Baoguo Sun

Analysis of volatile compounds in traditional smoke-cured bacon(CSCB) with different fiber coatings using SPME.

The volatile compounds of Chinese traditional smoke-cured bacon (CSCB) were studied using SPMS-GC/MS. There were 48 volatile compounds identified and quantified, which belonged to several classes of chemical: 1 alkane, 16 aldehydes, 5 ketones, 9 alcohols, 4 thioethers and thiols, 3 furans and 10 phenols compounds. All the volatile compounds except for alkane was responsible for CSCB characteristic flavor. The major volatile compounds of CSCB came from smoking, oxidation and Maillard reaction, etc. Many volatile compounds were not reported in previous paper isolated by steam distillation method or nitrogen purge-and-steam distillation method on CSCB. It should be because of different method of isolating volatile substances from CSCB. Among the fibers tested, CAR/PDMS (carboxen/polydimethylsiloxane) fiber coating showed the highest area counts for most volatile compounds. CAR/PDMS coating extracted better those compounds whose linear retention indices (LRI) was lower than 926 (on average) and DVB/CAR/PDMS (divinylbenzene/carboxen/polydimethylsiloxane) those with higher LRI.

Optimisation of ultrasound-assisted enzymatic extraction of arabinoxylan from wheat bran

Arabinoxylan, the major dietary fibre component of wheat bran, is important from both technological and nutritional points of view. In this study, ultrasound-assisted enzymatic extraction technology was first employed to extract arabinoxylan from wheat bran. The process for extraction of arabinoxylan was optimised using response surface methodology, employing a five-level, five-variable central composite rotatable design. The optimum extraction conditions were as follows: raw material concentration, 50g/l, enzyme dose, 4.5g/l, extraction temperature, 50°C; extraction time, 70min; and ultrasonic power, 180W. Under the above mentioned conditions, the experimental yield was 142.6±0.17mg/g of wheat bran, which is well matched with the predictive yield. Ultrasound increased the efficiency of enzymatic treatment with higher extraction yield.

Inhibitory effect of wheat bran feruloyl oligosaccharides on oxidative DNA damage in human lymphocytes.

The present work assessed the protective effect of feruloyl oligosaccharides (FOs), the ferulic acid ester of oligosaccharides from wheat bran, against oxidative DNA damage in normal human peripheral blood lymphocytes induced by hydrogen peroxide (H2O2). The DNA damage was measured by using the single cell gel electrophoresis assay (comet assay). Lymphocytes were subjected to DNA damage by exposure to a range of H2O2 concentrations (10-200μmol/l). H2O2, at a concentration of 200μmol/l, resulted in nearly all cells being highly damaged. FOs showed no cytotoxicity and genotoxicity to normal human lymphocytes at the tested concentrations (10-500μmol/l). In addition, DNA damage in human lymphocytes induced by 100μmol/l H2O2 was inhibited by FOs in a concentration-dependent fashion with 91.1% inhibition of lymphocyte DNA damage at 500μmol/l as compared with the control. The results suggest that water-soluble FOs from wheat bran are able to enhance the ability of human lymphocytes to resist H2O2 induced oxidative damage.

PREPARATIVE SEPARATION AND PURIFICATION OF ALKYLAMIDES FROM ZANTHOXYLUM BUNGEANUM MAXIM BY HIGH-SPEED COUNTER-CURRENT CHROMATOGRAPHY

High-speed counter-current chromatography (HSCCC) was successfully applied to preparative isolation and purification of alkylamides, the tingling-taste components, from pericarp extract of Zanthoxylum bungeanum Maxim (Dahongpao). With the lower phase of n-hexane-ethyl acetate-methanol-water (7:3:5:5, v/v) eluted at a flow rate of 1.5 mL · min−1, and the revolution speed at 850 rpm, 0.19 g of alkylamides in purity of 98.0% by the relative peak area of HPLC was obtained from 1.0 g of extract in one run within 2 hr. On the basis of MS, IR, and 1H NMR analysis, the product of alkylamides was confirmed to be composed of hydroxy-α -sanshool, hydroxy-β-sanshool, and hydroxy-ϵ-sanshool. Furthermore, using the HSCCC product as external standard, alkylamide in the extract was determined to be in total of 21.41%, among which hydroxy-α-sanshool, hydroxy-β-sanshool, and hydroxy-ϵ-sanshool were in 15.69%, 4.76%, and 0.96%, respectively.

Amylopectin is the anti-fatigue ingredient in glutinous rice

The anti-fatigue activities of glutinous rice (GR) and GR amylopectin (GRA) were investigated in mice by determining tissue glycogen, blood lactate dehydrogenase (LDH), and blood urea nitrogen (BUN) after the weight loaded forced swim test (WFST). GR and GRA were given by gavage at various doses of GR (7.5, 15, 30 g/kg body weight) and GRA (3.8, 7.5, 15 g/kg body weight) every day for 7 days, respectively. The results indicated that the hepatic glycogen levels significantly (P<0.05) increased 26-44% and 35-60% and the muscle glycogen levels significantly (P<0.05) increased 36-100% and 67-133% in GR and GRA treatment groups, compared with the negative control group. The GRA treatment groups also had significantly (P<0.05) higher (9.1-20.3%) blood LDH levels. Meanwhile, the blood LDH activities in GR and GRA treatment groups had a significantly positive correlation with the hepatic glycogen levels (r=0.978, P<0.01). Moreover, except of the low-dose GR (7.5 g/kg body weight) supplemented group, mice in all other treatment groups had significantly (P<0.05) lower (13-23%) BUN levels. Compared with the GR treatment groups, GRA treatment groups had similar or even higher anti-fatigue activities, which demonstrated that GRA might play the most important role on the anti-fatigue activities for GR.

Aromatic constituents from chinese traditional smoke-cured bacon of mini-pig

Volatile composition of Chinese traditional smoke-cured bacon of Mini-pig breed was first characterized. Both headspace solid phase microextraction (SPME) and simultaneous distillation and solvent extraction (SDE) were performed. SDE exhibited efficiency in the extraction of representative aromatic volatiles especially the phenolic smoky flavors from the bacon sample. In total, 104 different components were found with the major quantity and kinds of aromas being the volatile saturated and unsaturated aldehydes from lipid oxidation and the phenolic compounds from smoke. Olfactory evaluation (GC-O) of the SDE extract revealed five basic odor patterns pertaining to 53 odor active regions and 47 odorants. Some key flavors accounting for the bacon aroma were (E, E)-2, 4-decadienal, 3-(methylthio) propanal, 2-furanmethanol, guaiacol, 3-ethylphenol and 2, 5-dimethylpyrazine.

Improving special hydrolysis characterization into Talaromyces thermophilus F1208 xylanase by engineering of N-terminal extension and site-directed mutagenesis in C-terminal

The purpose of this study was to gain insights into the hydrolysis characteristics of xylanase in producing xylo-oligosaccharides and to improve these by protein engineering. In this study, a hybrid enzyme (T-XynFM) was created from Talaromyces thermophilus F1208 xylanase (T-Xyn) by replacement of the N-terminal extension Phe1-Pro16 with Ala1-Gln8 and substitution of amino acid Phe193 (185) with Ser in the C-terminal. The enzyme showed optimum activity at 55°C and pH 6.5. Its residual activity was more than 55% after treatment at 50°C, pH 6.5 for 12h Km values of T-XynFM for beechwood xylan, birchwood xylan, and oat-spelt xylan were 10.31, 10.03, and 8.90mgmL-1, respectively. The enzyme displayed special hydrolysis characteristics: almost no xylose was produced on using xylotriose (X3), xylotetraose (X4), and xylopentaose as substrates. Moreover, over 60% X4 existed in hydrolyzed products of X3, indicating that T-XynFM possesses formidable transglycosylation properties.

Wheat bran feruloyl oligosaccharides modulate the phase II detoxifying/antioxidant enzymes via Nrf2 signaling

The antioxidant activities of wheat bran feruloyl oligosaccharides (FOs) were determined in rats by determining the activities and mRNA expression levels of phase II detoxifying/antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and heme oxygenase-1 (HO-1) in rat organs. FOs was given by gavage at doses of 0.25, 0.5, and 0.75 mmol/kg body weight every day for 15 days. Compared with the control group, the activities of SOD, CAT, and GSH-Px in FOs treatment groups significantly (P<0.05) increased in heart, liver, and kidney. All the FOs treatment also significantly (P<0.05) increased the glutathione (GSH) contents in heart (28-58%), liver (32-71%), and kidney (31-73%) compared with the control. FOs up regulated the mRNA expression levels of SOD, CAT, and HO-1 in organs. Moreover, the immunoblot analysis revealed increased nuclear factor-E2-related factor (Nrf2) protein expression levels in organs and there were positive correlations between the mRNA expression of phase II detoxifying/antioxidant enzymes and the expressions of Nrf2 protein, which demonstrated FOs treatment could modulate the detoxifying/antioxidant enzymes via Nrf2 signaling.

Low-frequency and low-intensity ultrasound accelerates alliinase-catalysed synthesis of allicin in freshly crushed garlic.

BACKGROUND The well-known chemically and therapeutically active compound allicin is formed in crushed garlic by the interaction of alliin with alliinase. In this study, low-frequency and low-intensity ultrasound was employed to accelerate the alliinase-catalysed synthesis of allicin in freshly crushed garlic. RESULTS The optimal conditions for improvement of the alliinase-catalysed synthesis of allicin in freshly crushed garlic were found to be as follows: ultrasound intensity 0.4 W cm⁻², ultrasound frequency 50 kHz, enzymatic reaction temperature 35 °C and reaction time 30 min. Under these conditions the yield of allicin was increased by about 25.2% compared with the control without ultrasound. Alliinase in the freshly crushed garlic was purified by ammonium sulfate precipitation and gel filtration on a Sephacryl S-200 column. The employed ultrasound increased the activity of the purified alliinase by about 42.8%, did not affect the enzymes temperature optimum and improved its thermal stability. CONCLUSION The results of this study indicated that the activity of alliinase in freshly crushed garlic might be enhanced by low-frequency and low-intensity ultrasound, thereby accelerating the alliinase-catalysed conversion of alliin in garlic to allicin.

Engineering a xylanase from Streptomyce rochei L10904 by mutation to improve its catalytic characteristics

Protein engineering was performed by N-terminal region replacement and site-directed mutagenesis in the cord of a xylanase (Srxyn) from Streptomyce rochei L10904 to improve its catalytic characteristics. Three mutants SrxynF, SrxynM and SrxynFM displayed 2.1-fold, 3.2-fold and 5.3-fold higher specific activities than that of Srxyn, respectively. Moreover, all of the mutants showed greater substrate affinity and kcat/Km than the native Srxyn. In addition, the enzymes showed improved hydrolysis characteristics, of which the most noteworthy is the enhanced ability of producing xylobiose (X2) and xylotriose (X3) from polymeric substrates. The engineered xylanases have greater potential for applications in oligosaccharide preparation industry.