Acta Scientiarum Polonorum Technologia Alimentaria

Background. Polyphenols which are included in a group of food antioxidants have a beneficial impact on human organism, as they prevent the occurrence of life style diseases, including cardiovascular diseases and cancer. Cereals are the main source of polyphenols in a human diet, and especially rye is characterized by high level of these compounds. Many technological processes applied in food production cause a decrease of polyphenols in rye and reduce their antioxidative activity. The aim of the study was to estimate quantitative changes of polyphenols in rye grains subjected to extrusion, under varying process conditions and establish the antioxidant activity of the obtained rye extrudates.

Material and methods. The materials were extrudates prepared from grains of three rye cultivars, namely Amilo, Rostockie and Agrikolo. Extrusion was performed in a single-screw laboratory extruder Brabender 20 DN. Contents of phenolic acids and apigenin in analysed samples was checked by HPLC. Antioxidant activity was measured by FRAP and EPR methods.

Results. All rye extrudates contained ferulic acid levels (53-104 mg/100 g d.m.) approximately 112-316% higher as compared to raw material (25 mg/100 g d.m.). The highest antioxidant activity (using of FRAP method) was measured in extrudates prepared at extrusion parameters: 14% moisture of raw material and 180°C but the lowest at 20% moisture and 120°C. The analysis of spin label reduction kinetics (in EPR method) allowed to conclude, that its reduction was greater for extrudates (except extrudates obtained at moisture content 20% and 120°C) as compared to raw material.

Conclusions. Content of polyphenols and antioxidative activity of rye extrudates is highly dependant on the moisture content of raw material and extrusion temperature.