油桐品种五爪桐含油量及桐油质量研究

油桐品种五爪桐含油量及桐油质量研究

摘要:研究结果显示,五爪桐[Vernicia fordii (Hemsl.)Airy-Shaw cv. Five fingernails tung]的桐油组分中含有63种成分,其中18种十八-6,9,12-三烯酸甲酯顺反异构体的α-桐酸的总含量达63.94%,(Z,Z,Z)十八-9,12,15-三烯酸甲酯的β-桐酸含量为8.62%,十八-9-烯酸甲酯含量为6.23%,(Z,Z)十八-9,12-二烯酸甲酯含量为8.05%,棕榈酸甲酯含量为 3.30%,二十-11-烯酸甲酯含量为 1.19%｡五爪桐桐油总脂肪酸的相对含量为99.04%,其中有21种不饱和脂肪酸,干性油含量为90.63%;其种仁含油量为62.89%,折光指数1.520 6,酸化值5.1 mg/g,碘化值165 mg/g,皂化值190 mg/g,透明无异味,色泽0.1,密度0.937 6 g/mL,热聚合时间446 s｡五爪桐桐油脂肪酸因含β-桐酸高,桐油产品中有结晶析出,不能达到商品桐油的质量要求;但β-桐酸是一种治疗心血管疾病有显效的有效成分,含量高,有提取价值,可将它作为药用油桐树发展｡

关键词:油桐;含油量;质量指标

Study on the Oil Content and Quality of Vernicia fordii cv. Five Fingernail Tung Abstract: The results of the presented study showed that there were 63 substances in oil components of V ernicia fordii (Hemsl.) Airy-Shaw cv. Five fingernails tung including 63.94% of 18-6,9,12-Octadecatrienoic acid and methyl ester cis-trans isomer of α-eleostearic acid, 8.62% of Z,Z,Z-9,12,15-Octadecatrienoic acid, 6.23% of 9-Octadecenoic acid, 8.05% of(Z,Z)-9,12-Octadecadienoic acid, 3.30% of palmitic acid, 1.19% of 11-Eicosenoic acid. The relative content of Five fingernails tung fatty acid was 99.04% among which there were 21 unsaturated fatty acids; the total content of drying oil was 90.63%; the oil content of seed kernel was 62.89%; the refractive index was 1.520 6; the acidification value was 5.1 mg/g; the iodization value was 165 mg/g; the saponification value was 190 mg/g; It was transparent and without abnormal odour; the colour was 0.1; and the specific gravity was 0.937 6 g/mL; while the thermal pol ymerization time was 446 s. It contained much β-eleostearic acid so the products could not meet the need of commercial tung oil products; but β-eleostearic acid was an effective substance for the treatment of cardiovascular disease. It could be developed as medicinal tung tree.

Key words: Vernicia fordii (Hemsl.)Airy-Shaw; oil content; quality index

湖北省来凤县出产的五爪桐[Vernicia fordii (Hemsl.)Airy-Shaw cv. Five fingernails tung]是大戟科(Euphorbiaceae)油桐属(Vernicia Lour.)木本油料植物,是当地常见的油桐品种｡五爪桐主产于来凤县的百福司镇､漫水乡､大河镇等地海拔500 m以下的坡地,是当地重要的经济林木｡当地政府为加快山区经济的发展,正在

大力发展油桐产业｡为了指导五爪桐的开发利用,对五爪桐的含油量､理化特性及其成分进行了初步研究,现将结果报告如下｡

1材料与方法

1.1材料

五爪桐干燥种仁由湖北省来凤县四海贸易有限责任公司提供｡仪器主要有AL-204型电子天平(上海梅特勒-托利多仪器有限公司)､PHSJ-4A型pH计(上海精密科学仪器有限公司),GC6890N- MS5975气相色谱—质谱联用仪(安捷伦科技有限公司)｡

1.2方法

1.2.1油桐种仁含油量测定选择正常的五爪桐果实若干,取出种仁,将种仁烘干､磨碎,在电子天平上准确称取烘干的碎种仁若干,装入滤纸筒,放入索氏提取器,用无水乙醚提取,加热到50℃,7次/h,连续提取8 h,提取至抽提筒内乙醚用玻璃片检查无油迹为止｡回收乙醚;置入105℃烘箱,烘至恒重;计算含油量[1,2]｡

1.2.2桐油理化特性测定桐油折光指数用折光指数仪测定;桐油碘化值采用油料碘化值测定方法进行;桐油皂化值采用油料皂化值测定方法进行;桐油透明度鉴定方法为量取试样100 mL,注入比色管中,在20℃温度下静置24 h,然后移到乳白色灯泡前(或在比色管后衬以白纸)观察透明程度,记录观察结果;桐油色泽确定按表1进行处理;桐油气味鉴定方法为取少量试样注入烧杯中,加温至50 ℃,用玻璃棒边搅拌边嗅气味,凡具有该油固有的气味､并且无异味的为合格,不合格的注明异味情况;桐油比重的测定按比重瓶法进行｡

1.2.3桐油热聚合试验称取混匀试样100 g注入金属锅内,上挂温度计(水银球浸入油中),置于喷灯上加热,在4 min内达到282℃,即第一分钟要达到105℃;第二分钟要达到180℃;第三分钟要达到240℃ ;第三分钟50秒要达到265℃;第四分钟达到282℃｡调节灯焰,固定在282℃,同时开始记时,用玻璃棒不断搅动到完全胶化为止｡纯桐油从282℃开始到完全胶化,总计不超过7 min 30 s｡其中由初凝呈线状至完全胶化的时间约40 s,胶化物为淡黄色半透明状,在胶化后1 min取出一块,冷却2 min,用刀切时不粘刀,以刀压之变成粉末,则表示符合要求｡试验结果允许时间差不超过10 s,取平均值为测定结果｡

1.2.4β型桐油试验β-桐酸的存在表示桐油不稳定,习惯上将含β-桐酸的桐油称之为β型桐油｡将混匀过滤的试样注入干燥的试管中(约达试管容量的1/3处),用软木塞塞紧,置于冰箱中,在温度3.3~4.5℃冷却24 h,如有结晶析出,则表示有β-桐酸存在｡β型桐油的结晶为针叶状,熔点为62℃｡

1.2.5桐油脂肪酸含量的测定及脂肪酸甲酯化桐油脂肪酸的测定按脂肪酸测定方法进行｡脂肪酸甲酯化所用试剂有氢氧化钾甲醇溶液2 mol/L(将13.1 g氢氧化钾溶于100 mL无水甲醇中,可稍微加热,加入无水硫酸钠干燥,过滤,即得澄清溶液