Exploring lactic acid bacteria diversity of hop plant by-products to develop a multi-strain starter culture to be used in hop-supplemented sourdough bread

Abstract

The hop plant is gaining interest in the food, pharmaceutical, and cosmetics industries due to its abundance of secondary metabolites. However, branches and leaves, despite their antioxidant potential, are typically discarded. To valorize these components as functional ingredients they were dried, milled into hop powder (HP), and used to enrich bread. Polyphenol-resistant lactic acid bacteria (LAB) isolated in this study from HP, Leuconostoc pseudomesenteroides and Enterococcus lactis, were selected for their acidification capacity and combined with sourdough LAB to create a multi-strain starter culture for hop bread (HB) production. Three trials were conducted: HB-0 (control bread without HP), HB-2.5 (bread with 2.5 % HP), and HB-5 (bread with 5 % HP). All samples were evaluated for quality traits, phenolic content, antioxidant activity, and profiles of polyphenols and volatile organic compounds (VOCs). HP-supplemented breads showed reduced weight loss, increased firmness, and darker crust and crumb. Bioactive compounds such as xanthohumol, lupulone, and VOCs like beta-myrcene and alpha-humulene were retained. Sensory analysis revealed that HP addition enhanced aroma intensity, color, astringency, and bitterness, with HB-2.5 receiving the highest overall rating. Shelf life tests showed mold appeared on day 11 in HB-0, but was delayed to day 13 in HP breads. Staling, assessed via differential scanning calorimetry, showed increasing melting enthalpy (Delta H) over time in all samples, confirming starch retrogradation, with no significant differences among formulations. This study validates the use of HP as a functional ingredient, enhancing sensory profiles and bioactive compound content. The application of selected LAB and HP supports sustainable practices in the food sector.