Optimization of hydrolysis conditions for the identification of uronic acids in fruit using high-performance liquid chromatography

The pectic fraction of foods is constituted by uronic acids (mainly D-galacturonic acid) and neutral sugars. For individualized determination, the pectic fraction must be hydrolyzed to release the monomers. This study was made to find the optimal conditions for the acid hydrolysis of the constituents of the pectic fraction in their determination by high-performance liquid chromatography. The parameters studied were sample amount, acid concentration, and hydrolysis time. The process was perfected using a commercial apple pectin, The optimal conditions found were as follows: 0.1 g of the sample and either 80% sulfuric acid and 4 hours of hydrolysis, or 70% sulfuric acid and 6 hours of hydrolysis, Once the optimal hydrolysis conditions were established, the protocol was used with fresh fruit samples to confirm its applicability. The results showed that the protocol was suitable for identifying and quantifying the structural components of the pectic fraction of foods, and that it even detected constituents that are not usually identified.