Control of the Growth of Listeria monocytogenes in Cooked Ham through Combinations of Natural Ingredients.

In the ready-to-eat food industry, Listeria control is mandatory to ensure the food safety of the products since its presence could cause a disease called listeriosis. The objective of the present study was to carry out a challenge test to verify the efficiency of different combinations of natural antimicrobial ingredients against Listeria monocytogenes to be used in ready-to-eat foods. Six different formulations of cooked ham were prepared: a control formulation and five different formulations. An initial inoculation of 2 log cycles was used in the different products, and the growth of Listeria was monitored at different temperatures and times (4 °C for 17 w and 7 °C for 12 w). Control samples showed a progressive growth, reaching 5-6 log after 3 or 4 weeks. The rest of the samples showed constant counts of Listeria during the entire study. Only samples containing 100 ppm nitrite + 250 PPM ascorbic acid + 0.7% PRS-DV-5 did not control the growth of Listeria at 7 °C after 7 w of storage. The results obtained allowed us to classify the cooked ham prepared using natural ingredient combinations as a "Ready-to-eat food unable to support the growth of L. monocytogenes other than those intended for infants and for special medical purposes".

Reddish Colour in Cooked Ham Is Developed by a Mixture of Protoporphyrins Including Zn-Protoporphyrin and Protoporphyrin IX.

The nitrosyl-heme complex is considered the pigment responsible for the development of reddish colour in cooked hams. However, the same reddish colour was observed in a nitrite-free product elaborated with polyphenols, suggesting the presence of other red pigments that can contribute to generate this colour. In this study, the protoporphyrins composition of the pigment solution obtained from nitrite and nitrite-free cooked hams was analysed using 80% (v/v) acetone/water solution for extraction. Chromatographic analysis using a combination of diode array and fluorescence detectors revealed the presence of protoporphyrin IX and Zn-protoporphyrin IX in this solution, and these protoporphyrins were subsequently identified with complete certainty by mass spectrometry. These results show how the colour of cooked hams can be developed by a mixture of different protoporphyrins and also demonstrate the absence of selectivity of acetone/water extraction for measuring the content of nitrosyl-heme in cooked hams.

Ultrasound Assisted Extraction Approach to Test the Effect of Elastic Rubber Nettings on the N-Nitrosamines Content of Ham Meat Samples.

Nitrosamines (NAs), which are catalogued as carcinogenic compounds, may be present in meat products due to the conversion of nitrites and as result of migration from elastic rubber nettings used. A method based on ultrasonic assisted extraction coupled with dispersive liquid-liquid microextraction as sample treatment and gas chromatography-mass spectrometry as separation and detection technique was proposed for the determination of twelve NAs in cooked ham samples. The method was validated by evaluating linearity (0.5-1000 ng g-1), matrix effect, sensitivity (detection limits were between 0.15 and 1.4 ng g-1) and precision, which was below 12%. Five NAs were found in the samples with levels ranging from not quantifiable to 40 ng g-1. The effect of the elastic rubber nettings on the nitrosamine content of meat was evaluated by comparing the levels found in products made with several plastics or thread in the presence of additives.

Toward Nitrite-Free Curing: Evaluation of a New Approach to Distinguish Real Uncured Meat from Cured Meat Made with Nitrite.

After the International Agency for Research on Cancer (IARC) classified ingested nitrites and nitrates as "probably carcinogenic to humans" under conditions favoring endogenous nitrosation, several meat products labeled as "made without nitrite" were launched. In order to distinguish uncured products truly made without nitrite from cured products made with any nitrite source (vegetal or mineral), this article presents an approach to detect and quantify nitrite from different origins added to meat. The method consists on the determination of nitrous oxide as a target compound using headspace gas chromatography-mass spectrometry (HS-GC-MS). Nitrous oxide (N2O) is formed after two reduction steps: from nitrite to nitric oxide (NO) and then to N2O. The NO is bound to myoglobin (Mb) or metmyoglobin (Met-Mb), forming a complex, which is subsequently released using sulfuric acid, which also favors the reduction to N2O. The HS-GC-MS conditions were split ratio 1:10; injection temperature at 70 °C; incubation temperature at 30 °C and time 45 min; and injection volume 1 mL. As a result, a relationship was established between the concentration of nitrite in cooked ham samples and the area of the N2O peak generated, meaning that this method allows the quantification of added nitrite within a concentration range of 10 to 100 mg kg-1.

Ion mobility spectrometry and mass spectrometry coupled to gas chromatography for analysis of microbial contaminated cosmetic creams.

The most commonly used technique for monitoring microbial contamination in cosmetic products is plate counting. In this contribution, headspace - gas chromatography (HS-GC) coupled to mass spectrometry (MS) or ion mobility spectrometry (IMS) is proposed as a technique to evaluate rapidly and accurately the state of microbial colonies in cosmetic creams using the volatile organic compounds produced by microorganisms (MVOC). The work focuses on monitoring two of the microorganisms that most frequently occur in such creams, Candida albicans and Staphylococcus aureus. In addition, two different types of ingredient with antimicrobial properties (a chemical preservative and a natural preservative) were added to study the behaviour of these microorganisms under different conditions. The facial creams were elaborated and inoculated with the two above microorganisms, and then sampled weekly for 4 weeks, analysing the evolution of the MVOCs by HS-GC-MS and HS-GC-IMS. In addition, microbial contamination was determined by the classical plate counting method. The pH, colour, viscosity and water activity parameters were also measured. The use of chemometric tools is essential because of the large amount of data generated, and different models based on discriminant analysis with an orthogonal projection on latent structures (OPLS-DA) were constructed. The optimal models obtained by both analytical techniques allowed differentiation between contaminated and non-contaminated creams, with a validation success rate of 94.4%. In addition, MVOC monitoring also allowed assessment of the microbial concentration.