超声波辅助提取香蕉皮中果胶的研究

[目的]研究采用超声波辅助提取香蕉皮中果胶的工艺条件。[方法]采用超声波辐射萃取法从香蕉皮中提取果胶,并研究了不同萃取剂、溶剂、超声时间、超声波辐射功率、料液比、乙醇浓度及提取液pH对果胶提取率的影响。在此基础了进行了正交试验。[结果]确立了超声波条件下提取果胶的最佳工艺条件为：用盐酸调pH为2．0,用水作为溶剂,料液比为1：15,超声功率为500W．作用时间为50min,乙醇浓度为60％,在此条件下提取率可达20．5％。各因素对提取率的影响为：pH〉料液比〉超声功率〉超声时间〉乙醇浓度。[结论]为综合利用资源及利用超声波提取香蕉皮中果胶提供了一条可行性途径。     

桑枝皮果胶提取的试验研究

采用有机溶剂回流法提取桑枝皮中的果胶,通过正交试验,研究了桑枝皮中果胶的提取条件,并对提取条件进行优化。结果显示:当提取条件为提取时间120min,提取液为以pH2.0的盐酸为主,辅以少量磷酸时,提取效果最佳,最终可从桑枝皮中提取约7%的果胶。为进一步利用桑皮纤维提供了可参考的试验数据。     

Determination of the distribution and reaction of polysaccharides in wood cell walls by the isotope tracer technique VII: Double radiolabeling of xylan and pectin in magnolia (Magnolia kobus DC) and comparison of their behaviors during kraft pulping by radiotracer technique

myo-Inositol-[2-³H] and d-glucuronic acid-[6-¹⁴C] were administered simultaneously to a growing stem of magnolia (Magnolia kobus DC) to label xylan and pectin, respectively, in the cell wall. Determination of the radioactivity of nitrobenzene oxidation products and sulfuric acid hydrolysates of the newly formed xylem indicated that xylan and pectin were labeled with ³H and ¹⁴C, respectively. The doubly labeled wood tissue was treated to kraft pulping, and the radioactivity of the pulping black liquor and treated wood tissue were determined at various stages of the pulping to compare the dissolving behavior between pectin and xylan during the pulping. The results showed that pectin was not dissolved as easily as xylan and was not redeposited on pulp fiber at the late stage of the pulping.Part of this report was presented at the 40th Lignin Symposium at Tsukuba, October 1995     

番茄绿熟期果实硬度与果皮结构及果胶含量的关系

比较硬果型番茄TS330 和软果型番茄A57 不同发育阶段的果实硬度变化，结果表明：绿熟期、转色期、红熟期TS330 果实硬度均显著高于A57，其中绿熟期果实硬度差异最大。绿熟期TS330 果皮细胞壁厚度、细胞致密度（单位厚度的细胞层数）和果胶含量显著高于A57。TS330、F₁（TS330×A57）、A57 绿熟期果实硬度依次为26.86、21.09、19.11 kg ·cm^-2。番茄果实硬度与果皮细胞致密度（相关系数0.96）、果胶含量（相关系数0.99）密切相关。TS330×A57 的F₂ 果实硬度 趋向正态分布，表明果实硬度受多位点控制。     

果胶提取中沉淀方法及条件的研究

在柚皮果胶提取中,对醇析法和盐析法2种沉淀方法及条件进行了比较研究.结果表明,用醇析法分离沉淀柚皮果胶的最佳条件是:乙醇终浓度60%,果胶提取液pH值1.5,醇析温度5℃,醇析静置4 h,果胶得率为20.93%.用盐析法分离沉淀柚皮果胶的最佳条件是:Al2(SO4)3饱和溶液∶果胶提取液=1∶1,果胶提取液pH值5.5,盐析温度45℃,盐析静置1 h,果胶得率为20.33%.     

Biochemistry of Fruit Ripening of Guava (Psidium guajava L.): Compositional and Enzymatic Changes

Changes in chemical composition and the activities of hydrolytic enzymes during four different stages of maturity, viz. mature green (MG), color turning (CT), ripe (R), and overripe (OR), have been studied in guava fruits cv. Banarsi Surkha. Chlorophyll content decreased while carotenoid content increased during ripening. Starch content decreased with concomitant increase in alcohol-soluble sugars. Cellulose, hemicellulose, and lignin also decreased up to ripe stage, while pectin continued to decrease up to OR stage. PG (polygalacturonase) and cellulase exhibited progressive increase in activity throughout ripening, whereas pectin methyl esterase (PME) activity increased up to CT stage and decreased at R stage. The activities of alpha-amylase and beta-amylase decreased significantly with ripening. The most notable metabolic changes occurred between MG and CT stage, implying that for improved postharvest handling, guava fruits may be harvested at CT stage.     

微波辅助萃取法快速测定苎麻果胶含量的研究

采用微波辅助萃取法测定苎麻中的果胶含量,研究了苎麻粒径、液料比、微波功率、微波辐照时间、萃取次数等因素对微波辅助萃取果胶的影响。结果表明:苎麻浸泡20 min后,在微波功率450 W、苎麻粒径1.0 cm、液料比为1∶20(g/ml)条件下进行微波辅助萃取,辐照时间每次6 min,连续萃取2次后可达到GB5889-86中苎麻果胶的测定效果。试验将萃取时间从国标法的3 h缩短到12 min,测定的相对标准偏差为2.23%,并采用咔唑比色法对微波辅助萃取液中所含果胶进行了分析。     

梨黑星病抗性机理的研究进展

综述了梨黑星菌的分化类型、侵入机制、抗性遗传及抗性机理的研究进展。梨黑星菌在叶片中寄生的具体位置是果胶层。V．nashicola对抗性、易感和非寄主材料的初期侵染相似，当真菌侵入角质层之后，亚角质层菌丝在易感材料中的增长速率远远高于抗性和非寄主材料，并且在抗性和非寄主材料上出现死亡菌丝，这些都表明抗性是在真菌侵入角质层之后表达的。梨黑星病抗性等位基因和敏感性等位基因定位于不同的连锁基因组上，梨黑星病抗性基因与苹果黑星病抗性基因具有同源性。     

Developmental changes in cell wall polysaccharides from sweet cherry (Prunus avium L.) cultivars with contrasting firmness

Firmness is a major quality attribute of fresh cherries, and is also a main factor affecting susceptibility to bruising and postharvest rots. In order to identify the factors determining the textural differences between genotypes, we evaluated the solubilization, depolymerization and monosaccharide composition of pectin and hemicelluloses from two cultivars with contrasting firmness (‘Sweetheart’, firm and ‘Newstar’, soft) at four different developmental stages. Firm ‘Sweetheart’ cherries had higher contents of cell wall material than soft ‘Newstar’ fruit. Moderate depolymerization of hemicellulose and tightly bound pectins was detected irrespective of cultivar firmness. The general pattern and extent of uronic acid solubilization was quite similar in both cultivars. Rhamnogalacturonan I (RG-I) seemed to be preferentially solubilized in firm ‘Sweetheart’ fruit as opposed to tightly bound homogalacturonans (HG) in soft cherries. Pectic polymers with higher neutral sugar to uronic acids ratio were found from early development in soft ‘Newstar’ fruit. Overall, soft ‘Newstar’ fruit had reduced wall content and higher branching of tightly bound pectins than firm ‘Sweetheart’ fruit. These factors may be associated with the varietal differences in cherry firmness.     

Chicory （Cichorium intybus L.） and cereals differently affect gut development in broiler chickens and young pigs

Dietary fiber, resistant to host-mediated digestion in the small intestine due to lack of endogenous enzymes, impacts many facets of animal health and is associated with gut development especially in young monogastrics. Furthermore, it can be used as in-feed antibiotic alternative. Chicory （Cichorium intybus L.） forage with high content of pectin （uronic acids as building blocks） is a novel class of dietary fiber that is chemically different from cereal grains （with high content of arabinoxylans）. In the present study, we investigated effects of dietary inclusion of chicory forage on digestibility, gut morphology and microbiota in broilers and young pigs. In the chicken experiment, 160 1-d old broiler chicks were fed 3 nutritionally balanced diets for 30 d including a cereal-based diet and 2 diets with part of the cereals substituted with 60 and 120 g/k9 chicory forage （CF60 and CF120], whereas in the pig experiment, 18 seven-wk old Yorkshire pigs were fed 3 diets for 18 d including a cereal-based diet and 2 diets with 80 and 160 g/kg chicory forage inclusion （CF80 and CF160）. Our results showed that young pigs were capable to utilize chicory forage well with higher total tract apparent digestibility （TTAD） of all fiber fractions, particularly uronic acid, compared with the control （P 〈 0.01）. In contrast, a decreased TTAD of all fiber fractions was observed in chickens fed on diet CF120 （P 〈 0.05）. Moreover, diet induced changes in gut morphology were observed in the large intestine of chickens. The alteration of cecal mucosal thickness was further positively correlated with TTAD of non-starch polysaccharides （NSP） and its constituent sugars （P 〈 0.05）. In addition, in pigs, terminal restriction fragment length polymorphism （T-RFLP） analysis of intestinal microbiota revealed substantial dietary effects （cereal control diet vs. chicory forage inclusion） on the relative abundance of 2 dominant bacterial phylotypes （Prevotella sp. vs. Roseburia sp.） respective