Evaluation of RNA quality and functional transcriptome of beef longissimus thoracis over time post-mortem

Evaluating RNA quality and transcriptomic profile of beef muscle over time post-mortem may provide insight into RNA degradation and underlying biological and functional mechanisms that accompany biochemical changes occurring post-mortem during transformation of muscle to meat. RNA was extracted from longissimus thoracis (LT) sampled from British Continental crossbred heifer carcasses (n = 7) stored at 4°C in an abattoir drip cooler at 5 time points post-mortem, i.e., 45 min (0 h), 6 h, 24 h, 48 h, and 72 h. Following RNA-Sequencing, processed reads were aligned to the ARS-UCD1.2 bovine genome assembly. Subsequent differential expression (DE) analysis identified from 51 to 1434 upregulated and 27 to 2256 downregulated DE genes at individual time points compared to time 0 h, showing a trend for increasing counts of both upregulated and downregulated genes over time. Gene ontology and biological pathway term enrichment analyses on sets of DE genes revealed several processes and their timelines of activation/deactivation that accompanied or were involved with muscle transformation to meat. Although the quality of RNA in refrigerated LT remained high for several days post-mortem, the expression levels of several known biomarker genes for meat quality began to change from 24 h onwards. Therefore, to ensure accuracy of predictions on meat quality traits based on the expression levels of those biomarker genes in refrigerated beef muscle tissue, it is crucial that those expression measurements be made on RNA sampled within 24 h post-mortem. The present study also highlighted the need for more research on the roles of mitochondrial genes and non-coding genes in orchestrating muscle tissue processes after death, and how pre-mortem immune status might influence post-mortem meat quality.

STUDIES ON CHEMICAL AND ORGANOLEPTIC PROPERTIES OF DEHYDRATED FORMED BEEF

Product yield, chemical properties, rehydratability and organoleptic characteristics were studied in dehydrated blends of raw beef muscle and connective tissue minces untreated or pre-treated with either 1.0% sodium chloride (NaCl), 0.3% sodium tripolyphosphate (STPP) or a combination of 0.7% NaCl plus 0.3% STPP. Sodium Chloride and tripolyphosphate either individually or combined significantly (P<0.05) increased product yield, moisture and ash contents, improved flavour and acceptability but depressed tenderness and rehydratability of dehydrated formed beef steaks. The additives slightly reduced protein and fat contents but significant (P>0.05). The combination of NaCl and STPP was found in most cases to impart the greatest effect on parameters measured. Based on the result, it was concluded that the products would be suitable for local systems of meat usage without fear of possible disintegration.

Impact of Sampling and Storage Techniques on Beef Muscle Measurements During Aging

ObjectivesThis objective was to determine if variations in beef sampling techniques utilized by meat researchers have a significant impact on beef muscle measurements during aging.Materials and MethodsTen beef short loins (IMPS 180) were purchased from a commercial packing plant within 48 h of slaughter. Loins were transported to the NDSU Meat Science laboratory where they were mapped into four sections from most anterior (1) to most posterior (4). Within sections, two, 40-g samples were removed; one sample was vacuum packaged (SMALL-VAC) and the other sample was stored in a wire-closure sealed bag (SMALL-BAG). The remaining whole short loin was vacuum packaged. All samples and whole short loins were stored at 4°C for 10 d. At 10 d, the short loins were sampled again where one, 40-g sample was removed from each mapped section (WHOLE-VAC). Purge loss was measured by weighing each sample prior to packaging treatment and at the end of the 10-d aging period; percentage change in weight was calculated. Troponin-T degradation was determined by western blot. Briefly, protein was extracted in an SDS-phosphate buffer, separated by SDS-PAGE under reducing conditions, and transferred to PVDF membranes. Western analysis was done using an anti-troponin-T antibody (clone JLT 12), and immunoreactive bands (Band 1 = doublet ∼42 to 45 kDa; Band 2 = doublet ∼ 36 to 38 kDa, Band 3 = 30 kDa) were analyzed for differences in density. Sarcomere length was determined using HeNe laser diffraction. Thinly sliced samples (∼50 to 100 mg) were placed in a sucrose-phosphate buffer and subjected to beadmill homogenization. A drop of the homogenate was placed on a glass slide, diffraction patterns were measured, and sarcomere length was calculated. Thiobarbituric acid reactive substances (TBARS) were assessed using a colorimetric assay. Analysis was conducted using Proc Mixed procedure of SAS where storage type, section location, and their interaction were used as fixed effects.ResultsThere was a storage type by section interaction (P = 0.017) that occurred with purge loss. SMALL-VAC samples released more purge than SMALL-BAG from the more posterior samples. Troponin-T Band 1 tended to be less (P = 0.07) in WHOLE-VAC samples compared with SMALL-VAC and SMALL-BAG. There was a storage type by section interaction (P = 0.02) where the most posterior SMALL-BAG samples had greater Band 2. There were no differences (P ≥ 0.25) in Band 3 between treatments. There was no difference (P = 0.29) in sarcomere length due storage type. However, there was a difference (P = 0.01) in sarcomere length between sections, where the shortest sarcomeres were in the center of the strip loin and longest sarcomeres on either end. There was a storage type by section interaction (P = 0.02) for TBARS where concentration was greatest in the most posterior portion of SMALL-BAG compared with WHOLE-VAC.ConclusionCollection of smaller samples for aging studies may not be representative of samples aged in a whole primal cut and may influence research outcomes.