OCCURRENCE OF PROTEIN-BOUND LYSYLPYRROLALDEHYDE IN DRIED PASTA

The extent of the advanced Maillard reaction (MR) involving protein-bound lysylketoses degradation that occurs in pasta drying was studied by evaluating furosine and lysylpyrrolaldehyde (LPA). By enzymatic hydrolysis followed by solid-phase extraction and ion pair reversed-phase high-performance liquid chromatography (IP-RP HPLC) with 297-nm detection, protein-bound LPA was separated without interference and quantified in pasta products using carboxy-2-pyrrolaldehyde as the external standard. Model doughs containing different amounts of cold or [U-14C]-labeled glucose or maltose and pasta processed under different heating conditions were considered. A close relationship between the accumulation behaviors of furosine and protein-bound LPA was observed, confirming that LPA is a main derivative of lysylketoses residues. Further degradation of LPA was detected only under thermal treatments not applicable in pasta drying. Under the pasta processing conditions of a semipilot plant, and with semolina of known origin and free sugar composition, LPA formation was enhanced (> 12 mg/100 g of protein) when the drying cycle included temperatures close to 80-degrees-C or higher, and pasta moisture values were close to 15% or lower. Under low-temperature (50-degrees-C) conditions, no LPA was produced. Another key parameter was the concentration of reducing sugars, the most effective being glucose. Although other aminoketoses besides lysylketoses are probably formed and degraded, furosine and LPA evaluation seems to sufficiently describe the MR extent occurring on pasta protein. Considering the undesirable sensorial changes of pasta attributable to extensive MR, the possible antinutritional properties reported for LPA, and the wide range of LPA values (from 0 to over 40 mg/100 g of protein) found in commercial spaghetti, a better control of the advanced MR in this food is advisable.