Method for distinguishing true apple juice from false apple juice by virtue of liquid chromatogram-isotope ratio mass spectrometry (LC-IRMS) determination

The invention relates to a method for distinguishing true apple juice from false apple juice by virtue of liquid chromatogram- isotope ratio mass spectrometry (LC-IRMS) determination. The method can be used for effectively distinguishing true apple juice from false apple juice and ensuring the quality safety of apple juice products. The method comprises the following steps: respectively preparing apples from different places into apple juice samples; analyzing plant polysaccharides in the prepared apple juice samples to establish plant polysaccharide determination conditions, and analyzing malic acid in the apple juice to establish the plant polysaccharide determination conditions; and analyzing natural apple juice to establish a linear relationship between the delta C ratio of plant polysaccharides and malic acid in the apple juice to make judgment on the true and false apple juice, wherein if the delta Csuc (sucrose) ranges from -1.909% to -2.647%, the delta Cglu (glucose) ranges from -2.452% to -3.050%, the delta Cfru (fructose) ranges from 2.522% to 3.196%, the ratio delta 1 of plant polysaccharides ranges from 0.27 to 2.78, the delta Cmal (malic acid) ranges from -2.531% to 3.257% and the linear dependence coefficient R2 is more than 0.7255, the apple juice is true. The method is accurate in determination results and high in sensitivity, the quality of apple juice can be effectively guaranteed, adulterated apple juice can be prevented from causing injury to consumers, and economic and social benefits are tremendous.