| Citrus peel can be divided into white layer and pigmented layer. The pigmented layer is rich in a variety of carotenoids such as lutein, zeaxanthin, β-cryptoxanthin and so on, which have physiological functions on the human body. Therefore, the effecient utilization of citrus peel carotenoid has important significance in processing the citrus peel and reducing pollution. Using laying hens as carriers, citrus peel carotenoids can be transferred from feed into the egg yolk. Not only is the egg convenient for human consumption, but also carotenoids in the egg yolk are easily digested by human, thus enhancing its nutritional value.In this paper, by-products of process citrus canns and juice——Satsuma mandarin peel and Citrus sinensis Osbeck peel were used as materials. A citrus peel layered machine was applied for separating the citrus peel into white layer and pigmented layer, and ultrasonic technique was used to extract carotenoids from citrus peel. The effect of citrus peel carotenoids extracts as feed additive in hens diets on egg yolk carotenoids composition and its colour were investigated. On this basis, carotenoids stability in the egg yolk powder with high content of carotenoids was studied under the condition of daylight and high temperature.Citrus sinensis Osbeck peel can be divided into the white layer and the pigmented layer. The optimized manipulating process were40-60tablets of peel per minute in transfer rate,5mm depth of saw-tooth,1400r·min-1in the rotation speed of the band-saw and less than5cm in citrus peel area. Under this optimized condition, the layered homogeneity was98%. Compared with the pectin and the carotenoids extracted from the whole citrus peel, the brightness in L*value of the pectin from the white layer was increased by53%and the content of the carotenoids from the pigmented layer was increased by3.2times using the same volume of solvent as that in whole peel after cutting off2mm pigmented layer by the machine. The optimum process pamameters in ultrason-assisted extraction of carotenoids with95%ethanol were as follows:1:35g·mL-1in a ratio of material to solution,36℃in extraction temperature and9min in extraction time. Under this condition, the extraction rate was85.86%and the content of carotenoids was351.25μg·g-1. The yield of single extraction with the optimized conditions was increased by36%and the extraction time decreased by88.3%compared to those of extraction in control, respectively. The major carotenoids in Citrus sinensis Osbeck peel extract were lutein and zeaxanthin. The major carotenoids in Satsuma mandarin peel extract were found as lutein, zeaxanthin and β-cryptoxanthin.Citrus peel carotenoids extracts were added to rice-based feed for hens, the results were:1) With increasing supplementation of Citrus sinensis Osbeck peel carotenoid extract (CSPE,1.8-7.6%) in the diet, Roche colour value (RCF) for the egg yolk was significantly increased (p<0.01). In a stabilised yolk colour, RCF value of a high CSPE supplementation group (7.6%) for the yolk was8.88. The total carotenoid concentration of egg yolk for the A4group’s was65.65μg·g-1, and the lutein and zeaxanthin concentrations were39.77μg·g-1and19.48μg·g-1, respectively. In addition, CSPE could increase egg weight, albumen’s height and HU value, which improved egg’s quality to some extent.2) With increasing supplementation of Satsuma mandarin peel carotenoid extract (SMPE,0.9-3.6%) in the diet, RCF value for the yolk improved significantly (p<0.01). For the B4group’s, RCF value of egg yolk was increased to9.73, and the total carotenoids concentration of egg yolk was89.48μg·g-1, which was10times higher than that of control. The lutein and zeaxanthinin concentration were54.2μg·g-1and12.8μg·g-1, respectively. What’s more, β-cryptoxanthin was8.95μg·g-1which was found as a new carotenoid in the yolk. There was no significant influence of SMPE on the egg’s quality(P>0.05).The results for the study of caotenoids stability in the egg yolk were as follows: carotenoids in the yolk powder was more stable than that in the citrus peel powder. After treatment at80℃for4h or daylight light for20h, the preservation rate of carotenoids in egg yolk powder was27%and22%higher than that in the citrus peel powder, respectively.The citrus peel caotenoids extracts can be deposited in the egg yolk and enhance the carotenoids concentration and it’s colour. What’ more, the carotenoids in the egg yolk is more stable than that in the citrus peel. This research provides a reference for the citrus peel caotenoids extracts as additives in hens diets. |
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