Nutritional Characteristics of Alfalfa Sprout and the Impact of Fermentation with ‎Probiotic Bacteria on Its Antioxidant and Prebiotic Properties

Plant sprouts are receiving a great deal of attention because of their ‎abundance, bioavailability of components, and health benefits. Germinated legume seeds were the most ‎common sprouts consumed in the human diet. Alfalfa (Medicago sativa) sprout is a valuable source of ‎protein, fiber, minerals, vitamins (B vitamins), glucosinolate, and phenolic compounds. Alfalfa sprout is ‎usually consumed as dehydrated leaves, powder, or dietary supplements in the form of tablets. ‎Regarding nutritional values, alfalfa sprout powder (ASP) could act as a prebiotic agent. The present ‎study aimed to investigate the nutritional values and in vitro prebiotic potential of ASP on two probiotic ‎strains, namely Lactobacillus casei ATCC 393‎‏ ‏and Bifidobacterium longum ATCC 55813. Also, the ‎effects of fermentation of ASP by probiotics on polyphenolic content and antioxidant activity were ‎investigated. ‎

Fatty acid composition, amino acid profile, and mineral content of ASP were ‎determined using a gas chromatography-mass detector, amino acid analyzer, and inductively coupled ‎plasma-optical emission spectrometry, respectively. ASP at two concentration levels of 0.5 and 1% was ‎tested for its growth stimulation effect on two probiotics, L. casei and B. longum. Fructooligosaccharide ‎‎(FOS) and glucose were used as standard prebiotic and control positive, respectively. The changes in ‎probiotic populations and pH were monitored during 48 h fermentation in glucose-free MRS broth (GF-‎MRSB). The total phenolic content (TPC) and antioxidant activity of ASP were evaluated during ‎fermentation using the Folin–Ciocalteu method and the DPPH radical scavenging assay. ‎

ASP contains high levels of aspartic acid, glutamic acid, and essential amino acids, including ‎phenylalanine, leucine, and lysine. It also includes a high content of unsaturated fatty acids, including ‎linoleic and oleic acids. Potassium was found to be the mineral with the highest composition, followed ‎by phosphorus and calcium. Both probiotic strains could grow effectively in the presence of ASP. The ‎cell numbers of L. casei and B. longum increased by 4.91 and 5.11 Log CFU/ml after 48 h fermentation ‎of ASP-1%, which were comparable with the stimulatory effects of FOS and glucose. The pH decrease ‎of GF-MRSB was negatively‏ ‏correlated with the concentration of ASP. Antioxidant activity and TPC ‎increased continually during fermentation by both probiotics, with L. casei exhibiting a stronger impact. ‎

Results demonstrated that ASP is an excellent source of minerals, essential amino acids, ‎and unsaturated fatty acids. Probiotic bacteria not only survive in the presence of ASP but also increase ‎polyphenolic content, thus enhancing the antioxidant activity and functional capacity of the fermented ‎ASP. Fermenting phenolic compound-rich plant sprouts with probiotic bacteria can be considered a ‎novel approach to the development of functional foods.‎