ミラー型牛枝肉横断面撮影装置を用いた肉用品種における脂肪交雑形状特性の比較

摘要

切開面が狭い牛枝肉において広範囲かつ鮮明な横断面画像を得ることが可能なミラー型撮影装置を用い，新たな脂肪交雑粒子のあらさの指標を提案し，一般市場に出荷される肉用品種の肉質の特性を比較した.用いたミラー型撮影装置は，デジタルカメラ，フィルムタイプミラー，白色LEDライン型照明2燈を組み合わせ，切開幅が約25cmの枝肉に挿入可能であるくさび形の撮影装置である.黒毛和種(JB)58頭，黒毛和種と褐毛和種の交雑種(BBR)43頭，褐毛和種(JBR)42頭，黒毛和種とホルスタイン種の交雑種(JBH)60頭およびホルスタイン種(HOL)48 頭の5品種251頭について第6-7肋骨間のロース芯画像を解析した.得られた画像からロース芯面積，脂肪面積割合，全体のあらさなどの12形質を算出した.新たな脂肪交雑のあらさの指標として個々の脂肪交雑を面積の大きい順番に並べ替え，もっとも大きい脂肪交雑粒子から5個までを加算し，脂肪交雑総面積で除した指数(上位1～5のあらさ)が有効であった.脂肪面積割合の平均はJB43.02%，BBR 36.62%，JBR 29.72%，JBH 31.76%，HOL19.34%となり，JBRとJBHを除いたすべての品種間について有意差が認められた(Pく0.05).上位1～5のあらさはJBH (19.88) およびHOL(20.14) において有意に高い値となった(Pく0.05).We developed a mirror-type photography equipment to produce extensive and clear cross-sectionalimages of carcass at the 6th and 7th rib. We also proposed a new indicator for marbling coarseness and compared the marbling features among popular Japanese beef breeds. The mirror-type photographyequipment consisted of a digital camera，a film mirror and two white LED line lightings. The geometry of the equipment was wedge-shaped，so that the digital image of the carcass cross section could be obtained in thenarrow dissection space. Rib eye images of 58 Japanese Black (JB)，42 Japanese Brown(JBR)，48 Holstein (HOL)，43 JB X JBR (BBR) and 60 JB X HOL (JBH) were analyzed. Twelve meat quality traits (rib-eye area，marbling area percentage and overall coarseness，etc.) were calculated by image analysis. The area of eachmarbling particle was ranked in descending order. The sum of the top five particle areas divided by the total area of marbling was used as a good indicator of marbling coarseness (Coarseness of 1-5 particles). Least square means of the marbling area percentages of JB，BBR，JBR，JBH，HOL were 43.02%，36.62%，29.72%，31.76% and 19.34%，respectively. These values differ significantly，except for those corresponding to JBRand JBH. Coarseness of 1-5 particles of JBH (19.88) and HOL (20.14) were significantly higher than those of other breeds (Pく0.05).