Studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten
The taste of the dairy product is probably the main factor determining consumer's dairy products choice. Consequently it is of great importance that the product tastes good and as expected every time. Off-flavors in milk can be caused by for example oxidation of the milk fat. Since copper is a proox...
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| Formato: | L3 |
| Lenguaje: | sueco Inglés |
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SLU/Dept. of Animal Breeding and Genetics (until 231231)
2007
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| Materias: |
| _version_ | 1855571817447555072 |
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| author | Wiklund, Sofia |
| author_browse | Wiklund, Sofia |
| author_facet | Wiklund, Sofia |
| author_sort | Wiklund, Sofia |
| collection | Epsilon Archive for Student Projects |
| description | The taste of the dairy product is probably the main factor determining consumer's dairy products choice. Consequently it is of great importance that the product tastes good and as expected every time. Off-flavors in milk can be caused by for example oxidation of the milk fat. Since copper is a prooxidant, a high copper content in the milk can cause oxidation. The aim of this project was to investigate if there are differences between individual cows regarding the proportion of the copper totally excreted that was excreted through the milk compared to that excreted in faeces and urine. If there are differences between individual cows, this indicates a genetic influence and thus it may be possible to decrease the incidence of oxidized flavor in milk through breeding.
Off-flavors in milk are defined as unpleasant smell and/or taste of the milk. Most of the off-flavors in milk are related to the fat component of the milk. Milk fat may oxidize spontaneously and thereby cause oxidized flavor in milk. The fatty acid composition, or more specifically the degree of unsaturation of the milk fat, influences the milk fat's sensitivity to oxidation. The stability of unsaturated milk fat is also influenced by the copper content in the milk, due to the pro-oxidative characteristics of copper. The problems with spontaneous oxidation of milk fat have, according to the literature, been found to increase during the winter and spring seasons. This increase is thought to partly depend on that at that time the feed have been stored for quite some time and thereby may have lost some of its content of antioxidants. Important antioxidants in this respect may be first and foremost vitamin E, but also beta-carotene (precursor to vitamin A) and vitamin C (ascorbic acid).
The present study included eight cows of the Swedish Red and White dairy breed. The cows belonged to either of two selection lines, both selected for an equally high total production of milk energy. But one selection line was selected for a high milk fat content in the milk and the other line was selected for a low milk fat content. The cows were fed four different rations, containing 30 % or 50 % of hay or silage, respectively. Each ration was complemented with grain and concentrates to become comparable with respect to content of metabolizable energy and amino acids absorbed in the small intestine (AAT). All the cows were given all of the rations, but in a different order. Each ration was given during five weeks. The feed consumption was measured individually for each cow and analyses were made on milk, feces, urine and feeds (Gustafson, 2000).
This study showed significant differences between the different cows regarding how much of the total excreted copper that was excreted in the milk, which indicates individual differences in copper metabolism. This can have a partly genetic background, which is supported by observations on a number of other species. The results indicate that it may be possible to reduce the problem with oxidized flavour in milk through selection and thereby exceed the shelf life of dairy products. |
| format | L3 |
| id | RepoSLU11154 |
| institution | Swedish University of Agricultural Sciences |
| language | swe Inglés |
| publishDate | 2007 |
| publishDateSort | 2007 |
| publisher | SLU/Dept. of Animal Breeding and Genetics (until 231231) |
| publisherStr | SLU/Dept. of Animal Breeding and Genetics (until 231231) |
| record_format | eprints |
| spelling | RepoSLU111542017-09-27T10:57:44Z Studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten Wiklund, Sofia cow milk copper metabolism The taste of the dairy product is probably the main factor determining consumer's dairy products choice. Consequently it is of great importance that the product tastes good and as expected every time. Off-flavors in milk can be caused by for example oxidation of the milk fat. Since copper is a prooxidant, a high copper content in the milk can cause oxidation. The aim of this project was to investigate if there are differences between individual cows regarding the proportion of the copper totally excreted that was excreted through the milk compared to that excreted in faeces and urine. If there are differences between individual cows, this indicates a genetic influence and thus it may be possible to decrease the incidence of oxidized flavor in milk through breeding. Off-flavors in milk are defined as unpleasant smell and/or taste of the milk. Most of the off-flavors in milk are related to the fat component of the milk. Milk fat may oxidize spontaneously and thereby cause oxidized flavor in milk. The fatty acid composition, or more specifically the degree of unsaturation of the milk fat, influences the milk fat's sensitivity to oxidation. The stability of unsaturated milk fat is also influenced by the copper content in the milk, due to the pro-oxidative characteristics of copper. The problems with spontaneous oxidation of milk fat have, according to the literature, been found to increase during the winter and spring seasons. This increase is thought to partly depend on that at that time the feed have been stored for quite some time and thereby may have lost some of its content of antioxidants. Important antioxidants in this respect may be first and foremost vitamin E, but also beta-carotene (precursor to vitamin A) and vitamin C (ascorbic acid). The present study included eight cows of the Swedish Red and White dairy breed. The cows belonged to either of two selection lines, both selected for an equally high total production of milk energy. But one selection line was selected for a high milk fat content in the milk and the other line was selected for a low milk fat content. The cows were fed four different rations, containing 30 % or 50 % of hay or silage, respectively. Each ration was complemented with grain and concentrates to become comparable with respect to content of metabolizable energy and amino acids absorbed in the small intestine (AAT). All the cows were given all of the rations, but in a different order. Each ration was given during five weeks. The feed consumption was measured individually for each cow and analyses were made on milk, feces, urine and feeds (Gustafson, 2000). This study showed significant differences between the different cows regarding how much of the total excreted copper that was excreted in the milk, which indicates individual differences in copper metabolism. This can have a partly genetic background, which is supported by observations on a number of other species. The results indicate that it may be possible to reduce the problem with oxidized flavour in milk through selection and thereby exceed the shelf life of dairy products. Smaken är sannolikt den faktor som fäller avgörandet när konsumenten väljer livsmedel i butik, varför det är mycket viktigt att en produkt alltid har samma goda smak kunden förväntar sig. Smakfel hos mjölk kan orsakas av exempelvis oxidation av mjölkfettet. Då koppar är en prooxidant kan hög kopparhalt i mjölken bidra till oxidationssmak. Syftet med projektet var att undersöka om det finns skillnader mellan kor avseende hur stor andel av den totala mängden utsöndrad koppar som utsöndras via mjölken i relation till vad som utsöndras via träck respektive urin. Om så är fallet borde man kunna minska förekomsten av oxidationssmak i mjölk genom avelsåtgärder. Smakfel hos mjölk inbegriper avvikelser i såväl lukt som smak. Flertalet av smakfelen är kopplade till fettfraktionen i mjölken. Exempelvis kan mjölkfett oxidera spontant och därmed orsaka oxidationssmak hos mjölken. Mjölkfettets fettsyrasammansättning och då främst omättnadsgraden påverkar mjölkfettets benägenhet att oxidera. Oxidationsstabiliteten hos omättat mjölkfett påverkas i sin tur av kopparinnehållet i mjölken. Problemen med spontan oxidation har enligt litteraturen bedömts vara större under vintern och våren, vilket troligen har att göra med att fodret då har lagrats en längre tid och därmed förlorat en stor del av innehållet av antioxidanter. Antioxidanterna i fråga är främst vitamin E men även betakaroten (förstadium till vitamin A) och vitamin C (askorbinsyra). De åtta kor av rasen Svensk Röd boskap (SRB) som ingick i den föreliggande studien tillhörde endera av två selektionslinjer för hög respektive låg mjölkfetthalt i mjölken men med likvärdig och hög totalproduktion av mjölkenergi. De utfodrades med fyra olika foderstater, bestående av 30 % respektive 50 % hö alternativt ensilage, vilka alla kompletterades med kraftfoder och mineraler för att så långt möjligt ge samma innehåll av aminosyror absorberade i tunntarmen (AAT) och energi. Samtliga kor fick samtliga foderstater, men i olika ordningsföljd och varje foderstat gavs under en 5- veckorsperiod. Konsumtionen av foder mättes individuellt och analyser gjordes på träck, mjölk, urin och fodermedel (Gustafson, 2000). Försöket visade på signifikanta skillnader i andel koppar utsöndrad i mjölk mellan de olika korna, vilket indikerar att det finns individuella skillnader i kopparmetabolism. Detta kan ha en delvis genetisk bakgrund, vilket stöds av iakttagelser gjorda på en rad andra djurslag. Resultaten indikerar att det genom avelsurval kan finnas möjligheter att minska problemet med oxidationssmak hos mjölk och därmed förbättra mejeriprodukternas lagringsstabilitet. SLU/Dept. of Animal Breeding and Genetics (until 231231) 2007 L3 swe eng https://stud.epsilon.slu.se/11154/ |
| spellingShingle | cow milk copper metabolism Wiklund, Sofia Studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten |
| title | Studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten |
| title_full | Studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten |
| title_fullStr | Studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten |
| title_full_unstemmed | Studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten |
| title_short | Studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten |
| title_sort | studier av koppar i mjölk : en prooxidant med negativa effekter på mjölkkvaliteten |
| topic | cow milk copper metabolism |