Fig. 1 A schematic diagram of temperature profile in a food body and in its ambient. Fig. 2 A schematic diagram of temperature history at the center o

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1 A Practical Method for Estimating Temperature History in Individual-Packed Foods During Retort Sterilization Isamu MUKAI Hisaka Works, LTD. Vital Industry Division, Engineering Section, Higashi Konoikecho, Higashi-Osaka, Osaka , Japan It is very important but so difficult problem for food manufacturing industries to estimate the central temperature of Individual-packed foods accurately during retort sterilization. Not a few numbers of methods by heat transfer equations have been used traditionally to solve these problems, however, these methods are too difficult to apply in the actual fields. Because of these reasons, more practical and convenient methods are under the necessity to be developed. A new practical estimation method named as Ambient Temperature Slide Method (ATS method) was developed. ATS method can simulate changes of central temperatures of packed foods under various ambient temperatures by using only two parameters led from actually measured data. In this method, central temperatures are estimated directly from ambient temperatures without dividing each packed food into many grid points, and as a result, total quantity of efforts for calculation should be largely reduced and commercial spread-sheet software is available. In this study, adaptability of the ATS method was tested using the hot water spray retort. Values from actual measurement and simulation with five kinds of packed foods which have different characteristics from solid to liquid form showed good consistency. These results suggested that the ATS method could be used as a new convenient estimation method. Keywords: Retort Sterilization, F -value, Heat transfer parameter, Ambient Temperature Slide Method, Hot Water Spray Retort

estimate the central temperature of Individual-packed foods accurately during retort sterilization.

2 Fig. 1 A schematic diagram of temperature profile in a food body and in its ambient. Fig. 2 A schematic diagram of temperature history at the center of a food body and of the ambient during retort sterilization.

4 向 200 井である. 3.2試温度センサは,釜抵抗体(山勇の温度制御用に φ4.8 L100の武製,HYY-4.8-3/4-A-D)を,ア測温ルミトレー上の品物やそのまわりにセットするものは,φ2 L100 のサーミスタ(芝浦電子製,特THB-113形)を使用した. 料現在,レトルト品は食品及び医薬品を含めて多種多様なものが市場へ出回っている.熱水スプレー式のレトルト品について見てもその多様性は変わらない.本研究ではその多様性をカバーするために物性が大きく違う次の5種類のサンプルを選んだ(Fig.5).均体の模擬品として無包装のシリコンゴム,加一固熱工程での変性が認められるアルミパウチ詰めカレー,加熱するとすぐに凝固するブロー容器詰め玉子豆腐,同じカレーであっても上部に比較的大きな空気相を持ったカップ容器詰めの含気カレー,水様物性ではあるが大きな厚みをもった透明パウチ詰め輸液バッグの5種である. 4.結果および考察各種食品サンプルに対する実験値は本研究で提案し Fig. 4 Ambient temperature at six different histories positions are coincided, atmosphere in the retort. history during in the retort showing heating used homogeneous and cooling in this work. All temperature た推定値又は推定式と良く一致していた.以算の結果,各下に表計サンプルに対する収斂計算結果,収斂値の一致性などについて考察を加えた 4.1表計算ソフトによる計算 Excelを示す.表用いて計算した手順を,実計算シートに,Table1に際例を取り上げて示すように,制パラメータや収束条件を入力するA領域と,雰御用囲気温度や食品試料温度の実測値を入力してシミュレーション計算を行なうB領 A領域の2つの領域を設定した.ま域にサンプリング時間,食を入力する.次る.こ品試料厚み,目ず, 標F値いでパラメータ τ と δの初期値を入力すの例ではシリコンゴム((1))を 120,20分加熱し,F値8.0分初期値は,α に既知の値を使い β を1とる計算値を入れた.δ れていないので,試試料としてを目標値とした.τ して(6)式のによの初期値はまだ計算式が確立さみに6秒とした.この段階では τ と δの初期値は加熱工程も冷却工程も同一の値を入れる,なお,残り4試料の計算において τ0値は,α 明のため水の α をまた β は1を上記同様,小 (1)第1段単位の6秒階:実使って求め,まから出発した. 測した雰囲気温度tw,試度tpを経過時間に対してB領る.続けてtw列料中心部温域の対応する列へ入力すを仮想雰囲気温度twi列らせてコピーする.こが不た δ0はの時,仮へ δ秒だけ遅想雰囲気温度twi列の0 秒から δ秒までの空欄には食品試料の初期温度を入力する.twi<tpとなった1734sec以降は実質冷却工程となる. 経過時間 θ,推測した試料中心部温度tpcal,温度差(tw i-tp),実測した試料温度に基づいて計算したF値EFn, 推測した試料温度に基づいて計算したF値EF,aln,計 Fig. 5 Samples for this work 算順番n,試料中心部温度の実測値と推定値の偏差Qp

本研究ではその多様性をカバーするために物性が大きく違う次の5種類のサンプルを選んだ(Fig.5).

5 Table 1 Data sheet of Excel for calculation Sample : Silicon Rubber (SR70)

6 Fig. 6 The history of measured temperature of ambient (solid line) and at the center of food body (light solid line) when silicon rubber is used as the model of food. The calculated temperature at the center of the food body is shown as the broken line. Table 2 Data sheet of EXCEL for calculation [2nd Step Operation sheet No.1] [2nd Step Operation sheet No.2] [3rd Step Operation sheet]

The calculated temperature at the center of the food body is shown as the broken line.

7 203 Fig. 7 The history of measured temperature of ambient (solid line) and at the center of food body (light solid line) when curry is used as the food. The calculated temperature at the center of the food body is shown as the broken line. Fig.8 The history of measured temperature of ambient (solid line) and at the center of food body (light solid line) when egg tofu is used as the food. The calculated temperature at the center of the food body is shown as the broken line. Fig. 9 The history of measured temperature of ambient (solid line) and at the center of food body (light solid line) when curry is used as the food and air is remained in the package. The calculated temperature at the center of the food body is shown as the broken line. Fig. 10 The history of measured temperature of ambient (solid line) and at the center of food body (light solid line) when transfuse liquid is used as the model of food. The calculated temperature at the center of the food body is shown as the broken line. Table 3 Standard of Accuracy Evaluated

8 The history of measured temperature of ambient (solid line) and at the center of food body (light solid line) when egg tofu is used as the food.

8 QB heat accumulation in a small time increment QT : heat conduction in a small time increment ( ƒæ) two : simulated ambient temperature [ Ž] NOMENCLATURE A : effective heat transfer area [m2] F : F-value [min] L : distance from surface to center of food [m] (a e) [U] V : volume of food [m3] cp : specific heat [KJ kg-1 Ž-1] h : outside film heat-transfer coefficient [KJ] [W E m -2 Ž-1] k : thermal conductivity of food [W m-1 Ž-1] n : calculated order [-] tp : center temperature of food [ Ž] tp * : average temperature of food [ Ž] tw : ambient temperature [ Ž] ts : surfase temperature of package [ Ž] a : thermal diffusivity [cm2-1] ƒà : deviation ratio of central temperature from average temperature in food [-] S : sliding time of ambient temperature [s] ƒæ : time [s] ƒæ : small time increment [s] ƒï : density of food [kg m-3] ƒðp : deviation between food temperature-curve [ % ] ƒðf : deviation of F-value [ % ] Additional ƒñ : parameter of heat transfer [-] scripts c : cooling process h : heating process Subscripts 0 : initial value cal : calculated value

thermal conductivity of food [W m-1 Ž-1] n : calculated order [-] tp : center temperature of food [ Ž] tp * : average temperature of food [ Ž] tw : ambient temperature [ Ž] ts : surfase temperature

9 205 [1] K. Hayakawa; Estimating food temperatures during various processing or handling treatment, J. Food Sci., 36, (1971)

06-T08238-レトルト殺菌-167-180白.indd

06-T08238-レトルト殺菌-167-180白.indd , Vol. 9, No. 3, pp. 167-179, Sep. 2008 ATS 1 2 1 2 A Practical Verification of Ambient Temperature Slide Method (ATS Method) during Retort Sterilization Isamu MUKAI 1 and Noboru SAKAI 2 1 Hisaka Works,