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Abstract: Protein denaturation has a major impact on meat quality parameters such as water holding capacity, tenderness and color. Specific information about structural changes of the individual muscle proteins post-mortem could help understand the factors affecting meat quality. An aromatic dye, 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid (bisANS) that binds to the hydrophobic patches of proteins was used to monitor changes in the conformation of individual sarcoplasmic proteins caused by pH. The bisANS reagent was covalently linked to the proteins with UV-light and the proteins were separated and identified using gel electrophoresis and mass spectrometry. The results showed that the sarcoplasmic proteins creatine kinase M, aldolase A and lactate dehydrogenase showed increased hydrophobicity whereas carbonic anhydrase III showed decreased hydrophobicity with increasing pH. Temperature only had a marked effect on the results at around 40°C, there being no change between 25 and 35°C. [Copyright &y& Elsevier]

Abstract: Proper labeling of meat products is important to ensure fair-trading and to enable consumers to make informed choices. Different investigations indicate that wrong labeling where thawed meat is labeled as fresh meat is present in 8–15% of analyzed samples. Enforcement of regulations requires adequate analytical methods where enzymatic-, DNA based-, spectroscopic-, bio imaging- and sensory techniques constitute the majority of published papers. The molecular changes that these techniques detect are described. The capability of both discrimination between fresh and thawed meat, and determination of frozen storage time are discussed for each of the analytical techniques. The products included in this review are primarily whole meat from Bos taurus (cow), Sus scrofus (pig) and Gallus gallus (chicken). The best analytical choice in the discrimination of fresh vs. thawed meat is concluded to be a combination of analytical methods. [Copyright &y& Elsevier]

Abstract: Multi angle light scattering was used to determine the myofibril fragmentation of pig longissimus dorsi muscle which was then compared with results from the common turbidity method. The method is based on measurement of the myofibril particle size distribution with the use of a special optical unit containing several individual detectors. The method was able to determine post-mortem changes in a pig muscle homogenate without purification of the myofibrils and is therefore simpler and much faster than the traditional turbidity method. There was a significant correlation (p <0.01) between Warner–Bratzler shear force (WBSF) and particle size distribution. The root mean square error of prediction was found to be 6.1N (10–15% of the measured WBSF) when multivariate data analysis was used to make a prediction model for WBSF. Multi angle light scattering is very useful for estimation of myofibril fragmentation since the method is fast and the sample preparation is simple. [Copyright &y& Elsevier]

To identify myofibrillar substrates of μ-calpain under post-mortem conditions, a combination of SDS–PAGE, two-dimensional gel electrophoresis (2DE) and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) was used. Purified myofibrils were incubated with μ-calpain under post-mortem-simulated conditions for two or four days at 4 °C. The resulting protein changes were analyzed by SDS–PAGE and 2DE. The μ-calpain-mediated protein changes were identified by peptide-mass mapping using MALDI-TOF MS and revealed that desmin, actin, myosin heavy chain, myosin light chain I, troponin T, tropomyosin α1, tropomyosin α4, thioredoxin and CapZ are all degraded in vitro by μ-calpain. The findings that actin and myosin heavy chain are substrates of μ-calpain were rather surprising, as it has previously been reported that these proteins are resistant to μ-calpain degradation. However, both actin and myosin heavy chain are poor substrates compared with desmin. [Copyright &y& Elsevier]

During the thermal processing of milk, Maillard reactions occur between proteins and lactose to generate glycated proteins. In this study, a lactose-glycated caseinate was hydrolyzed by trypsin. The obtained glycated caseinate (GCN) hydrolysate had a lactose content of 10.8 g/kg of protein. We identified its glycation sites and then assessed it for its protective effect against lipopolysaccharide-induced barrier injury using a rat intestinal epithelial cell line (IEC-6 cells) as a cell model and unglycated caseinate (CN) hydrolysate as a reference. Results from our liquid chromatography–mass spectrometry analysis of the GCN hydrolysate verified that lactose glycation occurred at the Lys residues in 3 casein components (α S1 -casein, β-casein, and κ-casein), and this resulted in the formation of 5 peptides with the following amino acid sequences: EMPFPKYPKYPVEPF, HIQKEDVPSE, GSENSEKTTMPL, NQDKTEIPT, and EGIHAQQKEPM. The results from cell experiments showed that the 2 hydrolysates could promote cell growth and decrease lactate dehydrogenase release in the lipopolysaccharide-injured cells; more importantly, they could partially protect the damaged barrier function of the cells by increasing trans-epithelial electrical resistance, decreasing epithelial permeability, and upregulating the expression of the 3 tight junction proteins zonula occludens-1, occludin, and claudin-1. However, compared with CN hydrolysate, GCN hydrolysate showed lower efficacy in protecting against cellular barrier dysfunction. We propose that the different chemical characteristics of the CN hydrolysate and the GCN hydrolysate (i.e., amino acid loss and lactose conjugation) contributed to the lower barrier-protective efficacy of the GCN hydrolysate. During dairy processing, protein glycation of the Maillard type might have a non-negligible, unfavorable effect on dairy proteins, in view of the resulting protein glycation we found and the critical function of proteins for maintaining the integrity of the intestinal barrier. [ABSTRACT FROM AUTHOR]

Abstract: The effects of diacylglycerols (DAG), pork back fat and sunflower oil on water and fat mobility in fermented sausages were studied with 1H NMR relaxometry. The added fat affected the physicochemical parameters weight loss, water activity, moisture content and moisture content on a defatted-dry-matter basis of reduced-fat non-acid fermented sausages. The weight losses were the lowest in sausages prepared with DAG and sunflower oil, which resulted in higher water activity compared to sausages prepared with back fat. The relaxation times related to fat mobility differed between fat types and increased in the order: control

Abstract: This study aimed to detect variability in CAST, CAPN1 and CAPN3 porcine genes and to investigate the effect of CAST and CAPN1 polymorphisms on the activity of native and autolyzed μ-calpain and m-calpain, measured from 1 to 72h post-mortem in Longissimus dorsi (LD) muscle of 30 pigs. Effects of polymorphisms on meat quality parameter such as pH, color and drip loss were also evaluated. Samples carrying CAST EU137105:g.76,872AA genotype showed higher autolyzed μ-calpain activity 24 and 72h post-mortem, as well as lower drip loss values. Expression of CAST, CAPN1 and CAPN3 was assessed in LD muscles divergent for shear force. Higher CAST and CAPN3 expression was found in LD with high shear force (P <0.2), confirming a direct role for calpastatin but not for calpain 3 in meat tenderization. In conclusion, CAST gene affected post-mortem activation time of calpain and drip loss. [Copyright &y& Elsevier]