Martin Alewijn

A fast and simple method for quantitative determination of fat-derived medium and low-volatile compounds in cheese

Cheese flavour is a mixture of many (volatile) compounds, mostly formed during ripening. The current method was developed to qualify and quantify fat-derived compounds in cheese. Cheese samples were extracted with acetonitrile, which led to a concentrated solution of potential flavour compounds, mainly derived from milk fat. The solution was virtually free from triglycerides, protein and salt from the cheese matrix. Therefore, such an extract could be analysed directly by gas chromatography/mass spectroscopy (GC/MS). In the samples of the three cheese varieties analysed, 61 different compounds were identified, including 23 fatty acids, 14 lactones, 9 esters, 5 ketones, 10 alcohols, and several miscellaneous compounds. Furthermore, most compounds could be quantified by determining their distribution coefficients and thus correcting for their loss during extraction. This method was shown to be suitable for both qualitative and quantitative analysis of medium and low-volatile compounds.

Verification of Egg Farming Systems from the Netherlands and New Zealand Using Stable Isotopes

Stable isotopes were used to develop authentication criteria of eggs laid under cage, barn, free range, and organic farming regimens from The Netherlands and New Zealand. A training set of commercial poultry feeds and egg albumen from 49 poultry farms across The Netherlands was used to determine the isotopic variability of organic and conventional feeds and to assess trophic effects of these corresponding feeds and barn, free range, and organic farming regimens on corresponding egg albumen. A further 52 brands of New Zealand eggs were sampled from supermarket shelves in 2008 (18), 2010 (30), and 2014 (4) to characterize and monitor changes in caged, barn, free range, and organic egg farming regimens. Stable carbon (δ(13)C) and nitrogen (δ(15)N) isotopes of 49 commercial poultry feeds and their corresponding egg albumens reveals that Dutch poultry are fed exclusively on a plant-based feed and that it is possible to discriminate between conventional and organic egg farming regimens in The Netherlands. Similarly, it is possible to discriminate between New Zealand organic and conventional egg farming regimens, although in the initial screening in 2008, results showed that some organic eggs had isotope values similar to those of conventional eggs, suggesting hens were not exclusively receiving an organic diet. Dutch and New Zealand egg regimens were shown to have a low isotopic correlation between both countries, because of different poultry feed compositions. In New Zealand, both conventional and organic egg whites have higher δ(15)N values than corresponding Dutch egg whites, due to the use of fishmeal or meat and bone meal (MBM), which is banned in European countries. This study suggests that stable isotopes (specifically nitrogen) show particular promise as a screening and authentication tool for organically farmed eggs. Criteria to assess truthfulness in labeling of organic eggs were developed, and we propose that Dutch organic egg whites should have a minimum δ(15)N value of 4.8‰ to account for an organic plant derived diet. Monitoring of New Zealand egg isotopes over the past 7 years suggests that organic eggs should have a minimum δ(15)N value of 6.0‰, and eggs falling below this value should be investigated further by certification authorities.

Compositional Signatures of Conventional, Free Range, and Organic Pork Meat Using Fingerprint Techniques

Consumers’ interest in the way meat is produced is increasing in Europe. The resulting free range and organic meat products retail at a higher price, but are difficult to differentiate from their counterparts. To ascertain authenticity and prevent fraud, relevant markers need to be identified and new analytical methodology developed. The objective of this pilot study was to characterize pork belly meats of different animal welfare classes by their fatty acid (Fatty Acid Methyl Ester—FAME), non-volatile compound (electrospray ionization-tandem mass spectrometry—ESI-MS/MS), and volatile compound (proton-transfer-reaction mass spectrometry—PTR-MS) fingerprints. Well-defined pork belly meat samples (13 conventional, 15 free range, and 13 organic) originating from the Netherlands were subjected to analysis. Fingerprints appeared to be specific for the three categories, and resulted in 100%, 95.3%, and 95.3% correct identity predictions of training set samples for FAME, ESI-MS/MS, and PTR-MS respectively and slightly lower scores for the validation set. Organic meat was also well discriminated from the other two categories with 100% success rates for the training set for all three analytical approaches. Ten out of 25 FAs showed significant differences in abundance between organic meat and the other categories, free range meat differed significantly for 6 out of the 25 FAs. Overall, FAME fingerprinting presented highest discrimination power.

New approaches towards discrimination of fresh/chilled and frozen/thawed chicken breasts by HADH activity determination: Customized slope fitting and chemometrics

Fresh/chilled chicken breasts retail at a higher price than their frozen/thawed counterparts. Verification of the fresh/thawed status of chicken meat is determined by measuring β-hydroxyacyl-Coenzyme A-hydrogenase (HADH) activity present in meat intra-cellular liquids spectrophotometrically. However, considerable numbers of reference samples are required for the current arithmetic method, adding to laboratory costs. Therefore, two alternative mathematical approaches which do not require such reference samples were developed and evaluated: curve fitting and multivariate classification. The approaches were developed using 55 fresh/thawed fillet samples. The performance of the methods was examined by an independent validation set which consisted of 16 samples. Finally, the approach was tested in practice in a market study. With the exception of two minor false classifications, both newly proposed methods performed equally well as the classical method. All three methods were able to identify two apparent fraudulent cases in the market study. Therefore, the experiments showed that the costs of HADH measurements can be reduced by adapting alternative mathematics.