Technical note: The Effect of Freezing on Warner-Bratzler Shear Force Values of Beef Longissimus Steaks Across Several Postmortem Aging Periods

The objective of this study was to compare fresh and frozen protocol procedures for Warner- Bratzler shear force (WBSF) determination on steaks aged for different periods of time. The fresh protocol consisted of measuring WBSF on steaks cooked on the exact day the aging period ended. The frozen protocol consisted of measuring WBSF on steaks that were aged, frozen (−16°C) for approximately 2 mo, thawed for 24 h, and then cooked. Twenty-two strip loin steaks from each of 20 crossbred heifers and steers were individually vacuum-packaged and assigned to either the fresh or frozen protocol and one of 11 aging periods (1, 2, 3, 4, 5, 6, 7, 10, 14, 21, or 35 d). The frozen protocol resulted in lower (P \u3c 0.05) WBSF values than the fresh protocol for beef longissimus steaks that were aged for 1, 2, 3, 4, 6, 7, 10, 14, or 35 d postmortem. An interaction (P \u3c 0.05) between protocol and postmortem aging resulted from larger differences between protocols at shorter aging periods than at longer aging periods. Correlations and mean differences revealed that frozen protocol WBSF values were not highly indicative of fresh protocol WBSF values at the same period of postmortem aging, but rather suggested that frozen protocol WBSF values at shorter aging times were useful in estimating WBSF values from fresh protocols at longer aging times. Cooking loss was higher (P \u3c 0.05) for frozen vs fresh protocol steaks at all aging periods except for 14, 21, or 35 d. These findings suggest that if research constraints warrant the freezing of samples, shorter aging periods before freezing (6 and 7 d) should be used to estimate WBSF of fresh aged beef (14 to 21 d). In trials in which several postmortem aging periods or very short aging periods are of interest, we recommend that WBSF be assessed using the fresh protocol

Evaluating the Point of Separation, During Carcass Fabrication, Between the Beef Wholesale Rib and the Beef Wholesale Chuck

This study determined whether there is a logical point of value change, related to either tenderness or consumer acceptance, at which to separate the beef carcass within the rib/chuck region. Rib/chuck rolls (RCR); (n = 30) consisting of the ribeye roll and chuck eye roll subprimals (2nd through 12th rib locations) were cut into 22 steaks each (two steaks per rib location), and Warner-Bratzler shear force and consumer purchase preference were evaluated for steaks at each rib location. Steaks from different locations of the RCR were composed of differing proportions of several muscles: longissimus muscle (LM), spinalis dorsi and multifidus dorsi (SM), and complexus (CO). The LM(4th to 12th rib) contained three tenderness regions: 7th through 12th rib, 5th and 6th ribs, and 4th rib regions (lowest, intermediate, and highest shear force values, respectively; P \u3c 0.01). Shear force differed (P \u3c 0.05) among rib locations for the SM (2nd to 9th rib), but no logical pattern was evident. The CO (2nd to 7th rib) was more tender toward the anterior end (P \u3c 0.05). The region of the RCR represented by the 4th through 6th rib locations had steaks with higher weighted-average shear force (average shear force of each steak, weighted for surface area of each muscle) values than the remainder of the RCR (P \u3c 0.05). Animal-to-animal variation in shear force was 36% greater than rib-to-rib variation in shear force; thus, statistically significant differences in tenderness among rib locations may be undetectable by consumers. Steaks (n = 330) were offered for sale at a retail supermarket and case time was monitored on each steak to determine consumer purchase preference. Steaks from the 2nd through 4th rib locations required more time to sell (P \u3c 0.01) than steaks from the 5th through 12th rib locations. Two alternative locations for the rib/chuck separation point could be between the 6th and 7th ribs, yielding a ribeye subprimal useful in marketing a “premium quality” product, or between the 4th and 5th ribs, which would yield four more 2.5-cm ribeye steaks per carcass

Increasing Tenderness of Beef Round and Sirloin Muscles Through Prerigor Skeletal Separations

Crossbred steers (n = 30) were used to explore and compare tenderness improvements in beef round and sirloin muscles resulting from various methods of pre-rigor skeletal separations. Animals were slaughtered according to industry procedures, and at 60 min postmortem one of six treatments was applied to each side: A) control, B) saw pelvis at the sirloin round junction, C) separate the pelvic-femur joint, D) saw femur at mid-point, E) combination of B and C, and F) combination of B and D. After 48 h, the following muscles were excised from each side: semi-membranosus, biceps femoris, semi-tendinosus, and adductor from the round; vastus lateralis and rectus femoris from the knuckle; and gluteus medius, biceps femoris and psoas major from the sirloin. Following a 10-d aging period, samples were removed from each muscle to determine the effect of treatment on sarcomere length and Warner-Bratzler shear force. Most skeletal separation treatments resulted in longer sarcomeres than controls for semi-membranosus, adductor, semi-tendinosus, and gluteus medius muscles. All skeletal separation treatments yielded shorter sarcomeres for the psoas major as compared with controls. Warner-Bratzler shear force differed among treatments for rectus femoris, semi-tendinosus, and psoas major. For rectus femoris, treatments C, D, E, and F resulted in lower (P \u3c 0.05) shear values than for controls. Treatments B, D, and F increased shear force of the semi-tendinosus relative to controls (P \u3c 0.05) within muscle. Treatment F resulted in higher shear force values for the PM than controls (P \u3c 0.05). Correlations between sarcomere length and shear force were found to be low and quite variable among muscles. In general, treatments increased sarcomere length of several muscles from the sirloin/round region, but had mixed effects on shear force values

Composite reverberation mapping

Reverberation mapping offers one of the best techniques for studying the inner regions of quasi-stellar objects (QSOs). It is based on cross-correlating continuum and emission-line light curves. New time-resolved optical surveys will produce well-sampled light curves for many thousands of QSOs. We explore the potential of stacking samples to produce composite cross-correlations for groups of objects that have well-sampled continuum light curves, but only a few (∼2) emission-line measurements. This technique exploits current and future wide-field optical monitoring surveys [e.g. Pan-STARRS, Large Synoptic Survey Telescope (LSST)] and the multiplexing capability of multi-object spectrographs (e.g. 2dF, Hectospec) to significantly reduce the observational expense of reverberation mapping, in particular at high redshift (0.5–2.5). We demonstrate the technique using simulated QSO light curves and explore the biases involved when stacking cross-correlations in some simplified situations. We show that stacked cross-correlations have smaller amplitude peaks compared to well-sampled correlation functions as the mean flux of the emission light curve is poorly constrained. However, the position of the peak remains intact. We find that there can be ‘kinks’ in stacked correlation functions due to different measurements contributing to different parts of the correlation function. While the magnitude of the kinks must be fitted for, their positions and relative strengths are known from the spectroscopic sampling distribution of the QSOs making the bias a one-parameter effect. We also find that the signal-to-noise ratio in the correlation functions for the stacked and well-sampled cases is comparable for the same number of continuum and emission-line measurement pairs. Using the Pan-STARRS Medium-Deep Survey (MDS) as a template, we show that cross-correlation lags should be measurable in a sample size of 500 QSOs that have weekly photometric monitoring and two spectroscopic observations. Finally, we apply the technique to a small sample (42) of QSOs that have light curves from the MDS. We find no indication of a peak in the stacked cross-correlation. A larger spectroscopic sample is required to produce robust reverberation lags

Stacked reverberation mapping

Over the past 20 years reverberation mapping has proved one of the most successful techniques for studying the local ( 0.1, or for the more-luminous quasars that make up the majority of current spectroscopic samples, or for rest-frame ultraviolet emission lines available in optical spectra of z > 0.5 objects. Previously, we described a technique for stacking cross-correlations to obtain reverberation mapping results at high z. Here, we present the first results from a campaign designed for this purpose. We construct stacked cross-correlation functions for the C IV and Mg II lines and find a clear peak in both. We find that the peak in the Mg II correlation is at longer lags than C IV consistent with previous results at low redshift. For the C IV sample, we are able to bin by luminosity and find evidence for increasing lags for more-luminous objects. This C IV radius–luminosity relation is consistent with previous studies but with a fraction of the observational cost

Mutual Authentication for Low-Power Mobile Devices

Abstract. We propose methods for mutual authentication and key exchange. Our methods are well suited for applications with strict power consumption restrictions, such as wireless medical implants and contactless smart cards. We prove the security of our schemes based on the discrete log gap problem