimus muscle samples were collected from each carcass between the 10th and 13th ribs, trimmed of external fat, frozen in liquid nitrogen, homogenized, and used for fat extraction, using a modified Folch procedure. Extracted fat was analyzed for FA by using a GLC system with an HP-88 capillary column. Fatty acid composition was expressed using both a normalized percentage (%) and gravimetric calculation (mg/g of fresh muscle tissue) in relation to degree of saturation, which was determined using a saturation index (ratio of total SFA to total unsaturated FA). Crude fat determination revealed that LM from AN purebred cattle had the greatest amount of intramuscular fat (7.08%; P = 0.001). Although intramuscular fat of LM from RM contained a reduced percentage of total SFA (P = 0.002) compared with AN, it had the greatest percentage of total PUFA (P < 0.001 and P = 0.020). The percentages of total MUFA were similar among the 3 breeds (P = 0.675). The gravimetric calculation, a measure of actual FA concentration, showed significantly greater concentrations of SFA (26.67 mg/g), MUFA (26.50 mg/g), and PUFA (2.37 mg/g) in LM from AN cattle, as compared with LM from BR and RM cattle (P < 0.001). Interestingly, BR purebreds had the least PUFA concentration (1.49 mg/g; P <or= 0.001) in the LM, although their intramuscular fat content was similar to that of RM (P = 0.924). Regardless of breed, the MUFA proportion was always the greatest (47.58%; P <or= 0.005), whereas PUFA was the least contributor to FA composition (1.49 to 2.37 mg/g and 4.36 to 8.78%; P < 0.001). Beef LM fatty acid composition was characterized by palmitic and oleic acids being the most abundant FA (P < 0.001). These results suggested a genetic variation in FA synthesis and deposition among breeds that influenced both marbling and its composition.

Reduction of Microorganisms on Beef Surfaces Utilizing Electricity

The effects of continuous electrical current pulsed electrical current and voltage level on aerobic bacteria total coliforms and Salmonella typhimurium on top round beef steaks were examined. Electrical stimulation (620 v) for 20 and 60 s decreased (P<.05) coliform bacteria counts by an average of 81% (0.7 log CFU/cm2) compared to untreated steaks. Compared to non-sprayed steaks coliform counts were lower (P<.05) for steaks to which 3 ml of sterile deionized water was applied before electrical stimulation. Steaks subjected to 3 6 12 and 24 pulses (400 v/2.5 cm) reduced (P<.05) S. typhimurium counts compared to those on untreated steaks. A voltage level of 1200 v/2.5 cm reduced (P<.05) the numbers of S. typhimurium by 82% compared to steaks that Received no electrical stimulation. Electrical stimulation reduces numbers of bacteria present on beef surfaces.

Reduction of Salmonella Enteritidis in Shell Eggs Using Directional Microwave Technology

Microwaves have been shown to cause thermal as well as nonthermal destruction of pathogens such as Salmonella Enteritidis, which is commonly found in shell eggs. The objective of this study was to examine the use of new directional microwave technology to reduce Salmonella Enteritidis without causing any detrimental effects on quality in white and brown eggs. Treatments were control and microwaved white and brown eggs. Applying directional microwave technology resulted in a 2-log reduction of Salmonella Enteritidis in both the high (10(5) cfu/g) and low (10(2) cfu/g) inoculum. At d 0, there were no differences in water activities, albumen pH, and combined pH between treatments; however, there were significant changes in yolk pH. Collectively, these results indicate that applying directional microwave technology can reduce Salmonella Enteritidis in shell eggs without causing any detrimental effects to quality.

Relationships of slice shear force and Warner-Bratzler shear force of beef strip loin steaks as related to the tenderness gradient of the strip loin.

This study was conducted to investigate the effects of steak location within a strip loin and USDA quality grade on muscle fiber angle, slice shear force (SSF), and Warner-Bratzler shear force (WBSF) and to determine the relationship between SSF and WBSF. Steak location influenced both SSF and WBSF values, as steaks from the anterior portion were typically tenderer than steaks from the posterior end. Although there is some discrepancy between the two shear force methods, both agree that at least the first 5 anterior-most steaks are comparable. Muscle fiber angle was affected by steak position within the strip loin, as the fiber angle shifted between steaks 7 and 8. Quality grade had a significant effect on beef tenderness for both SSF and WBSF. Finally, there was a strong relationship between lateral SSF and average WBSF (r = 0.64), which are currently the most commonly used measurements for instrumental tenderness.

Chilling and trimming effects on the microbial populations of pork carcasses.

The effects of chilling (normal chill or freeze chill) and trimming (hot fat trim or no fat trim) on the microbial populations of pork carcases were evaluated. In a two-part study, composited ham, loin, belly, and shoulder samples from 30 park carcasses had similar aerobic plate counts, averaging 5.5 log10 CFU/cm2. The nofat trim, normal chill procedure typically used in the industry, however, produced higher coliform and Staphylococcus spp. counts (P < 0.05). The hot fat trim, freeze chill treatment had the lowest lactic acid bacteria counts. Only 1 sample in 60 tested positive for Salmonella spp. Vacuum-packaged hams and loins stored at 4 degrees C for 14 days had similar (P > 0.05) aerobic plate counts, lactic acid bacteria and Staphylococcus spp. counts regardless of trim, chill, or the location of treatment, averaging 5.7, 6.3 and 1.4 log10 CFU/cm2, respectively. Hams had higher counts than loins all three days; however, only the difference on day 2 was significant. The desire to reduce microbial populations on pork carcasses as a food-safety issue and the coming implementation of hazard analysis critical control points (HACCP) programs warrants the use of trimming and chilling methods as critical control points or good manufacturing practices and standard operating procedures in the pork slaughter, processing, and packaging industry.

Nutrient Database Improvement Project: The influence of USDA Quality and Yield Grade on the separable components and proximate composition of raw and cooked retail cuts from the beef chuck

This study was designed to provide updated information on the separable components, cooking yields, and proximate composition of retail cuts from the beef chuck. Additionally, the impact the United States Department of Agriculture (USDA) Quality and Yield Grade may have on such factors was investigated. Ultimately, these data will be used in the USDA - Nutrient Data Laboratorys (NDL) National Nutrient Database for Standard Reference (SR). To represent the current United States beef supply, seventy-two carcasses were selected from six regions of the country based on USDA Yield Grade, USDA Quality Grade, gender, and genetic type. Whole beef chuck primals from selected carcasses were shipped to three university laboratories for subsequent retail cut fabrication, raw and cooked cut dissection, and proximate analyses. The incorporation of these data into the SR will improve dietary education, product labeling, and other applications both domestically and abroad, thus emphasizing the importance of accurate and relevant beef nutrient data.

Reduction of microorganisms on beef surfaces with electricity and acetic acid

This study determined the effect of a 2% acetic acid spray, pulsed-power electricity, pulsed-power electricity with a spray of sterile deionized water, and a combination of acetic acid spray and pulsed-power electricity in reducing the pathogens Escherichia coli O157 and Salmonella typhimurium and aerobic plate counts on beefsteaks compared to an inoculated control. Ten steaks per treatment were inoculated with 1 ml of E. coli O157 (l05 CFU/ml) or S. typhimurium (105 CFU/ml) for 2 min and then subjected to one of the five treatments. Acetic acid spray and acetic acid spray and pulsed-power electricity treatments significantly (P < .05) reduced the incidence of Escherichia coli O157 compared to inoculated controls and produced a 1-log CFU/cm2 reduction in the incidence of S. typhimurium . Ten steaks per treatment were also inoculated with 1 ml of S. typhimurium (l05 CFU/ml) for 2 min, treated with acetic acid spray, pulsed-power electricity and a sterile deionized water spray, or acetic acid spray and pulsed-power electricity and stored in an incubator at -2°C for 48 h to stimulate chill-cooler conditions in the beef industry. Acetic acid spray with and without pulsed-power electricity caused a 1-log CFU/cm2 reduction in S. typhimurium . These data indicate a need for the use of both 2% acetic acid and pulsed-power electricity in packing-house facilities to help achieve the goal of improved microbiological safety of beef.