Moisture absorption early postmortem predicts ultimate drip loss in fresh pork

Variation in the terminology and methodologies applied to the analysis of water holding capacity in meat research

Studies examining meat quality variation, possibly resulting from animal physiology, processing, or ingredient additions, are likely to include at least one measure of water holding capacity (WHC). Methods for evaluating WHC can be classified as direct or indirect. Direct methods either gauge natural release of fluids from muscle or require the application of force to express water. The indirect methods do not actually measure WHC. They attempt to separate meat into two or three categories based on predictions of direct method results: the extreme of high and low WHC and an optional 'normal' group. Considerable statistical analyses are required to generate these predictive models. Presently, there are inconsistent terms (e.g., water holding, WHC, water binding, water binding potential/capacity) used to describe WHC and no standardized techniques recommended to evaluate it. To ensure that results can be compared across different laboratories, a better consensus must be reached in how these terms are employed and how this critical parameter is determined.

Weighted gene co-expression network analysis reveals potential candidate genes affecting drip loss in pork

Drip loss is an essential evaluation indicator for pork quality. It is closely related to other meat quality indicators, including water-holding capacity, water loss rate and pH value at 45 min (pH₁ ) and 24 h post-mortem (pH₂ ), and is influenced by environmental and genetic factors and their interactions. We previously conducted differentially expressed gene analysis to identify candidate genes affecting drip loss using eight individuals with extremely high- and low-drip loss selected from 28 purebred Duroc pigs. Using 28 identical samples, in the present study, we performed weighted gene co-expression network analysis with drip loss and drip loss-related traits, including water-holding capacity, water loss rate, pH₁ and pH₂ . A total of 25 modules were identified, and five of them correlated with at least two drip loss or drip loss-related traits. After functional enrichment analysis of genes in the five modules, three modules were found to be critical, as their genes were significantly involved in amino acid metabolism, immune response and apoptosis, which have potential relationships with drip loss. Furthermore, we identified five candidate genes affecting drip loss in one critical module, AASS, BCKDHB, ALDH6A1, MUT and MCCC1, as they overlapped with differentially expressed genes detected in our previous study, exhibited protein-protein interactions and had potential biological functions in affecting drip loss according to the literature. The outcomes of the present study enhance our understanding of the molecular mechanisms underlying drip loss and will aid in improving the pork quality.

The influence of marinade composition on pork tenderness

The aim of the study was to identify the effect of marinating meat on selected quality determinants. Fifty-four pork samples were prepared from longissimus dorsi muscles, each 2.5-cm-thick; they were subsequently marinated for 24 hours (n = 12) and control samples were also prepared (n = 6). The following marinades were used: base marinade (M) whose ingredients included a mixture of herbs and condiments (salt, pepper, juniper berries, rosemary, bay, pimento, garlic) and 3 liquid marinades obtained by adding to the base marinade of apple cider vinegar (MV), light beer (MB) and buttermilk (MM). In the samples pH, marinade absorption, drip loss, cooking loss, WBSF and tenderness by sensory assessment were measured(1,2).

The pH value of the material used for the study was 5.8 ± 0.02. The use of the base marinade increased the pH to 6.37 ± 0.03, whereas the liquids used in the marinades decreased the pH to 5.5 ± 0.05. Marination resulted in an increase in the material weight by 2.87 ± 0.05% (MB), 4.45 ± 0.07% (MM), 0.87 ± 0.03% (M). The addition of vinegar resulted in exuding meat juice and a decrease in the material weight by 2.53 ± 0.06% (MV). Using the base marinade reduced drip loss (0.53 ± 0.01%) compared with the control (1.37 ± 0.03%). Sour marinade (MV) increased cooking loss by 18% compared to the control, the MB and MM marinades did not affect this parameter significantly, and the base marinade had a significant effect on reducing cooking loss by 24%. Each of the marinades used had a significant effect on reducing the maximum shear strength by 31% (liquid marinades) and by as much as 46% – base marinade. This relationship was confirmed in a sensory assessment, where higher notes for tenderness were given when base marinade (9.2 ± 0.3pts), marinade with buttermilk (8.1 ± 0.2pts), and marinades with vinegar and beer (7.3 ± 0.3pts) was used compared with control samples (5.7 ± 0.4pts).

This study has shown a beneficial effect of the marinades on the tenderness of the products. The most beneficial effect on the quality determinants under study was exerted by the base marinade, which consisted of herbs and condiments only.

Comparative gene expression profiling of muscle reveals potential candidate genes affecting drip loss in pork

BACKGROUND

Drip loss is a key aspect of meat quality. Transcriptome profiles of muscle with divergent drip loss would offer important insight into the genetic factors responsible for the trait. In this study, drip loss and other meat quality traits of 28 purebred Duroc pigs were measured, muscles of these individuals were RNA sequenced, and eight individuals with extremely low and high drip loss were selected for analyzing their transcriptome differences and identifying potential candidate genes affecting drip loss.

RESULTS

As a result, 363 differentially expressed (DE) genes were detected in the comparative gene expression analysis, of which 239 were up-regulated and 124 were down-regulated in the low drip loss group. The DE genes were further filtered by correlation analysis between their expression and drip loss values in the 28 Duroc pigs measured and comparison of them with QTLs affecting drip loss. Consequently, of the 363 DE genes, 100 were identified as critical DE genes for drip loss. Functional analysis of these critical DE genes revealed some GO terms (extracellular matrix, cell adhesion mediated by integrin, heterotypic cell-cell adhesion), pathway (ECM-receptor interaction), and new potential candidate genes (TNC, ITGA5, ITGA11, THBS3 and CD44) which played an important role in regulating the variation of drip loss, and deserved to carry further studies to unravel their specific mechanism on drip loss.

CONCLUSIONS

Our study revealed some GO terms, pathways and potential candidate genes affecting drip loss. It provides crucial information to understand the molecular mechanism of drip loss, and would be of help for improving meat quality of pigs.

Drip Loss Assessment by Different Analytical Methods and Their Relationships with Pork Quality Classification

We analyzed drip loss in pork by comparing the standard bag (DL), filter-paper wetness (FPW), and EZ-DripLoss methods by weighing the meat juice container and dabbed sample after 24 h and 48 h. Samples were classified into quality categories based on pH, color, and drip loss. The relationship between DL and FPW revealed the cut-off of 5% DL as corresponding to FPW of 139 mg; 1.89% when analyzed by weighing meat juice container or dabbed sample after 24 h; and 3.18% and 3.74% for those analyzed by weighing both meat juice container and dabbed sample after 48 h, respectively. Highest correlations were observed between DL and EZ when the meat juice container was weighed after 48 h (r=0.86). The EZ-DripLoss method in which the meat juice container was weighed after 24 h was able to distinguish drip loss into meat-quality categories in accordance with the bag method. Therefore, this method is recommended for meat categorization because of its greater standardization and ease of application.