Solid-state fermentation of Silybum marianum L. seeds used as additive to increase the nutritional value of wheat bread

Abstract

In the present study Silybum marianum L. seeds were fermented using solid state fermentation (SSF) with several lactic acid bacteria (LAB) of Lactobacillus and Pediococcus genera, isolated from spontaneous Lithuanian rye sourdoughs. A possibility to improve sensory properties (flavour) of Silybum marianum L. seeds using LAB fermentation was investigated. The composition of volatile compounds of the non-fermented and LAB fermented seeds of this plant was analyzed using GC-MS. Fermented seeds have shown considerable differences mainly due to accumulation of higher alcohols. Total amount of phenolic compounds, flavonoids and 2,2- diphenylpicrylhydrazyl (DPPH) radical scavenging activity of non-fermented and fermented seeds were determined spectrophotometrically. The results obtained indicate, that seeds of Silybum marianum L, is a valuable source of bioactive compounds. The highest content of phenolic compounds and flavonoids (4596 and 1346 mg of rutin equivalents (RE)/100g, respectively) was determined for P. acidilactici KTU05-7 bacteria by solid state fermented seeds. Silybum marianum L. seeds fermented with P. acidilactici KTU05-7 and Pedioccus pentosaceus KTU05-9 showed stronger antioxidant activity (1263 and 1041 mg RE/100g respectively) comparing to un-fermented seeds (805 mg RE/100g). The addition of the P. acidilactici KTU05-7 bacteria fermented Silybum marianum L. seeds had the highest effect on the decrease of the bacterial spoilage of bread. The aroma compounds, extracted from this fermented seeds with supercritical carbon dioxide, demonstrated the highest antimicrobial activity against the tested microorganisms. Ultrasonic pre-treatment of the seeds reduced the total amount of microorganisms in the raw material. Microbiological tests revealed, that the highest antimicrobial effect is achieved using the solid-state fermentation conditions. [...]