基于最优阈值的叶类中药边缘检测算法研究

提出了一种利用最优阈值分割和形态学处理相结合的边缘检测方法,首先通过Otsu最优阈值算法分割数字图像,然后利用形态学腐蚀运算腐蚀图像,最后利用分割后图像与腐蚀过的图像的相减获得边缘.该方法实现了对叶类中药显微图像效果更优的边缘检测,同时对比了传统边缘检测算法对叶类中药显微图像的图像边缘检测效果,为下一步的叶类中药显微图像的分割与自动识别奠定基础.     

Browning susceptibility of minimally processed Baby and Romaine lettuces

 This study was conducted to determine the effects of cultivar, tissue susceptibility and storage temperature on the keeping quality of minimally processed Baby and Romaine lettuces. Midrib and photosynthetic tissues were lightly processed and stored for up to 7 days at 5  °C and 13  °C. Changes in L ^* and a ^* values and absorbance at 430 nm were compared. The relationship between polyphenols, phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) activities and browning was examined. Measurements of L ^* and a ^* values on midribs showed that browning discoloration was the same for Baby as for Romaine lettuces and there was no relationship for temperature. In addition, L ^* and a ^* values in photosynthetic tissue indicated a decrease in green pigmentation during storage, especially at 13  °C. For both kinds of tissue at the end of cold storage an increase in soluble brown polymers was detected. In midribs, total phenolics increased significantly throughout the storage period because of the tissue-wounding response. The photosynthetic tissue had a higher phenolic content than the midrib one. For both kinds of tissue an increase in PPO activity occurred throughout cold storage. On the other hand, PAL activity in midrib tissue only increased initially, followed by a slow decline to reach normal levels. Browning potential estimated by L ^* values correlated significantly (P>95%) with PPO activity and with absorbance at 430 nm for Romaine lettuce. Based on colour and browning potential no differences between Romaine and Baby lettuce cultivars were observed. However, photosynthetic tissue was the most suitable tissue for the preparation of minimally processed salad mixes because of its high phenolic content. Received: 28 September 1998     

Effects of Quillaja saponaria extract and Nα-lauroyl-l-arginine ethyl ester on reducing selected foodborne pathogens in vitro and maintaining quality of fresh-cut endive (Cichorium endivia L.) at pilot plant scale

The aim of the present study was to evaluate the applicability of Quillaja saponaria extract (QSE) and N^α-lauroyl-l-arginine ethyl ester (LAE) as antimicrobial wash water additives in fresh-cut lettuce processing. Antibacterial activities of LAE and QSE against selected strains of the foodborne pathogens Salmonella enterica, Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, and Listeria monocytogenes were examined in vitro. Minimum inhibitory concentrations determined by broth microdilution assay demonstrated that LAE exhibited a strong antimicrobial activity with MICs between 4 and 32 μg/mL against all tested strains, whereas QSE showed a weaker antimicrobial activity with MICs >512 μg/mL. On a pilot-plant scale, the effects of warm water washing at 45 °C for 120 s with and without 40 mg/L QSE or 100 mg/L LAE as well as cold water washing at 4 °C for 120 s with QSE or LAE, respectively, of shredded endive (Cichorium endivia L.) were investigated regarding microbiological and sensory quality as well as physiological properties. Samples were analyzed for headspace O₂ and CO₂ levels, phenylalanine-ammonia-lyase activity and contents of nitrite and nitrate during nine days of cold storage at 4 °C. By analogy to its antimicrobial effect against the foodborne pathogens in vitro, LAE allowed up to 4 log₁₀ cfu/mL reduction of the microbial load in the washing water of the pilot plant, and might therefore reduce cross-contamination while saving water. The addition of LAE to warm washing water impaired sensory properties of fresh-cut endive during storage, which was predicted by chlorophyll fluorescence imaging analyses. QSE treatment combined with warm water washing best retained sensory appearance throughout our study, being possibly suitable for the production of premium products.     

Chemoattraction ofBiomphalaria glabrata (Gastropoda: Planorbidae) to lipid standards and lipophilic factors in leaf lettuce and Tetramin

Chemoattraction of individualBiomphalaria glabrata snails for lipid standards and lipophilic fractions of leaf lettuce and Tetramin were studied in a Petri dish bioassay. Snails were more significantly attracted to a whole Tetramin lipophilic fraction than that of leaf lettuce. Thin-layer chromatography showed that major neutral lipid fractions in Tetramin were triacylglycerols, free fatty acids, and free sterols, and in leaf lettuce were free fatty acids and a mixed free sterol-chlorophyll fraction. Snails were significantly attracted to both the free fatty acid and free sterol fractions from Tetramin, but only to the free fatty acid fraction from leaf lettuce. Snails were significantly attracted to a mixed lipid standard containing equal amounts of phosphatidylcholine, cholesterol, oleic acid, triolein, and cholesteryl oleate. Of four individual neutral lipid standards tested, i.e., cholesterol, oleic acid, triolein, and cholesteryl oleate, snails were only attracted to cholesteryl oleate.     

Whole Plant Response of Lettuce After Root Exposure to BOA (2(3<Emphasis Type="Italic">H</Emphasis>)-Benzoxazolinone)

The goal of our work was to expand the knowledge about plant stress response to the allelochemical 2(3H)-benzoxazolinone (BOA). We focused on physiological processes that are affected by this secondary metabolite. Physiological and biochemical characteristics of plants exposed to BOA help us to better understand its mode of action and open the gate to the use of allelochemicals as “natural” herbicides. Measurements on photosynthesis, fluorescence, water relations, antioxidant enzymes (superoxide dismutase, peroxidase), ATPases, and lipid peroxidation indicated that a phytotoxic effect follows BOA exposition. This effect was intense enough to interfere with plant growth and development and to produce “induced senescence.” Based on this, we propose a multifaceted mode of action for BOA with effects at different levels and in different parts of the plant.     

Phenolic compounds isolated from bitter lupine seeds and their inhibitory effects on germination and seedling growth of lettuce

The phenolic acids, including 4-hydroxybenzoic and 4-hydroxycinnamic acids, and their derivatives, such as 6,7-dihydroxycoumarin and 1,2-dihydroxybenzene, were isolated from bitter lupine seeds and were identified using gas chromatography-mass spectrometry. These compounds inhibited lettuce seed germination in the first 24 hr after sowing, but after 72 hr germination was comparable with that of the control. However, very strong suppression of seedling growth, especially the roots, was observed for higher concentrations of the lupine seed fractions containing phenolic acids. Effects observed in the lettuce germination bioassays were compared with those produced by nine pure phenolic acids previously identified in the mixture. The ethyl acetate fraction from lupine seed extract inhibited seedling growth as effectively as pure 1,2-dihydroxybenzene, the strongest inhibitor of the pure phenolic compounds studied. The possible reason for this could be the synergistic effect created in the mixture of phenolic compounds isolated from the extract.     

Differential allelochemical detoxification mechanism in tissue cultures ofAntennaria microphylla andEuphorbia esula

Callus and suspension cultures ofAntennaria microphylla (small everlasting) and the noxious weedEuphorbia esula (leafy spurge) can glucosylate benzene-1,4-diol (hydroquinone) to the corresponding monoglucoside, arbutin. HPLC analysis of extracts from callus tissue corroborates the presence of hydroquinone in the cells of small everlasting. Constitutive levels of a UDPG-dependent glucosyltransferase were detected in cell-free extracts of this tissue. Although this detoxification enzyme was induced in leafy spurge suspension culture cells grown in the presence of hydroquinone, the activity was six-fold lower than that measured in small everlasting. Differential ability to detoxify hydroquinone provides a basis for the observed allelopathic interaction between small everlasting and leafy spurge.     

Isolation and Structural Characterization of a Water-Soluble Germination Inhibitor from Scotch Thistle (Onopordum acanthium) Cypselas

Cypsela dormancy in Scotch thistle (Onopordum acanthium) may be affected by the presence of chemical inhibitors. To investigate this phenomenon, a leachate from O. acanthium cypselas was tested for its ability to inhibit germination of the cypselas from which it was derived (i.e., autoinhibition). Leachates varied in their degree of autoinhibition, depending on the cypsela population from which they were prepared. Overall, removal of leachate from a group of O. acanthium cypselas increased their germinability. Using lettuce (Lactuca sativa) cypselas as an indicator species, bioactivity-guided fractionation was used to isolate a water-soluble, para-substituted benzamide from O. acanthium cypselas, which caused germination inhibition. Various chromatographic, spectroscopic, and spectrometric techniques were applied to the characterization of the bioactive compound.     

68.75%易保水分散粒剂对保护地生菜灰霉病的防治

田间试验结果表明，用68．75％易保水分散粒剂800、1000倍液对生莱灰霉病防治效果较好，达到极显著水平，平均防治效果为86．03％；1500倍液对该病防治效果与对照药剂50％速克灵可湿性粉剂800倍液相当；而50%扑海因可湿性粉剂800倍液则防效较差。易保水分散粒剂的室内抑菌效果也较为理想。     

基于响应面法优化鲜切莴笋复合涂膜保鲜剂

以鲜切莴笋为研究对象,根据12种化学物质对多酚氧化酶(PPO)和过氧化物酶(POD)活性的抑制作用,选择3种酶活抑制效果显著的化学物质(茶多酚、抗坏血酸和L-半胱氨酸)和4种涂膜剂(羧甲基纤维素钠、黄原胶、海藻酸钠和葡甘露聚糖),考察不同保鲜剂浓度对鲜切莴笋4 ℃贮藏4 d后外观和色泽的影响. 以此单因素实验为基础,进行响应面分析,结果显示复合涂膜最佳组合为0.38%抗坏血酸+0.85%L-半胱氨酸+0.67%羧甲基纤维素钠,在此条件下,鲜切莴笋在4 ℃贮藏6 d后红绿色差Δa^*值为0.170,与回归方程预测值0.166相近,且货架寿命可延长至12 d以上,表明优化后的复合涂膜保鲜剂具有良好的实际保鲜效果.