3.1. Total folate concentrations in raw and processed vegetables
All concentrations are expressed relative to fresh weight as this was most directly related to portions. In addition, dry matter content of vegetables varied throughout the processing due to dual mechanisms of water intake and loss of soluble solids, mechanisms which cannot be quantified independently in a continuous industrial process.
Dispersion of the total folates contents, in raw green beans and final products (vegetables and covering liquid) during the 2010 season, determined by HPLC with fluorimetric detection after precolumn derivatisation, is presented in Fig. 3. The average folates concentrations were 0.69 mg/kg fw (5.75 mg/kg dw) in raw vegetables and 0.39 mg/kg fw (3.75 mg/kg dw) in the final product. The average concentrations in the covering liquid were 0.40 mg/kg fw. Industrial processing involved folates losses which is in agreement with green beans sampled along the industrial canning chain, where average folates concentration was 0.52 mg/kg in the raw vegetables corresponding to 5.5 mg/kg dw (in the range observed for the 2010 season), while the average concentrations after canning were 0.36 mg/kg fw (4.25 mg/kg dm), and only 0.16 mg/l in the covering liquid (Table 3).