Histamine-forming ability of Lentilactobacillus parabuchneri in reduced salt Cheddar cheese

Lentilactobacillus parabuchneri, a member of the non-starter microbiota in cheese, was recently associated with fast and effective histamine-formation ability, a safety issue. The present study was performed to investigate Lentilactobacillus parabuchneri KUH8, a histamine-producer (HP) in reduced-salt Cheddar cheese. Four cheeses were manufactured: 1) normal-salt (NS); 2) reduced-salt (RS); 3) normal-salt with HP (NS+HP); 4) reduced-salt with HP (RS+HP). Two replicates were produced with milk from the same batch, and the cheeses ripened at 10 and 15 °C. Cheeses were sampled immediately after manufacture and after 1, 3 and 6 months of ripening. Ultra-high-performance-liquid chromatography indicated that with the HP, histamine reached higher levels in reduced-salt cheeses (3.5-3.7% S/M) at 15 °C (86, 1112, 2149 and 3149 mg kg^-1), compared to normal-salt cheeses (5.4-6.3% S/M) at 10 °C (78, 584, 593 and 1389 mg kg^-1), at each respective cheese-sampling point. Higher salt-content reduced the growth rate of non-starter microbiota, but after six months the levels in all cheeses were similar, according to the ripening temperature: at 10 °C (8.05-8.30 log₁₀ cfu g^-1), and at 15 °C (6.00-6.94 log₁₀ cfu g^-1). A correlation between increased histamine levels, non-starter-cell development and pH was found. This study highlights the importance of normal-salt content and low-ripening temperature as measures to control histamine-formation and to improve safety in cheese.