Zhifei He

Effect of high-pressure treatment on the fatty acid composition of intramuscular lipid in pork.

To investigate the effect of high-pressure (HP) treatment on lipid oxidation and fatty acid composition of intramuscular lipid in pork, the longissimus muscles from Rongchang (RC) pig were pressurized at 200, 350 and 500 MPa for 20 min at 20°C prior to 7 days storage at 4°C. The changes in TBARS number, lipid content and fatty acid composition of total intramuscular lipids, phospholipids, triglycerides and free fatty acids in untreated and HP treated samples were analyzed. HP treatment had no significant effect on the content and fatty acid composition of total lipids and triglycerides in the samples, but treatment at 350 MPa and above led to marked increases in TBARS values and lipolysis of partial phospholipids causing a correlative increase of free fatty acid content. A preferential hydrolysis for polyunsaturated fatty acids (PUFA) in phospholipids was observed, which resulted in the percentage of PUFA in phospholipids decreasing markedly and thereby that in free fatty acids increasing significantly.

Development and application of a method for the analysis of two trichothecenes: Deoxynivalenol and T-2 toxin in meat in China by HPLC–MS/MS

A reliable and sensitive method was developed and successfully applied for the determination of deoxynivalenol and T-2 toxin simultaneously in pig dorsal muscle, pig back fat and chicken muscle by high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) analysis. Limit of detection of deoxynivalenol and T-2 was 0.02μg/kg and 0.007μg/kg, and limit of quantification of deoxynivalenol and T-2 was 0.07μg/kg and 0.02μg/kg, respectively. Sixty-six meat samples were analyzed and deoxynivalenol was detected in the samples of pig back fat, with concentrations lower than 0.5μg/kg, and T-2 toxin was detected in the samples of pig dorsal muscle, pig back fat and chicken muscle, with concentrations lower than 0.5μg/kg. The results of sample analysis show that only trace residues of deoxynivalenol and T-2 toxin were detected in the samples analyzed.

In vitro removal of deoxynivalenol and T-2 toxin by lactic acid bacteria

Five strains of lactic acid bacteria were tested for their ability to remove deoxynivalenol (DON) and T-2 toxin from MRS broth. The ability of Lactobacillus plantarum strain 102 (LP102) was the strongest among 5 strains after incubation at 37°C for 72 h. The mode of removal was physical binding, rather than biotransformation. The abilities were not significantly different between when removing single toxin and when removing mixed toxins by viable cells of LP102. DON and T-2 toxin released from LP102 viable cell-toxin complexes were 28.22±1.55 and 35.42±2.02% of total bound toxins respectively after 3 times of wash with posphate buffered saline, respectively, those were 4.59±0.86 and 5.59±1.47% after incubation with simulated gastric fluid (SGF) at 37oC for 4 h, and 6.86±0.81 and 9.04±1.13% after incubation with simulated intestinal fluid (SIF) at 37oC for 4 h, respectively.

Optimization of nobiletin extraction assisted by microwave from orange byproduct using response surface methodology

Nobiletin (NOB) is a well-known polymethoxylated flavone that has only been found in citrus. The objective of this study is to obtain the optimal conditions for extracting nobiletin from sweet orange residues by microwave-assisted extraction (MAE) using response surface method. By using the Box-Behnken experimental design and SAS software 3 independent variables including solid/solvent ratio, microwave power, and treatment time were examined for the response variable nobiletin extraction yield. The regression Eq. 7 statistically significant (p<0.001) and R2 was 0.9189. Based on our regression result and considering the feasibility of experiment conduction, we chose the following independent variable values as the optimized conditions for the extraction of NOB: 1:21.91 (g/mL) for the solid/solvent ratio, 14.16 min for the treatment time, and 693.72 W for the microwave power. Under these conditions, the nobiletin yield of 267.8 μg/g of byproduct was achieved.

Effect of antioxidant on the fatty acid composition and lipid oxidation of intramuscular lipid in pressurized pork

To investigate the effect of antioxidants on lipid oxidation and fatty acid composition in pressurized pork, minced pork with or without 1% Na(2)EDTA was pressurized at 500MPa before 7days storage at 4°C. TBARS value, lipid content and fatty acid composition in untreated and high-pressure (HP) treated samples were analyzed. HP treatment induced marked increases in TBARS values and lipolysis of partial phospholipids causing an increase of free fatty acid content. Preferential hydrolysis for polyunsaturated fatty acids (PUFA) in phospholipids resulted in the percentage of PUFA in phospholipids decreasing markedly and thereby that in free fatty acids increasing significantly. Addition of 1% Na(2)EDTA to minced pork before HP significantly decreased the TBARS values in pressurized samples, but did not inhibit the lipolysis of phospholipids, causing the fatty acid composition of phospholipids and free fatty acids to change similarly to those samples without Na(2)EDTA.

The citrus flavonoid nobiletin inhibits proliferation and induces apoptosis in human pancreatic cancer cells in vitro

The cellular effects of nobiletin on human pancreatic cancer cells (PANC-1) and the mechanisms by which nobiletin inhibits the proliferation of these cells were investigated. A MTT assay and flow cytometry were used to examine cell proliferation and apoptosis, respectively. A Western blot assay was used to examine expression levels of the apoptotic proteins bax, bcl-2, and p53. NOB induced apoptosis in these cells via up-regulation of the proapoptotic protein bax and down-regulation of the antiapoptotic proteins bcl-2 and p53. The normal cell cycle of PANC-1 cells was arrested by NOB with a significant increase in the proportion of G0/G1 phase cells (p<0.05) and a significant decrease in the proportion of S phase cells (p<0.05). NOB can inhibit the proliferation of human pancreatic carcinoma cells by inducing apoptosis and arresting the cell cycle progression.

Removal of 3-methylindole by lactic acid bacteria in vitro

3-Methylindole (3MI) is a substance with an unpleasant odor that is found in intact male pigs and is known to negatively affect consumers of pork. The growth of four strains of lactic acid bacteria [Lactobacillus brevis 1.12 (L. brevis 1.12), L. plantarum 102, L. casei 6103 and L. plantarum ATCC8014] in incubation medium with 3MI was studied. The four strains were tested for their ability to remove 3MI from the medium. The growth of L. brevis 1.12 remained steady as the levels of 3MI increased 3MI from 0.2 to 1.0 μg/ml. The 3MI removal ability of L. brevis 1.12 was the strongest among the four strains, and the highest removal rate was 65.35±0.3% in 1 ml incubation medium containing 1.0 μg/ml 3MI for 120 h. Furthermore, the supernatant fluid of the fermentation broth of L. brevis 1.12 had a stronger ability to remove 3MI than cell pellets and cell extracts and the removal rate was 14.4±0.3% in 24 h. Further results indicate that the mode of removal of 3MI was not through the physical binding of cells by L. brevis 1.12.

Interrelationship among ferrous myoglobin, lipid and protein oxidations in rabbit meat during refrigerated and superchilled storage

This work investigated the interrelationship among myoglobin, lipid, and protein oxidations in rabbit meat during refrigerated and superchilled storage. Peroxide value gradually increased (p < 0.05) and decreased thereafter (p > 0.05) with increased storage time for both storage treatments. Thiobarbituric acid-reactive substances (TBARS) significantly increased (p < 0.05) throughout the storage time for the storage temperature considered. The metmyoglobin proportion markedly increased (p < 0.05) and remained constant thereafter (p > 0.05). For both storage temperature levels, the extractable heme iron content significantly declined (p < 0.05), whereas non-heme iron content considerably increased (p < 0.05). With prolonged storage time, the protein carbonyl content significantly increased (p < 0.05), along with significant loss in sulfhydryl content (p < 0.05). Superchilled samples maintained lower rates of increase in metmyoglobin content, TBARS, and protein carbonyl content compared with refrigerated samples. Moreover, principal component analysis presented good correlations between TBARS, protein carbonyls and metmyoglobin content. Taken together, myoglobin, lipid and protein oxidations occurred concurrently in rabbit meat during both storage treatments and each oxidation process seemed to promote the other.

Does protein oxidation affect proteolysis in low sodium Chinese traditional bacon processing

This work investigated protein oxidation, proteolysis and their interrelationship during the manufacturing process of low-sodium Chinese traditional bacon. The bacons were prepared by four different salting treatments: substituting sodium chloride (NaCl) using 0, 30, 50, and 70% of potassium chloride (KCl). Protein oxidation was evaluated by total carbonylation, thiol oxidation, and tryptophan fluorescence changes. Proteolysis was detected by non-protein nitrogen, free amino acid, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the manufacturing process of low-sodium Chinese bacon, protein oxidation and protein proteolysis were simultaneously observed. Electrophoresis pattern showed that 70% substitution of KCl could promote proteolysis, meanwhile, protein oxidation possibly facilitated by 70% KCl replacement resulted in reduced tryptophan fluorescence and increased total carbonyl content. Additionally, a good correlation between protein oxidation and proteolysis was observed.

Rabbit meat production and processing in China

Rabbit meat has become increasingly popular in China; however, the main available products are still as cut-up parts or whole carcass due to a lack of processing. Currently, rabbit meat products do not fully meet the consumer demand for convenience, thus hindering the further development of the rabbit meat industry. As the biggest rabbit meat producer globally, China has conducted a series of studies on rabbit meat processing and the development of new products. This review presents rabbit breeds, meat importation, exportation, and meat production in China. The development of the rabbit meat industry and research on rabbit meat processing are discussed. The main problems, including a lack of leading enterprises and brand products, insufficient investment and research, and the weakness of fundamental studies on traditional products, are highlighted. Furthermore, current trends of rabbit meat production and processing of being centralized and regionalized, as well as being intelligentized and standardized, are discussed.