Qianqian Yu

Towards muscle-specific meat color stability of Chinese Luxi yellow cattle: A proteomic insight into post-mortem storage

Searching for potential predictors of meat color is a challenging task for the meat industry. In this study, the relationship between meat color parameters and the sarcoplasmic proteome of M. longissimuss lumborum (LL) and M. psoas major (PM) from Chinese Luxi yellow cattle during post-mortem storage (0, 5, 10 and 15days) were explored with the aid of the integrated proteomics and bioinformatics approaches. Meat color attributes revealed that LL displayed better color stability than PM during storage. Furthermore, sarcoplasmic proteins of these two muscles were compared between days 5, 10, 15 and day 0. Several proteins were closely correlated with meat color attributes and they were muscle-specific and responsible for the meat color stability at different storage periods. Glycerol-3-phosphate dehydrogenase, fructose-bisphosphate aldolase A isoform, glycogen phosphorylase, peroxiredoxin-2, phosphoglucomutase-1, superoxide dismutase [Cu-Zn], heat shock cognate protein (71kDa) might serve as the candidate predictors of meat color stability during post-mortem storage. In addition, bioinformatics analyses indicated that more proteins were involved in glycolytic metabolism of LL, which contributed to better meat color stability of LL than PM. The present results could provide a proteomic insight into muscle-specific meat color stability of Chinese Luxi yellow cattle during post-mortem storage.

Unraveling proteome changes of Holstein beef M. semitendinosus and its relationship to meat discoloration during post-mortem storage analyzed by label-free mass spectrometry.

Label-free proteomics was applied to characterize the effect of post-mortem storage time (0, 4, and 9days at 4°C±1°C) on the proteome changes of M. semitendinosus (SM) in Holstein cattle, and correlations between differentially abundant proteins and meat color traits were investigated. The redness (a*) value decreased significantly (P<0.05) during post-mortem storage, meanwhile, the relative proportion of metmyoglobin increased significantly (P<0.05) from 16.99% at day 0 to 40.26% at day 9. A total of 118 proteins with significant changes (fold change>1.5, P<0.05) was identified by comparisons of day 4 vs. day 0, day 9 vs. day 0, and day 9 vs. day 4. Principal component and hierarchical cluster analyses of these proteins were performed, and results exhibited clear distinctions among samples from different storage times. Eighteen differentially abundant proteins were correlated closely with the a* value of meat. Bioinformatics analyses revealed that most of these proteins were involved in glycolysis and energy metabolism, electron-transfer processes, and the antioxidation function, which implied an underlying connection between meat discoloration and these biological processes. SIGNIFICANCE It is always a challenge for scientists to improve the stability of meat color during post-mortem storage and retail display. However, the mechanism involved in meat discoloration has not been unraveled completely, and the application of label-free proteomics in studying meat discoloration has not been reported. Our work discovers some key proteins in SM muscle of Holstein cattle that were correlated with a* value of meat via label-free proteomics. Bioinformatics analyses revealed that some of these differentially abundant proteins were involved in glycolysis and energy metabolism, electron-transfer processes, and the antioxidation function, which implied an underlying connection between meat discoloration and these biological processes. These results provide the theoretic basis on understanding of complicated biochemical changes and underlying molecular mechanisms responsible for meat discoloration.

Bacterial diversity analysis of pork longissimus lumborum following long term ohmic cooking and water bath cooking by amplicon sequencing of 16S rRNA gene

The bacterial ecology of long term ohmic- (LTOH) and water bath- (WB) cooked pork longissimus lumborum during refrigerated storage was investigated by culture-dependent and amplicon sequencing of 16S rRNA gene. High bacterial diversity was observed in both LTOH- and WB-cooked meat, and the diversity decreased with prolonged storage, however, it was more complex in LTOH-cooked meat compared with WB treated ones. Bacillus, Pseudomonas, Enterococcus and Lactococcus were the most prevalent genera in the first two weeks and were replaced by Carnobacterium by the end of storage. Brevundimonas, Bacteroidaceae, Lactobacillaceae, uncultured Clostridiales Family_XIII, Alcaligenaceae and Micrococcales were more abundant in LTOH-cooked meat, while only Moraxellaceae were more abundant in WB-cooked samples. The different abundances may have resulted from the reaction of bacteria to different heating mechanisms. Overall, LTOH-cooked meat has a similar shelf-life with shorter processing time compared to WB treated ones.

Comparative proteomics to reveal muscle-specific beef color stability of Holstein cattle during post-mortem storage

Label-free strategy was applied to elucidate muscle-specific beef (M. longissimuss lumborum (LL) and M. psoas major (PM)) color stability of Holstein cattle during post-mortem storage at 4°C±1°C. LL showed greater (p<0.05) redness (a∗) value than PM at day 4 and 9 storage, while the proportion of metmyoglobin in PM exhibited a greater increase than in LL muscle. Furthermore, an overabundance of proteins with the functions of antioxidation, protection, and repair in LL were conducive to its color stability, whereas the overabundant proteins/subunits involved in tricarboxylic acid (TCA) cycle and mitochondrial electron transport chain (ETC) in PM indicated greater oxidative metabolism and degradation of ETC complexes, resulting in poor color stability. Bioinformatic analyses indicated that these proteins mainly participated in oxidation-reduction processes, TCA cycle, and ETC processes. All of these results provided a deeper understanding of muscle-specific beef color stability from the perspective of proteomics.

Comparative proteomic analysis of Escherichia coli O157:H7 following ohmic and water bath heating by capillary-HPLC-MS/MS

Escherichia coli O157:H7 is an important food-borne pathogenic microorganism that has been used as a model organism for studying microbial inactivation effects and inactivation mechanism in various sterilization technologies. The objective of this study was to investigate the effects of high voltage short time ohmic- (HVST), low voltage long time ohmic- (LVLT), and water bath- (WB) heating on inactivation and proteome changes of E. coli O157:H7 cells at the same endpoint temperature of 72 °C, and to analyze whether a non-thermal death effect existed in ohmic heating. The inactivation effect of E. coli cells after HVST was comparable to WB, and the largest inactivation was observed after LVLT. There was lower intracellular protein content detected in LVLT and HVST samples than those of WB (P < 0.05). Quantitative proteomic profiles using capillary-HPLC-MS/MS technology identified 2626 proteins, among them, a total of 142 (62 up-regulated and 80 down-regulated), 129 (37 up-regulated and 92 down-regulated), and 61 (20 up-regulated and 41 down-regulated) differential proteins were obtained by comparisons of HVST vs. CT (control), LVLT vs. CT, and WB vs. CT samples, respectively, and revealing a strongest cell response to HVST followed by LVLT and WB. Compared with WB samples, more protein changes in HVST and LVLT samples were mainly attributed to the leakage of intracellular proteins due to the damage of cell membrane by current of ohmic heating. Bioinformatics analysis indicated that the differential proteins were mainly involved in transcription, translation, cell wall and membrane biogenesis, amino acid, carbohydrate, and lipid metabolism. KEGG enrichment analysis indicated that the ribosome, terpenoid backbone biosynthesis, glycerophospholipid metabolism, ABC transporters, and folate biosynthesis were significantly enriched. Overall, the application of both HVST and LVLT treatments had the potential to inactivate E. coli cells, especially HVST with a shorter heating time, and the results in this study presented an important step toward understanding the response of E. coli cells to ohmic heating on proteome level.

Unravelling proteome changes of chicken egg whites under carbon dioxide modified atmosphere packaging

Unfertilized chicken eggs within 24h of laying were chosen and stored at 25°C and 45% humidity for 0, 20, and 40days. The experimental group (EG) was the carbon dioxide-modified atmosphere packaging (CDMAP) group, whereas the control group (CG) contained eggs without special handling. Egg freshness indexes were measured. The proteome of the egg whites was determined by LC-MS/MS using isobaric tags for relative and absolute quantitation (iTRAQ). A total of 87 proteins were detected. The results indicated that CDMAP can control the change in protein abundance. Using a correlation analysis between the protein abundance and freshness indexes of the EG, Beta-hexosaminidase, Trypsin inhibitor ClTI-1 and Apolipoprotein D were determined to be potential predictors of egg freshness. In comparing the proteomes of the EG and CG, it was concluded that CDMAP could affect the proteins related to egg vitelline membranes, eggshell matrix and metabolic intensity to maintain egg freshness.

Label-free proteomic strategy to compare the proteome differences between longissimus lumborum and psoas major muscles during early postmortem periods

Beef M. longissimus lumborum (LL) and M. psoas major (PM) muscles showed significant differences in various meat quality attributes (such as pH, lipid oxidation, and color stability). To better understand the underlying molecular variations between LL and PM, the proteome changes at early postmortem periods were investigated by comparative proteomic approach. A total of 504, 519, and 487 mutual proteins of each comparison (LL vs. PM at 1 h, 12 h, and 24 h, respectively) were successfully identified. Among these proteins, 238 proteins were differentially expressed in LL samples compared to PM ones. Proteins involved in glycolysis and with functions of protection and repair were overabundant in LL, whereas those participating in tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and fatty acid β-oxidation were overabundant in PM. Furthermore, the bioinformatics analyses provided insightful information for explaining the differences in meat quality traits between LL and PM, and for further metabolomics studies.