不同干燥方法下红枣蜜饯水分状态变化研究

基于低场核磁共振(LF-NMR)技术研究热风干燥与真空微波干燥下红枣蜜饯内部水分分布及干燥过程中水分迁移规律、水分状态及含量的变化,为其干制提供理论依据.结果表明:MRI图像可以清晰反映水分分布情况,枣中含有3种状态的水,分别是结合水、不易流动水和自由水,成熟鲜枣中94％以上的水都是自由水,红枣蜜饯热风干燥最初2 h自由水含量显著降低,干燥后期自由水向组织内迁移减弱,最终不易流动水含量增加至43.9％,自由水含量散失降至55.99％;红枣蜜饯真空微波干燥过程中自由水快速向不易流动水迁移,6 min时自由水含量为0,结合水含量降低,不易流动水含量高达99.94％,因此真空微波干燥较热风干燥具有时间短、效率高的优势.     

铁棍山药等温吸附特性研究

分别采用热风、真空、微波3种干燥方式处理铁棍山药,用静态称质量法测定铁棍山药在10,20,30,40℃下,水分活度为0.2～1.0的平衡含水率,并绘制等温吸附曲线。选用6种吸附模型对铁棍山药的吸湿数据进行拟合比较,以模型的均方差、残差平方和、相关系数、相关系数的平方为评价指标。结果表明,不同干燥方式处理后的铁棍山药,其平衡含水率均随水分活度的升高而升高,在相同水分活度时平衡含水率均随温度升高而升高。在相同水分活度下,热风干燥与真空干燥铁棍山药的平衡含水率均高于微波干燥铁棍山药的平衡含水率。GAB和Peleg模型适用于模拟热风干燥和真空干燥处理后铁棍山药的等温吸湿规律;Peleg模型适用于模拟微波干燥处理后铁棍山药的等温吸湿规律。     

热风干燥对黑木耳品质的影响

为探索黑木耳的热风干燥工艺技术，比较不同热风温度对黑木耳干燥特性的影响，以自然晾晒干燥和冷冻干燥为对照，对热风干燥黑木耳的水分分布、复水性能和抗氧化活性进行分析。结果表明：黑木耳在85 ℃下的热风干燥速率高于55 ℃和70 ℃，干燥过程由升速阶段和降速阶段组成。对干燥动力学模型进行拟合，发现Page模型为最佳干燥动力学模型。低场核磁共振横向弛豫时间曲线显示，热风干燥前黑木耳中的水分以自由水为主；85 ℃热风干燥黑木耳的复水性能略高于55 ℃和70 ℃，显著高于自然晾晒样品（P＜0.05）。热风干燥黑木耳的1,1-二苯基-2-三硝基苯肼（DPPH）自由基清除能力和β-胡萝卜素保护能力均显著高于自然晾晒样品（P＜0.05），85 ℃热风干燥黑木耳的DPPH自由基清除能力和β-胡萝卜素保护能力分别为150.6、138.9 μg Trolox/g md。综上所述，85 ℃热风干燥工艺操作简单，可以较好地保持黑木耳干制品的品质，该研究为黑木耳干燥干燥过程中的品质调控提供了理论依据。     

微波干燥过程中的土豆组织温度变化及水分迁移特性

为探索淀粉类果蔬多孔介质在微波干燥过程中的热质传递特性,以土豆为研究对象,测量其不同功率下微波干燥过程中土豆组织的温度和质量以及水分状态变化。结果表明,微波干燥过程中土豆组织的温度可以分为快速升温、恒温及降温段3个阶段,土豆质量减少主要发生在恒温段,且该阶段物料的失重率占总失重率的90%以上。微波干燥过程中自由水短暂升高至93.21%后逐渐降低至15.61%,而不易流动水和结合水均先降低后升高。淀粉对于微波干燥中的水分迁移有重要影响,淀粉失去薄膜水后固化,使得土豆片的骨架硬度增加,从而增大水分迁移阻力。     

不同干燥条件对山富士苹果总多酚及多酚氧化酶活性的影响

利用热风干燥,在40,50,60,70℃的干燥条件下,将日本山富士苹果片干燥至干基含水率分别为50%,20%。对其总多酚含量以及多酚氧化酶活性进行分析。结果表明,在2种含水率下,总多酚含量均在70℃干燥条件下呈现最大;在含水率为50%时,多酚氧化酶活性在60℃最小;在含水率为20%时,50℃干燥条件下多酚氧化酶活性最大。     

山核桃吸附-解吸等温线及平衡水分研究

以带壳山核桃和山核桃仁为试材，采用静态称量法测定带壳山核桃和山核桃仁在25、35、45 ℃的吸附-解吸等温线，并采用等温线数学模型进行拟合，测定其热力学参数。采用低场核磁研究不同水分活度下带壳山核桃和山核桃仁中的水分结合状态。结果表明：带壳山核桃和山核桃仁的吸附与解吸等温线属于Ⅱ型，GAB模型拟合精度最高。带壳山核桃和山核桃仁的净等量吸附热、微分熵和积分焓均随含水率的增加而降低，积分熵随含水率的增加而上升，扩张压力随水分活度的增大而上升，并随温度的上升而下降。带壳山核桃的净等量吸附热、微分熵和积分焓均大于山核桃仁，而积分熵则相反。因此，带壳山核桃的贮藏稳定性较高，而山核桃仁易于干燥。根据安全水分活度可以得出带壳山核桃和山核桃仁的安全贮藏含水率分别为7.38%和5.61%。此外，根据解吸过程净等量吸附热可以得出，带壳山核桃和山核桃仁含水率分别低于14%和12%时需提供更多的热量以维持脱水速率。低场核磁结果表明，在高水分活度下，水分子主要以自由水和不易流动水状态存在，在低水分活度下，水分子主要以结合水状态存在。     

切片厚度对苦瓜片热风干燥特性及相关品质的影响研究

以新鲜苦瓜为原料,研究切片厚度分别为2,4,6 mm的苦瓜片在65℃热风干燥后,其热风干燥特性及理化品质的变化。结果表明,切片厚度对苦瓜片干燥特性和理化品质具有重要影响。在65℃热风干燥下,切片厚度从6 mm减至2 mm,干基含水量和水分比下降增快,干燥速率增快,有效扩散速率减小。同时,随着切片厚度减小,干制苦瓜片复水比越大,收缩比越小,干制品色泽越好。因此,结合苦瓜片热风干燥特性及品质变化,切片厚度为4 mm是进行苦瓜片热风干燥的适宜厚度。     

玉米降水与容重的关系

1水分和容重的关系 1．1粮油水分是指粮食和油料中所含水分的量。一般用所含水分的重量占粮食油料总重量的百分率来表示。按水分在籽粒中的分布状态,有自由水和结合水。自由水也称游离水,它存在于粮油籽粒的细胞间隙和毛细管中。它具有普通水的性质,在粮油籽粒中很不稳定,随着环境温、湿度的变化而增减,参与粮油籽粒的生理生化反应。结合水也称束缚水,它存在于籽粒的细胞内,与淀粉、蛋白质等亲水胶体牢固地结合在一起。结合水的性质稳定,在0℃时不结冰,不易随环境的变化而增减。     

不同干燥工艺对稻谷导热系数影响的研究

采用自然干燥(15℃)、热风干燥(45℃、55℃、65℃)、流化床干燥(45℃、55℃、65℃)对初始湿基含水率21.2%的稻谷进行降水处理,选取适当水分间隔测量稻谷导热系数和爆腰率,得到不同干燥工艺条件下的导热系数与含水率的拟合曲线、导热系数与爆腰率的拟合曲线,并对降水速率与爆腰增率、导热系数与爆腰率做相关分析。结果表明,降水速率与爆腰增率,导热系数与爆腰率都存在极显著相关性。干燥工艺影响稻谷降水速率,产生不同爆腰率,改变内部结构进而影响导热系数测量值。随爆腰率增大,导热系数呈非线性递增。流化床干燥对稻谷导热系数测量造成的影响大于薄层热风干燥。低温薄层热风干燥稻谷的导热系数最接近自然干燥处理值。     

脱水冻豆腐冷冻工艺研究

对传统冻豆腐的生产工艺进行改进,采用单因素试验和正交试验确定了脱水冻豆腐的冷冻工艺条件为-10℃下冷冻3 h,之后-5℃下冷冻48 h;然后将冷冻的豆腐在40℃水浴中解冻,挤去水分,30℃下鼓风干燥1 h,35℃鼓风干燥1.5 h,45℃鼓风干燥1.5 h,55℃鼓风干燥10 h。在此条件下,得到的冻干豆腐产品感官评分最高。该工艺可以为实际生产提供参考,并有助于冻干豆腐在市场上的推广。     

A note on the origin of Kalanchoë x vadensis Boom & Zeilinga (Crassulaceae)

Summary K x vadensis is a hybrid of K. blossfeldiana and K. marmorata obtained after doubling the number of chromosomes.     

Mechanisms and diversity of resistance to sorghum shoot fly,Atherigona soccata

Sorghum shoot fly, Atherigona soccata, is one of the important pests of postrainy season sorghums. Of the 90 sorghum genotypes evaluated for resistance to this pest, RHRB 12, ICSV 713, 25026, 93046 and 25027, IS 33844‐5, Giddi Maldandi and RVRT 3 exhibited resistance in postrainy season, while ICSB 463, Phule Anuradha, RHRB 19, Parbhani Moti, ICSV 705, PS 35805, IS 5480, 5622, 17726, 18368 and 34722, RVRT 1, ICSR 93031 and Dagidi Solapur showed resistance in rainy season, suggesting season‐specific expression of resistance to A. soccata. ICSB 461, ICSB 463, Phule Yasodha, M 35‐1, ICSV 700, 711, 25010, 25019 and 93089, IS 18662, Phule Vasudha, IS 18551 and 33844‐5 and Barsizoot had fewer deadhearts than plants with eggs across seasons, suggesting antibiosis as one of the resistance mechanism. Five genotypes exhibited resistance with high grain yield across seasons. Correlation, path and stepwise regression analyses indicated that leaf glossiness, seedling vigour, trichome density, oviposition and leaf sheath pigmentation were associated with the expression of resistance/susceptibility to shoot fly, and these can be used as marker traits to select and develop shoot fly‐resistant sorghums.     

Reaction of tritordeum to Fusarium culmorum and Septoria nodorum

Summary Hordeum chilense is a wild barley extensively used in wide crosses in the Triticeae. It could be a valuable source of resistance to Fusarium culmorum and Septoria nodorum. Some H. chilense x Triticum spp. amphiploids, named tritordeums, were more resistant than the parental wheat line to these diseases, others were not. Average contents of ergosterol and deoxynivalenol (DON) suggested that resistance to colonization by Fusarium was the highest for Hordeum chilense, followed by tritordeum and wheat in decreasing order. In particular, the H. chilense genotypes H7 and H17 enhanced the wheat resistance to F. culmorum in its tritordeum offsprings. Resistance to S. nodorum in tritordeum was not associated with tall plant height. There is sufficient genetic variation for resistance to F. culmorum and S. nodorum among tritordeum to allow the breeding of lines combining short straw and resistance to both diseases.     

Avoidance of leaf rust fungi in wild relatives of cultivated cereals

Summary Avoidance of rust fungi that was based on poor appressorium induction was previously found in Hordeum chilense. In the present study 95 accessions of Triticeae were screened for avoidance of Puccinia hordei. The percentage of appressorium formation per germinated spore ranged from 6 to 90%. On none of the 41 accessions of Aegilops, Agropyron, Elymus, Secale, Thinopyrum or Triticum studied was the rate of appressorium formation lower than 25%. Lower rates of appressorium formation were, however, found on accessions of wild barley species Hordeum brachyantherum, H. marinum, H. parodii and H. secalinum. Its implications in cereal breeding are discussed.     

Disease resistance in protected crops and mushrooms

Summary Cultivars of tomatoes, cucumbers, lettuce and peppers have been bred for resistance to one or more pathogens. Some tomato and cucumber cultivars have resistance to a wide range of diseases. Resistance has been transient in many cases and a succession of cultivars with new genes or new combinations of resistance genes has been necessary to maintain control. There has been a number of notable exceptions and these have included durable resistance to such pathogens asFulvia fulva and tomato mosaic virus. With lettuce the resistance situation is complicated by the occurrence of fungicide resistant pathotypes. There are no strains ofAgaricus bisporus purposely bred for disease resistance.In protected flower crops only resistance to Fusarium wilt in carnations has been purposely bred but differences in disease resistance are apparent in cultivars of many ornamental crops. This is particularly so in chrysanthemums where there are cultivars with resistance to many of the major pathogens. Similar situations occur with other flower crops and pot plants. Cultivars of some species have not been systematically investigated for resistance.The need for genetic resistance will increase with the further reduction, in the limits on pesticide use and an increasing public awareness and importance of pesticide pollution.ADAS is an executive agency of the Ministry of Agiculture, Fisheries and Food and the Welsh Office.     

Genetic constitution and diversity in four narrow endemic redwoods from the family Cupressaceae

The genetic constitution and diversity of four relictual redwoods are discussed in this review. These include monotypic genera of the family Cupressaceae: coast redwood (Sequoia sempervirens), giant sequoia (Sequoiadendron giganteum), dawn redwood (Metasequoia glyptostroboides), and alerce (Fitzroya cupressoides). All four species are narrow endemics, share a number of common phenotypic traits, including red wood, and are threatened species. Fossil history suggests that the ancestors of redwoods probably originated during the Cretaceous and Tertiary periods and flourished thereafter for millions of years. Towards the end of the Tertiary period began their decline and struggle for existence that continued during the subsequent geologic upheavals and climate changes, until the survival of the present-day redwoods in the current restricted locations in the world (USA, China, and South America). Although two species, Sequoiadendron and Metasequoia, are diploids (2n = 22), and the other two are polyploids: Fitzroya a tetraploid (2n = 4x = 44), and Sequoia a hexaploid (2n = 6x = 66); they all share the same basic chromosome number x = 11. The genome size in the hexaploid Sequoia is one of the largest (31,500 MB) in the conifers, while the genome sizes of diploid Metasequoia and Sequoiadendron are about one-third (~10,000 MB) of Sequoia. Genetic diversity in the redwoods is lower than most other gymnosperms, except in Sequoia, which seems to rank near the upper quarter of the coniferous forest trees. Genomic research is sparse in the redwoods, and should be pursued for a better understanding of their genome structure, function, and adaptive genetic diversity.     

Distribution,ecology and reproductive biology of wild tomatoes and related nightshades from the Atacama Desert region of northern Chile

Over the past 20 years, several expeditions were made to northern Chile to collect populations of wild tomatoes (Solanum chilense, S. peruvianum) and allied nightshades (S. lycopersicoides, S. sitiens), and obtain information about their geographic distribution, ecology and reproductive biology. Restricted mainly to drainages of the Andean and the coastal cordillera, populations are geographically fragmented. The two nightshade species are rare and threatened by human activities. Adaptation to extreme aridity and soil salinity are evident in S. chilense and S. sitiens (the latter exhibits several xerophytic traits not seen in the tomatoes) and to low temperatures in S. lycopersicoides and S. chilense. All tested accessions are self-incompatible, with the exception of one S. peruvianum population collected at the southern limit of its distribution. Several distinguishing reproductive traits—anther color, attachment, and dehiscence, pollen size, and flower scent—suggest S. sitiens and S. lycopersicoides attract different pollinators than S. chilense and S. peruvianum. The four Solanum spp. native or endemic to Chile provide a variety of novel traits which, through hybridization and introgression with cultivated tomato, could facilitate development of improved varieties, as well as research on a variety of basic topics, including plant-pollinator interactions, abiotic stress responses, and evolution of reproductive barriers.     

The induction in vitro of adventitious shoots in Rosa

Summary Adventitious shoots were formed on excised leaves, roots and callus of Rosa persica x xanthina and on excised leaves of R. laevigata and R. wichuraiana on culture media that included BAP and NAA as growth regulators. Shoots formed freely on freshly cultured callus of R. persica x xanthina but their production declined in successive cultures and ceased after twelve weeks. Transplantation to soil was improved by rooting plantlets in cellulose plugs in vitro and transferring plantlets to soil while still in the plugs.     

The exploration of genetic resources of Portuguese cabbage and kale for resistance to several Brassica diseases

Summary Twenty three accessions of nine Portuguese cabbage and kale land races from different geographic origins were tested at the seedling stage for resistance to several important brassica diseases. Resistance to downy mildew (Peronospora parasitica), expressed as necrosis of the cotyledon mesophyll, was found in all the accessions. Type A resistance to cabbage yellows (Fusarium oxysporum f. sp. conglutinans race 1) was present in most of the landraces. Resistance to clubroot (Plasmodiophora brassicae race 6) was found in one accession of the Portuguese tree kale. High resistance to blackleg (Leptosphaeria maculans) and white rust (Albuco candida) was not detected, although several accessions showed 20 to 30% of plants with intermediate expression of resistance. All Portuguese cole accessions were susceptible to blackrot (Xanthomonas campestris pv. campestris).     

Production and characterization of intergeneric diploid cybrids derived from symmetric fusion between Microcitrus papuana Swingle and sour orange (Citrus aurantium)

Plants were regenerated from intergeneric somatic hybridization between embryogenic protoplasts of Microcitrus papuana Swingle and leaf-derived protoplasts of sour orange (Citrus aurantium L.) via electrofusion. The regenerated plants were morphologically similar to the leaf parent in growth vigor, leaf and branch structure. FCM analysis showed that they were diploids. Simple-sequence-repeat (SSR) and cleaved-amplified-polymorphic-sequence(CAPS) were employed for hybridity characterization. SSR banding patterns of the regenerated plants were identical to the leaf parent, sour orange, indicating that they possessed nuclear component derived from sour orange. DNA amplification with chloroplast and mitochondrial universal primers, followed by restriction endonuclease digestion, revealed polymorphism between the fusion parents. Therefore, this method was used to determine the cytoplasmic compositions of the regenerated plants. Banding patterns for all the polymorphic primer/enzyme combinations of the regenerated plants were similar to those of the embryogenic parent, M. papuana, suggesting that only the cytoplasmic components derived from the embryogenic parent were present in the regenerated plants. FCM, SSR and CAPS demonstrated that intergeneric diploid cybrids have been successfully obtained by symmetric fusion. Related results concerning nuclear and cytoplasmic composition of previous diploid somatic hybrids and potential mechanism for regeneration of such kind of plants are discussed herein. This revised version was published online in July 2006 with corrections to the Cover Date.