Occurrence of maltose in apple juices: Improved method of analysis, typical levels, and factors affecting it

Abstract

Maltose is a disaccharide produced during the enzymatic hydrolysis of starch. Fruit juices generally contain low levels of this sugar, therefore high concentrations of maltose are perceived as an indication of the adulteration or use of low-quality material. The sole recommendation published by the International Fruit Juice Association (AIJN) states that maltose levels in clear apple juices should not exceed 100 mg/L. Silylated oxime derivatives formed in a two stage reaction were used to develop and validate an improved gas chromatography method for maltose analysis. The average content of maltose in 84 tested commercial concentrated apple juices was 164 mg/L, while NFC juices were characterized by average level of 31 mg/L. Levels of indigenous maltose in apples varied during the cultivation seasons; however, they did not exceed 100 mg/kg. The juice clarification process using amylolytic enzymes showed to be crucial for the maltose content in the product. Differences in the activity and selectivity of amylolytic enzymes lead to huge variances in the sugar profile of the final products; however, the nutritional values of the juices remained equal. Therefore, the data presented imply that the limit suggested by the AIJN should be reconsidered.