Combining the practical problems encountered by the author in daily work, using the commonly used feed ingredients such as fishmeal, soybean meal and soybean powder as the research object, borrowing the fat analyzer, respectively, three factors affecting the fat determination results (sample particles, extraction solvent, pumping) The time for analysis and discussion of the test, the preliminary results show that: the sample particles are ground to less than 1.00mm, the fat extraction effect can meet the current national standard GB/T 6433-1994; to eliminate safety hazards, the boiling point range can be selected For petroleum ether of 30~60 °C instead of ether as extraction solvent; extraction time is recommended for 60min recommended by the manual of the automatic fat analyzer (soaking for 15min, rinsing for 45min). Regulating test fat is the second most important quality item in feed and its raw materials, and its content is generally determined by the national standard GB/T 6433-1994. The Soxhlet extraction principle is used to influence the main factors of the test results. Sample granules, extraction solvent, extraction time, accuracy of the balance and oven, performance of the extraction unit, ambient temperature, cleanliness of the instrument used, moisture level in the sample, operator level, etc. In the specific operation process of daily testing, the author sometimes encounters the phenomenon that the detection result is unstable due to certain factors. In order to explore the reasons for this phenomenon, we analyzed and studied fishmeal, soybean meal and soybean powder for the three main influencing factors of sample granules, extraction solvent and extraction time. The results are reported below.
1 Materials and methods
1.1 Sample collection and preparation Fishmeal, soybean meal and soybean powder imported from Guangzhou Huangpu Port were randomly selected. The sample was extracted and prepared according to SN/T 0800.1-1999 “Import and Export Grain and Oil, Feed Inspection Sampling and Sample Preparation Methodâ€.
1.2 Main instruments and reagents Wheat mill, KNIFETEC Model 1095; Standard sieve, BS 410/1986; Crude fat analyzer, Soxtec Avanti 2050; Oven, Oriental B; Crude balance, PB5001, Sensing 0.1g; Analytical balance, AE163, sensible 0.0001g; The reagents required are mainly analytical ether and petroleum ether (30#) with a boiling range of 30~60 °C.
1.3 Test method According to the actual problems encountered in daily inspection work, for different sample particles, different extraction solvents, different extraction time, refer to the current national standard GB/T6433-1994 "Method for determination of feed fat fat" for fat Determination of content.
1.4 Judging basis The validity of the measurement result data is evaluated according to the current national standard GB/T 6433-1994 "Methods for the determination of crude fat in feed". The national standard stipulates: When the fat content is greater than or equal to 10%, the relative deviation is allowed to be 3%; when the fat content is less than 10%, the relative deviation is allowed to be 5%.
1.5 Main calculation formula
1.5.1 Fat content Fat content (%) = (constant weight of aluminum cup after extraction - constant weight of aluminum cup before pumping) / air dry sample weight × 100
1.5.2 Relative deviation relative deviation = (measured value - average value) / average value × 100%
2 Results and analysis
2.1 The effect of different sample particle size on feed fat extraction In the current national standard GB/T 6433-1994 "Method for determination of feed fat", the extraction of fat components is mainly carried out by immersing the sample in the extraction solvent. Solvent wash samples are used to achieve this. The size of the sample particles directly affects the breadth and depth of contact between the sample and the extraction solvent, which will directly affect the extraction (extraction) efficiency of the fat component of the sample. Usually under the same test conditions, the smaller the sample particles, the higher the extraction (extraction) efficiency of the fat component, and the measured fat content of the sample will be higher. In daily inspection work, it is sometimes suspected that the test results are low due to insufficient sample grinding. Based on the 0.45mm (40 mesh) particle size specified in the current national standard GB/T 6433-1994, the fishmeal sample (ie, without any grinding) and the daily grinding method (KNIFETEC 1095 grinding machine, 2s) are randomly selected. Or 5s mode, the number of runs depends on the sample properties.) The prepared soybean meal and soybean meal samples were used as test groups. The particle size distribution of the samples was checked by using a 1 mm (18 mesh), 0.45 mm (40 mesh), 0.212 mm (70 mesh) standard sieve for all experimental samples, as shown in Table 1. For the sample to be used as the reference group, if there is an increase in the grinding time of the 0.45 mm sieve, until the 0.45 mm sieve is completely passed. Then, all the samples were extracted with diethyl ether, soaked for 15 minutes, and rinsed for 45 minutes for fat content detection.
As can be seen from the “particle size distribution†column, as a reference group of soybean powder, soybean meal, fish meal samples, we strictly prepare according to the current national standard GB/T 6433-1994, to 100% over 0.45mm standard sieve, as a test The samples of the group, soybean powder and soybean meal were treated by daily grinding method, and the 0.45mm sieve materials were 52% and 41% respectively, of which 1.00mm or more of the particles accounted for 2% and 4% respectively. The fishmeal samples were unloaded and unloaded, without any Grinding, 0.45mm sieve material is 36%, of which 1.00mm or more particles account for 5%. The “Ether Extraction Effect†column shows that the relative deviation between each pair of parallel samples of soybean meal, soybean meal and fish meal is far lower than the current national standard GB/T6433-1994. The specified allowable relative deviation, which indicates that the sample prepared by daily grinding method (SZF-06A model in fat analyzer, 2s or 5s mode, depending on sample properties), although not meeting 100% over 0.45mm standard The requirements of the sieve, but the extraction effect of the two is within the experimental error range. The results suggest that for soybean powder, soybean meal and fishmeal samples, the particles are ground to less than 1.00mm, and the fat extraction effect can reach the current national standard GB/T 6433-1994.
1 Materials and methods
1.1 Sample collection and preparation Fishmeal, soybean meal and soybean powder imported from Guangzhou Huangpu Port were randomly selected. The sample was extracted and prepared according to SN/T 0800.1-1999 “Import and Export Grain and Oil, Feed Inspection Sampling and Sample Preparation Methodâ€.
1.2 Main instruments and reagents Wheat mill, KNIFETEC Model 1095; Standard sieve, BS 410/1986; Crude fat analyzer, Soxtec Avanti 2050; Oven, Oriental B; Crude balance, PB5001, Sensing 0.1g; Analytical balance, AE163, sensible 0.0001g; The reagents required are mainly analytical ether and petroleum ether (30#) with a boiling range of 30~60 °C.
1.3 Test method According to the actual problems encountered in daily inspection work, for different sample particles, different extraction solvents, different extraction time, refer to the current national standard GB/T6433-1994 "Method for determination of feed fat fat" for fat Determination of content.
1.4 Judging basis The validity of the measurement result data is evaluated according to the current national standard GB/T 6433-1994 "Methods for the determination of crude fat in feed". The national standard stipulates: When the fat content is greater than or equal to 10%, the relative deviation is allowed to be 3%; when the fat content is less than 10%, the relative deviation is allowed to be 5%.
1.5 Main calculation formula
1.5.1 Fat content Fat content (%) = (constant weight of aluminum cup after extraction - constant weight of aluminum cup before pumping) / air dry sample weight × 100
1.5.2 Relative deviation relative deviation = (measured value - average value) / average value × 100%
2 Results and analysis
2.1 The effect of different sample particle size on feed fat extraction In the current national standard GB/T 6433-1994 "Method for determination of feed fat", the extraction of fat components is mainly carried out by immersing the sample in the extraction solvent. Solvent wash samples are used to achieve this. The size of the sample particles directly affects the breadth and depth of contact between the sample and the extraction solvent, which will directly affect the extraction (extraction) efficiency of the fat component of the sample. Usually under the same test conditions, the smaller the sample particles, the higher the extraction (extraction) efficiency of the fat component, and the measured fat content of the sample will be higher. In daily inspection work, it is sometimes suspected that the test results are low due to insufficient sample grinding. Based on the 0.45mm (40 mesh) particle size specified in the current national standard GB/T 6433-1994, the fishmeal sample (ie, without any grinding) and the daily grinding method (KNIFETEC 1095 grinding machine, 2s) are randomly selected. Or 5s mode, the number of runs depends on the sample properties.) The prepared soybean meal and soybean meal samples were used as test groups. The particle size distribution of the samples was checked by using a 1 mm (18 mesh), 0.45 mm (40 mesh), 0.212 mm (70 mesh) standard sieve for all experimental samples, as shown in Table 1. For the sample to be used as the reference group, if there is an increase in the grinding time of the 0.45 mm sieve, until the 0.45 mm sieve is completely passed. Then, all the samples were extracted with diethyl ether, soaked for 15 minutes, and rinsed for 45 minutes for fat content detection.
As can be seen from the “particle size distribution†column, as a reference group of soybean powder, soybean meal, fish meal samples, we strictly prepare according to the current national standard GB/T 6433-1994, to 100% over 0.45mm standard sieve, as a test The samples of the group, soybean powder and soybean meal were treated by daily grinding method, and the 0.45mm sieve materials were 52% and 41% respectively, of which 1.00mm or more of the particles accounted for 2% and 4% respectively. The fishmeal samples were unloaded and unloaded, without any Grinding, 0.45mm sieve material is 36%, of which 1.00mm or more particles account for 5%. The “Ether Extraction Effect†column shows that the relative deviation between each pair of parallel samples of soybean meal, soybean meal and fish meal is far lower than the current national standard GB/T6433-1994. The specified allowable relative deviation, which indicates that the sample prepared by daily grinding method (SZF-06A model in fat analyzer, 2s or 5s mode, depending on sample properties), although not meeting 100% over 0.45mm standard The requirements of the sieve, but the extraction effect of the two is within the experimental error range. The results suggest that for soybean powder, soybean meal and fishmeal samples, the particles are ground to less than 1.00mm, and the fat extraction effect can reach the current national standard GB/T 6433-1994.
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