罗布麻抑菌物质及其作用机制的研究进展

为阐明罗布麻抑菌功能的物质基础,促进罗布麻纤维在医疗保健用纺织品领域的开发和应用,综述了罗布麻韧皮和精干麻纤维中存在的主要抑菌物质,包括:黄酮类化合物、鞣质、甾体及其苷类、香豆素类化合物、酚酸类和苯甲醛类化合物、脂肪酸以及挥发油。分析了各类抑菌物质的化学成分和抑菌活性,并着重从抑制核酸合成、破坏细胞膜、抑制能量代谢、影响脂肪酸合成、抑制运动性、阻断电子传递链、抑制酶活性、减弱营养物质的吸收以及通过过氧化和自氧化形成具有毒性的降解产物等方面介绍了抑菌作用机制。最后针对精干麻纤维抑菌物质的来源问题,指出韧皮中功能性成分在脱胶过程中的演化行为应成为未来研究的一个重要方向。     

Steam-assisted roasting inhibits formation of heterocyclic aromatic amines and alters volatile flavour profile of beef steak

In order to evaluate the effect of steam addition during meat roasting, beef sirloin steaks were cooked at five humidities (0%, 25%, 50%, 75% and 100%) under 230 °C to a centre temperature of 71 °C. With increased humidity, heating rate generally increased and the cooked steak gradually lost the typical roasted appearance. Thiobarbituric acid-reactive substances (TBARS) values generally increased, while carbonyl groups were not affected. Increased humidity promoted the formation of volatile aldehydes and alcohols, while pyrazines decreased significantly from 0% to 25% humidity. Steam-assisted roasting inhibited the formation of heterocyclic aromatic amines (HAAs; except for IQ and Norharman). However, further increase in humidity (larger than 25%) did not have additional inhibition effect. Based on the results, it is recommended to roast beef with steam addition to reduce toxic HAAs, but the humidity should be kept at a relatively low level to maintain a typical roasted appearance and flavour profile.     

Steam radish sprout (Raphanus sativus L.): active substances,antioxidant activities and non-targeted metabolomics analysis

Various active substances, antioxidant activities and primary differential metabolite profiles were investigated to assess the nutritional quality of radish sprouts steamed for 0–300 s. The levels of flavonoids, total phenolic content and isothiocyanate in radish sprouts decreased with increased steaming time, and DPPH radical scavenging activity levels and superoxide dismutase levels also exhibited a downward trend (P < 0.05). By contrast, total phenolic acid, ferric-reducing antioxidant power and reducing power levels exhibited significant increases in the early short-term steaming process (P < 0.05). Steaming for 30 s promoted the accumulation of vitamin B₂, whereas, steaming for 300 s promoted the accumulation of phospholipids and myristic acid to a greater extent than steaming for 30 s. Overall, there was a partial non-decreased nutritional indicator in short-term steaming of radish sprouts, and a longer steaming time positively affected the differential metabolites.     

实时荧光定量PCR监测镇江香醋醋酸发酵过程中微生物变化

对镇江香醋醋酸发酵阶段醋醅中功能微生物的变化进行定量分析。建立了实时荧光定量PCR方法,对醋酸发酵阶段醋醅中总细菌、总真菌、醋酸菌、乳酸菌和酵母的动态变化进行了定量分析。研究结果表明,发酵起始阶段(1～7天)醋醅中总细菌、醋酸菌和乳酸菌的生物量快速上升,分别于第6、7、4天达到最大值,为4.85×1011,1.14×1010和3.37×1011copies/g干醅。随后各类细菌的生物量逐渐下降,并维持在一定水平。醋醅中总真菌和酵母的生物量在发酵前期变化不大,7天后至发酵结束总真菌的生物量逐渐下降为7.59×104copies/g干醅,而酵母生物量则在发酵8～12天内下降为0。     

蒸煮工艺对砀山梨汁香气组成的影响

采用顶空固相微萃取和气质联用技术对砀山梨蒸煮前后香气组成的变化进行分析。结果表明:砀山梨汁的香气成分主要由单萜类、醛类、醇类、酯类、酮类、烃类及芳香族类化合物组成;砀山梨经过蒸煮后所得梨汁的香气成分比煮前多了2种,即正戊醛和3-甲硫基丙醛;与生梨汁相比,己醛、乙醇、反-2-己烯醛和己醇的相对百分含量分别增加了81.7%、653.8%、381.8%和102.7%,1-甲基-4-(1-甲基乙烯基)环己烯的相对百分含量下降了44.7%,乙酸、壬醛、乙醛、3-己烯-1-醇、2-呋喃甲醛、2-呋喃甲醇、2,6,6-三甲基-双环((3,1,1)-2-庚烯、2,2-二甲基-3-亚甲基二环(2,2,1)庚烷和乙酸己酯等的相对百分含量也大幅增加。这些变化导致生梨汁香气微弱且清新,熟梨汁香气浓郁,且具有强烈的果香和甜香。     

天然物质对切割蔬菜中常见微生物的抑制作用研究

研究了正离子水和姜黄、虎杖、艾叶、丁香提取物对切割蔬菜中常见微生物(大肠杆菌、荧光假单胞菌、啤酒酵母)的抑制作用,结果表明:正离子水对大肠杆菌、荧光假单胞菌、啤酒酵母无抑制作用,抑制率均为0;姜黄、虎杖、艾叶、丁香提取物对3种微生物均有一定的抑制作用。适宜温度培养7d后,姜黄、虎杖、艾叶、丁香提取物对大肠杆菌的抑制率从大到小依次为:姜黄(51.7%),艾叶(37.2%),虎杖(36.5%),丁香(30.4%);对荧光假单胞菌的抑制率从大到小依次为:丁香(100%),姜黄(55.8%),艾叶(55.8%),虎杖(46.7%);对啤酒酵母的抑制率从大到小依次为:丁香(100%),姜黄(35.3%),艾叶(35.3%),虎杖(33%)。     

Effect of selected commercial substances with cryoprotective activity on the quality of mechanically recovered,washed and frozen stored poultry meat

Investigations were conducted on mechanically recovered poultry meat (MRPM) and on protein preparation obtained from MRPM by washing it first with 1% water solution of sodium chloride and with water afterwards. The raw materials were frozen at the temperature of –23°C. The effect of added stabilizers on the quality of gels produced from fresh raw materials, and after freezing and frozen storage was assessed. The following additives were used: 1% pork hydrolizate (Pork Stock( 0.5% Cremodan containing carrageens, and 1.5% bovine blood plasma (AMP 600N). Freezing and frozen storage caused a significant reduction of functional properties of MRPM and its protein preparation. None of the examined additives protected simultaneously all the investigated functional properties of the frozen samples. The amount of thermal drip, the gel texture and the amount of protein transition heat were determined by scanning differential calorimetry. The lowest thermal drip in gels obtained from frozen‐stored samples was observed when bovine blood plasma was used as a stabilizer. On the other hand, the most advantageous protective effect on the proteins of the frozen MRPM and on the preparation, determined by mechanical strain resistance of the gels, was found with 1% pork hydrolizate added. The results of thermodynamic investigations of proteins revealed that the best protective effect on the frozen preparation was observed with 1.5% blood plasma added. No protective activity of added Cremodan on proteins of the frozen protein preparation was noted.