葵花籽油中吡嗪类风味化合物形成机理的研究进展

吡嗪类化合物是葵花籽油Maillard反应形成风味的重要物质,Maillard反应的前体物质(游离氨基酸和肽)与葵花籽油中主体特征性风味化合物形成密切相关。游离氨基酸在一般食品体系中含量较少,肽的种类及肽的结构在吡嗪类化合物的形成方面发挥着重要的作用。本文对形成葵花籽油风味的化合物进行分析,重点综述了葵花籽油特征风味化合物吡嗪类风味物质的形成机理,突出肽尤其是小分子量多肽的作用。从二肽的结构角度展望,结合稳定同位素示踪法和碳模块标记技术深入探究吡嗪类化合物的形成机理,为食用油生产过程中风味化合物的控制奠定技术和理论基础。     

PCR-DGGE技术检测速冻饺子馅料中微生物区系

以速冻饺子为研究对象,对速冻饺子冻前的微生物多样性进行研究分析,为速冻饺子馅料的存放期限及防腐技术提供参考,避免后期出现卫生问题。利用传统分离培养的方法,对饺子肉馅中的细菌进行分离,得到30株纯菌株。通过菌株形态学鉴定、基因组DNA提取、聚合酶链式反应(polymerase chain reaction,PCR)扩增及16S rDNA测序及序列比对分析来鉴定菌株的属种、构建种群结构进化树。结果表明:30株纯菌株中有14个属,22个种,优势菌分布在γ-变形菌纲中的假单胞菌属。     

葡萄籽-亚麻籽调和油的研制及理化性质测定

亚麻籽因含有丰富的ω3等不饱和脂肪酸及等营养物质,成为人们关注的小宗油脂,但因其抗氧化性较差,保质期限较短,成为较受关注的问题。通过单因素和正交试验确定添加抗氧化能力较好的天然葡萄籽油,制成葡萄籽-亚麻籽调和油,经测试制成的调和油比例为：5%葡萄籽油、95%亚麻籽油,所制得葡萄籽-亚麻籽调和油,在理化性质指标上均符合食用油的国标水准。     

Viability and Resistance of Lactobacilli Isolated from Cocoa Fermentation to Simulated Gastrointestinal Digestive Steps in Soy Yogurt

To study the potential probiotic characteristics such as decrease of pH, microbial viability, and tolerance to simulated digestive steps of fermented soy beverage (“soy yogurt”) produced with lactobacilli isolated from cocoa fermentation (Lactobacillus fermentum TcUESC01 and Lactobacillus plantarum TcUESC02) during fermentation and refrigerated storage. The sensory acceptance of the yogurts was also tested. Samples of soy yogurt produced with L. fermentum TcUESC01 or L. plantarum TcUESC02 were collected during fermentation (0, 4, 8, and 12 h) and refrigerated storage (1, 9, 18, and 27 d), and submitted to pH and bacterial viability determinations. Tolerance to simulated digestion steps was done with refrigerated storage samples at 9 °C. Simulated digestion was performed in 3 successive steps: exposure to pepsin‐HCl solution, bile shock, and simulated small intestinal juice. During storage, a decrease in pH and lactobacillus viability was observed. L. fermentum TcUESC01 showed to be more resistant than L. plantarum TcUESC02 to simulated gastrointestinal digestion. All soy yogurts showed acceptable hedonic scores (greater than 5 in a 9‐point hedonic scale ranging from “like extremely” to “dislike extremely”) in sensory evaluation for flavor, aroma, color, consistency, and overall impression. L. plantarum TcUESC02 and, especially, L. fermentum TcUESC01 showed potential probiotic characteristics when considering pH, cell viability, and tolerance to simulated digestive steps and did not affect the sensory characteristics when supplemented to soy yogurt during storage.     

微波消解-原子吸收光谱法测定玉米油中的矿物质含量

采用HNO_3-50%H_2O_2微波消解体系,空气-乙炔火焰原子吸收光谱法,分析不同来源、不同品牌玉米油中Ca、K、Mg、Fe、Na、Zn 6种矿物质元素含量。结果表明:该方法能准确测定玉米油中矿物质元素含量,线性方程相关系数均在0.995以上,相对标准偏差在1.8%~4.3%,方法精密度高,回收率为89.30%~115.80%,回收结果满意,且方法简单。同时发现大型超市购买的玉米油中矿物质含量稳定,且含量顺序均为CaKMgFeNaZn,农贸市场购买的玉米油矿物质含量差异较大,存在个别元素过高或过低现象。     

酒花香气成分的检测及富含典型酒花香气啤酒的试验研究

单萜类物质是贡献啤酒酒花香气的重要成分。本研究在100L中试规模,原麦汁浓度为14°P,苦味质为20BU的条件下,从不同酒花添加工艺、添加量和品种三方面分析了啤酒中8种单萜类酒花香气物质的含量,并进行感官品评,发现在发酵罐中添加l％o香花的效果最好,啤酒风格因酒花品种不同而有异。8种酒花香气物质中里那醇、香叶醇、口．香茅醇和α-萜品醇最为重要,其啤酒中的含量与酒花中里那醇和香叶醇含量密切相关,前三者与前人研究-致,但本研究发现“α-萜品醇”也是重要香气物质之-。但啤酒中的酒花香气物质含量高,酒花香味不-定强,这可能与其构型有关,因此,又研究了三种酒花在啤酒酿造过程中酒花香气物质的同分异构体,包括（R）-（-）-里那醇、（S）-（＋）-里那醇、（-）-α-萜品醇、（十）-α-萜品醇、（R]-（＋）-卢-香茅醇、（S）-（-）-卢-香茅醇的含量。研究发现酒花品种的差异会引起同分异构体含量及比例的显著差异,加上其阈值的变化。进-步验证了同分异构体对啤酒中酒花香味的影响。     

葵花籽油模拟液中甲基丙烯酸甲酯迁移量的测定

目的 建立了葵花籽油模拟液中甲基丙烯酸甲酯迁移量的测定方法。方法 采用乙醇漩涡提取葵花籽油中甲基丙烯酸甲酯2 min, 用GC/MS检测, 外标法定量。结果 本法的定量限(LOQ)为0.75 mg/kg, 线性范围为0.75~30.00 mg/kg, 线性相关系数为0.9998。在1倍LOQ、2倍LOQ、0.5倍限量、1倍限量及2倍限量5个添加水平下平均回收率在86.71％~100.45%之间, 相对标准偏差(n=6)均小于5%。结论 方法的灵敏度、回收率高、选择性好, 能满足实际工作的要求。     

无患子油的提取、理化性质及其制备生物柴油的研究

研究了无患子油脂的提取条件、理化性质和以该油制备生物柴油的工艺.结果表明:油脂提取最佳条件:石油醚体积与种籽质量比5∶1,提取时间为2h,提取温度为70℃,无患子得油率为42.0％;无患子油脂主要由棕榈酸、硬脂酸、油酸、亚油酸、亚麻酸、花生酸、二十碳烯酸、山嵛酸、芥子酸等脂肪酸组成,其中不饱和脂肪酸质量分数91.85％,其主要理化性质为酸值:4.1 mg KOH/g、皂化值:184.83 mg KOH/g、碘值:110.16 gI2/100 g、折光率:1.480 8,脂肪酸组成、质量分数及理化性质等符合生物柴油标准.应用L9(34)正交试验得出无患子油酯交换反应制备生物柴油的最佳条件为:油醇物质的量比1∶6、催化剂用量为油质量的1.2％、反应时间2h、反应温度60℃,转化率为93.6％.并对无患子生物柴油性能进行了检测,它与0#柴油、国标GB/T 20828-2007《柴油机燃料调和用生物柴油》的主要性能指标相接近,它是一种理想的0#柴油的替代品.     

固定化酶催化菜籽油合成生物柴油稳定性研究

研究了固定化脂肪酶催化菜籽油与甲醇合成生物柴油的反应,探索了有机溶剂和甲醇投加方式对固定化脂肪酶的催化活性和稳定性的影响,并比较了国产和进口固定化脂肪酶的活性和稳定性.研究结果表明,有机溶剂的使用可明显改善固定化脂肪酶的活性和稳定性;分批加入甲醇可以避免甲醇一次性加入对固定化脂肪酶活性的抑制作用;国产酶重复使用15次(连续反应45d),仍具有良好的催化活性,其稳定性可与进口酶相媲美,国产脂肪酶可代替进口酶用于生物柴油的生产.     

Effect of modified atmosphere and vacuum packaging on some quality characteristics of sliced ‘sucuk’ produced using probiotics culture

The effects of probiotics (Lactobacillus acidophilus and Bifidobacterium lactis), packaging (vacuum, 50% N₂ + 50% CO₂ or 100% CO₂), storage temperature (4 and 10 °C) and storage time (90 d) on lipid oxidation, colour and microbial properties of sliced dry fermented sausage ‘sucuk’, which has a long storage time at low temperatures, was investigated. Probiotic‐added samples showed a significant reduction in the thiobarbituric acid‐reactive substances (TBARS) values compared with a control and starter culture groups. The analysis showed that control groups had the highest pH and that the pH was not affected by packaging or storage temperature. Probiotic use had a significant effect on total aerobic bacteria, lactic acid bacteria and Micrococcus/Staphylococcus counts, and bacterial counts decreased with storage time. The Enterobacteriaceae count was below detectable levels (<2.00 CFU g⁻¹) throughout the storage period. The storage temperatures had no effect on the microbial counts. Packaging had a significant effect on lactic acid bacteria, and the highest value was determined with 50% N₂ + 50% CO₂. The addition of probiotics and the storage time resulted in a significant decrease of colour values (L*, a* and b*). Copyright © 2005 Society of Chemical Industry