Evaluation of In Vitro Simulated Digestion and Fermentation Characteristics of Fermented Quinoa and Oat

In this study, the nutritional value of fermented quinoa (FQ) and fermented oat (FO) was evaluated by using Lactiplantibacillus plantarum, Lactobacillus delbrueckii subsp. lactis, and L. delbrueckii subsp. bulgaricus in liquid fermentation, and the characteristics in simulated digestion and fermentation were studied. The results revealed that the contents of protein, β-glucan, and total amino acids in FQ increased by 4.09%, 28.20%, and 9.30%, respectively, whereas those in FO increased by 5.27%, 16.07%, and 11.37%, respectively. The fat, carbohydrate, and phytic acid contents in FQ decreased by 48.17%, 12.12%, and 61.59%, respectively, whereas those in FO decreased by 32.17%, 7.08%, and 53.64%, respectively. After simulated digestion, compared with those of the unfermented samples, the hydroxyl radical scavenging ability, iron ion reducing ability and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic) acid (ABTS) scavenging ability of the FQ increased by 50.29%, 20.34%, and 27.57%, respectively, whereas those of the FO increased by 58.90%, 15.63%, and 12.07%, respectively. After simulated fermentation, compared with those of the unfermented samples, the total short-chain fatty acid contents of FQ and FO significantly increased (p < 0.05). Moreover, the relative abundance of Megamonas in FQ significantly increased (p < 0.01), that of Streptococcus in FQ was significantly decreased (p < 0.01), and those of Lactococcus and Phascolarctobacterium in FO significantly increased (p < 0.01). These findings demonstrated that fermentation enhanced the nutritional value of quinoa and oats, providing a reference for the development of fermented grain-based food.