Review of the structural characterization,quality evaluation,and industrial application of Lycium barbarum polysaccharides

BackgroundLycium barbarum polysaccharides (LBPs) are considered to be the major bioactive components in L. barbarum. Due to the considerable health benefits of LBPs, and the significant research interest in LBPs, quality evaluation of LBPs and their related products is imperative for ensuring their efficacy and safety. The bioactivities of polysaccharides are closely associated with their physicochemical properties, which can be easily monitored via chemical techniques. Therefore, analysis of physicochemical properties is a more straightforward and viable approach for the quality control of polysaccharides.Scope and approachIn this review, special techniques for the structural characterization of LBPs are summarized and discussed. In addition, quality evaluation approaches of LBPs that have never been emphasized are highlighted herein. Furthermore, industrial applications of LBPs are reviewed and discussed.Key findings and conclusionsHigh-performance anion-exchange chromatography coupled with pulsed amperometric detection is one of the most effective techniques for analysis of both acidic and neutral LBPs. Size-exclusion chromatography coupled with multi-angle laser light scattering and refractive index detection is able to determine absolute molecular weights, chain conformations, and contents of LBPs. Fingerprinting analysis and saccharide mapping analysis are effective approaches for quality evaluation of LBPs. However, the lack of appropriate quality evaluation approaches indicates an unreliable regulation of LBPs and their related products. This reveals the deficiency in the quality control of commercial products. Thus, the development of reliable approaches for pharmacological activity-based quality control of LBPs and their related products must be extensively investigated.     

中空纤维膜液相微萃取-液相色谱法测定己烯雌酚

目的 建立鸡肉中己烯雌酚残留的中空纤维膜液相微萃取-液相色谱分析方法。方法 对影响萃取富集效率的实验条件进行优化, 采用聚丙烯中空纤维膜, 以叔丁基甲基醚为萃取溶剂, 萃取溶剂用量20 μL, 萃取温度35 ℃, 萃取时间30 min, 搅拌速率为500 r/min, 萃取液40 ℃水浴, 氮气吹干后用流动相溶解, 取10 μL进行液相色谱检测。结果 该方法对己烯雌酚的富集倍数为40倍, 己烯雌酚在7.814~97.670 μg/mL质量浓度范围内线性关系良好, 相关系数均大于0.99, 检测限(S/N=3)为2.0 μg/kg, 实际样品中的加标回收率为78.07%~ 88.46%, 相对标准偏差为0.99%~8.36%。结论 本方法灵敏、简便, 适用于鸡肉中己烯雌酚残留的检测。     

In vitro antibacterial and antioxidant properties of chitosan edible films incorporated with Thymus moroderi or Thymus piperella essential oils

The aim of this work was to evaluate chitosan edible films incorporated with the EOs of two aromatic herbs, Thymus moroderi and Thymus piperella for (i) the growth inhibition of some bacterial strains (ii) their total phenolic content (TPC), and (iii) their antioxidant activity by means of three different antioxidant tests to define if the chitosan edible films incorporated with these EOs could be used as natural active films for food use. The agar disc diffusion method was used to determine the antibacterial activities of chitosan edible films. For the antioxidant activity, three different analytical assays were used (DPPH, FRAP and FIC). The chitosan films containing T. piperella EO (CH + TPEO) were more effective (p < 0.05) against Serratia marcenscens and Listeria innocua than chitosan films containing T. moroderi EO (CH + TMEO), while no statistically differences were found (p > 0.05) between CH + TPEO and CH + TMEO against Aeromonas hydrophila and Achromobacter denitrificans. The CH + TMEO films showed lower (p < 0.05) antioxidant activity, at all concentrations and with all methods assayed, than CH + TPEO. The antioxidant activity occurred in a concentration dependent manner.The results showed that chitosan edible films incorporated with T. piperella and T. moroderi EOs could be used as active films due to its excellent antibacterial and antioxidant activities.     

The control of Listeria innocua and Lactobacillus sakei in broth and meat slurry with the bacteriocinogenic strain Lactobacillus casei CRL705

The effect of the bacteriocin-producing strain, Lactobacillus casei CRL705, in the control of Listeria innocua 7 and Lactobacillus sakei CRL1424 in MRS medium and meat slurry during the storage under vacuum at chill temperatures was evaluated. L. sakei CRL 1424 isolated from vacuum-packaged contaminated raw meat was identified as the predominant indigenous lactic acid bacterial flora. Co-inoculation of MRS broth at 8°C with L. casei CRL705 caused growth inhibition of L. sakei CRL1424 and L. innocua 7 after 10 and 4 days of storage, respectively. At 4°C the complete inhibition of both strains occurred within 14 and 8 days for L. sakei CRL1424 and L. innocua 7, respectively. Bacteriocin activity in broth was observed to be maximal at 8°C reaching 2130 AU ml⁻¹ after10 days and 400 AU m1⁻¹ after 8 days of storage, while at 4°C maximal activities, 690 and 30 AU ml⁻¹ were obtained at 14 and 10 days, respectively. Addition of bacteriocinogenic strain to the meat slurry did not allow the growth of L. sakei and L. innocua, showing a bacteriostatic effect during 21 days of storage at 4°C. In addition, L. casei CRL705, as a protective culture did not change significantly the pH of the meat slurry in the assayed storage conditions. The results presented here confirm that the bacteriocinogenic strain L. casei CRL705 can be used as a useful tool to improve the microbial stability and safety in the commercial meat preservation.     

Prevalence and quantification of Campylobacter contamination on raw chicken carcasses for retail sale in China

The quantitative contamination load of Campylobacter on raw chicken carcasses at retail outlets in seven provinces and cities of China was determined. A total of 1587 carcasses over 12 consecutive months were sampled. The overall Campylobacter contamination rate was 45.1% and 19.8% of contaminated carcasses was higher in the load than 3.0 log₁₀CFU/g. The median load was 2.1 log₁₀CFU/g with 1.4 log₁₀CFU/g as the 25th percentile and 2.9 log₁₀CFU/g as the 75th percentile, respectively. Using logistic regression, it observed the significant provincial and monthly variations in prevalence, freshly slaughtered chicken carcasses (63.1%) were found to be 2.3 times higher compared to chilled carcasses (32.9%), while no statistical significance was observed in prevalence among chicken carcasses that had various packaging solution (P = 0.370) nor from different market types (P = 0.680) suggesting that possible cross-contamination had occurred during processing and transportation. The present study found that 52.1%, 59.9%, 2.9%, 8.8% and 8.3% of carcasses were contaminated with C. jejuni, C. coli, C. lari, C. fetus, and C. upsaliensis, respectively. A higher proportion of C. coli (45.4%) than C. jejuni (39.5%) were cultured from the contaminated carcasses and this finding was suggestive of a high degree of cross-contamination occurred not just among poultry products, but also with pork products before/at retail points in China. This study provided quantitative data suitable for a risk assessment model designed to evaluate useful intervention methods to facilitate a reduction in the risk of campylobacteriosis arising from the consumption of contaminated domestically produced chicken meat in China.     

基于SmartChip HT-qPCR分析不同食品中抗生素抗性基因的多样性及丰度

抗生素抗性基因（Antibiotics Resistance Genes,ARGs）广泛存在于各种环境中,被认为是一种新型环境污染物,对环境及人类健康具有潜在威胁。但是目前对于不同食品中多种ARGs赋存状况的研究仍然有限。该研究采用SmartChip高通量实时定量PCR方法（High-Throughput Quantitative Real-Time PCR,HT-qPCR）对水产品、发酵食品、肉类、蔬菜四大类样品中的ARGs及可移动遗传元件（Mobile Genetic Elements,MGEs）进行了定量分析。结果显示,被分析的15个样品中共检出9个ARGs大类,涉及234个ARGs亚类。所有样品中共有的ARGs亚类为79个,特有的为51个;水产品和肉类样品富集多种ARGs,这些基因表现出较高的丰度（最高可达3.6 copies/16S rRNA gene）。MGEs的检出数量达10个,其中所有样均检出整合子基因intI-1(clinic)和转座酶基因tnpA-01。ARGs抵抗机制分析结果表明,抗生素灭活机制、外排泵机制和细胞保护机制为主要的ARGs抵抗机制,抵抗机制贡献大小依次为：抗生素灭活机制>外排泵机制>细胞保护机制。该研究进一步丰富了对不同食品中ARGs赋存情况的认识,可为食品中ARGs的风险分析提供依据。