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1、37.1.11 AOAC Of fi cial Method 972.20 Mois ture in Prunes and Rai sins Mois ture Me ter Method First Ac tion 1972 Fi nal Ac tion 1980 A. Ap pa ra tus Dried fruit mois ture tester me ter.Type A se ries (DFA of Cal i for nia, 710 Striker Av e , Sac ra mento, CA 95834, USA); see Fig ure 972.20 for elec
2、 tric cir cuit. B. De ter mi na tion Grind test sam ple 3 times through food chop per, us ing cut ter with 16 teeth. If test ing hot fruit from pro ces sor, cool fruit as fol lows: Mix ca 60 g chopped solid CO2 with fruit and then grind mix ture 3 times be fore tak ing mois ture read ing. Pack groun
3、d test sam ple into Bakelite cyl in der with fin gers, mak ing cer tain that it is packed tightly around bot tom elec trode. Fill cyl in der com pletely with tightly packed test sam ple, and level. Lower top elec trode and press it into test sam ple un til top elec trode le ver is against stop. In s
4、ert ther mom e ter un til ther mom e ter bulb is ca half way be tween elec trodes. Se lect cor rect ta ble for type and con di tion of fruit be ing tested (Ta ble 972.20A: nat u ral or low mois ture; Ta ble 972.20B: pro cessed). Set switch (S2) to num ber given on ta ble se lected. Plug tester into
5、110 V ac out let and put switch to “on.” (Red light in di cates cur rent.) Keep push but ton down and turn dial so that me ter nee dle moves to ward 0. Ad just dial so that nee dle is at its low est, or turn ing, point. Af ter mak ing fine ad just ment of dial to me ter 0 or turn ing point, read dia
6、l and then read ther mom e ter. C. Use of Ta bles Choose tem per a ture col umn of ap pro pri ate ta ble near est to test sam ple tem per a ture. Read down this col umn to fig ure clos est to dial read ing, then read across to “% Mois ture” col umn. D. Ex am ple Ex am i na tion of pro cessed rai sin
7、 test sam ple gave fol low ing data: dial set ting 76 and tem per a ture 74F (23.3?C), on tap 3. Looking down 74F (23.3?C) col umn (Ta ble 972.20B), ob tain 75.2 at 18.5% mois ture and 78.4 at 19.0% mois ture. Since read ing is nearer to 18.5 than 19.0%, re port as con tain ing 18.5% mois ture, or i
8、n ter po late. Ref er ences: JAOAC 52, 858(1969); 54, 219(1971); 55, 202(1972); 59, 331(1976). 2005 AOAC IN TER NA TIONAL Figure 972.20. Elec tri cal cir cuit di a gram for dried fruit mois ture tester. 2006 AOAC INTERNATIONAL 2005 AOAC IN TER NA TIONAL Ta ble 972.20A. Con duc tance-temperature cor
9、re la tion for nat u ral or low mois ture rai sins; switch set ting, tap 6 % Mois ture Con duc tance read ings at tem per a ture (?Fa): 56586062646668707274767880828486889092949698100102 9.0 9.015.021.025.029.033.036.039.042.0 9.5 4.011.017.522.527.032.537.040.544.047.049.051.5 10.0 1.0 7.013.517.52
10、3.028.534.038.041.545.549.052.054.557.059.061.5 10.5 7.513.018.024.029.535.040.044.549.051.554.057.060.062.064.066.068.070.0 11.0 8.516.022.528.034.039.044.048.553.056.059.061.564.066.068.570.572.573.875.376.8 11.5 9.018.026.031.036.042.047.551.555.558.762.564.767.569.571.073.075.076.578.379.681.082
11、.5 12.023.530.537.542.547.052.056.560.063.366.569.071.073.074.576.078.079.781.082.083.885.286.5 12.516.527.034.540.046.050.555.059.063.065.868.671.073.375.076.678.079.781.382.684.085.486.788.089.3 13.030.537.242.548.052.356.560.564.367.770.072.574.876.778.379.781.282.683.885.286.587.889.290.591.3 13
12、.540.045.049.754.058.061.565.068.571.373.475.477.579.480.782.083.585.086.287.388.589.891.092.293.0 14.048.352.556.560.063.066.069.272.074.576.478.080.081.783.084.485.687.088.089.390.391.592.693.894.6 14.555.359.062.365.067.670.472.775.077.078.780.482.083.785.086.287.388.789.790.891.893.094.095.095.8
13、 15.061.664.567.770.872.474.376.078.079.781.182.684.085.686.787.989.190.391.492.593.594.595.596.497.0 a ?C = ? - F32 9 5. Ta ble 972.20B. Con duc tance-temperature cor re la tion for pro cessed rai sins; switch set ting, tap 3 % Mois ture Con duc tance read ings at tem per a ture (?Fa): 565860626466
14、68707274767880828486889092949698100102 13.00.06.712.818.022.226.831.435.439.543.748.052.255.859.0 13.52.59.015.421.025.229.434.038.342.746.550.554.358.061.564.8 14.05.711.717.023.027.532.436.640.844.248.352.656.259.662.866.369.2 14.51.07.514.019.024.329.434.239.042.846.750.954.457.560.864.267.270.37
15、3.0 15.02.59.315.521.727.031.636.340.945.549.253.056.859.762.765.468.270.973.676.1 15.54.011.017.723.129.734.038.242.747.351.655.258.562.164.967.269.772.074.276.678.7 16.013.520.025.331.036.041.045.550.054.058.061.664.567.469.672.073.775.577.379.381.0 16.513.020.526.532.036.642.046.550.754.858.562.0
16、65.568.871.073.075.277.078.479.781.382.884.3 17.013.522.028.434.039.043.547.251.755.759.462.666.068.871.574.176.077.879.480.982.083.284.285.586.7 17.531.036.041.045.049.052.556.059.563.066.069.071.674.076.278.480.081.582.683.984.885.886.887.888.7 18.043.047.050.053.557.059.762.764.869.071.573.876.07
17、8.079.881.682.784.085.086.086.887.788.589.590.2 18.550.553.356.059.462.565.067.770.473.075.277.379.281.082.483.884.885.886.787.788.489.089.990.791.3 19.056.058.561.264.066.869.271.674.076.478.480.281.783.384.585.786.787.688.589.389.890.491.091.792.3 19.560.763.065.568.370.572.774.777.279.280.882.583.985.286.287.288.088.889.590.390.991.491.992.593.0 20.065.067.569.671.874.076.077.979.881.783.184.685.787.087.888.789.590.190.791.491.892.392.893.493.9 20.569.271.373.375.277.278.680.682.483.985.386.487.488.489.390.090.691.291.892.592.993.393.894.394.7 a ?C = ? - F32 9 5. 2006 AOAC INTERNATIONAL