Hop bitter acids inhibit carbohydrate metabolism, enhance biogenic amine metabolism and alter L‐malic acid, glutamic acid and arginine metabolism of Lactobacillus brevis 49

Abstract

Summary Beer contains only limited amounts of readily fermentable carbohydrates and amino acids. Beer spoilage lactic acid bacteria have to come up with metabolic strategies in order to deal with selective nutrient content. The research was performed to investigate the influence of iso‐α‐acids on the metabolism of organic acids, biogenic amines (BAs), off‐flavour compounds, carbohydrates and amino acids of Lactobacillus brevis 49. Only glyoxylic acid and ethyl formate in de man, rogosa, sharpe broth was consumed, and multiple organic acids, BAs and off‐flavour compounds were produced. By supplementing a series of concentrations of hop iso‐α‐acids, consumption of L‐malic acid, glutamic acid and arginine and generation of BAs were found benefit for bacteria to develop hop‐resistance. In the metabolism of carbohydrates, glucose was preferred over maltose and maltriose, and hops significantly inhibited the utilisation of carbohydrates. The results provide comprehensive information of metabolites of L. brevis 49 under various concentrations of hop stress.

The assessment of commercial beef and chicken bouillons in terms of heterocyclic aromatic amines and some of their precursors

“…This is also stated on the labels of bouillons. Glutamic acid is a non‐essential amino acid present in both free and protein‐bound form and can be isolated from different sources (wheat gluten, soybean, hops, vegetable leaves and casein) (Cebi et al ., 2018; Li et al ., 2018; Sun et al ., 2019). MSG, the sodium salt of glutamic acid, is also found naturally in many foods and can be added as a flavour enhancer ingredient to the products.…”