Scope extension validation of a LC-MS method for the inspection of preservatives in butter

A unique implementation of Hantzsch reaction for determination of natamycin in Yoghurt: Hyphenated with Box-Behnken-design for optimization

This study aims to develop a novel and selective method for the detection of natamycin (E235) in yoghurt. The suggested method adopts an application of Hantzsch reaction to turn on the fluorescence behavior of natamycin (blue fluorescence), allowing its sensitive and selective determination in yoghurt samples without any overlapping at 485 nm. The originality of the research lies in the fact that this application takes place for the first time, also the detection (LOD) and quantification (LOQ) limits were very low (0.02 and 0.06μg mL-1, respectively) with a linear concentration range of 0.1-1.0 μgmL-1. Moreover, the developed method was employed for the detection of E235 in yoghurt sample with a good recoveries (98.80 ± 1.20-99.20 ± 1.15 (%), over a concentration range of 0.5-1.0 μgmL-1, (LOD = 0.04 and LOQ = 0.12 μgmL-1). Furthermore, the specificity and convenient application of our intended method is an attempt to determine E235 in milk anddairy products with easily followable steps.

Determination of Sorbic Acid in Cheese by High Performance Liquid Chromatography

Background

Sorbic acid (E, E-2, 4-hexadienoic acid) is added as a preservative to cheese because of its fungistatic and antimicrobial activity.

Objective

A facile method for the analysis of sorbic acid that is applicable to sliced processed cheese and grated cheese products.

Method

A cheese sample and dry-ice mixture was blended and sorbic acid was extracted with methanol and analyzed by HPLC-ultraviolet with external standardization. A large sample size was used to overcome sample inhomogeneity due to imprecise sorbic acid addition techniques during production and sorbic acid migration through the fat over time.

Results

The method was shown to be accurate for both processed cheese and grated Cheddar cheese, with acceptable spike recovery (93.7, 103.7%, respectively), and no bias (α = 0.05) against an international reference method (p = 0.59, p = 0.13, respectively) was found. Acceptable precision was confirmed for both processed cheese slices and grated Cheddar cheese, with repeatability of 5.3% and 4.3% relative standard deviation, respectively, and intermediate precision Horwitz ratio values of 1.3 and 1.7 for processed cheese slices and grated Cheddar cheese, respectively. Method detection limit and ruggedness experiments further demonstrated the suitability of this method for routine compliance testing.

Conclusions

A method for high-throughput, routine testing of sorbic acid is described. The method was subjected to single-laboratory validation and was found to be accurate, precise, and fit-for-purpose.

Isotopic dilution assay development of nisin A in cream cheese, mascarpone, processed cheese and ripened cheese by LC-MS/MS method

The current food safety concern for food integrity demands the availability of an accurate, easy and reliable analytical tool for assay development of nisin A in cheese. To address this, we report the application of isotopically labelled peptide sequence MSTKDFNLDLVSVSKKDSGASP(R) (without thioether bridges) as internal standard for determination of nisin A in cream cheese, mascarpone, processed cheese and ripened cheese without the need for matrix-matched calibration by triple-quadrupole mass spectrometry. Full method validation was performed according to the modified Commission Decision 2002/657/EC criteria and method robustness was checked on 10 random cheese samples. Internal standard provided significant improvement (p < 0.05) in method precision for determination of nisin A in all four types of cheese. Significant losses (p < 0.05) for Nisin A in cheese was observed one week later. A fit-for-purpose method using internal standard procedure for accurate quantitation of Nisin A in cheese becomes available.