桑叶各部位的水分和干物含量及主要元素的分布

Study on the Water Content,Dry Matter Content and Distribution of Main Elements in Different Parts of Mulberry Leaves

为了更加准确地测算家蚕对桑叶的食下消化率和饲料转化效率以及桑叶作为食品与畜禽饲料其重金属含量的安全阈值,采用现代检测技术与相应的检测标准,对桑品种“桂桑优62”相同叶位成熟叶片的带皮叶肉、叶脉、叶柄等部位中水分和干物含量以及大量营养元素氮、磷、钾、钙、镁与常见重金属元素铬、铅、镉、汞、砷的分布规律进行了检测分析。桑叶各部位的含水率从高到低依次为叶柄、叶脉、带皮叶肉,而干物含量从高到低依次为带皮叶肉、叶脉、叶柄。桑叶的带皮叶肉部位是家蚕可食用部位,也是在叶片总质量中占比最高和干物质含量最高的部位,全叶干物质的70%~76%、大量营养元素的47%~87%和常见重金属元素的60%~91%均分布在这个部位。总体而言,桑叶中的氮、磷营养元素含量较为丰富,钙、镁、钾营养元素的含量较少;桑叶中的几种常见重金属元素含量由高到低依次是铬、铅、砷、镉和汞,但这些重金属元素的含量均在药品、食品和畜禽饲料的国家标准限量范围之内。

In order to more accurately calculate the digestibility and feed conversion efficiency of mulberry leaves by silkworm,and the safety threshold of heavy metal content of mulberry leaves as feed and food for livestock and poultry,the modern testing technology and corresponding national standards were used to detect the content of nitrogen(N)and phosphorus(P),and the content of total potassium(K),calcium(Ca),magnesium(Mg),chromium(Cr),lead(Pb),cadmium(Cd),hydrargyrum(Hg)and arsenic(As).The water content and dry matter contents in the covered mesophyll,veins and petioles of mature leaves of mulberry variety“Guisangyou 62”at the same leaf position,as well as the distribution regularity of a large number of nutrient elements such as N,P,K,Ca,Mg and common heavy metal elements such as Cr,Pb,Cd,Hg and As were detected and analyzed.From high to low,the water content of each part of mulberry leaves were petiole,vein and mesophyll with skin,while the dry matter content were mesophyll with skin,vein and petiole.The mesophyll with skin of mulberry leaves was the edible part of silkworm,and it was also the part with the highest proportion and the highest dry matter content in the total leaf mass.The 70%~76%of dry matter,47%~87%of macronutrients and 60%~91%of common heavy metal elements were all distributed in this part.Generally speaking,the mulberry leaves were rich in N and P,but less in Ca,Mg and K.The contents of several common heavy metal elements in mulberry leaves were Cr,Pb,As,Cd and Hg from high to low,and their contents were all within the national standard limits of medicines and foods.