Biogenic amines content in Fiore Sardo cheese in relation to free amino acids and physicochemical characteristics

Rapidly and accurately screening histidine decarboxylase inhibitors from Radix Paeoniae alba using ultrafiltration-high performance liquid chromatography/mass spectrometry combined with enzyme channel blocking and directional enrichment technique

Histidine Decarboxylase (HDC), an unique enzyme responsible for the synthesis of histamine, which is an important mediator in allergy. Inhibition of HDC activity to decrease histamine production is one way to alleviate allergic symptoms. Traditional Chinese medicines (TCMs) with reported anti-allergy effect is one of important source to search for natural HDC inhibitor. Ultrafiltration combined with high-performance liquid chromatography/mass spectrometry (UF-HPLC/MS) is an effective method for screening HDC inhibitor from TCMs. Nevertheless, false-positive and false-negative results caused by the non-specific binding and the neglection of the trace active compounds are major problems in this method. In this study, an integrated strategy that combined UF-HPLC/MS with enzyme channel blocking (ECB) technique and directional enrichment (DE) technique was developed to seek natural HDC inhibitors from Radix Paeoniae alba (RPA), and at the same time, to reduce false-positive and false-negative results. HDC activity was detected to determine the validity of the screened compounds by RP-HPLC-FD in vitro. Molecular docking was applied to assay the binding affinity and binding sites. As a result, three compounds were screened from low content components of RPA after the DE. Among them, two non-specific compounds were eliminated by ECB, and the specific compound was identified as catechin, which has obvious HDC inhibition activity with IC₅₀ 0.52 mM. Furthermore, gallic acid (IC₅₀ 1.8 mM) and paeoniflorin (IC₅₀>2 mM) from high content components of RPA were determined having HDC inhibitory activity. In conclusion, the integrated strategy of UF-HPLC/MS combined with ECB and DE technique is an effective mode for rapid and accurate screening and identification of natural HDC inhibitors from TCMs.

Evaluation of Pediococcus acidilacticiAS185 as an adjunct culture in probiotic cheddar cheese manufacture

A novel probiotic Pediococcus acidilactici AS185, isolated from traditional Chinese fermented foods, was used as an adjunct culture for probiotic cheddar cheese production. The physicochemical composition, textural, free amino acids (FAAs), short-chain fatty acids (SCFAs) profiles, sensory properties, and microbial survival, was evaluated during the 90-day ripening period. The addition of P. acidilactici AS185 did not influence the physicochemical composition of cheddar cheese but significantly decreased the hardness without affecting its textural profile. During ripening, P. acidilactici AS185 was able to grow and promote the generation of FAAs and SCFAs, but did not alter the overall sensory properties; it rather improved the flavor and taste of cheese. In addition, the cheese matrix protected strain P. acidilactici AS185 during transit throughout the simulated gastrointestinal system. These results demonstrated that P. acidilactici AS185 adjunct cultures might be useful for producing high-quality probiotic cheddar cheese.

Effect of somatic cells count in cow milk on the formation of biogenic amines in cheese

Comparative studies on physicochemical characteristics of milk with different somatic cells count (SCC) (L-low < 400,000 cells/ml, M-medium between 500,000 and 600,000 cells/ml and H-high > 1,000,000 cells/ml) and obtained cheeses, were conducted. No significant differences between samples were found. The H SCC milk was characterized by the highest total viable count. Higher levels of proteolysis were established in cheeses made from milk with SCC exceeding 500,000 cells/ml. After 10 months of ripening and cold storage the water-soluble nitrogen in total nitrogen (WSN/TN), noncasein nitrogen in total nitrogen (NCN/TN), nonprotein nitrogen in total nitrogen (NPN/TN) and free amino groups values of the sample with the highest SCC reached 28.4 ± 0.8%, 24.8 ± 0.9%, 18.3 ± 0.9% and 83.6 ± 0.3 mg/kg respectively. The biogenic amine concentration in the cheese samples from the L and M batches remained below 10 mg/kg throughout the ripening and cold storage period. The present study established an increase in the biogenic amine content during the ripening period and the cold storage of the cheeses made from milks with high SCC (batch H). The main amines accumulated at the end of the storage period (10th month) were tyramine (31.7 ± 0.3 mg/kg), putrescine (20.5 ± 0.2 mg/kg) and cadaverine (14.6 ± 0.2 mg/kg). Histamine was not found in any of the studied cheese samples.

Levels of biogenic amines in cheese: correlation to microbial status, dietary intakes, and their health risk assessment

Biogenic amines (BAs) are natural toxicants produced during the metabolism of their precursor amino acids or due to the proteolytic activities of some microorganisms. The objective of this study was to estimate the formed BAs in five types of the most commonly consumed and retailed cheese in Egypt. The examined cheese types included Feta, Karish, Mozzarella, Rumy, and Mish. Besides, the total mesophilic (TMC) and total psychrophilic (TPsC) bacterial counts were investigated. Furthermore, the estimated daily intakes (EDI) of BAs via the ingestion of various types of cheese were calculated, and their potential health risks were discussed. The achieved results indicated the formation of histamine (HIS), tyramine (TYR), cadaverine (CAD), putrescine, spermine, and spermidine at different concentrations. Except for Feta cheese, all samples (100%) of other cheese types had HIS concentrations higher than the established maximum permissible limits. Mish cheese contained the highest concentrations of total BAs, particularly, HIS, TYR, and CAD. TBA content showed significant positive correlations with TMC in the examined cheese types. The recorded EDI values of the different BAs in the current study would not have adverse effects. However, excessive consumption of cheese contaminated with BA might have serious health implications such as symptoms of histamine poisoning. Therefore, the adoption of strict hygienic measures during the production, storage, and distribution of cheese is highly recommended to reduce the formation of BAs in cheese.