M. Teresa Veciana-Nogués

Evaluation of biogenic amines and microbial counts throughout the ripening of goat cheeses from pasteurized and raw milk

The effect of the hygienic quality of milk on changes in microbial counts and biogenic amine content was evaluated during ripening of goat cheeses manufactured from pasteurized and raw milks at 1, 14, 30, 60 and 90 d. The original milk, rennet, curd and whey were also included in the study. The pH, salt content and extent of proteolysis in the cheese were also evaluated. Spermidine and spermine were the main amines in raw milk, while they were minor amines in cheeses. Other amines increased markedly during ripening, tyramine being the main amine in cheese made from raw milk and cadaverine and putrescine in those produced from pasteurized milk. Enterobacteriaceae counts decreased during ripening whereas those of lactic acid bacteria increased, especially lactobacilli and enterococci. Cheese made from raw milk showed higher microbial counts during ripening than those made from pasteurized milk, especially for Enterobacteriaceae and enterococci, counts being 2 or 3 log units higher. Raw milk cheese showed remarkably higher biogenic amines compared with pasteurized milk cheeses. Therefore, pasteurization of milk causes a decrease in final biogenic amine content of cheese as a result of the reduction of its microbial counts.

Starter cultures and high-pressure processing to improve the hygiene and safety of slightly fermented sausages.

The effectiveness of selected starter cultures and high hydrostatic pressure after ripening was evaluated to improve the safety and quality of slightly fermented sausages. Inhibition of common foodborne pathogens, spoilage bacteria, and biogenic amine content was studied. Random amplification of polymorphic DNA and plasmid profiles were used to monitor the competitiveness of the starter cultures during fermentation and ripening. Lactobacillus sakei CTC6626 and Staphylococcus xylosus CTC6013 dominated L. sakei CTC6469 and S. xylosus CTC6169 independently of the product assayed. Starter cultures were able to control the growth of Listeria monocytogenes, Enterobacteriaceae, Enterococcus, and the biogenic amine content. A pH decrease below 5.3 at the seventh day of fermentation was crucial. Salmonella spp. counts decreased significantly during ripening independently of the use of starter culture and product. High hydrostatic pressure treatment was necessary to ensure absence of Salmonella spp. in final products.

Comparison of biogenic amine profile in cheeses manufactured from fresh and stored (4°C, 48 hours) raw goat's milk

In this study, the evolution of microbial counts, biogenic amine contents, and related parameters (pH, moisture, and proteolysis) in goat cheese made from fresh raw milk or raw milk stored for 48 h at 4 degrees C was examined. In both cases the milk was nonpasteurized. This study was designed to evaluate the effect of milk quality on the profile of biogenic amines in relation to the evolution of the microbial population during cheese making. Cheese made from raw milk stored for 48 h at 4 degrees C showed the highest microbial counts and biogenic amine levels. The storage of milk under refrigeration caused significant increases in the levels of some microbial and biogenic amines during ripening, but not initially. Tyramine was the main biogenic amine in the two cheeses tested, followed by cadaverine. However, the main differences in amine contents between batches were found for putrescine, histamine, and beta-phenylethylamine, whose levels were more than twofold higher in samples from raw milk refrigerated for 48 h than in samples from fresh milk.

Influence of ultra-high-pressure homogenization treatment on the phytosterols, tocopherols, and polyamines of almond beverage.

Ultra-high-pressure homogenization (UHPH) is an emerging technology based on the dynamic application of high pressure to obtain safe and high-quality liquid foods. The effect of six UHPH treatments at 200 and 300 MPa with different inlet temperatures (T(in)) (55, 65, and 75 °C) on the content of tocopherols, polyamines, and phytosterols of almond beverage was studied in comparison with the base product. Total tocopherol contents decreased about 80-90% as temperature and pressure increased, and whereas both parameters affected the tocopherol content, especially the effect of temperature was noticeable. α-Tocopherol was the most predominant type of tocopherol present and was also the most affected by UHPH treatments. Spermidine was the only polyamine found not to be affected by UHPH treatments. UHPH treatments resulted in an increase of 20-40% in the total phytosterol extractability. The highest extractability was obtained at the most severe conditions (300 MPa, 75 °C T(in)).

New approach for the diagnosis of histamine intolerance based on the determination of histamine and methylhistamine in urine

HighlightsA method based on solid phase extraction and UHPLC‐FL was developed and validated.The method is reliable for histamine and methylhistamine determination in human urine.The method is a potential new approach for the diagnosis of histamine intolerance. Abstract Histamine intolerance is a disorder in the homeostasis of histamine due to a reduced intestinal degradation of this amine, mainly caused by diamine oxidase (DAO) enzyme deficiency, which provokes its accumulation in plasma and the appearance of adverse health affects. A new approach for the diagnosis of this intolerance could be the determination of histamine and its metabolites in urine. The aim of this work was to develop and validate a rapid method to determine histamine and methylhistamine in human urine by Ultra High Performance Liquid Chromatography and Fluorimetric detection (UHPLC‐FL). The proposed method is a consistent procedure to determine histamine and methylhistamine in less than 11 min with adequate linearity and sensitivity. Relative standard deviation was always lower than 5.5%, ensuring method precision; and mean recovery was greater than 99% for both analytes. The structure of histamine and methylhistamine conjugated with OPA were confirmed by UHPLC‐ITD‐FTMS which enabled to unequivocally identify both analytes in standards and also in urine samples. The analysis of histamine and methylhistamine in urine samples could be a potential new approach for the routine diagnosis of histamine intolerance, more patient‐friendly and with clear advantages in terms of equipment and personnel demand for sample collection in comparison with current plasmatic DAO activity determination.