Review: Authentication of grass-fed meat and dairy products from cattle and sheep

Abstract

Meat and dairy products derived from grassland carry premium values and sensory and nutritional qualities that aroused much interest for authentication methods to guarantee grassland origin claims. This article reviews the current state of knowledge on the authentication of meat and dairy of grassland origin from food analysis in both cattle and sheep. A range of methods alone or combined, involving analysis of elemental or molecular constituents of food product and fingerprinting profiling combined with chemometrics, have been developed and proved useful to differentiate contrasted feeding regimes and authenticate grass-fed meat and dairy. Their robustness and discriminatory reliability in more complex feeding conditions, such as in the case of dietary switches or when grass only makes up part of the animal's diet, are under active investigation. Our review highlights the possibilities and limitations of these methods, the latter being chiefly posed by variations in the quantity, characteristics and composition of grassland feedstuffs consumed by animals, which are nevertheless inherent to grassland-based production systems, variations in animal responses within and across breeds, and difficulties in detecting the consumption of non-grass feedstuffs by the animal. It also highlights a number of issues for consideration, points of caution and caveats in applying these methods. Scientists agree that much of the research carried out so far has been a 'proof of concept' type and that efforts should be made in the future to develop more databases to help gain genericity and robustness.

Keywords: dairy products; fraud; grass-feeding; muscle; spectroscopy.

Figure 1

Discrimination of feeding regimes in dairy cattle on the basis of discriminant analysis of fatty acids (FAs) in milk samples from animals fed grass (more than 70% of fresh herbage in the diet DM during the grazing season and more than 70% of conserved grass in the winter season) (triangles); maize silage (more than 35% maize silage in the diet DM during the grazing season and more than 60% maize silage in the diet DM in the winter season) (circles); maize silage + flaxseed: maize silage (more than 35% maize silage in the diet DM during the grazing season and more than 60% maize silage in the diet DM in the winter season, + 3% extruded flaxeeds) (diamonds) (from Hurtaud et al., , reprinted with permission).

Figure 2

Mean reflectance spectra of perirenal adipose tissue of lambs fed grass at pasture (solid line) or with a concentrate-based diet indoors (dotted line). The spectro-colorimetric index is calculated as the absolute value of the integral of the translated spectrum between 510 and 450 nm (i.e. the light-absorbing region of carotenoids). The integral is the area comprised between the curve and the x-axis in the zone 450 to 510 nm (from Prache et al., , reprinted with permission).