From Medical Herb to Functional Food: Development of a Fermented Milk Containing Silybin and Protein from Milk Thistle

Milk thistle is a traditional medicinal herb. Silybin is a medicinal component found in the seed coat of milk thistle, which has liver-protective and anti-cancer properties. Conventional studies have focused on the extraction of silybin with organic reagents, which was inapplicable to the food industry. This study aims to develop a fermented milk containing silybin and protein from the milk thistle seeds. A three step procedure was developed, comprising homogenization of milk thistle seeds, NaHCO₃ heat treatment, and microbial fermentation. The silybin was characterized by high performance liquid chromatography, and the protein was quantified and electrophorized. It was found that the homogenization step was essential for the preparation of protein, and the NaHCO₃ heat treatment was the crucial step in obtaining silybin. The optimal NaHCO₃ treatment settings were 1% NaHCO₃, 60°C, and 3 h, and the optimal strains for microbial fermentation were L131 (Rummeliibacillus stabekisii) and RS72 (Lactobacillus plantarum). The silybin yield in the fermented milk reached 11.24-12.14 mg/g seeds, accounting for 72.6-78.4% of the total silybin in the milk thistle seeds, and the protein yield reached 121.8-129.6 mg/g seeds. The fermented milk had a slightly sweet yoghurt-like flavor and could be used as a dietary supplement for silybin and protein.