羊奶果的试种及果实营养成份研究

羊奶果引进厦门地区试种,生长迅速,适应性强,具有早产高产特性,其果实营养丰富,蛋白质、氨基酸、还原糖、有机酸、维生素Ｃ等含量均较高。     

羊奶果结瘤固氮特性研究

羊奶果根瘤多年生,初发生时呈2—3分又状,后经多次分叉生长,形成珊瑚状的根瘤簇,外形球状或扁球状,直径可达数厘米。根瘤固氮活性较高,全年平均固氮活性8.86微摩乙烯/克鲜瘤/小时。固氮活性秋夏较高,冬春较低。根瘤离体后固氮能力持续时间较长,可达9小时。固氮作用最适温度为30℃,低温使固氮活性显著下降,短时间高温(37℃)能提高根瘤固氮活性,但持续高温会抑制固氮活性。 羊奶果根瘤具有氢酶,表现出较高吸氢活性(9.52微摩氢/克鲜瘤/小时),且持续时间较长。外源氢能明显提高根瘤固氮活性,提高幅度达60％左右。 羊奶果各器官硝酸还原酶活力为根>根瘤>叶片>枝条,叶片NR活力呈季节性变化,秋夏较高,冬春较低。根瘤NR活力变化较大,且与根瘤固氮活性变化的趋势基本一致。     

羊奶果采后贮藏保鲜初步研究

本文探讨了羊奶果果实成熟度、包装方法、带枝叶与否、气调、温度以及保鲜剂处理对其贮藏效果的影响。试验结果表明,带枝叶的黄色果用3％硫脲等保鲜剂浸果10分钟,晾干后装入干燥器(5％CO_2气调)或塑料框外套2层0.03mm厚的聚乙烯薄膜塑料袋包装,贮藏于室温(15～20℃)下可保鲜38～42天,好果率在97.3％以上;于较适温度6～12℃下,可保鲜75～90天,好果率在90.0％以上。     

羊奶营养研究进展及羊乳基婴儿配方奶粉开发

牛奶和羊奶都可以作为婴儿配方奶粉的乳基来源,但二者的营养素构成和维生素和矿物质含量存在明显的差异。羊奶比牛奶含有较少的αs1酪蛋白和较多的β酪蛋白,非蛋白氮含量也高于牛奶。羊奶中的脂肪球要显著小于牛奶,小直径的脂肪球分布明显高于牛奶,脂肪球总表面积明显大于牛奶,山羊奶中还含有很高比例的短链和中链脂肪酸、共轭亚油酸和长链多不饱和脂肪酸,而且ω-3 长链多不饱和脂肪酸含量高于牛奶。羊奶中的低聚寡糖含量比牛奶中的更多,且种类和结构也更接近于人乳寡糖。羊奶作为乳基的婴儿配方奶粉较之牛乳基配方奶粉具有特有的营养特性和潜在的健康益处。     

羊奶果根瘤侵入线和被侵染细胞的亚显微结构

羊奶果根瘤的侵入线总是在几个相邻细胞的细胞间隙中出现。在根瘤发生部位未根毛的变形。侵入线似一囊状物,其内含物有丝状物和基质,侵和主线的壁部分或全部加厚,并与周围的寄主细胞壁相连。侵入线呈多种形态,在被侵染细胞中,细胞核膨大,并分叉变成指状核。     

山茱萸果实发育过程中单宁物质的分布与积累特征

选取不同发育时期的山茱萸果实作为研究对象,采用果实形态观察法、显微及超微技术、组织化学定位法以及紫外分光光度计法对山茱萸果实发育过程中单宁物质分布及积累特征进行观察分析,并以单因素ANOVA检验不同发育时期单宁含量的差异,以揭示单宁物质在山茱萸果实发育中的变化规律,为山茱萸果实涩味调控机制研究提供理论依据。结果表明:(1)山茱萸果实发育过程中果皮颜色和果实体积变化明显,可将其发育过程划分为幼果期、中果期、成熟期3个时期;单宁物质主要分布在山茱萸果实中果皮的单宁细胞中。(2)在山茱萸果实发育过程中单宁细胞数目呈先增后减的变化趋势,幼果期单宁细胞从无到有,随着果实发育单宁细胞数目不断增多,至中果期单宁细胞数目开始减少。(3)单宁含量的变化规律与单宁细胞数目的变化一致,单宁含量在花后120 d时达到最多,随后逐渐减少。(4)单宁物质首先在细胞质的小液泡中积累,中央大液泡形成后则为单宁物质积累的主要场所,其积累形态主要有颗粒状、不规则状和板块状3种;单宁细胞中线粒体数目较多,中果期后期及成熟期在中央大液泡液泡膜附近有电子致密物质积累。研究认为,山茱萸果实中中果皮薄壁细胞为单宁物质积累的专属细胞,即单宁细胞,单宁物质的合成运输与液泡、囊泡以及线粒体的作用密切相关;成熟期山茱萸果实总单宁含量降低,涩味降低,表明单宁物质积累的动态变化与植物对环境的适应性和果实涩味息息相关,可结合代谢组和转录组的方法对山茱萸果实中单宁物质的合成机制进行进一步研究。     

羊奶果根瘤侵入线和被侵染细胞的亚显微结构

羊奶果根瘤的侵入线,总是在几个相邻细胞的细胞间隙中出现。在根瘤发生部位未出现根毛的变形。侵入线似一囊状物,其内含物有丝状物和基质,侵入线的壁部分或全部加厚,并与周围的寄主细胞壁相连。侵入线呈多种形态,在被侵染细胞中,细胞核膨大,并分叉变成指状核。随着细胞的衰老,被侵染细胞中的内生菌、细胞器也逐渐消失。     

环介导等温扩增技术检测山羊奶中的牛奶成分

目的:建立一种快速检测山羊奶中是否含有牛奶成分的方法。方法:首先针对山羊的甘油醛-3-磷酸脱氢酶(GAPDH)基因和牛的线粒体基因(Cyt-b)分别设计环介导等温扩增(LAMP)引物,将不同比例的山羊奶与牛奶按不同比例混合制备样品,进行LAMP扩增,检测方法的灵敏度;从北京市场上购买6种不同的山羊奶产品进行扩增,检测方法的实用性。结果:该方法的灵敏度可达1%,浓度约为0.1 ng/mL;通过对市场上6种不同羊奶制品的检测,发现1种羊奶制品中含有牛奶成分。结论:采用LAMP技术检测羊奶产品具有快速、简单和特异的优点,不需特殊加热仪器,可用于奶制品现场检测。     

羊奶果根瘤内生菌的亚显微结构

羊奶果是桤木型根瘤。根瘤的横切面是轴对称的圆形结构,含菌细胞分散于皮层组织中。随着根瘤的发育,内生菌也有不同的形态结构。侵染初期的内生菌是一种分枝、具隔膜的菌丝体。幼龄菌丝中含有电子半透明的颗粒,成熟菌丝没有这种颗粒。成熟菌丝顶端会臌大形成具隔膜的椭圆球状泡囊,直径比菌丝大。不同发育时期的泡囊,其形态结构也有差异。     

羊奶果种子脂肪酸组成和矿质元素分析

测定了羊奶果(Elaeagnus conferta Roxb.)种子脂肪酸组成以及矿质元素含量。结果表明:脂肪酸含量为1.98%,主要是油酸(C18:1)34.15%、亚油酸(C18:2)31.51%、软脂酸(C16:0)13.83%、硬脂酸(C18:0)2.88%。饱和脂肪酸:单不饱和脂肪酸:多不饱和脂肪酸含量比为1:2.23:2.75。矿质元素K高达7837.69mgkg-1,Fe为30.99mgkg-1、Zn为10.13mgkg-1,Na为259.5mgkg-1。     

Identification of loci affecting flavour volatile emissions in tomato fruits

Fresh tomato fruit flavour is the sum of the interaction between sugars, acids, and a set of approximately 30 volatile compounds synthesized from a diverse set of precursors, including amino acids, lipids, and carotenoids. Some of these volatiles impart desirable qualities while others are negatively perceived. As a first step to identify the genes responsible for the synthesis of flavour-related chemicals, an attempt was made to identify loci that influence the chemical composition of ripe fruits. A genetically diverse but well-defined Solanum pennellii IL population was used. Because S. pennellii is a small green-fruited species, this population exhibits great biochemical diversity and is a rich source of genes affecting both fruit development and chemical composition. This population was used to identify multiple loci affecting the composition of chemicals related to flavour. Twenty-five loci were identified that are significantly altered in one or more of 23 different volatiles and four were altered in citric acid content. It was further shown that emissions of carotenoid-derived volatiles were directly correlated with the fruit carotenoid content. Linked molecular markers should be useful for breeding programmes aimed at improving fruit flavour. In the longer term, the genes responsible for controlling the levels of these chemicals will be important tools for understanding the complex interactions that ultimately integrate to provide the unique flavour of a tomato.     

Biochemical changes in tomatoes stored in modified gas atmospheres. I. Sugars and acids

During long-term storage in modified gas atmospheres (MGA), some of the biochemical changes occurring in tomato fruit, cv. Sleaford Abundance, were compared with those in fruit of some Israeli cultivars which had been selected for firmness and slow ripening. The MGA used in the experiments did not succeed in completely restricting changes in sugars and acids during storage, although colour change was prevented. This separation of processes is discussed in relation to the practice of long-term storage and its implications for fruit flavour.     

Biochemical characterisation of MdCXE1, a carboxylesterase from apple that is expressed during fruit ripening

Esters are an important component of apple (Malus × domestica) flavour. Their biosynthesis increases in response to the ripening hormone ethylene, but their metabolism by carboxylesterases (CXEs) is poorly understood. We have identified 16 members of the CXE multigene family from the commercial apple cultivar, ‘Royal Gala’, that contain all the conserved features associated with CXE members of the α/β hydrolase fold superfamily. The expression of two genes, MdCXE1 and MdCXE16 was characterised in an apple fruit development series and in a transgenic line of ‘Royal Gala’ (AO3) that is unable to synthesise ethylene in fruit. In wild-type MdCXE1 is expressed at low levels during early stages of fruit development, rising to a peak of expression in apple fruit at harvest maturity. It is not significantly up-regulated by ethylene in the skin of AO3 fruit. MdCXE16 is expressed constitutively in wild-type throughout fruit development, and is up-regulated by ethylene in skin of AO3 fruit. Semi-purified recombinant MdCXE1 was able to hydrolyse a range of 4-methyl umbelliferyl ester substrates that included those containing acyl moieties that are found in esters produced by apple fruit. Kinetic characterisation of MdCXE1 revealed that the enzyme could be inhibited by organophosphates and that its ability to hydrolyse esters showed increasing affinity (K_m) but decreasing turnover (k_cat) as substrate acyl carbon length increases from C2 to C16. Our results suggest that MdCXE1 may have an impact on apple flavour through its ability to hydrolyse relevant flavour esters in ripe apple fruit.     

Estimation of genetic parameters and prediction of breeding values for apple fruit-quality traits using pedigreed plant material in Europe

Genetic parameters for apple (Malus x domestica) fruit external traits (fruit size, ground colour, proportion of over colour and attractiveness) and sensory traits (firmness, crispness, texture, juiciness, flavour, sugar, acidity and global taste) were estimated using 2,207 pedigreed genotypes from breeding programmes in six European countries. Data were scored for 3 years and four periods during storage. Analyses were performed with a restricted maximum likelihood method using VCE 5.1.2 software. Heritability estimates ranged from medium to high for instrumental traits. Genetic correlations between firmness and sugar were medium and low between firmness and acidity. Sensory traits showed low to high heritability, acidity and flavour being, respectively, the most and the less heritable. Global taste was strongly correlated with texture, juiciness, and flavour and relatively less correlated with crispness and acidity. Sensory sugar and acidity showed highly negative correlations whereas their instrumental measurements showed low and increasing positive correlations from harvest to 4 months post-harvest. Sugar exhibited a higher sensory/instrumental divergence. Conversely, instrumental and sensory firmness were highly correlated. Fruit external characteristics had medium heritability. Fruit attractiveness had highest and lowest correlations with fruit size and ground colour, respectively. Best linear unbiased predictors of breeding values were computed for all genotypes with the software PEST. The results were analysed with regard to the dynamic and the reliability of genetic parameters according to the scoring dates. Original issues of the study and the importance of the obtained results for efficient designs of further apple fruit quality breeding programmes were discussed.     

QTL analysis of fruit quality in fresh market tomato: a few chromosome regions control the variation of sensory and instrumental traits

The organoleptic quality of tomato fruit involves a set of attributes (flavour, aroma, texture) that can be evaluated either by sensory analyses or by instrumental measures. In order to study the genetic control of this characteristic, a recombinant inbred line (RIL) population was developed from an intraspecific cross between a cherry tomato line with a good overall aroma intensity and an inbred line with medium flavour but bigger fruits. A total of 38 traits involved in organoleptic quality were evaluated. Physical traits included fruit weight, diameter, colour, firmness, and elasticity. Chemical traits were dry matter weight, titratable acidity, pH, and the contents of soluble solids, sugars, lycopene, carotene, and 12 aroma volatiles. A panel of trained assessors quantified sensory attributes: flavour (sweetness and sourness), aroma (overall aroma intensity, together with candy, lemon, citrus fruit, and pharmaceutical aromas) and texture (firmness, meltiness, mealiness, juiciness, and skin difficult to swallow). RILs showed a large range of variation. Molecular markers were used to map a total of 130 quantitative trait loci (QTL) for the 38 traits. They were mainly distributed in a few chromosome regions. Major QTLs (R(2) >30%) were detected for fruit weight, diameter, colour, firmness, meltiness, and for six aroma volatiles. The relationships between instrumental measures and sensory traits were analysed with regard to the QTL map. A special insight was provided about the few regions where QTLs are related to multiple traits. A few examples are shown to illustrate how the simultaneous analysis of QTL segregation for related traits may aid in understanding the genetic control of quality traits and pave the way towards QTL characterization.     

Novel tomato flavours introduced by plastidial terpenoid pathway engineering

Until recently breeding efforts centred on high-yield production while sacrificing flavour and taste quality traits of mass produced food products, such as tomatoes. The recent publication of Davidovich-Rikanati et al. demonstrates the technical feasibility of the genetical engineering of pathways in tomato plants to modify their fruit flavour profile in a proof-of-concept approach. The reported work ranks among an increasing number of reported successful modifications of edible plants with a focus on the benefits to end-consumers.     

Biotechnological suitability of Saccharomycodes ludwigii for fermented beverages

Nineteen Saccharomycodes ludwigii strains were tested for the production of secondary products in grape must fermentation. A predominant metabolic pattern characterized by high production of isobutyl alcohol, acetoin and ethyl acetate was obtained. The occurrence of some strains producing enhanced amounts of these compounds suggests a potential utilization of this species for industrial applications. Feijoa juice was inoculated with a selected S'codes ludwigii strain in comparison to a control strain of S. cerevisiae and evaluation of the fermented products was carried out by 30 consumers with respect to the odour, flavour and taste. The sample fermented by S'codes ludwigii was characterized by a fresh odour with a fruity flavour, identified as flavour of apple and kiwi-fruit. This product was compared to apple juice, with a more acid taste. Despite the high concentrations of acetic acid, this beverage might be considered a potential summer refreshing drink, addressed to a target of consumers who prefer fruit drinks that leave a slightly acid and little sugary taste in the mouth.     

The fruit ripening-related gene FaAAT2 encodes an acyl transferase involved in strawberry aroma biogenesis

Short-chain esters contribute to the blend of volatiles that define the strawberry aroma. The last step in their biosynthesis involves an alcohol acyltransferase that catalyses the esterification of an acyl moiety of acyl-CoA with an alcohol. This study identified a novel strawberry alcohol acyltransferase gene (FaAAT2) whose expression pattern during fruit receptacle growth and ripening is in accordance with the production of esters throughout strawberry fruit ripening. The full-length FaAAT2 cDNA was cloned and expressed in Escherichia coli and its activity was analysed with acyl-CoA and alcohol substrates. The semi-purified FaAAT2 enzyme had activity with C1-C8 straight-chain alcohols and aromatic alcohols in the presence of acetyl-CoA. Cinnamyl alcohol was the most efficient acyl acceptor. When FaAAT2 expression was transiently downregulated in the fruit receptacle by agroinfiltration, the volatile ester production was significantly reduced in strawberry fruit. The results suggest that FaAAT2 plays a significant role in the production of esters that contribute to the final strawberry fruit flavour.     

Genetic architecture of apple fruit quality traits following storage and implications for genetic improvement

Accurate prediction of genetic potential and response to selection in breeding requires knowledge of genetic parameters for important selection traits. Data from breeding trials can be used to obtain estimates of these parameters so that predictions are directly relevant to the improvement program. Here, a factor allocation diagram was developed to describe the sampling design used to assess the quality of fresh and post-storage (2 months) fruit from advanced selection trial in an apple breeding program from which models for analyses were developed. Genetic variation was the largest source of variation for the fruit size, red colour type, proportion of red skin colour and lenticels, and instrumentally assessed fruit diameter, mass, puncture force and titratable acidity. In contrast, residual variation was the largest for fruit shape, juiciness, sweetness, aromatic flavour, eating and overall quality, and instrumental crispness. Genetic effects for traits were generally stable over fixed effects, except for a significant interaction with storage duration for firmness. Genetic correlations among traits were generally weak except between fruit mass (and diameter) and sensory size (0.98), titratable acidity and sensory acidity (0.97), puncture force and sensory firmness (0.96–0.90), crispness and juiciness (0.87), sweetness and aromatic flavour (0.84) and instrumental and sensory crispness (0.75). Predictions of the performance for seven commercial cultivars are presented. This study suggests that the Washington State apple production area can be treated as a single target environment and sufficient diversity exists to generate new elite cultivars. In addition, options for evaluating the efficiency of apple breeding are discussed.