丝瓜中的皂甙及其生物活性

详述了国内外丝瓜中皂甙的提取和分离过程,概括了其组成及结构和生物活性研究,并对丝瓜的利用前景进行了分析.     

提高果蔬维生素C含量研究进展

随着人们生活水平不断提高,营养健康问题越来越受到重视。维生素C作为一种对人体具有重要作用的营养物质倍受人们关注;提高果蔬中维生素C的含量已经成为园艺领域研究热点之一。本文从果蔬种质资源选择,育种手段、栽培管理方法、土壤成分和生物技术等几个方面进行分析、研究和总结,综述了当前国内外提高果蔬维生素C含量的研究情况,并对各种方法和技术面临的一些问题进行总结和介绍,也对未来提高果蔬维生素C的方法进行展望。      

Short communication: Effect of environment on the expression of breed and heterosis effects for production traits

Character states of New Zealand herds were formed within the environmental ranges of herd average total lactation yield of fat plus protein (MS), which is a proxy for feeding level, summer heat load index (HLI), herd size, and altitude. A univariate multibreed sire model was applied to first-lactation (2 yr old) records of milk, fat, and protein within each environmental character state to estimate breed and heterosis effects. A scaling effect was observed for MS yield between overseas Holstein-Friesian (OHF) and New Zealand Jersey (NZJ) animals when comparing breed performance in extreme MS character states. For example, differences for milk, fat, and protein yield between these breeds were 561, 1.3, and 9.3 kg, respectively, in the character state averaging 227 kg of MS/cow, much smaller than the differences of 1,151, 3.1, and 23.0 in the character state averaging 376 kg of MS/cow. Heterosis levels for milk, fat, and protein yields were highest for OHF × NZJ, followed by New Zealand Friesian (NZF) × NZJ and OHF × NZF with average heterosis for all traits of 7.3, 5.7, and 2.7%, respectively. Heterosis levels for OHF × NZF were suppressed in very low MS yield environments and in many cases were not significantly different from zero. Heterosis was suppressed in crosses with OHF in the high HLI environment. Crossbred animals (OHF × NZJ, NZF × NZJ, and OHF × NZF) generally achieved higher fat yields than any of the straight-bred animals.     

Effects of genotype and cultivation environment on lycopene content in red‐ripe tomatoes

Lycopene, a natural red pigment found in tomato, is correlated with reduced incidence of some cancers. Forty tomato varieties, including cluster F₁ hybrid tomatoes, round breeding line tomatoes (Lycopersicon esculentum Mill) and cherry tomato types (L esculentum var cerasiforme), grown under greenhouse and field conditions were evaluated for their lycopene content using high‐performance liquid chromatography (HPLC) and spectrophotometry. Lycopene content varied significantly among the tomato varieties, with cherry tomato types having the highest lycopene content. Greenhouse‐grown cluster and round tomatoes contained more lycopene (mean = 30.3 mg kg^?1) than field‐grown tomatoes (mean = 25.2 mg kg^?1), whereas cherry tomato types had a higher lycopene content in field‐grown (mean = 91.9 mg kg^?1) than in greenhouse‐grown (mean = 56.1 mg kg^?1) fruits. HPLC analysis of lycopene isomeric forms revealed a higher content of all‐trans isomers in all tomato genotypes examined. However, the cis isomeric form was exceptionally higher in the field‐ and greenhouse‐grown cherry tomato L esculentum var cerasiforme cv Gardener's Delight, which contained ～9.3 and 9.9 mg kg^?1 cis isomers respectively. Results indicate that genetics and choice of cultivation environment may have a strong influence on tomato lycopene content. Copyright © 2005 Society of Chemical Industry     

Short communication: Heterosis by environment and genotype by environment interactions for protein yield in Danish Jerseys

Crossing of lines or strains within and between breeds has been demonstrated to be beneficial for dairy cattle performance. However, even within breed, differences between strains may also give rise to heterosis. A key question is whether an interaction exists between heterosis and environment (H × E) that is independent of genotype by environment (G × E) interactions. In this study, H × E and G × E interactions were estimated in a population of approximately 300,000 Danish Jersey cows. The cows were a mixture of pure Danish Jerseys and crosses of US and Danish Jerseys. The phenotype studied was protein yield. A reaction norm model where the unknown environmental covariates are inferred simultaneously with the other parameters in the model was used to analyze the data. When H × E, but not G × E, was included in the model, heterosis was estimated to be 3.8% for the intermediate environmental level. However, when both H × E and G × E were included in the model, heterosis was estimated to be 4.1% for the intermediate environmental level. Furthermore, when only H × E was included in the model, the regression on the unknown environmental covariate was estimated to be 0.15, interpreted as meaning that an increase of average herd-year protein yield by 1 kg of protein led to an increase in heterosis of 0.15 kg above the average heterosis for a first-cross cow. When both H × E and G × E were included in the model, the regression on the unknown environmental covariate was not significantly different from zero, meaning that heterosis was similar in all environments investigated. The genetic correlation of protein yields for different environmental levels ranged from 0.72 to 0.93, which was significantly different from unity, indicating that G × E exist for protein yield.     

香兰素和维生素C对卤煮牛肉中杂环胺含量的影响

目的探索牛肉卤煮加工过程中添加香兰素和维生素C对杂环胺形成含量的影响。方法采用固相萃取前处理技术,结合不同处理情况下高效液相紫外和荧光检测法测定肉样中杂环胺的含量。结果香兰素和维生素C都能够减少卤煮牛肉中杂环胺的形成。当维生素C的添加浓度量达0.15%时,杂环胺总量减少90%以上。当维生素C浓度增大到0.5 mg/m L时,维生素C对1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除率高达90%;当维生素C添加浓度为0.4 mg/m L时,其对超氧阴离子的清除率高达84%左右。结论维生素C和香兰素均可减少卤煮牛肉中杂环胺的生成,维生素C对DPPH自由基清除率和超氧阴离子自由基清除率均比香兰素高,且对卤煮牛肉中杂环胺的抑制效果比香兰素好。     

预处理及干燥方法对果蔬干制品VC含量影响的研究进展

文章从干燥预处理和干燥技术2个果蔬干制的重要环节出发,对国内外关于预处理和干燥方法对果蔬干制品V_C含量影响的研究现状进行了较全面的综述。     

昭通特色水果中维生素C的提取工艺及含量测定

目的优化提取昭通特色水果中的维生素C,并测定其含量。方法设计单因素实验优化提取昭通特色水果中的维生素C,并采用2,4-二硝基苯肼法和紫外分光光度法测定其含量。结果最佳提取条件为:温度37℃,恒温水浴3 h和活性炭用量1.0 g。以抗坏血酸为标准溶液在497 nm处测定昭通产山楂、梨、苹果和葡萄中维生素C含量分别为30.3、6.3、7.1和25.8 mg/100 g。结论该方法可为昭通特色水果中维生素C的提取及含量测定提供参考。     

UHT乳贮存过程中V_A和V_C的变化

选择市场上3种UHT乳通过25、37℃和45℃恒温进行贮存温度加速实验比较VA和Vc含量的变化。结果表明,对于VA在3个不同的贮存温度下随贮存时间延长均不断下降,下降速率最高为45℃贮存,最高下降率达到82%,且随贮存温度升高下降越快;贮存中Vc含量变化在3种产品间无差异,且随贮存时间延长略下降,不同贮存温度间变化无差异。对于贮存中UHT乳的品质变化可以选择VA作为指标之一。     

无花果中维生素C含量的测定

目的 采用分光光度法测定无花果和无花果干中维生素C的含量。方法 选取一定浓度维生素C标准液进行波长扫描, 确定维生素C的最大吸收波长, 将待测样品匀浆处理后在此波长下进行分光光度测定。结果 维生素C的最大吸收波长为520 nm, 校准曲线方程Y=0.0208X+0.001(r2=0.9998), 无花果和无花干果中维生素C含量分别为69.08 mg/100 g和64.06 mg/100 g, 加标回收实验中回收率均在90%以上。结论 无花果中含有较高的维生素C, 且无花果维生素C含量高于无花果干中维生素C含量。     

Effects of genotype by environment interactions on milk yield, energy balance, and protein balance

Increases in genetic merit for milk yield are associated with increases in mobilization of body reserves. This study assessed the effects of genotype by environment (G×E) interactions on milk yield and energy and protein balances. Heifers (n = 100) with high or low genetic merit for milk yield were milked 2 or 3 times a day and received rations of low or high caloric density. The management factors were selected to induce substantial differences in milk production levels and model different management strategies. The 2 × 2 × 2 factorial arrangement enables the assessment of the effects of genotype, environment, and G×E interactions. Mean daily energy-corrected milk production in the first 100 d in milk varied between 21.8 and 35.2 kg among the groups. The experimental factors affected milk production in the presumed direction. Ration was the most determinant factor on milk production. Effects of milking frequency and genetic merit were significant only in the groups that were fed rations with high caloric density. Signs for severe negative energy balances, protein balances, and low body condition scores, all of which may be indicative of health risks, were not concentrated in the highest producing cows. Feed caloric density and milking frequency had stronger effects on energy balances and protein balances, with unfavorable effects of low caloric density feed and an extra milking. This emphasizes the possible effect of mismanagement on animal health risks. High genetic merit cows had significantly lower postpartum body condition scores. Genotype × environment interactions existed, but more information is needed to determine if cows of different genetic merit for milk yield are differently at risk for disease under specific conditions. High milk production levels per se will increase allostatic load, but need not compromise the health status of relatively young cows. Ongoing one-sided selection for high yield may be combined with good animal health, but because high genetic merit for milk yield seems intrinsically connected to the allocation of resources from maintenance toward milk, this puts increasing demands on farmers’ time and management skills.     

Influence of commercial freezing and storage on vitamin C content of some vegetables

Vitamin C levels of commercially frozen okra, potatoes, green beans, broccoli, spinach and peas, including the impact of processing and storage, were studied. Depending on the vegetable type, prefreezing operations caused a 19.1–51.5% decrease in the initial vitamin C levels. The freezing process alone did not influence the vitamin levels except in the cases of green beans and spinach. Total losses (%) were between 27.6 and 57.9 for the vegetables at the end of commercial frozen storage (6 months). All the data obtained from this study confirmed that, depending on the vegetable type, prefreezing operations have a major impact on the vitamin C contents and this influence persists in the frozen storage.     

苦瓜原汁中Vc稳定性的研究

探讨了苦瓜原汁中Vc在贮藏加工过程中的稳定性。结果表明:苦瓜原汁中Vc在加热、与空气接触、日照及Fe3+存在条件下不稳定、易损失,而适当降低pH值以及添加适量蔗糖、麦芽糊精、β-环糊精等化合物对苦瓜原汁中Vc具有保护作用。     

氢化物发生-原子荧光光度法测定维生素C中砷的含量

研究了采用氢化物发生-原子荧光光度法测定维生素C中砷的含量。结果表明,该方法的检出限为0．031μg／L,回收率为89．9％～117．0％,符合维生素C中砷的测定要求。     

不同加热处理对花生维生素含量的影响研究

以花生为原料,研究加热处理(水煮、蒸煮、油炸)对花生中维生素的影响.结果 表明:以湿基计,油炸处理后维生素E含量未发生显著变化,其他处理均使维生素E含量下降,花生中的烟酸在水煮处理之后保留率最低;以干基计,加热处理前后维生素E含量无显著变化,花生中的维生素B1在油炸处理之后保留率最低.不同加热处理后花生中烟酸、维生素B...     

Antioxidant actions and phenolic and vitamin C contents of common Mauritian exotic fruits

Seventeen commonly consumed exotic fruits from Mauritius were analysed for their antioxidant capacity, total phenolics, proanthocyanidins, flavonoids and vitamin C content. Two independent methods were used to evaluate the antioxidant potential of total fruit extracts. The antioxidant activities of the fruits ranged from 1 to 47 µmol Trolox equivalent antioxidant capacity (TEAC) g^?1 fresh weight and from 0.3 to 34 micro/mol g fresh weight (FRAP) g^?1 fresh weight. Total phenolics in the fruits ranged from 118 to 5638 µg g^?1 fresh weight, proanthocyanidins from 7 to 2561 µg g^?1 fresh weight, flavonoids from 21 to 712 µg g^?1 fresh weight and vitamin C content from 8 to 1426 µg g^?1 fresh weight. There were strong correlations between antioxidant activity (assessed by both TEAC and FRAP) and total phenolics and proanthocyanidins. Flavonoids seemed to contribute less to the antioxidant potential of the fruits, while very poor correlations were observed between ascorbate content and antioxidant activity. The highest antioxidant capacities were observed in red and yellow Psidium cattleianum Sabine ‘Chinese guava’, sweet and acid Averrhoa carambola L ‘starfruit’, Syzygium cumini L Skeels ‘jamblon’ and white Psidium guajava L ‘guava’. These fruits were also characterised by high levels of total phenolics. Mauritian exotic fruits are thus a significant source of phenolic antioxidants, which may have potential beneficial effects on health. Copyright © 2003 Society of Chemical Industry     

Effects of processing on anthocyanins,carotenoids and vitamin C in summer fruits and vegetables

The purpose of this study was to evaluate the effects of processing, i.e. heating (98 °C, 10 min), freezing (−20 °C) and freeze-drying on anthocyanins, carotenoids, and vitamin C in summer fruits and vegetables, i.e. cherries, nectarines, apricots, peaches, plums, carrots and red bell peppers. The commodities were collected from growers located in the Otago region (namely Cromwell, Roxburgh, Mosgiel and Clinton), New Zealand. The results revealed that each commodity contained different contents of phytochemicals. The content and the process stability of phytochemicals in each commodity were influenced by the geographical location of the growers. In general, a high content of phytochemicals was found in summer fruits and vegetables grown in Otago compared to those grown in the Northern Hemisphere, e.g. anthocyanins in cherries, nectarines, peaches and plums; total carotenoids in red bell peppers and nectarines and vitamin C in cherries, peaches, red bell peppers and carrots. Heating and freezing enhanced the release of membrane bound anthocyanins, resulting in higher content after processing compared to fresh commodities. In the commodities studied, with the exception of red bell peppers, the stability of ascorbic acid was increased if ascorbic acid oxidase was inactivated for example by heating.     

不同蔬菜热烫对维生素C的影响

对黄瓜、菠菜、藕、蒜苔四种新鲜脆性蔬菜在不同温度、时间下进行热烫,运用2,6-二氯靛酚法测定其中的维生素C含量。结果表明:在70～100℃内,热烫温度越低,所需时间越长,而维生素C的损失越高;热烫温度升高,热烫时间缩短,维生素C损失降低;当热烫温度过高时,维生素C的损失增加。大多数蔬菜热烫的温度为90℃,时间为40～60s时,维生素C的保存率最高。      

Effects of dietary vitamin C on neutrophil function and responses to intramammary infusion of lipopolysaccharide in periparturient dairy cows

Neutrophil function and the severity and incidence of mastitis in dairy cows is related to the intake of many antioxidant nutrients. Because vitamin C is the major water-soluble antioxidant in mammals, we examined the effect of dietary vitamin C on neutrophil function and responses to intramammary infusion of lipopolysaccahride (LPS) in periparturient dairy cows. At 2 wk before anticipated calving, Holstein cows were fed diets that provided 0 (16 cows) or 30 (15 cows) g/d of supplemental vitamin C (phosphorylated ascorbic acid). Treatments continued until 7 d after cows received an infusion of 10 μg of LPS into one quarter of the mammary gland (on average, this occurred 32 d postcalving). Supplementation of vitamin C increased plasma concentrations of vitamin C at calving, but no differences were observed in samples taken 24 h postinfusion. Concentrations of vitamin C in milk (24 h postinfusion) and in neutrophils (calving and 24 h postinfusion) were not affected by treatment, but vitamin C concentrations in neutrophils isolated from milk were about 3 times greater than concentrations in blood neutrophils. The LPS infusion did not alter concentrations of vitamin C in plasma or milk, suggesting that the LPS model did not produce the same effects as a bacterial infection of the mammary gland with respect to antioxidant effects. Supplemental vitamin C had no effect on neutrophil phagocytosis or bacterial kill. Dietary vitamin C reduced the milk somatic cell count but did not affect the febrile response or milk production following LPS infusion.