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The red-pigmented yeast, Phaffia rhodozyma, containing high concentration of astaxanthin (Ax) was evaluated as a dietary pigment source for egg yolk of laying hens fed on a low-carotenoid diet. Diets supplemented with the yeast to provide 0 to 16ppm Ax were fed for 4 weeks, while canthaxanthin (Cx), a synthetic pigment source, was added to diets at 0 to 1.5ppm as the comparing counterpart in 2 experiments. Roche color fan score and a* value on Chroma Meter increased linearly with the increase of logarithmic concentration of dietary Ax and Cx. Cx (Carophyll Red(R)) was 4 to 5 times as potent as Ax in the yeast for the pigmentation of egg yolk probably because of low digestibility of the yeast. Ax concentrations in plasma and egg yolk increased with dietary Ax concentration and the increases paralleled with the pigmentation of egg yolk. These results suggest that Phaffia yeast containing high concentration of Ax has the potential as natural pigment source for egg yolk of laying hens.

Two experiments were conducted if the meat color-modifying potential of Phaffia rhodozyma, a yeast containing high levels of astaxanthin (Ax), is influenced by the feeding duration and the dietary concentration and if the potential is enhanced by an addition of lecithin+α-tocopherol in broiler chickens. Experimental diets supplemented with cell wall-fractured yeast to provide 10, 20 and 30ppm Ax were fed to 3, 5 and 7 week-old chickens for 5, 3 and 1 weeks, respectively, prior to market in Experiment 1. In Experiment 2, Phaffia yeast-supplemented diets (20ppm Ax), which were supplemented with or without lecithin (5g/kg diet)+α-tocopherol (0.1g/kg diet), were fed to 5 week-old chickens for 3 weeks prior to market. Feeding of Phaffia yeast influenced neither performance of broilers nor edible meat yields, irrespective of either the feeding duration, the dietary concentration or the addition of lecithin+α-tocopherol. Concern-ing the color analysis of edible meats using with Minolta reflectance colorimeter, light-ness (L* value) was not essentially influenced by feeding of the yeast-supplemented diets, while yellowness (b* value) was slightly increased by the yeast feeding. On the other hand, the redness (a* value) of edible meats and abdominal adipose tissues was significantly or numerically increased by feeding of the yeast-supplemented diets, in which the increase was less extent in chickens received the yeast-supplemented diet (30ppm Ax) for 1 week prior to market than chickens received the yeast-supplemented diets (20ppm Ax) for 3 weeks. The extent of increase in a* values of edible meats was relatively dependent on the total Ax intake. Addition of lecithin+α-tocopherol did not intensify the coloration (redness) of edible meats by the feeding of yeast-supplemented diets. These results show that cell wall-fractured Phaffia yeast containing high concen-trations of Ax can be a useful source for modification of meat color and the effect is briefly due to the total Ax intake in broiler chickens.

トウモロコシ•大豆粕主体の慣用飼料を給与した産卵鶏を供試し,カロチノイドの一種であるアスタキサンチン(Ax)を高濃度に含む赤色酵母の卵黄色強化効果を検討した。飼料中のアスタキサンチン濃度が0から6ppmになるように赤色酵母を段階的に添加した飼料,赤色酵母からアセトンで抽出したAx 3ppm添加飼料,市販Ax製剤3ppm添加飼料,市販カンタキサンチン(Cx)製剤1ppm添加飼料,試薬用Cx 1ppm添加飼料を2-4週間給与した。赤色酵母,AxおよびCx給与では産卵鶏の増体量,飼料摂取量,産卵率および卵重に変化は見られなかった。ロッシュカラーファンスコアおよびChroma Meterによる赤色度(a*値)はいずれのAxおよびCx添加でも有意に上昇した。また,カラーファンスコア,a*値および卵黄中のAx濃度のいずれもが飼料中Axの添加濃度にしたがって有意に上昇した。抽出Axは赤色酵母中Axに比較して,卵黄色強化効果では8倍以上,卵黄へのAx移行率では約3倍高く,赤色酵母中のAxの利用性を高めるためには酵母の細胞壁破砕などの処理により消化性(酵母の分解性)を高めることが有効であると推定された。試薬用Cxの卵黄着色効果は市販Cx製剤よりも小さいことが示された。以上のことから,産卵鶏の実用的飼育条件下でも,赤色酵母は天然の卵黄色強化用の飼料原料として有用であること,そして,その利用性は酵母細胞壁の破砕処理などにより大きく改善可能であることが示唆された。