液相色谱法测定猕猴桃果实中抗坏血酸含量的前处理技术优化

Optimization of Pretreatment Conditions for Determination of Ascorbic Acid Content in Kiwi Fruit Pulp by Liquid Chromatography

以猕猴桃果实为试材,去除果皮,切取月牙形果块,按样液比1∶4(g/m L)进行研磨和匀浆破碎处理,通过浸提剂种类与质量分数、浸提温度与时间以及贮存条件等实验优化,分析各处理样品中抗坏血酸含量差异显著性。结果表明:人工研磨与机械匀浆都是破碎处理的有效手段,其中机械匀浆是更为理想的破碎方法。浸提温度、时间以及振荡处理是影响样品提取效果的主要因素,要把握适度,以在0℃条件下超声波振荡提取15 min为宜。样品经前处理后立即检测与贮藏后检测结果差异很大,最好立即分析。浸提液种类与质量分数、浆液是否分离、贮存温度、光照是影响贮存效果的主要因素,利用较高质量分数的酸性溶液作为浸提剂,破碎后进行离心分离处理,然后置于冷、冻且避光条件下保存是比较理想的样品贮存办法。猕猴桃不同果实间抗坏血酸含量不存在显著性差异,但仍应十分注意材料的选取。

Ripe kiwi fruits were peeled, cut into crescent pieces and ground with aqueous metaphosphoric acid at a solid to water ratio of 1：4 manually or by mechanical homogenization, and then the mash was ultrasonically extracted, centrifuged and stored until being analyzed for the ascorbic acid content by liquid chromatography. The pretreatment conditions including manual or mechanical grinding, extractant type and concentration, extraction temperature and time, and storage conditions were optimized. Signifi cant difference analyses were carried out among various processed samples. The results showed that both manual grinding and mechanical homogenization were effective means of mashing the fruit, and the latter method was superior to the former. Extraction temperature and time were identifi ed as main factors infl uencing extraction effi ciency. An extraction temperature of 0 ℃ and 10 min extraction proved optimal. Accurate results were obtained when the analysis was carried out immediately after sample preparation, signifi cantly different from those reported for the stored samples. Extractant type and concentration, separation of the mash, storage temperature, and light condition were main factors affecting the accuracy of the determination of ascorbic acid using the stored samples. The samples prepared by extraction using higher concentrations of acid and centrifugation should be stored at low temperatures in darkness if analysis cannot be performed immediately. Though no signifi cant difference in ascorbic acid content existed among three kiwifruits, much attention should be paid to selection of the test material.