Antioxidants in spring leaves of Oxalis acetosella L.

Oxalis acetosella L. is a common, edible wild plant native to the northern hemisphere. The contents of selected antioxidants, and the antioxidant capacity of young and old spring leaves of O. acetosella, were evaluated. The present study reports foliar contents of ascorbic acid, tocopherols, carotenoids, chlorophyll, flavonoids, phenolic acids and total phenolics, and compares the nutritional value of O. acetosella with other cultivated and wild plants. The composition of foliar antioxidants was found to depend on leaf age. On the other hand, the antioxidant capacity of old leaves were in the same range as young leaves. A comparison between O. acetosela with lettuce analysed in our study, and with numerous cultivated and wild edible plants from other studies, showed that O. acetosella is very rich in β-carotene, ascorbic acid, tocopherols and xanthophylls, and that it is one of the best sources of flavonoids (flavonol glycosides and flavan-3-ols), especially rutin. Therefore, O. acetosella is a potentially important dietary source of antioxidants.     

SPME-GC-MS分析荸荠皮及其乙醚提取物的挥发性成分

采用顶空固相萃取(SPME)结合气相色谱-质谱技术(GC-MS)对荸荠皮粉及其乙醚提取物的挥发性成分进行分析,比较挥发性化合物的相对含量和种类。结果显示,荸荠皮粉含93个挥发性化合物,荸荠皮乙醚提取物中含57个挥发性化合物;两者的挥发性化合物组成存在显著差异,其中荸荠皮粉主要为脂肪酸类和醇类,其他组分含量很低,而乙醚提取物主要为酯类、醇类、醚类和烷类。两者拥有5种相同挥发性化合物,分别是乙醇、乙酸、乙酸乙酯、正己醛、乙醛、正十六烷。在化合物类型分布上,荸荠皮乙醚提取物中酯类含量最高,其次分别为醇类、醚类和烷类,荸荠皮粉中脂肪酸含量最高,其次是醇类和烯类;两者在醇类、酮类和醛类分布方面最为接近,酯类和脂肪酸类相差最大。分析发现,荸荠皮粉及其乙醚提取物的挥发性成分在种类和含量上有显著差异,乙醚对香味贡献率高的酯类和醇类的提取有较好效果,但应防止原料在热加工脱水过程中的酸败反应,为改进荸荠皮香味剂的开发提供参考价值。     

荸荠皮提取物对细菌的作用方式研究

以B.subtilis;E.coli,S.aureus为指示菌,用生长曲线法、琼脂块再培养法对荸荠皮提取物抗细菌作用的方式进行探测,结果表明:低浓度(0.1%～0.2%)的荸荠皮提取物可抑制细菌的生长,较高浓度(0.4%)的荸荠皮提取物则具有一定的杀菌作用。用相差显微镜进行观察,可见加有荸荠皮提取物的培养液中细菌的菌体密度明显下降,菌体形态有明显的改变。     

Isolation and Partial Characterization of Mexican Oxalis tuberosa Starch

The chemical, physicochemical and rheological characteristics of Oxalis tuberosa starch were investigated. Oxalis starch presented an apparent amylose content of 33%, similar to maize starch used as control, with a granule size between 25–50 μm with oval and elliptical shapes and A‐type X‐ray diffraction pattern. The gelatinization temperature of oxalis starch was 64.0°C, that was lower than the one determined in maize starch (73.0°C), with an enthalpy value of 12.2 J/g, which was similar to that of maize starch. Both oxalis and maize starch pastes behaved as weak viscoelastic systems with the elastic character (G′) predominating over the viscous character (G′′). An increase in the level of solids in the pastes increased the values of the moduli. The results suggest that heating the systems (gelatinization), causes a more pronounced enhancement in the structure of the maize starch pastes than in that of oxalis starch pastes. Overall, it was concluded that due to its physicochemical, functional and rheological properties, Oxalis starch could be suitable for testing its use in the cosmetic and in the food industry.     

The low‐temperature method for study of coniferous tissues in the environmental scanning electron microscope

The use of non‐standard low‐temperature conditions in environmental scanning electron microscopy might be promising for the observation of coniferous tissues in their native state. This study is aimed to analyse and evaluate the method based on the principle of low‐temperature sample stabilization. We demonstrate that the upper mucous layer is sublimed and a microstructure of the sample surface can be observed with higher resolution at lower gas pressure conditions, thanks to a low‐temperature method. An influence of the low‐temperature method on sample stability was also studied. The results indicate that high‐moisture conditions are not suitable for this method and often cause the collapse of samples. The potential improvement of stability to beam damage has been demonstrated by long‐time observation at different operation parameters. We finally show high applicability of the low‐temperature method on different types of conifers and Oxalis acetosella. Microsc. Res. Tech., 78:13–21, 2015. © 2014 Wiley Periodicals, Inc.     

乙烯利通过调节酚类物质和活性氧代谢维持鲜切荸荠的贮藏品质

目的 探究乙烯利处理对鲜切荸荠贮藏品质的影响及其潜在机制。方法 以鲜切荸荠为实验材料, 每12 h测定其在常温贮藏期间的色泽、酚类物质含量及其相关酶活性、活性氧及抗氧化酶活性变化。结果 2.0 g/L乙烯利溶液处理鲜切荸荠5 min有效抑制了切面的黄化与褐变, 显著减缓了b*的增加以及L*的降低。在整个贮藏期间, 与对照相比, 乙烯利处理显著延缓了鲜切荸荠中总酚和总黄酮的积累, 并降低了苯丙氨酸解氨酶及多酚氧化酶活性。乙烯利通过抑制超氧阴离子自由基的产生速率, 显著抑制过氧化氢和丙二醛的积累, 并增强超氧化物歧化酶、过氧化氢酶和过氧化物酶的活性。结论 2.0 g/L乙烯利处理可以通过抑制酚类化合物代谢和提高自身抗氧化能力来延缓鲜切荸荠品质劣变, 可为维持果蔬品质方面的应用提供参考。     

荸荠皮中抗菌物质的提取条件研究

在单因素实验的基础上,用正交实验法优选从荸荠皮中提取抗菌物质的最佳工艺条件。结果表明:浸提剂为乙酸/乙醇溶液;液固比为12:1;浸提温度为30℃～37℃;浸提时间为3h～6h;浸提处理1次的条件下制备的荸荠皮提取物,可获得较好的效果。     

马蹄皮果酒制作的工艺研究

以新鲜的马蹄皮为原料,经过清洗、干燥、粉碎,酶解取汁制成发酵液,经发酵制成马蹄皮果酒。实验中分析了发酵过程中酒度的变化,研究发酵温度,酵母菌接种量和发酵液的糖度对酵母菌发酵的影响,最后得出马蹄皮发酵液的最佳发酵工艺条件:糖度为12%,发酵温度为32℃,接种量为1%。     

在酿造酱油中应用荸荠皮提取物抗菌效果的研究

用比浊法和平板菌落计数法测定酿造酱油中菌数的变化,研究荸荠皮提取物在酱油中的抗菌效果。结果表明,在酿造酱油中荸荠皮提取物具有较强的抗菌效力,37℃下,28d内酿造酱油中0.1%荸荠皮提取物的抑菌率在90%以上,与常用的食品防腐剂相比其抗菌效果优于苯甲酸钠,与山梨酸钾相近。     

几种加工处理对鲜切荸荠褐变的影响

为了减少鲜切荸荠的褐变并延长其货架期,采用L9(34)正交表筛选亚硫酸钠、柠檬酸、Vc、白砂糖等抑制褐变的护色剂,比较柠檬酸、葡萄糖酸内酯、乳酸等食用酸对褐变和风味的作用,探讨室温和冰箱存放温度对褐变和食用品质的影响。结果表明:Vc是较好的护色剂,葡萄糖酸内酯用作护色剂时兼有改善产品风味的作用,鲜切荸荠在2～4℃冰箱中可以存放10d以上。综合采用这些处理措施,可以大大延迟褐变,并使鲜切荸荠具有较长的货架期。