Discrimination of haymilk and conventional milk via fatty acid profiles

Claudia L Laguna Paredes,Birgit Rossmann,Julia Keplinger,Matthias Schreiner,Isabel L Olschewski,Manfred Werteker

doi:10.1007/s11694-018-9753-0

Abstract

Milk produced by feeding silage-free feed has become popular in Europe. This kind of milk has recently been recognized as “traditional speciality guaranteed” by the European Union. As a consequence, an analytical discrimination of this silage-free produced milk quality has become necessary. In this study, discrimination of “haymilk” (HM) from conventional milk (CM) in retail samples was attempted taking in consideration all feeding seasons. For analytical discrimination, a partial least square discriminant analysis (PLS-DA) to fatty acids methyl esters (FAMEs) obtained from analysis by gas chromatography was applied. All groups of long-chain fatty acids, including saturated, odd chain fatty acids, mono- and polyunsaturated fatty acids of both cis/trans configuration, contributed to discrimination of the two types of milk, where alpha linolenic acid (+ 37% in HM) and conjugated linoleic acid (C18:2c9t11—+ 22% in HM) were the most relevant for calibration. Applying PLS-DA was successful in discriminating CM and HM from retail milk in all seasons. From 48 identified fatty acids, 18 showed different levels in CM and HM samples and could be used for discrimination of the two groups. The method was able to discriminate HM and CM produced in the cold season, but showed unclear results in the warm season due to a higher scattering of both groups. These higher deviations were attributed to the fact that most dairy cows are able to consume fresh grass during summer. Although it is not possible to discriminate HM and CM produced in warm season, the fatty acid pattern of HM can be taken as a reference, from which a properly produced HM should not deviate. A separate calibration for each season is recommended for optimal results.

Highlights

Hard cheese from raw milk has been produced in the Alpine region for centuries
When silage feeding of dairy cows became standard in the late eighteenth century, problems with high spore counts of clostridia occurred in matured hard cheese
C14:0 and C18:0 showed significant differences between HM and conventional milk (CM) in the cold season (Q1 and Q4). An explanation for this behavior of SFA can be seen in the fact that C18:0 in contrast to all the other even chained SFA is synthesized de novo in the mammary gland, by the regular fatty acids (FA) metabolism or provided by the diet, and the final product of bio hydrogenation [22, 26, 36]. This result was expected, since any possible differences could only be attributed to crowding-out effects of other FAs, which are affected by feed or microbial activity, which obviously did not occur to a significant extent

Summary

Introduction

Hard cheese from raw milk has been produced in the Alpine region for centuries. When silage feeding of dairy cows became standard in the late eighteenth century, problems with high spore counts of clostridia occurred in matured hard cheese. This feeding results in an increase of PUFA including CLA, as confirmed in different studies [9, 22,23,24,25,26]. It was shown that cyclopropane fatty acids, which occur in milk fat as minor component, can be used as markers for silage feeding [29] and an enzymatic hydrolyzation provoke reduction of short and medium fatty acids and increase of long fatty acids which could produce differences in the physical proprieties of FA profiles [30].

Results

Conclusion