Studies On Nutrition Value And Effect Of Natural Red Yolk Of Duck's Egg On Serum Lipids

The duck eggs with natural red yolk are laid by the ducks which are grew in lake, and the chrominance of the yolk can be generally reached to above RCF (Roche Yolk Color Fan ) 15. The bright color of natural red yolk of duck's eggs were favorably received in market, but whether the high cholesterol of eggs boosts blood cholesterol level in everyone were still a question. Therefore the consumers are fond as well as afraid of eating eggs with red yolk. The problem was not only vexed in academia but also related to the uninterrupted development of agriculture. For clearing up the problem, the paper evaluated the effect of the natural red yolk of duck's egg on serum lipids level and analyzed its nutrition components. The structures and the antioxygenation of carotenoids in the natural red yolk were researched at the same time. The main results indicated as followed: Nutrition components of the natural red yolk of duck's eggThe nutrition components of the natural red yolk were analyzed. The results showed that the contents of proteins were 15.41%, lipids 29.51%, carbohydrates 3.4%, ashes 1.26% and cholesterols 12.95mg/g (wet stuff).The carotenoids of the natural red yolk and common yolk were analyzed by TLC and chemistry means. The result showed that the sorts and contents of carotenoids of the natural red yolk were more than common yolk. The contents of carotenoids of these two kinds of eggs were 10.27mg/100g(the natural red color yolk, RCF≥5) and 4.65 mg/100g(common yolk, RCF≤5) respectively. Extraction and stability of Carotenoids of the natural red yolkThe best extracting condition of the freeze-dried natural red yolk power was: petroleum ether: acetone=2:1 (v/v), 40 ℃, Red yolk power: Solvent = 1:4 (w/v), extracting 3 times, 60min per time.Fe²⁺, ray, methanol and ethanol strongly destroyed carotenoids of the natural red yolk.Acidic condition was disadvantage of the preservation of carotenoids. The low temperature was advantage of the preservation of carotenoids. Identification Carotenoids of the natural red yolkThe structures of carotenoids of the natural red yolk are analyzed and identified by UV-VIS, TLC, HPLC, HPLC/MS/MS and chemistry means. The result showed that the carotenoids of the natural red yolk included Lutein and Astaxanthin besides a special kind of red carotenoids, whose molecular weight was 562 and molecular formula was C₄0H₅0O₂. Antioxidation of carotenoids of the natural red yolkThe antioxygenic effects of carotenoids of the natural red yolk in vitro were studied in this paper. Carotenoids of the natural red yolk had the inhibiting effects on lipid peroxidation with mice liver in vitro. It could protect liver from peroxidation induced by Fe²⁺+H₂ O₂, and inhibit the hemolysis of red blood cells. It also could protect the photosensitive oxidation of rape oil and bean oil. Effects of Carotenoids of the natural red yolk on serum lipids in miceAccording to serum cholesterol level, 32 female Kun-Ming mice were divided into 4 groups: normal control group; natural red yolk low, middle and high dose group; Normal control group was fed basic diet and the other groups were fed diet added different content natural red yolk for six weeks. The result indicated that low dose group (5g·kg^-1·d^-1) had no effect on TC, TG and LDL-C level in serum and liver, and increased the HDL-C level. High dose group(20g·kg^-1·d^-1) increased TC,TG and LDL-C level in serum, and increased MDA level and decreased the activity of SOD in liver. The results of RT-PCR showed that middle and high dose group all increased the activity of LPL and LPLmRNA in liver.