食品分析实验报告DNS

1、date: 2011-05-22experimental title： determination of reducing sugar content一dns methodprinciple： determi nation of reduci ng sugar is the basic method for the determi nation of sugar content. reducing sugar is free aldehyde or ketone contai ning sugar. mono saccharides are reduci ng sugars, disaccha

2、rides and polysaccharides are not necessarily reducing sugar. lactose and maltose are reducing sugars, sucrose and starch non-reducing sugar. the solubility of the d iff ere nt use of sugar, you can sample mono saccharide, disaccharides, and polysaccharides were extracted (not reduci ng) disaccharid

3、es and polysaccharides can be double-acid hydrolysis method. outing to double sugar and reduci ng the degradati on into a single sugar determi nation. in the sample were calculated reduci ng sugars con tent. con tent of reducing sugar with glucose in stead.procedures:cq reagent preparation:> dns

4、reagent configuration1) in naoh solution, by adding dinitrosalicylic acid solution and potassium sodium titrate2) naoh solution by adding crystalline phenol, add water to dissolve, and finally set the volume.3) take (2) 69ml anhydrous sodium sulfite 6.9 g, to dissolve4) to (3) into (1), the complete

5、ly dissolved, stored in brown reagent bottle. at room temperature, place 7-10 days later to use> glucose standard solution configurationaccurately weigh 100 mg of analytical grade glucose (pre-dried at 105 °c to constant weight), dissolved in distilled water with a small amount of volume to1

6、 ooml, refrigerator use.q operation methods1) take six clean test tubes, adding various reagents in the following orderlglucose solution 11.distilled water 111.dns reagentx012345the amount of sugar contai ne d(mg)00.81.0distilled water(ml)0.20dns reagent3mldistilled water(ml)2.5ml

7、heati ngheat 5 minutes(90° c)cooli ngimmediately with the flow of cold water to cooloptical density0.761.0861.5222.0532.7833.342(od)results:mix the above solution, each tube after the photoelectric colorimeter (510 nm) for colorimetric determination of the blank control solution with zero adjus

8、tment, recording the optical density value. glucose concentration as the abscissa, the ordinate is optical density standard curve plotted.discussion:in alkaline solution, the reducing sugar into ene glycol (1,2 - ene glycol).ene glycol of various oxidants such as iron cyanide easily, 3,5 - dinitrosa

9、licylic acid and cu2 + oxidized to sugar acids. cyanide and dynatron-salicylic acid salt reduction is the basis for quantitative determination of reducing sugar. dinitrosalicylic acid reducing sugar and alkaline reagent is heated together to produce a brown-red amino compounds, at a certain concentr

10、ation range, the depth of the color brown material degree proportional to the amount of reducing sugar. therefore, we can determine the sample amount of reducing sugar and total suga匸when you configure dns reagent, to note 3,5 - dinitrosalicylic acid and naoh, adding time must be very close, or to j

11、oin the naoh. or will cause the precipitation of insoluble, leading to the preparation of the solution to fail. and the configuration process, the solution heating temperature should not exceed 50 degrees celsius.when you configure dns to add potassium sodium titrate solution was to remove the insid

12、e of the dissolved oxygen, dissolved oxygen and more so, shorten the shelf life of a sample at different times, the results of the determination of large differences (sugar dissolved oxygen serious interference color). anhydrous sodium sulfite is stable color, and phenol with the color of the color

13、is more stableconclusion:in the 3,5 - dinitrosalicylic acid reducing sugar in colorimeters, nds is the main reagent. it is red and brown sugar reaction material. but the color just the words with the dns, not a linear relationship between color and concentration. or linear poo匚 add the aim of increa

14、sing dns phenol color reagent for quantitative determination of the linear relationship between reducing sugar concentration. the presence of phenol is essential. nds does not participate in the color of phenol not quantitative. however, due to the air easily oxidized phenol case, the remaining phen

15、ol in order to ensure that all steps are not oxidized. adding a sufficient amount of potassium sodium tartrate is to eliminate the impact of dissolved oxygen, sodium sulfite can be added to further enhance the stability of reagents.dns standard curve preparation, set a concentration gradient when th

16、e content should be zero dns reagent as reference instead of using dns as a reference.standard curve should be within the concentration range in a linear relationship. best r = 0.999 or more. this of course does not rule out the possibility of a large concentration range. dns and the role of the linear relationship between reducing sugar and the amount of reagent have nothing to do. 3,5 - dinitrosalicylic acid