EFFECT OF PH ON BIOHYDROGENATION OF POLYUNSATURATED FATTY-ACIDS AND THEIR CA-SALTS BY RUMEN MICROORGANISMS IN-VITRO

The influence of different pH values on the protection of Ca-salts of polyunsaturated fatty acids (PUFA) against ruminal biohydrogenation wa s investigated. Ca-salts were prepared from soya bean oil fatty acids (SOH) and incubated in vitro with rumen fluid at different pH values. Biohydrogenation of Ca-salts of the PUFA's and their corresponding fre e fatty acids in SOH was compared. Two series of incubations were carr ied out, a first series with pH varying between 6.9 and 5.5, while in the second series, a narrower pH range was studied (6.8-6.3). The expe riments showed that between pH 6.9 and 6.3, Ca-salts of PUFA's are par tly protected against biohydrogenation. Ca-salt of linoleic acid was p rotected to a greater extent than Ca-linolenate. Biohydrogenation of t he salts is most probably due to dissociation of the solubilized Ca-sa lts. For efficient protection of Ca-salts of PUFA's against hydrogenat ion, maintenance of pH values above 6.3 will be necessary.