engleski

OCCURRENCE OF SOME C18:1 FATTY ACID ISOMERS IN GOAT’S MILK AND SERUM

Milk fat contains over 400 fatty acids (FAs) with a different number of carbon atoms, various degrees of saturation: saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA), with cis and trans configuration and straight or branched carbon chains. Natural trans FAs typically arise from ruminant microbiota activity during the ruminal biohydrogenation of dietary FAs. Mainly C18 monoenoic trans FAs are formed with predominance of the 11 isomer trans- vaccenic (C18:1t-11) and trans-elaidic FA (C18:1t- 9). The FA composition of milk has numerous effects on milk quality including its physical properties and nutritional value. Approximately half of the FAs in the milk are sourced from the blood. The aim of this study was to determine C18:1 isomers in goat’s milk and serum. The research was carried out on 15 clinically healthy Saanen goats in two lactational phases (early, around 30th lactational day, L1 ; late lactation, around 150th lactational day, L2) and dry period (D). After the extraction of total lipids from the milk and serum samples, the analysis of methyl esters of FAs was performed using gas chromatography. The most predominant isomer in goat’s milk, expressed as % of total FAs in milk (mean±SD), was C18:1c-9 (20.2±3.4%), followed by C18:1t-11 (6.6±1.7%), then by C18:1t-9 (1.8±0.8%) and C18:1c-11 (0.8±0.2%). Only C18:1c-9 showed significant difference in representation in two lactational phases, being significantly higher in L1 compared to L2 (22.9±2.6% vs. 17.8±1.9% ; p<0.01). The percentages of C18:1t-11 in L1 was positively correlated with that of C18:1c-9 (r=0.66, p<0.05) and negatively with SFA (r=-0.7, r<0.05). In goat’s serum the pattern of predominance of C18:1 isomers was similar as in milk (C18:1c-9, 16.9±8.1% ; C18:1t-11, 3.3±1.4%) with the difference of C18:1c-11 being more represented than C18:1t-9 in serum than in milk (0.9±0.5% ; 0.8±1.5%, respectively). Significantly higher percentages of C18:1t-9, C18:1c-9 and C18:1c-11 were determined in L1 compared to D period (1.1±2.3% vs. 0.3±0.3%, p=0.04 ; 19.5±8.0% vs. 9.1±2.4%, p<0.01 ; 1.1±0.5% vs. 0.6±0.1%, p<0.01, respectively). Furthermore, significantly higher percentages of C18:1t-9 and C18:1c-9 were determined in L2 compared to D period (0.8±0.5% vs. 0.3±0.3%, p=0.03 ; 18.6±8.0% vs. 0.6±0.1%, p<0.01 ; respectively). Since trans FAs have both positive and negative effects on obesity, insulin resistance, cardiovascular disease, cancer and inflammation in human organism, there is a general suggestion to reduce their consumption. There is also interest in the role of trans isomers of 18:1 in mediating the milk fat depression associated with certain dairy diets

C18:1 isomers, milk, serum, goat

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