Transfer to the milk of rumen bypass CLA emulsions created by potato tuber peel polyphenol oxidase

Rumen bypass technologies aim at protecting nutrients, for example polyunsaturated fatty acids against degradation, in this case biohydrogenation, to ensure an unaffected passage through the rumen and enhanced intestinal absorption. Recently, a new encapsulation technology has been proposed based on the properties of the naturally occurring enzyme polyphenol oxidase (PPO). However, up till now no in vivo approval of the PPO-based bypass technology nor evidence of post-ruminal absorption is available. Proteins and PPO in this study were extracted from potato (Solanum tuberosum L.) tuber peels and used to emulsify triacylglycerols of a mixture of conjugated linoleic acid (CLA) isomers (Tonalin TG80, BASF-AG, Ludwigshafen, Germany) in water (20 mg oil per ml extract) before encapsulation was created by the cross-linking of interfacial proteins upon addition of the diphenol 4-methylcatechol (20 mM). This rumen bypass CLA emulsion or a commercially available protected CLA product (Lutrell Combi, BASF-AG, Ludwigshafen, Germany) as positive control was used to dose 7 g trans-10, cis-12 C18:2 per day to eight dairy cows during five consecutive days in a sequential set-up. Milk fat content and fatty acid composition was monitored to assess the transfer to milk of dietary CLA. Evidence for the protection in vivo against ruminal degradation, post-ruminal uptake and transfer to the milk was given as increased proportions of trans-10, cis-12 C18:2 were found in milk fat of cows compared with the periods before and after supplementation of both additives. Extra proof for the transfer to the milk was given because both supplements resulted in similar reductions in milk fat content, since trans-10, cis-12 C18:2 is known as an inhibitor of milk fat synthesis if sufficient amounts of this CLA reach the mammary gland. However, somewhat lower transfer efficiencies of trans-10, cis-12 C18:2 from the diet to the milk in the case of the rumen bypass CLA emulsions compared with the positive control and the occurrence of non-negligible levels of CLA in faecal material indicates there is still scope for further improvement of the new technology. In conclusion, the PPO based lipid protection technology could provide a worthy alternative for current rumen bypass products as the encapsulated CLA was effectively transferred to the milk.

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