Impact of management system and lactation stage on fatty acid composition of camel milk

Highlights

• Impact of management system and lactation stage on camel milk fat quality was studied.

• The lactation stage affected the odd- and branched-chain fatty acids profile.

• Mid-lactation fatty acid profile was different to that of early and late stages.

• Trans and conjugated linoleic fatty acids were lower in milk from intensive system.

• Milk from semi-intensive system had more beneficial fatty acid profile.

Abstract

This study aimed to investigate the impact of management system and lactation stage on camel milk fatty acid (FA) composition, with emphasis on odd and branched-chain FA (OBCFA), conjugated linoleic acids (CLA), and trans-FA (TFA). Milk samples were collected from thirteen camels managed under intensive and semi-intensive systems at early, mid, and late lactation. Our results provided for the first time the OBCFA profile in camel milk. Eleven OBCFA were identified with a predominance of C15:0, anteiso-C15:0, anteiso-C17:0, and C17:0. The vaccenic acid (VA) was the predominant TFA; other isomers appeared in smaller amounts. The Δ9-desaturase activity measured as desaturation index of C14:0 was relatively high in the mammary gland of camel. Milk from the semi-intensive system was characterized by a higher nutritional value, due to the higher contents of total CLA, rumenic acid (RA), VA, linoleic, α-linolenic, and polyunsaturated FA compared with milk from the intensive system. Few differences were found in the OBCFA profile throughout lactation. Our study provided deeper information on FA composition, showing that camel milk is a good source of OBCFA, RA and VA. These results have to be taken into account in the investigation of the functional properties of camel milk fat as well as in the ongoing intensification of camel farming systems.

Introduction

In the last decades, a rising interest in camel milk resulting in increasing market demand has been observed owing to its nutritional and health-promoting properties. Accordingly, camel farming system is changing from the traditionally extensive pasturing system to the modern intensive system and machine milking has been introduced in several countries (Nagy and Juhasz, 2016).

Camel milk has been reported to have a beneficial effect on many diseases such as diabetes (Agrawal et al., 2003; Sboui et al., 2010), hypertension (Quan et al., 2008) cancer (Habib et al., 2013; Magjeed, 2005) and hepatitis (El Miniawy et al., 2014; Esmail et al., 2008). These potential health claims of camel milk were attributed to the particularity of its composition. Indeed, camel milk differs from other ruminant milk as it is devoid of β-lactoglobulin and contains low content of cholesterol and high contents of minerals (sodium, potassium, iron, copper, zinc, and magnesium), vitamins (C, A and E), polyunsaturated fatty acids (PUFA), and protective proteins (Al haj and Al Kanhal, 2010; Konuspayeva et al., 2009). These different characteristics of camel milk have made it a focus area of research. Several researches have highlighted the presence of biologically active components of medicinal interest in camel milk. Most of the studies on the functionalities of the bioactive components related to the functional properties of camel milk were concerned with protein-related components; however, studies on functionality related to fat components are neglected.

Fatty acids (FA) are one of the most important nutritional components of milk. Over recent decades, dairy products have gained much attention as functional foods mainly due to the health benefits associated with the biologically active conjugated linoleic acids (CLA) (Blaško et al., 2010). The beneficial effects of CLA include anti-carcinogenic, anti-atherogenic, anti-obesity and anti-diabetic properties (Rodríguez-Alcalá et al., 2017). The most biologically active isomer of CLA is cis-9, trans-11 C18:2, which accounts for 75–90% of total CLA (Blaško et al., 2010). CLA in milk originates from the ruminal biohydrogenation of dietary PUFA and the mammary gland Δ9-desaturation of the rumen-derived vaccenic acid (trans-11 C18:1, VA). Despite that trans fatty acids (TFA) intake has been linked to cardiovascular diseases and liver diseases, recent researches have shown that vaccenic acid has a positive effect on breast and colorectal cancers (Qu et al., 2017; Oh et al., 2014). Vaccenic acid is the common intermediate during the biohydrogenation of both α-linolenic (ALA) and linoleic (LA) acids.

Another group of specific odd- and branched-chain acids (OBCFA) has recently emerged as an important class of bioactive FA. Branched-chain fatty acids (BCFA) are claimed to have anti-tumor activity against breast cancer (Wongtangtintharn et al., 2004), reduce the incidence of necrotizing enterocolitis (Ran-Ressler et al., 2011) and improve pancreatic β-cell function (Kraft et al., 2015). Equally important, a negative association has been shown between the concentrations of certain odd-chain fatty acids (OCFA) in the human plasma phospholipids and the risk of type2 diabetes (Forouhi et al., 2014; Sun et al., 2007) and cardiovascular diseases (Khaw et al., 2012; Sun et al., 2007). The main source of OBCFA in the human diet is attributed to ruminant fats. They are produced de novo in relatively high levels by rumen microbial flora (Vlaeminck et al., 2006). Moreover, it has been shown that linear OCFA (C15:0 and C17:0) and anteiso-isomers can partially be synthesized in the mammary glands and adipose tissues (Massart-Leën et al., 1983; Vlaeminck et al., 2006).

Numerous studies in ruminants have been carried out to understand the sources of variability of CLA, TFA, and OBCFA, with the aim of improving milk nutritional quality. The feeding system has been shown to be the main factor; in particular, pasture feeding increases the concentration of FA that are more favorable to human nutrition (Lopez et al., 2019; Chilliard et al., 2002). The profile of these FA seems to be influenced by the stage of lactation and breed (Currò et al., 2019; Bainbridge et al., 2016; Kay et al., 2005; Craninx et al., 2008). In camel, studies focusing on CLA and TFA are scarce or even non-existent in OBCFA. Considering the growing interest in camel milk, the analysis of these FA should be investigated. Therefore, this study aimed to investigate the FA composition of camel milk, focusing on OBCFA, CLA, and TFA and to evaluate the impact of the lactation stage and management system on the FA profile. Such investigations are important regarding the possible consideration of camel milk as a functional food.