Xinglian Xu

Changes in flavor compounds of dry-cured Chinese Jinhua ham during processing

Sixty experimental Jinhua hams were processed by a traditional method using green hams from local Liangtouwu cross-bred pigs. Samples of Biceps femoris were taken from five hams randomly at each of the key stages of production, i.e., green ham, end of salting, end of sun-drying, middle of loft-aging, end of loft-aging, post-aging-1 and post-aging-2. Analysis of flavor compounds showed 89 compounds at the green ham stage and at the end of salting, 90 at the end of sun-drying, 91 at the middle of loft-aging, 96 at the end of loft-aging, 93 at the post-age-1 and 94 at the post-age-2. The flavor compounds could be clustered in the following chemical families: alkanes and alkenes, aromatic hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters, oxygenous heterocycle compounds, nitrogenous compounds, sulphur compounds, chloride compounds, amides, and terpenes. During processing, the concentrations of aldehydes and carboxylic acids increased; while the concentrations of alcohols, ketones, alkanes, alkenes, aromatic and cyclic hydrocarbons decreased. Sulphur compounds and pyrazines were formed and increased continuously during processing. In the final Jinhua ham, the contents of aldehydes, carboxylic acids, alcohols and ketones were 45.07%, 18.39%, 13.93% and 9.00% of the total flavor substances, respectively. The first principal component was a group dominated by five unbranched aldehydes; the second principal component was a group dominated by five branched and unbranched alcohols, two branched ketones, toluene, hexane and 4-nitrophthalamide. The two principal components explained 90.6% of the total flavor variance in Jinhua ham.

Meat quality and cooking attributes of thawed pork with different low field NMR T21

A relationship of low field NMR T(2) components to meat quality and cooking attributes of pork was investigated. Longissimus muscle was removed from 23 pig carcasses at 24h postmortem for meat quality measurements and cooking test. Frozen samples were classified into three groups by LF-NMR T(21) of thawed samples: A (<40ms), B (40-44ms) and C (>44ms). There were significant differences (P<0.05) in pH, lightness (L* value) and pressing loss among the three groups. Cooking time to attain 70°C was slightly lower in group C than the other groups. Shear force value of cooked samples was not affected by T(21). The component T(21) correlated (P<0.05) with L* value, muscle pH and pressing loss, while L* value correlated (P<0.05) with thawing loss and muscle pH. Therefore, combined LF-NMR and color measurements could be a good way to differentiate water holding capacity of pork.

Isolation and identification of antioxidant peptides from jinhua ham.

The antioxidant activities of the peptides extracted from Jinhua ham were evaluated on the basis of hydroxyl radical scavenging activity, DPPH radical scavenging activity, and Fe(2+) chelating ability. The peptide extracts exhibited great hydroxyl radical scavenging activity and DPPH radical scavenging activity as well as Fe(2+) chelating ability at the concentration of 1 mg/mL, which suggested the presence of peptides with antioxidant activity. The peptides were separated using size exclusion chromatography and reversed-phase HPLC. The fraction with highest DPPH radical scavenging activity was further purified and identified using liquid chromatography tandem matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (HPLC-MALDI-TOF/TOF-MS). The sequence of the antioxidant peptide was identified as Gly-Lys-Phe-Asn-Val. The assessment of fractions indicated that the hydrophobic fractions contributed more to free radical scavenging activities than the hydrophilic peptides. It was concluded that natural peptides extracted and isolated from the Jinhua ham by several chromatographic techniques have antioxidant activities.

China's meat industry revolution: Challenges and opportunities for the future

From a very limited ration of meat only for urban citizens to the worlds largest meat-producing country, from a handful of processing facilities in major cities to thousands of modern meat packing and processing plants throughout the country, the Chinese meat industry has gone through drastic revolutionary changes particularly in the last three decades. Before the national economic reform in the late 1970s, meat production in China was extremely limited; hence, meat was rationed, treated as a highly precious food, and was highly valued. However, new processing technology developments, as related to meat animal production, slaughtering, processing, and distribution have transformed the inefficient Chinese meat industry that prepared only a handful of traditional products into a vast enterprise today that is manufacturing a huge variety of fresh and further processed items enjoyed by the average Chinese household. Along with this evolution, there has been the emergence of mega-scale meat companies and rapid advances in meat science and technology that address many aspects of meat. This review will highlight some milestone changes of the Chinese meat industry and discuss challenges and opportunities ahead in the global market for China.

Redox Regulation in Cancer Stem Cells

Reactive oxygen species (ROS) and ROS-dependent (redox regulation) signaling pathways and transcriptional activities are thought to be critical in stem cell self-renewal and differentiation during growth and organogenesis. Aberrant ROS burst and dysregulation of those ROS-dependent cellular processes are strongly associated with human diseases including many cancers. ROS levels are elevated in cancer cells partially due to their higher metabolism rate. In the past 15 years, the concept of cancer stem cells (CSCs) has been gaining ground as the subpopulation of cancer cells with stem cell-like properties and characteristics have been identified in various cancers. CSCs possess low levels of ROS and are responsible for cancer recurrence after chemotherapy or radiotherapy. Unfortunately, how CSCs control ROS production and scavenging and how ROS-dependent signaling pathways contribute to CSCs function remain poorly understood. This review focuses on the role of redox balance, especially in ROS-dependent cellular processes in cancer stem cells (CSCs). We updated recent advances in our understanding of ROS generation and elimination in CSCs and their effects on CSC self-renewal and differentiation through modulating signaling pathways and transcriptional activities. The review concludes that targeting CSCs by manipulating ROS metabolism/dependent pathways may be an effective approach for improving cancer treatment.

Changes of intramuscular phospholipids and free fatty acids during the processing of Nanjing dry-cured duck

In this study, changes of intramuscular phospholipids and free fatty acids were tracked during the processing of Nanjing dry-cured duck. Phospholipids were identified and quantified by high performance liquid chromatography combined with UV and evaporative light scattering detectors. The types and quantities of free fatty acids and fatty acids derived from phospholipids were analyzed by capillary gas chromatography. The results showed that raw duck meat had high quantities of phosphatidylethanolamine, and phosphatidylcholine (37.95% and 54.07% of total phospholipids, respectively), which contained high percentages of polysaturated fatty acids. The percentages of total phospholipids, phosphatidylethanolamine, and phosphatidylcholine decreased during processing, with a concomitant increase in quantities of free fatty acids. The lipolysis of phospholipids, especially phosphatidylethanolamine is the main contributor to the increase of free fatty acids.

Meat, dairy and plant proteins alter bacterial composition of rat gut bacteria.

Long-term consumption of red meat has been considered a potential risk to gut health, but this is based on clinic investigations, excessive intake of fat, heme and some injurious compounds formed during cooking or additions to processed meat products. Whether intake of red meat protein affects gut bacteria and the health of the host remains unclear. In this work, we compared the composition of gut bacteria in the caecum, by sequencing the V4-V5 region of 16S ribosomal RNA gene, obtained from rats fed with proteins from red meat (beef and pork), white meat (chicken and fish) and other sources (casein and soy). The results showed significant differences in profiles of gut bacteria between the six diet groups. Rats fed with meat proteins had a similar overall structure of caecal bacterial communities separated from those fed non-meat proteins. The beneficial genus Lactobacillus was higher in the white meat than in the red meat or non-meat protein groups. Also, rats fed with meat proteins and casein had significantly lower levels of lipopolysaccharide-binding proteins, suggesting that the intake of meat proteins may maintain a more balanced composition of gut bacteria, thereby reducing the antigen load and inflammatory response in the host.

Influence of Various Levels of Flaxseed Gum Addition on the Water-Holding Capacities of Heat-Induced Porcine Myofibrillar Protein

UNLABELLED As a food hydrocolloid, flaxseed gum (FG) can significantly increase the water-holding capacity (WHC) of food, which is important to both yield and texture of related products. The main purpose of this study is to examine the WHC increase by FG in a meat product and the mechanism of the interactions between proteins and polysaccharides when FG is added into porcine myofibrillar protein (PMP). Increasing the FG concentration caused a significant increase in WHC (P<0.001). Scanning electron micrographs (SEM) showed that WHC in the protein gel network was related to gel microstructure. Distributed analysis of the T2 relaxation revealed that addition of FG significantly decreased water mobility of porcine myofibrillar protein (PMP) (P<0.05). The Fourier transform infrared spectroscopy (FT-IR) analysis suggested that the FG adding strengthened electrostatic attraction of PMP system. Improvement of WHC in heat-induced PMP by FG is concentration dependent and achieved by a finer gel network, lower relaxation time, and stronger electrostatic attraction. PRACTICAL APPLICATION   Flaxseed gum (FG) addition significantly increased water holding capacity (WHC) of porcine myofibrillar protein (PMP). In addition, the improvement of WHC in heat-induced PMP by FG was concentration dependent and achieved by a finer gel network, lower relaxation time, and stronger electrostatic attraction. Thus, FG has potential for use in meat products.

Phospholipase A2 and antioxidant enzyme activities in normal and PSE pork

In order to reveal the relationship between phospholipase A(2) and antioxidant enzymes and drip loss in pork, the study was designed to examine the effects of phospholipase A(2) and antioxidant enzymes on the water-holding capacity of pork during postmortem chilling. Six PSE and RFN samples (longissimus muscle) were used to determine the activities of phospholipase A(2) (tPLA(2,) cPLA(2)+sPLA(2) and iPLA(2)), superoxide dismutase (SOD) and GSH-Px, and acid phospholipase. The results showed that pH(1 h) and pH(24 h) from PSE pork were lower (p<0.01) than for normal pork (RFN), but the L* value at 1h and 24h postmortem, TBARS content, drip loss at 48 h and 96 h, cooking loss, tPLA(2) activity and iPLA(2) were higher (p<0.01) than of normal pork. Correlation analysis indicated that drip loss at 48 h was negatively related to pH(1 h) (p<0.01) and pH(24 h) (p<0.01) but positively to T(1 h) (p<0.01) and the activities of total phospholipase A(2) (p<0.05) and calcium-independent phospholipases A(2) (p<0.01). The tPLA(2) and GSH-Px play important roles in drip loss.

Effect of fasting on energy metabolism and tenderizing enzymes in chicken breast muscle early postmortem.

Pre-slaughter fasting is a very important practice in the meat industry. The present study was designed to investigate the effect of fasting on energy metabolism and tenderizing enzymes in chicken muscle early postmortem. A total of 30 Yellow-feathered chickens were deprived of feed for 0 h, 12 h and 24 h before slaughter (n=10 each group). Breast muscles were removed and cut into 3 parts and stored at 0°C for 0 h, 3 h and 10 h. Samples were used for analyses of zymography, cathepsins, pH, glycogen/ATP/ADP/AMP, hormones and ultrastructure. Fasting caused the accelerated depletion (p<0.05) of glycogen, ATP and ADP before or immediately after slaughter, but no difference existed in ATP at 3 and 10 h (p>0.05). Fasting resulted in greater ultimate pH (p<0.05). Zymography indicated that fasting delayed the activation of μ/m-calpain (p<0.05), however, it accelerated the release of lysosomal enzymes (p<0.05). Fasting for 24 h resulted in greater ultrastructural changes and plasma corticosterone levels than fasting for 12 h and control groups. Therefore, fasting for no more than 12 h is acceptable in practice.