Ruitong Dai

Colour and sarcoplasmic protein evaluation of pork following water bath and ohmic cooking.

The objective of this study was to investigate the effects of ohmic (OH) and waterbath (WB) cooking on colour attributes and sarcoplasmic changes of porcine longissimus dorsi muscle at the same endpoint temperatures (EPTs; range 10°C-80°C). The OH treatment was carried out at 10 Vcm(-1), and the WB temperature at 85°C. The colour parameters, deoxymyoglobin% (DeoMb) and metmyoglobin% (MetMb) of the OH-cooked meat were significantly lower (P<0.05) than those obtained by WB-cooking at the same EPTs (range 60°C-80°C). SDS-PAGE analysis showed that the meat treated with WB-cooking had a lower sarcoplasmic protein solubility (5.97 mg/g vs.14.89 mg/g, P<0.05) and fainter protein bands than that of OH-cooking thus, indicating paler colour, and lower water-holding capacity especially in WB-cooked meat at EPTs above 40°C. Strong correlations among lightness, browness, metmyoglobin% and soluble proteins were observed in meat following OH-cooking.

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.

Feasibility assessment of vacuum cooling followed by immersion vacuum cooling on water-cooked pork

Vacuum cooling followed by immersion vacuum cooling was designed to cool water-cooked pork (1.5±0.05 kg) compared with air blast cooling (4±0.5°C, 2 m/s), vacuum cooling (10 mbar) and immersion vacuum cooling. This combined cooling method was: vacuum cooling to an intermediate temperature of 25°C and then immersion vacuum cooling with water of 10°C to the final temperature of 10°C. It was found that the cooling loss of this combined cooling method was significantly lower (P<0.05) than those of air blast cooling and vacuum cooling. This combined cooling was faster (P<0.05) than air blast cooling and immersion vacuum cooling in terms of cooling rate. Moreover, the pork cooled by combined cooling method had significant differences (P<0.05) in water content, color and shear force.

Molecular Understanding of Meat Quality Through Application of Proteomics

Proteomics, as a significant and potent postgenomic tool in the field of meat science, allows researchers to decipher underlying molecular mechanisms behind different meat quality traits. In recent years, growing attention has been paid to biomarkers accounting for meat quality attributes by means of potent proteomic technologies with the objective to gain deeper insight. This review will focus on the biomarkers of protein changes associated with the most important meat quality traits, including tenderness, color, and water-holding capacity. Molecular understanding of meat quality through application of proteomics will be conducive to generating a large amount of scientific knowledge that helps improve our understanding of meat quality, improve control, and tailor better meat quality.

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.

Influence of different production strategies on the stability of color, oxygen consumption and metmyoglobin reducing activity of meat from Ningxia Tan sheep

Fifty male Ningxia Tan sheep were randomly divided into five groups (10 per group). Different feeding strategies were applied to each group for 120 days prior to slaughter. The sheep belong to five groups were pastured for 0 h (feedlot-fed), 2h, 4h, 8h, 12h per day on a natural grazing ground, respectively. M. semitendinosus muscle from Tan sheep was obtained after slaughter. Instrumental color, pH values, oxygen consumption rate, metmyoglobin reducing activity and relative metmyoglobin percentages were analyzed after 1, 3, 5, 7 and 9 days of refrigerated storage. Long-term daily grazing and herbage-based diet were conducive to maintain a lower oxygen consumption rate, higher metmyoglobin reducing activity and lower metmyoglobin accumulation. The combination of pasture-fed and feedlot-fed was conducive to weight gain, and at the same time, increased the color stability of the meat from Ningxia Tan sheep.

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.

Modeling and predicting the effect of temperature on the growth of Proteus mirabilis in chicken.

A predictive model to study the effect of temperature on the growth of Proteus mirabilis was developed. The growth data were collected under several isothermal conditions (8, 12, 16, 20, 25, 30, 35, 40, and 45°C) and were fitted into three primary models, namely the logistic model, the modified Gompertz model, and the Baranyi model. The statistical characteristics to evaluate the models such as R(2), mean square error, and Sawas Bayesian information criteria (BIC) were used. Results showed that the Baranyi model performed best, followed by the logistic model and the modified Gompertz model. R(2) values for the secondary model derived from logistic, modified Gompertz, and Baranyi models were 0.965, 0.974, and 0.971, respectively. Bias factor and accuracy factor indicated that both the modified Gompertz and Baranyi models fitted the growth data better. Therefore, the Baranyi model was proposed to be the best predictive model for the growth of P. mirabilis.

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.