Abstract: Studies were carried out on changes of amino acids,reduce sugar and 5-HMF contents in apple juice concentrate of Lujial and Lujia3(Lu for Shandong province,China;Jia for processing)derived from the cross between Telamon and Fuji. Maillard reaction had been simulated with amino acids(lysine,phenylalanine,leucine,isoleucine,methionine,threonine)and reduce sugars(fructose,glucose,arabinose,galactose,xylose)respectively in citric acid-phosphate buffer(pH3.20)and in apple juice concentrate.The results showed that lysine,phenylaianine,leucine,isoleucine,methionine and threonine contents in apple juice concentrate decline during storage.Reduced sugar content increases first,then decreases,while roses and descends again.5-HMF content increases first,then descreases.Amino acids activities in Maillard reaction show great differences between in citric acid-phosphate buffer(pH3.20)and in apple juice concentrate,and also in reduce sugars activities. Lysine activity is high in both experiments.

Key words: apple juice concentrate, amino acids, reduce sugar, 5-HMF(5-hydroxymethyl furfuraldehyde), Maillard reaction