Use of Directed Lactic Fermentation to Obtain Plant-Based, Upcycled Beverage from Milk Thistle Endosperm

Abstract

This study aimed to evaluate the possibility of using milk thistle endosperm (MTE) extract with a protein content of >2 g/100 mL to obtain a fermented product, an alternative to milk beverages. Directed lactic fermentation with Lacticaseibacillus rhamnosus was carried out. The course of the process was monitored. The changes in pH, the saturation of the medium with dissolved oxygen, and temperature were measured. The values of the main nutritional parameters, silymarin content, amino acid profile/content, and the PDCAAS value (Protein Digestibility-Corrected Amino Acid Score) were determined in the extract before and after fermentation. The lactic acid fermentation of the MTE extract took place in four phases, with the activity of L. rhamnosus being the most intense between 4 and 8 h into the process. As a result of fermentation, there were changes in the total amino acid content in the tested medium, suggesting the catabolism of aspartic acid, arginine, proline, and isoleucine via LAB took place. Particularly significant was the increase in the content of lysine and valine (4.95 and 4.68 g/100 g of total AA, respectively), which are the limiting amino acids in MTE. Although MTE contained approximately 1% silymarin, no presence of this flavonolignan complex was found in the extracts.