Solid-State Fermentation of Silybum marianum L. Seeds Used as Additive to Increase the Nutritional Value of Wheat Bread

Grazina Juodeikiene^1*, Dalia Cizeikiene¹, Vaida Ceskeviciute¹, Daiva Vidmantiene¹, Loreta Basinskiene¹, Ieva Akuneca², Mantas Stankevicius², Audrius Maruska², Elena Bartkiene³, Ona Ragazinskiene⁴ and Algimantas Petrauskas<sup>5

1</sup>Department of Food Technology, Faculty of Chemical Technology, Kaunas University of Technology, Radvilenu Rd. 19, LT-50254 Kaunas, Lithuania
²Department of Biochemistry and Biotechnologies, Vytautas Magnus University, Vileikos st. 8, LT-44404 Kaunas, Lithuania
³Department of Food Safety and Animal Hygiene, Lithuanian University of Health Sciences, Tilzes st. 18, LT-47181 Kaunas, Lithuania
⁴Kaunas Botanical Garden, Vytautas Magnus University, Z. E. Zilibero st. 6, LT-46324 Kaunas, Lithuania
⁵Prof. Kazimieras Barsauskas Ultrasound Research Institute, Studentu st. 50, LT-51368 Kaunas, Lithuania

Article history:
Received February 9, 2013
Accepted March 29, 2013

Key words:
solid-state fermentation, lactic acid bacteria, Silybum marianum L., ultrasound, phenolic compounds, flavonoids, flavour compounds, antioxidant activity

Summary:
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 spontaneously fermented Lithuanian rye sourdough. A possibility to improve sensory properties (flavour) of Silybum marianum L. seeds using LAB fermentation was investigated. The composition of volatile compounds of the unfermented and LAB-fermented seeds of this plant was analyzed using gas chromatography-mass spectrometry (GC-MS). Fermented seeds have shown considerable differences mainly due to the accumulation of higher alcohols. Total amount of phenolic compounds, flavonoids and 2,2-diphenylpicrylhydrazyl (DPPH) radical scavenging activity of unfermented and fermented seeds were determined spectrophotometrically. The obtained results indicate that Silybum marianum L. seeds are a valuable source of bioactive compounds. The highest content of phenolic compounds and flavonoids (4596 and 1346 mg of rutin equivalents (RE) per 100 g, respectively) was determined in the seeds fermented with Pediococcus acidilactici KTU05-7 bacteria in solid-state fermentation. Silybum marianum L. seeds fermented with P. acidilactici KTU05-7 and Pediococcus pentosaceus KTU05-9 showed stronger antioxidant activity (1263 and 1041 mg of RE per 100 g, respectively), compared to the unfermented seeds (805 mg of RE per 100 g). The addition of Silybum marianum L. seeds fermented with P. acidilactici KTU05-7 bacteria had the highest effect on the decrease of the bacterial spoilage of bread. The aromacompounds from the fermented seeds extracted with supercritical carbon dioxide demonstrated the highest antimicrobial activity against the tested microorganisms. Ultrasonic pretreatment of the seeds reduced the total amount of microorganisms in the raw material. Microbiological tests revealed that the highest antimicrobial effect was achieved using the solid-state fermentation conditions. This study revealed that fermented Silybum marianum L. seeds are a suitable additive for natural flavouring of baked goods.

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