超声波-中性甲醛浸提-固定pH法快速测定水果中的总酸度

Rapid Determination of Fruit Total Acidity by Fixed pH Method with Ultrasound Extraction in Formaldehyde Solution

利用超声波-甲醛浸提法从水果中提取酸性物质,通过单因素试验和正交优化试验确定提取的最佳工艺条件。用固定pH滴定法测定水果中的总酸度,以每千克样品消耗KOH标准溶液的物质的量(mol/kg)为计算指标,并与国标方法进行比较,从而为水果总酸度的测定提供了一种全新的分析方法。结果表明:超声波浸提时的料液比、浸提时间,水浴温度对酸性物质的提取效果影响较大。固定功率为500W时,其优化工艺条件为:中性甲醛2.00ml,料液质量比1:16、超声15min,80℃水浴中提取7min。结论:用中性甲醛浸提并转换弱酸为强酸,固定pH8.20滴定水果总酸度,同时规范和统一计算方法,是更为科学、合理的新型分析方法,用于实际样品的测定,结果令人满意。

A new method of ultrasonic-formaldehyde extraction was applied to extract acid materials from fruit. By using the parameters of total acidity with fixed pH titration method, the extraction conditions were optimized with single factor and orthogonal tests. The results showed that the mass ratio of fruit to water, processing time of ultrasonic and temperature of water have significant effects on the extraction. And the optimizing conditions are： power 500 W, ratio of material to water 16：1, 2.00 mi neutral formaldehyde, processing time 15 min and ultrasonic treatment at normal temperature, for 7 rain at 80 ℃. The conclusion is that the ultrasonic extraction- formaldehyde method is superior to the traditional water extraction method in determining the fruit acidity comparably.