贵州米酸汤发酵过程中风味品质的研究

通过HS-SPME-GC-MS技术对贵州米酸汤发酵过程中的挥发性风味成分进行测定,并结合理化指标及主成分分析,探究其风味品质的变化。研究发现贵州米酸汤的风味物质组成丰富,发酵过程中共计检出109种挥发性风味成分,其中酸、酯类是主体物质;米酸汤挥发性成分随发酵时间的延长而增加,不同发酵时期对挥发性组分影响不一。发酵0～1d为米酸汤发酵的初期,风味成分变化显著,酸、酮、醛、呋喃类物质降低,醇、酯类物质增加,总相对含量从83.941%增加到96.716%;发酵1～10d为米酸汤发酵的产酸阶段,风味成分组成稳定,仅出现1.322%增减幅度;发酵10～15d为米酸汤风味的成型阶段,酮、呋喃、烃、酚、醛、醇及酸类物质的含量明显提高,各物质复合形成米酸汤的独特风味。通过主成分分析发现,醛类、酸类、酯类、酮类、呋喃类物质对发酵10d及15d的米酸汤影响较大,酚类、醇类、烯烃类、烷烃类物质对发酵0d及1d的米酸汤影响较大,各阶段米酸汤的风味品质差异显著,发酵15d的米酸汤风味品质最佳。     

资兴柑橘皮总黄酮的微波辅助提取及其抗氧化活性研究

采用正交试验设计研究微波辅助提取资兴柑橘皮中总黄酮的工艺条件,并对资兴柑橘皮中总黄酮的抗氧化活性进行探讨。结果表明:资兴柑橘皮中总黄酮的最佳微波提取工艺为乙醇溶液体积分数70%、料液比1∶40(g/mL)、微波提取功率600W、提取温度70℃条件下提取20min,在此条件下,柑橘皮中总黄酮提取量可达21.11mg/g。影响柑橘皮中总黄酮提取效果的主次因素为:料液比>乙醇体积分数>提取温度>微波功率。柑橘皮总黄酮对清除自由基有明显的作用,且黄酮类化合物的添加量在实验范围内与其抗氧化性呈正相关,是一种潜在的具有抗氧化功能食品原料,该工艺技术适用于工业化大批量提取柑橘皮中总黄酮。     

白蚁肠腔内纤维素酶概述及在食品发酵中的应用

白蚁纤维素酶的研究与开发已成为近年来的热点.本研究从白蚁肠腔纤维素酶的来源、国内外白蚁纤维素酶的研究状况、白蚁降解木质纤维素的机理及纤维素酶在发酵食品中的应用等方面综述了白蚁纤维素酶的研究现状.     

洋葱汁对结肠癌细胞SW620株增殖和凋亡的影响

目的:初步探讨洋葱汁对结肠癌细胞株SW620增殖的影响及可能的机制。方法:通过MTT法及对比绘制处理组与对照组生长曲线验证不同浓度洋葱汁对肿瘤细胞增殖的影响;对比观察处理前后的细胞形态及荧光定量PCR检测Caspase-3基因检测洋葱汁对SW620细胞凋亡的影响。结果:通过MTT法检结果表明,不同浓度洋葱汁对结肠癌细胞株SW620均有明显的抑制作用,且其抑制作用随着浓度的升高而明显增强;通过绘制对照组和IC50浓度刺激下的SW620细胞的生长曲线,两者对比表明,IC50浓度刺激下的SW620的生长情况明显受到抑制;通过对比处理前后细胞的形态学观察,细胞基因组DNA变化,初步表明,处理组出现了凋亡现象;通过荧光定量PCR法检测对照组及IC50浓度刺激下结肠癌细胞株SW620中凋亡相关的基因——Caspase-3,结果表明,该基因参比未刺激结肠癌细胞株中Caspase-3的表达量增加10倍以上。结论:通过本研究初步说明了不同浓度洋葱汁对结肠癌细胞株SW620的生长有抑制作用,且随浓度的增加抑制能力增强,其抑制机制可能与细胞凋亡有关。     

AKT signalling and mitochondrial pathways are involved in mushroom polysaccharide-induced apoptosis and G1 or S phase arrest in human hepatoma cells

This study describes molecular mechanisms for inhibiting tumour cell proliferation using polysaccharides from medicinal mushrooms in human hepatoma cells. The results show that regarding cell cycle-related proteins, three types of polysaccharides significantly enhance the expression of p27^Kip in HepG2 and Bel-7404 cells, while suppressing the activity of cyclin D1/CDK4 and/or cyclin E/CDK2. Considering apoptosis-related factors, the polysaccharides suppressed AKT activity through the inhibition of AKT phosphorylation at Thr³⁰⁸ and/or Ser⁴⁷³. The growth of HepG2 and Bel-7404 cells was suppressed by the up-regulation of a subunit of PI3K and phospho-PTEN, which are modulators of AKT activity. The polysaccharides also activated the mitochondria-mediated apoptosis pathway by stimulating the activation of Bcl-2 family proteins to release cytochrome c and Smac and cleave caspase-9 and caspase-3 in HepG2 and Bel-7404 cells. These factors have a potent effect on cell cycle arrest in G₁ and/or S phase and induce apoptosis in HepG2 and Bel-7404 cells.     

Coumestrol induces senescence through protein kinase CKII inhibition-mediated reactive oxygen species production in human breast cancer and colon cancer cells

An inhibitor of the protein kinase CKII (CKII) was purified from leaves of Glycine max (L.) Merrill and was identified as coumestrol by structural analysis. Coumestrol inhibited the phosphotransferase activity of CKII toward β-casein, with an IC₅₀ of about 5 μM. It acted as a competitive inhibitor with respect to ATP as a substrate, with an apparent K_i value of 7.67 μM. Coumestrol at 50 μM resulted in 50% and 30% growth inhibition of human breast cancer MCF-7 and colorectal cancer HCT116 cells, respectively. Coumestrol promoted senescence through the p53-p21^Cip1/WAF1 pathway by inducing reactive oxygen species (ROS) production in MCF-7 and HCT116 cells. The ROS scavenger N-acetyl-l-cysteine (NAC), NADPH oxidase inhibitor apocynin and p22^phox siRNA almost completely abolished this event. Overexpression of CKIIα antagonised cellular senescence mediated by coumestrol, indicating that this compound induced senescence via a CKII-dependent pathway. Since senescence is an important tumour suppression process in vivo, these results suggest that coumestrol can function by inhibiting oncogenic disease, at least in part, through CKII inhibition-mediated cellular senescence.     

Antioxidant polyketide phenolic metabolites from the edible mushroom Cortinarius purpurascens

Phytochemical investigation of the ethyl acetate extract of the edible macrofungus, Cortinarius purpurascens, led to the isolation of nine anthraquinone-related pigments, citreorosein 6,8-dimethyl ether (1), physcione (2), rufoolivacin (3), rufoolivacin C (4), rufoolivacin D (5), leucorufoolivacin (6), verbindung cr11 (7), verbindung cr60 (8) and 1-Hydroxy-3-methyl-2-isopropanyl-6,8-dimethoxyanthraquinone (9). The structures of these isolated compounds were characterised by spectroscopic methods and comparison with published data. Among the tested compounds, 3–6 exhibited potent DPPH radical-scavenging activity with IC₅₀ values in the range of 3–8 μg/ml. The results indicated that the fungus is a possible source of natural products with potential antioxidant activity.     

Masked mycotoxins: A review

The aim of this review is to give a comprehensive overview of the current knowledge on plant metabolites of mycotoxins, also called masked mycotoxins. Mycotoxins are secondary fungal metabolites, toxic to human and animals. Toxigenic fungi often grow on edible plants, thus contaminating food and feed. Plants, as living organisms, can alter the chemical structure of mycotoxins as part of their defence against xenobiotics. The extractable conjugated or non‐extractable bound mycotoxins formed remain present in the plant tissue but are currently neither routinely screened for in food nor regulated by legislation, thus they may be considered masked. Fusarium mycotoxins (deoxynivalenol, zearalenone, fumonisins, nivalenol, fusarenon‐X, T‐2 toxin, HT‐2 toxin, fusaric acid) are prone to metabolisation or binding by plants, but transformation of other mycotoxins by plants (ochratoxin A, patulin, destruxins) has also been described. Toxicological data are scarce, but several studies highlight the potential threat to consumer safety from these substances. In particular, the possible hydrolysis of masked mycotoxins back to their toxic parents during mammalian digestion raises concerns. Dedicated chapters of this article address plant metabolism as well as the occurrence of masked mycotoxins in food, analytical aspects for their determination, toxicology and their impact on stakeholders.     

山胡椒提取物的抑菌活性及其稳定性

为了解山胡椒提取物的抑菌活性和稳定性,通过抑菌实验和稳定性实验,研究了山胡椒水提物、75%乙醇提取物和乙酸乙酯提取物对5种常见食源性污染菌的抑制作用,并探讨了热处理、pH值及紫外照射对山胡椒75%乙醇提取物及乙酸乙酯提取物抑菌稳定性的影响。结果表明,3种提取物对供试菌的抑菌效果大小顺序为:乙酸乙酯提取物>75%乙醇提取物>水提物。稳定性实验表明,山胡椒提取物的热稳定性良好;pH值和紫外照射对山胡椒提取物抑菌活性有一定影响,最适pH值为5～7;紫外照射不超过10 min时抑菌活性稳定,超过30 min后抑菌活性减弱,甚至消失。     

番石榴果实采后生理和采后病害研究进展

番石榴果实采后易腐烂劣变,不耐贮运,制约着中国番石榴产业的进一步发展。本文就国内外关于番石榴果实采后生理和采后病害的研究进展进行综述,指出了番石榴果实采后研究存在的问题和今后需要进一步研究的领域。