Beef meat sexing by lipidomics: an alternative approach against food fraud

Frauds linked to meat and meat products, as well as to food ingredients, dominate the reports on food fraud cases [1,2]. In general, it is possible to differentiate authentication problems linked to meat and meat products into four major categories: meat origin; meat substitution; meat processing treatment; non-meat ingredient addition [3]. Meat is one of the most widely consumed high-value foods in the world, opening it up to fraudulent replacement/substitution of some, or all, of the premium meat content with lower grade cuts of meat or meat from other species. In particular, minced meat is an easy target for food fraud, because the original meat cut cannot be visibly recognized by the consumer. One of the most distinctive and quali-quantitative interesting macro components of meat are lipids, since they are linked to dietary health concerns, besides being an important flavor component. In this case, lipidomics, the global study of molecular lipids, could potentially provide an insight into the discovery of lipid biomarkers for identification of food fraud, especially minced meat. In fact, it is necessary to provide additional analytical tools for the authentication of beef meat as further support to the existing ones, in order to defeat meat fraud. The aim of present study was to apply analytical methods for characterizing the lipid matter of ground beef meat prepared with both male and female meat. Through a chemiometric approach, new possible markers of meat authenticity as related to the sex of animal, were disclosed.

Forty-two samples (21 males and 21 females) of beef ground meat were randomly selected from 7 different retail stores. Male beef samples were homogenized (particle size < 0.9 mm) with female ones at five different ratios, in order to obtain different representative treatments: 100% male (M-100), 75% male – 25% female (M-75), 50% male –50 % female (M50-F50), 25% male – 75% female (F-25), 100% female (F-100). The main lipid classes (free fatty acids (FFAs), non-esterified (STE) and esterified sterols (E-STE), triacylglycerols (TGs), diacylglycerols (DGs) and monoacylglycerols (MGs)), total sterols and cholesterol oxidation products (COPs), were determined by gas-chromatography-flame ionization detection (GC-FID) and Fast GC-mass spectrometry (GC-MS) [4-5].

The lipid content did not significantly change as related to animal sex, while some significant changes were detected in the main lipid classes. In particular, FFAs were significantly higher in M-100 and M-75 samples than in female ones. A lower amount of non-esterified cholesterol was present in samples containing female meat and, as the percentage of female meat increased, the level of non-esterified cholesterol decreased; a similar behavior was displayed by TGs. These results allowed to hypothesize that female meat could display some differences in the lipid profile. The main sterol was cholesterol (~99% of total sterols), followed by lanosterol, sitosterol, campesterol and lathosterol. The highest level of cholesterol was detected in F-100 and significantly decreased as the percentage of female meat in the sample formulation decreased. In any case, considering the lipid matter, phytosterols (sitosterol and campesterol) were significantly more present in samples where female meat was more than 50%; in fact, in samples M-75 and M-100, only traces of phytosterols were detected. Finally, total COPs were significantly higher in M-100, M-75 and M-50/F-50, while the F-75 and F-100 displayed the lowest amount. In particular, the epoxy derivatives were the main oxysterols found, followed by 7-KC. Triol, 25-OH and 7α/β-OH isomers were also detected. The principal component analysis (PCA) was used to evaluate the effect of meat sex on the presence and composition of the main lipid classes, total sterols and COPs. The PCA revealed that sterol composition was inversely correlated to COPs and FFAs; in addition, the biplot analysis completely separated the five treatment groups (Figure 1). In particular, F-100 was characterized by the presence of cholesterol and sitosterol, F-75 by DGs and campesterol, M-75 by TGs and M-100 by 7a-OH. On the other hand, the M-50/F-50 was equally characterized by all parameters (Figure 2).

The aim of present study was to apply analytical methods, coupled with chemiometrics, for characterizing the lipid matter of ground beef meat using both male and female meat, in order to identify possible lipid biomarkers of meat authenticity. On the basis of these results, it can be concluded that the chemiometric approach applied to lipidomics could be a useful tool for identifying the origin and authenticity of ground meat as related to the sex of animal. However, this represents a preliminary study and a bigger sampling, as well as a deeper investigation that includes other breeding parameters and meat components (such as the volatile fraction and fatty acid composition), is required in order to confirm the actual data reported in this study.

[1] Tähkäpää S et al. (2015). Food Control, 47, 175-184.

[2] RASFF, Annual Report 2013, ec.europa.eu/food/sites/…/rasff_annual_report_2013

[3] Ballin N.Z. (2010). Meat Science, 86, 577-587.

[4] Gallina Toschi et al. Journal of Agricultural and Food Chemistry, 62, 10836−10844.

[5] Cardenia et al. (2012). Journal of Separation Science, 35, 424-430.

The research activity of the present study is promoted by the H2020 project “PLOTINA – Promoting gender balance and inclusion in research, innovation and training” (www.plotina.eu). We thank Basic Research Funding (RFO 2016, Alma Mater Studiorum Università di Bologna, Italy) for financial support.