食品中还原糖的测定

1、第九章食品中还原糖的测定【教学目标】 ：1. 掌握还原糖的概念和相关知识2. 能正确地配置和标定标准葡萄糖液、碱性酒石酸铜溶液和高锰酸钾溶液，熟练掌握滴定的操作技能。食品中常见的碳水化合物的种类很多，可分为单糖、双糖和多糖，不同品种的食品中所含糖类物质的品种及数量上有较大的差异。一、标准方法(GB 5009 7-85)（一）高猛酸钾滴定法1.原理样品经除去蛋白质后，其中还原糖把铜盐还原为氧化亚铜，加酸性硫酸铁后，再把氧化亚铜氧化为铜盐，以高猛酸钾溶液滴定生成的亚铁盐，根据高猛酸钾溶液消耗量，计算氧化亚铜含量，再查表得还原糖量。2.试剂（ 1）碱性酒石酸铜甲液：称取34.639g 硫酸铜（ Cu

2、SO4?5H2O）,加适量水溶解，加0.5mL, 硫酸，再加水稀释至500mL ，用精制石棉过滤。（ 2）碱性酒石酸铜乙液： 称取 173g 酒石酸钾钠与 50g 氢氧化钠，加适量水溶解， 并稀释至 500mL ，用精制石棉过滤，贮存于橡胶塞玻璃瓶内。（ 3）精制石棉：取石棉，先用 3moL/L 盐酸浸泡 2-3d，用水洗净，再加 10%氢氧化钠溶液浸泡2-3d，倾去溶液， 再用热碱性酒石酸铜乙液浸泡数小时， 用水洗净。 以 3moL/L 盐酸浸泡数小时，用水洗至不呈酸性。然后加水振摇，使成微细的浆半软纤维，用水浸泡并贮存于玻璃瓶中，即可用作填充古氏坩埚用。（ 4）高锰酸钾标准滴定溶液 c(1

3、/5KmnO 4)=0.1000moL/L 。（ 5）氢氧化钠溶液（40g/L）：称取 4g 氢氧化钠，加水溶解并稀释至100mL 。（ 6）硫酸铁溶液：称取50g 硫酸铁，加入200mL 水溶解后，慢慢加入100mL 硫酸，冷后加水稀释至 1000mL 。（ 7） 3moL/L 盐酸：取30mL 盐酸，加水稀释至120mL 。3.仪器（ 1） 25mL 古氏坩埚或 G4 垂融坩埚。（ 2）真空泵或水泵。4.操作方法（ 1）样品处理乳类、 乳制品及含蛋白质的冷食等。 称取约2.5-5.0g 固体样品 (吸取 25.00-50.00mL 液体样品 )，置于 250mL 容量瓶中，加50mL 水，

4、摇匀后加10mL 碱性酒石酸铜甲液及4mL(40g/L) 氢氧化钠溶液，加水至刻度，混匀。静置30min, 用干燥滤纸过滤，弃去初滤液，滤液备用。酒精性饮料。吸取100.0mL样品，置于蒸发皿中，用 (40g/L) 氢氧化钠溶液中和至中性，在水浴上蒸发至原体积的1/4，移入 250mL 容量瓶中，加 50mL 水，混匀，加 10mL 碱性酒石酸铜甲液及 4mL(40g/L)QING氢氧化钠溶液，加水至刻度，混匀，静至30min, 用干燥滤纸过滤，弃去除滤液，滤液备用。含多量淀粉的食品。称取10.00-20.00g 样品，置于 2500mL 容量瓶中，加200mL 水，在 45水浴中加热 1h，

5、并时时振摇。冷后加水至刻度，混匀，静置。吸取200mL上清液于另一 250mL容量瓶中，加入 10mL碱性酒石酸铜甲液及 4mL(40g/L) 氢氧化钠溶液，加水至刻度，混匀。静置 30min, 用干燥滤纸过滤，弃去初滤液，滤液备用。汽水等含有二氧化碳的饮料。吸取 100.0mL 样品，置于蒸发皿中，在水浴上除去二氧化碳后，移入 250mL容量瓶中，并用水洗涤蒸发皿，洗液并入容量瓶中，再加水至刻度，混匀后，备用。（ 2）测定 50.00mL 处理后的样品溶液于400mL烧杯中，加入 25mL碱性酒石酸铜甲液及 25mL乙液，于烧杯上盖一表面皿，加热，控制在4min 内沸腾，再准确煮沸 2min

6、，趁热用铺好石棉的古氏坩埚或 G4垂融坩埚抽滤， 并用 60热水洗涤烧杯及沉淀， 至洗液不呈碱性为止。 将古氏坩埚或垂融坩埚放回原 400mL烧杯中，加 25mL硫酸铁溶液及 25mL水，用玻璃棒搅拌使氧化亚铜完全溶解，以高猛酸钾标准溶液c(1/5KmnO 4 )= 1.000moL/L 滴定至微红色为终点。同时吸取 50mL 水，加与测样品时相同量的碱性酒石酸铜甲液、乙液，硫酸铁及水，按同一方法做试剂空白试验。5.计算X 1=(V-V 0)× c× 71.54 （ 3-12 ）式中： X 1- 样品在还原糖质量相当于氧化亚铜的质量，mg；V-样品液消耗高锰酸钾标准滴定溶液

7、的体积，mL ；V0- 试剂空白消耗高锰酸钾标准滴定溶液的体积，mL;c-高锰酸钾标准滴定溶液的浓度,moL/L ；71.54-1mL 高锰酸钾标准滴定溶液c(1/5KmnO4)=1.000moL/L ，相当于氧化亚铜的质量，mg。根据式（ 3-12 ）中计算所得的氧化亚铜质量，查表3-1 氧化亚铜质量相当于葡萄糖、果糖、乳糖、转化糖的质量表，再计算样品中还原糖的含量。X 2m1100 （ 3-13）V1m21000250式中： X 2-样品中还原糖含量，g/100g；m1- 查表得还原糖质量，mg；m2- 样品质量（或体积） ， g(mL) ；V 1-测定用样品处理液人体积，mL ； 250

8、- 样品处理后的总体积 mL 。表 3-1相当于氧化亚铜质量的葡萄糖、果糖、乳糖、转化糖质量表氧化葡果糖乳 糖转氧 化葡 萄果糖乳 糖转 化亚铜萄糖（含水）化糖亚铜糖（含水）糖11.34.65.17.75.278.834.037.453.635.812.45.15.68.55.779.934.537.954.436.313.55.66.19.36.281.135.038.555.236.814.66.06.710.06.782.235.539.055.937.415.86.57.210.87.283.336.039.656.737.916.97.07.711.57.784.436.540.15

9、7.538.418.07.58.312.38.285.637.040.758.238.919.18.08.813.18.786.737.541.259.039.420.38.59.313.89.287.838.041.759.840.021.48.99.914.69.788.938.542.360.540.522.59.410.415.410.290.139.042.861.341.023.69.910.916.110.791.239.543.462.141.524.810.411.516.911.292.340.043.962.842.025.910.912.017.711.793.440.

10、544.563.642.627.011.412.518.412.394.641.045.064.443.128.111.913.119.212.895.741.545.665.143.629.312.313.619.913.396.842.046.165.944.130.412.814.220.713.897.942.546.766.744.731.513.314.721.514.399.143.047.267.445.232.613.815.222.214.8100.243.547.868.245.733.814.315.823.015.3101.344.048.369.046.234.91

11、4.816.323.815.8102.544.548.969.746.736.015.316.824.516.3103.645.049.470.547.337.215.717.425.316.8104.745.550.071.347.838.316.217.926.117.3105.846.050.572.148.339.416.718.426.817.8107.046.551.172.848.840.517.219.027.618.3108.147.051.673.649.441.717.719.528.418.9109.247.552.274.449.942.818.220.129.119

12、.4110.348.052.775.150.443.918.720.629.919.9111.548.553.375.950.945.019.221.130.620.4112.649.053.876.751.546.219.721.731.420.9113.749.554.477.452.047.320.122.232.221.4114.850.054.978.252.548.420.622.832.921.9116.050.655.579.053.049.521.123.333.722.4117.151.156.079.753.650.721.623.834.522.9118.251.656

13、.680.554.151.822.124.435.223.5119.352.157.181.354.652.922.624.936.024.0120.552.657.782.155.254.023.125.436.824.5121.653.158.282.855.755.223.626.037.525.0122.753.658.883.656.256.324.126.538.325.5123.854.159.384.456.757.424.627.139.126.0125.054.659.985.157.358.525.127.639.826.5126.155.160.485.957.859.

14、725.628.240.627.0127.255.661.086.758.360.826.128.741.427.6128.356.161.687.458.961.926.529.242.128.1129.556.762.188.259.463.027.029.842.928.6130.657.262.789.059.964.227.530.343.729.1131.757.763.289.860.465.328.030.944.429.6132.858.263.890.561.066.428.531.445.230.1134.058.764.391.361.567.629.031.946.0

15、30.6135.159.264.992.162.068.729.532.546.731.2136.259.765.492.862.669.830.033.047.531.7137.460.266.093.663.170.930.533.648.332.2138.560.766.594.463.672.131.034.149.032.7139.661.367.195.264.273.231.534.749.833.2140.761.867.795.964.774.332.035.250.633.7141.962.368.296.765.275.432.535.851.334.3143.062.8

16、68.897.565.876.633.036.352.134.8144.163.369.398.266.377.733.536.852.935.3145.263.869.999.066.8氧化亚铜葡萄糖果糖乳 糖转化糖氧化亚铜葡萄糖果糖乳 糖转化糖（含水）（含水）146.464.370.499.867.4213.995.7104.3146.299.9147.564.971.0100.667.9215.096.3104.8147.0100.4148.665.471.6101.368.4216.296.8105.4147.7101.0149.765.972.1102.169.0217.397.31

17、06.0148.5101.5150.966.472.7102.969.5218.497.9106.6149.3102.1152.066.973.2103.670.0219.598.4107.1150.1102.6153.167.473.8104.470.6220.798.9107.7150.8103.2154.268.074.3105.271.1221.899.5108.3151.6103.7155.468.574.9106.071.6222.9100.0108.8152.4104.3156.569.075.5106.772.2224.0100.5109.4153.2104.8157.669.

18、576.0107.572.7225.2101.1110.0153.9105.4158.770.076.6108.373.2226.3101.6110.6154.7106.0159.970.577.1109.073.8227.4102.2111.1155.5106.5161.071.177.7109.874.3228.5102.7111.7156.3107.1162.171.678.3110.674.9229.7103.2112.3157.0107.6163.272.178.8111.475.4230.8103.8112.9157.8108.2164.472.679.4112.175.9231.

19、9104.3113.4158.0108.7165.573.180.0112.976.5233.1104.8114.0159.4109.3166.673.780.5113.777.0234.2105.4114.6160.2109.8167.874.281.1114.477.6235.3105.9115.2160.9110.4168.974.781.6115.278.1236.4106.5115.7161.7110.9170.075.282.2116.078.6237.6107.0116.3162.5111.5171.175.782.8116.879.2238.7107.5116.9163.311

20、2.1172.376.383.3117.579.7239.8108.1117.5164.0112.6173.476.883.9118.380.3240.9108.6118.0164.8113.2174.577.384.4119.180.8242.1109.2118.6165.6113.7175.677.885.0119.981.3243.1109.7119.2166.4114.3176.878.385.6120.681.9244.3110.2119.8167.1114.9177.978.986.1121.482.4245.4110.8120.3167.9115.4179.079.486.712

21、2.283.0246.6111.3120.9168.7116.0180.179.987.3122.983.5247.7111.9121.5169.5116.5181.380.487.8123.784.0248.8112.4122.1170.3117.1182.481.088.4124.584.6249.9112.9122.6171.0117.6183.581.589.0125.385.1251.1113.5123.2171.8118.2184.582.089.5126.085.7252.2114.0123.8172.6118.8185.882.590.1126.886.2253.3114.61

22、24.4173.4119.3186.983.190.6127.686.8254.4115.1125.0174.2119.9188.083.691.2128.487.3255.6115.7125.5174.9120.4189.184.191.8129.187.8256.7116.2126.1175.7121.0190.384.692.3129.988.4257.8116.7126.7176.5121.6191.485.292.9130.788.9258.9117.3127.3177.3122.1192.585.793.5131.589.5260.1117.8127.9178.1122.7193.

23、686.294.0132.290.0261.2118.4128.4178.8123.3194.886.794.6133.090.6262.3118.9129.0179.6123.8195.987.395.2133.891.1263.4119.5129.6180.4124.4197.087.895.7134.691.7264.6120.0130.2181.2124.9198.188.396.3135.392.2265.7120.6130.8181.9125.5199.388.996.9136.192.8266.8121.1131.3182.7126.1200.489.497.4136.993.3

24、268.0121.7131.9183.5126.6201.589.998.0137.793.8269.1122.2132.5184.3127.2202.790.498.6138.494.4270.2122.7133.1185.1127.8203.891.099.2139.294.9271.3123.3133.7185.8128.3204.991.599.7140.095.5272.5123.8134.2186.6128.9206.092.0100.3140.896.0273.6124.4134.8187.4129.5207.292.6100.9141.596.6274.7124.9135.41

25、88.2130.0208.393.1101.4142.397.1275.8125.5136.0189.0130.6209.493.6102.0143.197.7277.0126.0136.6189.7131.2210.594.2102.6143.998.2278.1126.6137.2190.5131.7211.794.7103.1144.698.8279.2127.1137.7191.3132.3212.895.2103.7145.499.3280.3127.7138.3192.1132.9氧化亚铜葡萄糖果糖乳 糖转化糖氧化亚铜葡萄糖果糖乳 糖转化糖（含水）（含水）281.5128.2138

26、.9192.9133.4349.0161.9174.4239.8168.0282.6128.8139.5193.6134.0350.1162.5175.0240.6168.6283.7129.3140.1194.4134.6351.3163.0175.6241.4169.2284.8129.9140.7195.2135.1352.4163.6176.2242.2169.8286.0130.4141.3196.0135.7353.5164.2176.8243.0170.4287.1131.0141.8196.8136.3354.6164.7177.4243.7171.0288.2131.6142

27、.4197.5136.8355.8165.3178.0244.5171.6289.3132.1143.0198.3137.4356.9165.9178.6245.3172.2290.5132.7143.6199.1138.0358.0166.5179.2246.1172.8291.6133.2144.2199.9138.6359.1167.0179.8246.9173.3292.7133.8144.8200.7139.1360.3167.6180.4247.7173.9293.8134.3145.4201.4139.7361.4168.2181.0248.5174.5295.0134.9145

28、.9202.2140.3362.5168.8181.6249.2175.1296.1135.4146.5203.0140.8363.6169.3182.2250.0175.7297.2136.0147.1203.8141.4364.8169.9182.8250.8176.3298.3136.5147.7204.6142.0365.9170.5183.4251.6176.9299.5137.1148.3205.3142.6367.0171.1184.0252.4177.5300.6137.7148.9206.1143.1368.2171.6184.6253.2178.1301.7138.2149

29、.5206.9143.7369.3172.2185.2253.9178.7302.9138.8150.1207.7144.3370.4172.8185.8254.7179.2304.0139.3150.6208.5144.8371.5173.4186.4255.5179.8305.1139.9151.2209.2145.4372.7173.9187.0256.3180.4306.2140.4151.8210.0146.0373.8174.5187.6257.1181.0307.4141.0152.4210.8146.6374.9175.1188.2257.9181.6308.5141.6153

30、.0211.6147.1376.0175.7188.8258.7182.2309.6142.1153.6212.4147.7377.2176.3189.4259.4182.8310.7142.7154.2213.2148.3378.3176.8190.1260.2183.4311.9143.2154.8214.0148.9379.4177.4190.7261.0184.0313.0143.8155.4214.7149.4380.5178.0191.3261.8184.6314.1144.4156.0215.5150.0381.7178.6191.9262.6185.2315.2144.9156

31、.5216.3150.6382.8179.2192.5263.4185.8316.4145.5157.1217.1151.2383.9179.7193.1264.2186.4317.5146.0157.7217.9151.8385.0180.3193.7265.0187.0318.6146.6158.3218.7152.3386.2180.9194.3265.8187.6319.7147.2158.9219.4152.9387.3181.5194.9266.6188.2320.9147.7159.5220.2153.5388.4182.1195.5267.4188.8322.0148.3160

32、.1221.0154.1389.5182.7196.1268.1189.4323.1148.8160.7221.8154.6390.7183.2196.7268.9190.0324.2149.4161.3222.6155.2391.8183.8197.3269.7190.6325.4150.0161.9223.3155.8392.9184.4197.9270.5191.2326.5150.5162.5224.1156.4394.0185.0198.5271.3191.8327.6151.1163.1224.9157.0395.2185.6199.2272.1192.4328.7151.7163

33、.7225.7157.5396.3186.2199.8272.9193.0329.9152.2164.3226.5158.1397.4186.8200.4273.7193.6331.0152.8164.9227.3158.7398.5187.3201.0274.4194.2332.1153.4165.4228.0159.3399.7187.9201.6275.2194.8333.3153.9166.0228.8159.9400.8188.5202.2276.0195.4334.4154.5166.6229.6160.5401.9189.1202.8276.8196.0335.5155.1167

34、.2230.4161.0403.1189.7203.4277.6196.6336.6155.6167.8231.2161.6404.2190.3204.0278.4197.2337.8156.2168.4232.0162.2405.3190.9204.7279.2197.8338.9156.8169.0232.7162.8406.4191.5205.3280.0198.4340.0157.3169.6233.5163.4407.6192.0205.9280.8199.0341.1157.9170.2234.3164.0408.7192.6206.5281.6199.6342.3158.5170

35、.8235.1164.5409.8193.2207.1282.4200.2343.4159.0171.4235.9165.1410.9193.8207.7283.2200.8344.5159.6172.0236.7165.7412.1194.4208.3284.0201.4345.6160.2172.6237.4166.3413.2195.0209.0284.8202.0346.8160.7173.2238.2166.9414.3195.6209.6285.6202.6347.9161.3173.8239.0167.5415.4196.2210.2286.3203.2氧化亚铜葡萄糖果糖乳糖转化

36、糖氧化亚铜葡萄糖果糖乳糖转化糖（含水）（含水）416.6196.8210.8287.1203.8453.7216.5231.3313.4224.1417.7197.4211.4287.9204.4454.8217.1232.0314.2224.7418.8198.0212.0288.7205.0456.0217.8232.6315.0225.4419.9198.5212.6289.5205.7457.1218.4233.2315.9226.0421.1199.1213.3290.3206.3458.2219.0233.9316.7226.6422.2199.7213.9291.1206.945

37、9.3219.6234.5317.5227.2423.3200.3214.5291.9207.5460.5220.1235.1318.3227.9424.4200.9215.1292.7208.1461.6220.8235.8319.1228.5425.6201.5215.7293.5208.7462.7221.4236.4319.9229.1426.7202.1216.3294.3209.3463.8222.0237.1320.7229.7427.8202.7217.0295.0209.9465.0222.6237.7321.6230.4428.9203.3217.6295.8210.546

38、6.1223.3238.4322.4231.0430.1203.9218.2296.6211.1467.2223.9239.0323.2231.7431.2204.5218.8297.4211.8468.4224.5239.7324.0232.3432.3205.1219.5298.2212.4469.5225.1240.3324.9232.9433.5205.1220.1299.0213.0470.6225.7241.0325.7233.6434.6206.3220.7299.8213.6471.7226.3241.6326.5234.2435.7206.9221.3300.6214.247

39、2.9227.0242.2327.4234.8436.8207.5221.9301.4214.8474.0227.6242.9328.2235.5438.0208.1222.6302.2215.4475.1228.2243.6329.1236.1439.1208.7232.2303.0216.0476.2228.8244.3329.9236.8440.2209.3223.8303.8216.7477.4229.5244.9330.1237.5441.3209.9224.4304.6217.3478.5230.1245.6331.7238.1442.5210.5225.1305.4217.947

40、9.6230.7246.3332.6238.8443.6211.1225.7306.2218.5480.7231.4247.0333.5239.5444.7211.7226.3307.0219.1481.9232.0247.8334.4240.2445.8212.3226.9307.8219.9483.0232.7248.5335.3240.8447.0212.9227.6308.6220.4484.1233.3249.2336.3241.5448.1213.5228.2309.4221.0485.2234.0250.0337.3242.3449.2214.1228.8310.2221.648

41、6.4234.7250.8338.3243.0450.3214.7229.4311.0222.2487.5235.3251.6339.4243.8451.5215.3230.1311.8222.9488.6236.1252.7340.7244.7452.6215.9230.7312.6223.5489.7236.9253.7342.0245.86、说明（1）还原糖能在碱性溶液中将两价铜离子还原为棕红色的氧化亚铜沉淀， 而糖本身被 211.7 氧化为相应的羧酸。这是还原糖定量测定的基础。（ 2）氧化亚铜沉淀的量与还原糖的量成正比，计算氧化亚铜沉淀方法很多， 高酸钾滴定法是其中之一。当样品中的还原

42、糖与 Cu2+作用后，生成定量的氧化亚铜沉淀，收集、清洗沉淀，将其置于硫酸中，加入硫酸铁与氧化亚铜作用，硫酸铁还原成硫酸亚铁，用高锰酸钾标准溶液滴定生成的硫酸亚铁，终点为粉红色。根据消耗的高锰酸钾量可计算氧化亚铜质量，再表 3-1 可计算出样品中还原糖的量。（ 3）样品的处理：应除去蛋白质、脂肪、乙醇、二氧化碳、纤维素、淀粉等。（ 4）还原糖与碱性酒石酸铜试剂作用， 必须加热至沸腾下进行， 因此加热至沸时间及保持沸腾时间是需要严格控制的条件，并保持一致。（ 5）煮沸后溶液应保持蓝色，使碱性酒石酸铜过量，使还原糖完全反应。（ 6）在古氏坩埚中铺好精制石棉，必须密实，以免使氧化亚铜沉淀损失。（ 7

43、）高锰酸钾法测定食品中的还原糖测定结果准确性较好， 但操作繁琐费时， 并在抽滤过程在应注意防止氧化亚铜沉淀暴露于空气中而氧化，将沉淀终保持在液面下，严格掌握反应条件。（二）直接滴定法1.原理样品经除去蛋白质后， 在加热条件下， 直接滴定标定过的碱性酒石酸铜溶液， 以次甲基蓝作指示剂。 根据磁品液消耗体积， 计算还原糖量 （用还原糖标准溶液标定碱性酒石酸铜溶液）。2.试剂（ 1）碱性酒石酸铜甲液：称取 15.00g 硫酸铜（ CuSO4?5HO 2）及 0.05g 次甲基蓝，溶于水中并稀释至 1000mL 。（2）碱性酒石酸铜乙液：称取50.00g 酒石酸钾钠及75g 氢氧化钠，溶于水中，再加入4g亚铁氰化钾，完全溶解后，用水稀释至1000mL ，贮存于橡胶塞玻璃瓶中。（3）乙酸锌溶液：称取 21.9g 乙酸锌，加 3mL 冰乙酸，加水溶解并稀释至100mL 。（ 4）亚铁氰化钾溶液（ 106g/L ）。（ 5）盐酸。（ 6）葡萄糖标准溶液：精密称取1.000g 经过 98-100 干燥至恒量的纯葡萄糖，加水溶解后加入 5mL 盐酸，并以水稀释至1000mL 。此溶液每