不同采收时期对香椿饲用品质的影响

目的]对不同采收时期所得香椿复叶的粗蛋白、类黄酮、总硝酸盐含量及其抗氧化活性进行分析比较,确定饲用香椿复叶的最佳采收时期。方法]以5月15日至11月1日逐月采收的香椿复叶为材料,测定其粗蛋白、类黄酮及总硝酸盐含量,并利用ORAC、DPPH、FRAP法测定其抗氧化活性,综合营养及保健活性分析,筛选最适饲用采收时期。结果]不同采收期,香椿复叶粗蛋白、类黄酮、硝酸盐含量及抗氧化活性差异显著(P0.05)。其中,复叶粗蛋白含量(全采收期13.17%～22.65%)随其成熟度增加而呈下降趋势,除10月中旬后的样品外,其余采收期复叶粗蛋白含量均大于15%,远高于常规粮食饲料,具有高蛋白的饲用优势;类黄酮含量突出(全采收期均值15.87 mg·g~(-1)),远高于蓝莓等常见果蔬,且随复叶成熟而持续积累,并于10月达到最高27.02 mg·g~(-1);ORAC、DPPH、FRAP法测定结果均表明香椿复叶具有突出的抗氧化活性,且随复叶成熟而持续增加,并与其类黄酮含量呈极显著正相关(P0.01);香椿复叶大量富集硝酸盐(全采收期2 306.39～7 346.80 mg·kg~(-1)),且随其叶片成熟呈"V"形积累,7—8月中旬采收的香椿复叶硝酸盐含量处峰谷阶段,此间均值为2 603.78 mg·kg~(-1),相对适于进行饲用采收。结论]不同采收期香椿复叶的饲用品质差异显著,综合考虑其营养价值及保健功效, 7—8月中旬是对香椿复叶进行饲用采收的最适采收时期。

Effect of Harvest Time on Forage Quality of Toona sinensis

Objective] To reveal and compare the contents of crude protein, flavonoids, nitrates and their antioxidant activity of Toona sinensis harvested in different time, and to find the optimal harvest time for fodder utilize.Method] The contents of crude protein, flavonoids and total nitrates of rachises of T. sinensis harvested from May to November were analyzed, and their antioxidant activity were determined by ORAC, DPPH and FRAP. Combining the nutritional and healthy analysis, the optimal harvest time was determined.Result] There were significant differences in the crude protein, flavonoids, total nitrates contents and antioxidant activity of T. sinensis harvested in different time(P<0.05). The crude protein content (varied from 13.17% to 22.65%) presented a downward trend with the maturity of T. sinensis. But except the samples harvested after mid-October, the rest samples showed protein forage advantage with the crude protein contents higher than 15%, which were far higher than the conventional grain feedstuffs. The flavonoids content of T. sinensis harvested at any time were highlighted (15.87 mg·g^-1 in average), which was far higher than that of the common fruits and vegetables, such as blueberries, and was persistently accumulated with the maturity of rachises, and reached the highest in October (27.02 mg·g^-1). The results of ORAC, DPPH and FRAP assay all showed outstanding antioxidant activities which increased with the maturity of rachises. Meanwhile, very significant positive correlations (P<0.01) were detected between the flavonoids content and the antioxidant activities. A large amount of nitrates was detected in T. sinensis from different harvest time (2 306.39~7 346.80 mg·kg^-1). The accumulation of nitrates in T. sinensis followed a V-shape along with its maturity. The T. sinensis harvested in the mid-July and August, with the average nitrates content of 2 603.78 mg·kg^-1, contained the lowest nitrates content.Conclusion] The feeding quality of T. sinensis harvested in different time is proved to be significantly different. Comprehensively considering the nutritional value and health care effect of T. sinensis, the mid-July and August are the optimum harvesting time for the forage development of T. sinensis.