Effects of extended postmortem aging and intramuscular location on protein degradation, muscle fiber morphometrics, and tenderness of beef longissimus lumborum and semitendinosus steaks

The objective of this study was to determine effects of extended aging and intramuscular location on Warner-Bratzler shear force (WBSF), muscle fiber cross-sectional area (CSA), and protein degradation of semitendinosus (ST) and longissimus lumborum (LL) steaks. Left ST and LL were removed from 40 carcasses at 6 d postmortem. The ST was fabricated into 5 locations (LOC), with LOC 1 being most proximal and LOC 5 being most distal. The posterior LL was fabricated into 3 LOC, with LOC 1 being most anterior. Vacuum sealed ST steaks were aged 7, 14, 28, 56, or 112 d postmortem, while LL steaks were aged 7, 28, or 112 d postmortem at 2 ± 1°C. A steak from each LOC was assigned to WBSF or laboratory analyses. There were no Day of Aging (DOA) × LOC interactions for all dependent variables (P > 0.06). There were DOA effects for ST and LL WBSF values and degraded 38-kDa desmin (DES; P < 0.01). Day-7 ST-steak WBSF value was greater than all other days (P < 0.01) and d-14 steaks had greater WBSF value than remaining days (P < 0.05). Day-28 ST-steak WBSF values were greater than d-56 and -112 (P < 0.01), which did not differ (P = 0.53). In the LL, d-7 steaks had greater WBSF values than the other two timepoints (P < 0.01) and d-28 steaks had greater (P < 0.01) WBSF values than d-112 steaks. Degraded ST 38-kDa DES content was less on d 7 and 14 compared to all other days (P < 0.03), but did not differ (P = 0.79) from each other. Days 28 and 56 38-kDa DES content was less than d 112 (P < 0.01), but did not differ (P = 0.34) from each other. Degraded LL 38-kDa DES content was less on d 7 than d 28 and 112 (P < 0.02), which did not differ (P = 0.67). There were LOC effects for only ST WBSF and muscle fiber CSA (P < 0.05). Semitendinosus steak LOC 1 and 2 had greater WBSF values than all other locations (P < 0.01), but did not differ (P = 0.32) from each other. Semitendinosus steak LOC 3 and 5 had greater WBSF values than LOC 4 (P < 0.01), but did not differ (P = 0.85) from each other. The CSA of all ST fiber types were largest in LOC 1 compared to all other fiber types (P < 0.01). The CSA of all LOC 2 and 3 fiber types was greater than LOC 4 and 5 (P < 0.01), but were not different from each other (P > 0.81), and LOC 4 had greater CSA than LOC 5 (P < 0.01). Steak aging WBSF value improvements seemed proteolysis catalyzed, while the ST intramuscular tenderness gradient was more likely due to muscle fiber CSA.

Surface-Engineered Li4Ti5O12 Nanostructures for High-Power Li-Ion Batteries

Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries. In this study, a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio. A Li-deficient off-stoichiometry leads to the coexistence of phase-separated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate performances. However, after the solvothermal process, an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2. The Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahigh-rate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates, respectively. Furthermore, the electrode exhibits an ultrahigh-charging-rate capability up to 1200C (60 mAh g−1; discharge limited to 100C). Unlike previously reported high-rate half cells, we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 cathode. The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity, respectively. Room- (25 °C), low- (− 10 °C), and high- (55 °C) temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.

Modifications of Membrane Phospholipids in Response to Extended Aging from Pork Loins

ObjectivesIt is well established that fresh meat shelf-life deteriorates during aging process. We hypothesize that part of the shelf-life reduction is due to membrane phospholipid deterioration through phospholipase activity and/or phospholipid oxidation during aging. Therefore, the objective of this study was to characterize the modifications/deterioration of phospholipid classes/species in pork loins from 3 different aging periods.Materials and MethodsLoins from 20 carcasses were collected at a commercial harvest facility in the Midwest 1 d postmortem from carcasses of Duroc sired crossbred pigs. Four chops from each carcass containing only the longissimus muscle were vacuum packaged and aged at 4°C for 1, 8, and 21 d. A sensitive approach based on electrospray ionization tandem mass spectrometry was used to comprehensively analyze phospholipid composition using the lipid extract from each sample at each aging period (n = 60). Unsaturation index (UI; measurement of the number of double bonds) for each phospholipid species class was also calculated to quantify fatty acyl chain unsaturation for each sample in each aging period.ResultsTotal phospholipid quantity in pork loins was not different between 1d and 8d aged chops but decreased significantly from 8d to 21d of aging (806.6 vs. 297.5 nmol phospholipid/mg lipid; P < 0.01). On the other hand, the mol% data (distribution of each phospholipid species in relative % of total phospholipid) revealed that phosphatidylinositol (PI) and phosphatidylserine (PS) increased in mol% from 1d to 21d of aging in pork loins (P < 0.01). This increase was mainly due to the increase of PI 38:4 (primarily 18:0/20:4) and PS 36:2 (primarily 18:0/18:2) between 1d and 21d samples (P < 0.01). The results showed that phospholipid degradation products like lysophosphatidylcholine (LPC) mol% rose quickly after short term aging (8d) but remained constant through the rest of the 21d aging period (P < 0.01). Conversely, lysophosphatidylethanolamine (LPE) was unaltered between 1d and 8d of aging but decreased between 8d and 21d aged pork loins (P < 0.01). The mol% of phosphatidic acid (PA) also increased between 1d and 21d aged pork loins (P < 0.05). Extended aging did not alter the mol% of total phosphatidylcholine (PC), ether-linked PC (ePC), sphingomyelin (SM), phosphatidylethanolamine (PE) or ether-linked PE (ePE; P > 0.05). Surprisingly, UI revealed the exact opposite trend as the mol% data. The UI of PI and PS decreased (P < 0.01) from 1d to 21 d of aging in pork loins due to the disappearance of many minor PI and PS species with very long chain fatty acids and multiple double bonds such as PI 42:10 and PS 44:10. There was also a slight increase of PC UI after 8 d of aging in pork loins (P < 0.01). The UI for LPC, ePC, SM, LPE, PE, ePE and total phospholipid were not altered in any of the aging periods (P > 0.05).ConclusionThese results confirmed our hypothesis that phospholipids undergo extensive degradation during aging. The data also indicated that the majority of phospholipids in pork loins may maintain integrity over short period aging (1–8d). Among the phospholipid classes, PI and PS were slightly more resistant to deterioration compared with the others due to their ability to modify fatty acyl chain saturation. Additional investigations are necessary to define the role of phospholipid modifications in fresh pork shelf-life and flavor.

Effects of Extended Aging on the Flavor Characteristics of Grass and Grain Fed Australian Beef Longissimus Thoracis

ObjectivesThe objective of this study was to investigate the effects of extended wet ageing on the flavor characteristics, of grass and grain fed Australian beef lumborum thoracis.Materials and MethodsCube rolls (HAM #2244) were collected from grass and grain fed cattle (n = 30) at a commercial abattoir near Brisbane, Australia. Cube rolls were vacuum packaged and shipped under refrigeration (0–2°C) to Texas Tech University. Each cube roll was cut into 2.5-cm steaks and labeled according to position from posterior to anterior end. Steaks were vacuumed packaged, stored through the appropriate postmortem ageing period (35, 45, 55, or 65 d postmortem), and then frozen until further analysis. One steak from each cube roll was used for trained descriptive flavor analysis with 8 trained panelists comprised of mostly graduate students from Texas Tech University. Flavor attributes of cooked steaks were scored using 100-point anchored line scales (0 = none, 50 = moderate, and 100 = strong).Data were analyzed used PROC GLIMMIX of SAS with diet, postmortem ageing, and their interaction as fixed effects and panelist as a random effect. Final temperature was tested as a covariate for all the flavor attributes.ResultsAn interaction was detected only for the bitter flavor and overall juiciness (P ≤ 0.03). Beef flavor ID, fat-like, metallic, umami, and sweet were not influenced by diet or postmortem ageing (P > 0.05). Ageing influenced bloody serumy flavor (P > 0.05) with 45 d samples having greater flavor than 55 d samples, but not differing (P > 0.05) from any other ageing period. Diet and ageing influenced rancid flavor (P > 0.05), with grass fed samples having a stronger rancid flavor than grain fed samples. Samples aged 65 d had a stronger rancid flavor than 45 or 55-d samples, and 35-d samples had the lowest rancid flavor. Diet and ageing influenced grassy flavor (P > 0.05), again being stronger in grass than grain fed samples. Samples aged 35 d had a weaker (P > 0.05) grassy flavor than any other ageing period, which did not differ (P > 0.05). Diet and ageing had an effect on liver-like flavor (P < 0.05) with stronger flavors in grain than grass fed samples and liver-like flavor increasing with postmortem ageing time. Sour flavor was affected by diet only (P < 0.05) with grass fed samples having stronger sour flavor than grain fed samples. Ageing had an effect on overall tenderness (P < 0.05); samples aged 35 d were least tender, and samples aged 45 d were more tender than 55 d samples but did not differ from 65 d samples.ConclusionThe results suggest that beef flavor as measured by beef flavor ID and umami were not impacted by extended ageing; however, some off-flavors grew stronger as ageing time extended. Flavor attributes such as rancid, grassy, sour were stronger in grass than grain fed samples, but grain fed has a stronger liver-like flavor. Ageing influenced both overall tenderness and juiciness, but typically not in a linear fashion.

Long-Term Aging Performance Analysis of Oil Modified Asphalt Binders

Oil modification of asphalt binders is a widely adopted strategy for meeting low temperature performance grade (PG) specifications. There is no shortage of data characterizing the rheological benefits of several oil modifiers. Current AASHTO M320/M332 specifications evaluate low-temperature performance using the bending beam rheometer which measures creep stiffness and relaxation properties of the asphalt binder after 20 h of aging using a pressure aging vessel (PAV). In this study, extended aging effects on oil and polymer modified binders are investigated using three oil-modified binders compared against a control binder using PG and PG+ testing methods. The oils evaluated include bio-oil and re-refined engine oil bottoms. All binders were subjected to a rolling thin film oven and 20-h PAV aging, as well as extended PAV aging of 40 and 60 h. Binders are evaluated using multiple stress creep recovery, AASHTO TP123 dynamic shear rheometry elastic recovery, and linear amplitude sweep tests in addition to standard PG methods. The results show that many of the rheological benefits supplied by the oils tend to diminish after 40 h of PAV aging. However, the long-term effects depend greatly on the type of oil used, as well as the type of polymer modification used. The results suggest that 20-h PAV aging may not be sufficient to predict the long-term performance of the binder, and that extended aging periods (40-h PAV aging) should be considered when selecting oil modified asphalts.

78 Effects of extended aging, modified atmospheric packaging, and display time on metmyoglobin reducing activity and oxygen consumption of high-pH beef

Metmyoglobin reducing activity (MRA) and oxygen consumption (OC) are two important biochemical processes that can influence beef color. Several studies have determined the effects of aging and modified atmospheric packaging (MAP) on biochemical properties of normal-pH beef (5.5–5.7 pH range). However, limited knowledge is currently available on the effects of aging and MAP on biochemical properties of high-pH beef (> 6.2). Therefore, the objective was to determine the effects of extended aging, MAP, and display time on MRA and OC of high-pH beef. Ten USDA Choice (pH = 5.6) and ten ‘No-Roll’ dark cutting (high-pH; pH > 6.4) strip loins were obtained from a commercial packing plant within 72 hours of harvest. Loins were vacuum packaged and aged for 0, 21, 42, and 62 days at 4 °C. Following aging, from each normal- and high-pH loin sections, 2.5cm thick steaks were cut and packaged in PVC, high oxygen- (HiOx-MAP), and carbon monoxide modified atmospheric (CO-MAP) packaging. The surface color, MRA, and OC were determined on day 0 and 6 of the respective aging period. The experiment was replicated ten times (n = 10). High-pH steaks in all packaging and aging times had more stable red color than normal-pH steaks. High-pH steaks packaged in PVC and HiOx-MAP had greater (P < 0.05) MRA than normal-pH steaks. There were no differences (P > 0.05) in MRA between normal- and high-pH steaks on day 21 when steaks were packaged in CO-MAP, but high-pH had greater (P < 0.05) MRA on day 62. At all aging periods, high-pH steaks had greater (P < 0.05) OC than normal-pH steaks. However, a decrease in OC was greater (P < 0.05) for high-pH than normal-pH steaks. The results suggest that normal- and high-pH beef have different trends for the changes in MRA and OC.