曲げ荷重により切断した凍結魚肉の切断面角度の予測 <報文>

Prediction of Cut Surface Angle of the Frozen Fish by Bending

岡本 清

羽倉 義雄

鈴木 寛一

久保田 清

日本食品科学工学会誌

We have proposed a new cutting method (cryo-cutting method) in which a frozen fish is cut by applying the 3-point bending force, instead of a band saw in the conventional cutting method using. We have already reported that the cutting destruction of fish meat occurred in two typical destruction modes of "the destruction across the muscle fiber" and "the destruction along the muscle fiber" when frozen fish are cut by the new method. The frequency of these two destruction modes was dependent on muscle fiber orientation angle (θf). In order to obtain the accurate cut section of frozen fish, it is necessary that only "the destruction across the muscle fiber" would be developed. In this paper, we tried to predict the range of muscle fiber orientation angle for yielding only "the destruction across the muscle fiber", based on the assumption the fish muscular tissue is the unidirectional composite material strengthened with the muscle fiber. By modifying the fracture theory of the unidirectional composite material strengthened in the fiber, we proposed a prediction equation for the destruction mode in 3-point bending fracture. Using the equation and the bending fracture stress of test pieces at θf= 0° and 90° (S0 and S90), we estimated the range of muscle fiber orientation angle only for "the destruction across the muscle fiber" in order to prove the effectiveness of the equation, three-point bending test of frozen tuna muscle was carried out at -70, -100 and -130°C and the generation frequency of each destruction mode was measured. The following results were obtained. (1) At all the temperatures tested, only "the destruction across the muscle fiber" was generated muscle fiber orientation between θf=0° and 20°. (2) The frequency of each destruction mode measured in the experiments agreed with the predicted at all the temperature tested, when the mean value of bending fracture stress (S)±double of the standard deviation (σ), S0(mean)±2σ0 and S90(mean)±2σ90, were used for the prediction calculation.

本研究では曲げ荷重下での凍結魚肉における「垂直切断」が起こる範囲を容易に予測する方法を明らかにすることを目的とした.

凍結マグロ赤身肉を試料として, θfの異なる試験片を作成し, -70, -100, -130℃で3点曲げ試験を行い, 試験片の切断様式(「垂直切断」が起こる割合)を測定した. またθf=0°, 90°の試験片については破壊応力を測定し, 切断様式の予測に利用した. 次に一方向強化材料の引張荷重下での破壊理論(最大応力説)を曲げ荷重に適用できるよう修正し, 試験片の切断様式の筋線維配向角度(θf)依存性の予測方法を提案した. さらにこの方法による予測結果と凍結マグロによる切断様式の測定結果との比較より, 予測式の適用の可能性について検討を行った. その結果以下のことが明らかとなった.

(1) 試験片の切断試験の結果, -70℃における20°<θf<40°の範囲と, -100℃, -130℃における20°<θf<50°の範囲では, 「垂直切断」と「平行切断」の両方が起こり得ることが明らかとなった. またこれらの切断挙動には温度依存性が見られた.

(2) 破壊応力測定の結果, θf=0°, 90°の試験片とも, 破壊応力の温度依存性が見られ, 試験温度の低下とともに試験片の破壊応力は増加した.

(3) 切断様式の予測において, θf=0°, 90°における破壊応力のばらつきを導入して計算することにより, 「垂直切断」と「平行切断」の両方が起こり得る筋線維配向角度範囲を表現することが出来た. そこで破壊様式の予測は, 破壊応力の標準偏差範囲を考慮して行う必要があることが明らかとなった.

(4) θf=0°, 90°における破壊応力の分布範囲を平均値±(標準偏差×2)の範囲として予測することで, 実測値に最も近似した切断様式の予測が可能であった.

家政学・生活科学 [ 590 ]

日本語

日本食品科学工学会

[ISSN] 1341-027X

[NCID] AN10467499

[URI] http://www.journalarchive.jst.go.jp/japanese/jnlabstract_ja.php?cdjournal=nskkk1995&cdvol=49&noissue=5&startpage=297