Precautions in the determination of crude fat

In crude fat determination, the most classic is based on the Soxhlet extraction principle, using the gravimetric method to determine the fat content. The SZF-06A Crude Fat Analyzer, SZF-06B Crude Fat Analyzer, and SZF-06 Crude Fat Analyzer that are currently on the market are based on the Soxhlet extraction principle. Zhejiang Top Instrument Co., Ltd. produces various types of crude fat analyzers, including SZF-06A Crude Fat Analyzer, SZF-06B Crude Fat Analyzer, SZF-06 Crude Fat Analyzer, and SZF-06C Crude Fat Analyzer.

Extracting method is the most common method for determining crude fat content. The principle of gravimetric method is used in the extraction method. That is, the sample is first dissolved in a fat solvent, then the fat cycle is extracted using a Soxhlet extractor, and finally the extract is measured again. Before and after the instrument's weight is poor, that is, the weight of fat. The extraction method requires a rigorous experimental process. If the process is not mastered, it may seriously affect the final fat content. Below, we mainly look at the matters that should be taken into account when using Soxhlet extraction to determine fat.

(1) The sample should be dried and then studied carefully. The filter paper tube of the sample must be tight and cannot be leaked out of the sample, otherwise it will be redone.

(2) The height of the filter paper tube should not exceed the return bend, otherwise ether cannot easily penetrate the sample, and fat cannot be completely presented, causing errors.

(3) When encountering a sample containing a large amount of sugar and dextrin, first treat it with cold water and wait until it is dried and then put the filter paper into the extractor.

(4) The temperature of the water bath during extraction should not be too high. Generally, the boiling of ethyl ether can begin (about 45°C or so). The reflow speed is preferably 8-12 times per hour.

(5) The ether used must be anhydrous ether. If it contains moisture, the sugar and inorganic substances in the sample may be extracted, causing errors.

(6) For the determination of fat in the sample, the fat content of the original sample can be calculated as follows.

Fat () = (W1-W0)/W* (100-A)

Fat (%) = The salt tolerance of the product is improved to varying degrees. Among them, Zhang and Blumwald (2001) and Zhang et al. (2001) reported that transgenic ToNHX1 tomato could tolerate 200 mmol/L sodium chloride and accumulate absorbed sodium in the leaves without affecting fruit quality. These studies indicate that the selective absorption of ions and genetic engineering of transmembrane transport are effective ways to improve plant salt tolerance.

A-100 grams of water content (grams).

(7) The upper end of the condenser is preferably connected to a calcium chloride drying tube, which not only prevents the entry of moisture in the air, but also prevents the ether from being volatilized in the air, thus preventing contamination of the laboratory's tiny ambient air. If there is no such device, a stick of dry absorbent cotton balls can also be added.

(8) If no anhydrous ether can be prepared by itself, the preparation method is as follows: In 1000 ml of ether, add 50 g of anhydrous gypsum, shake it several times, and let it stand for more than 10 hours to distill, collect the distillate below 35°C, Apply it.

(9) When the extraction bottle is dried in an oven, the mouth of the bottle is inclined to one side at 45°C to allow the volatile matter ether to easily form a convection with the air.

(10) Samples and ether extracts should not be dried too long in the oven because some very unsaturated fatty acids are easily oxidized in the heating process to ether-insoluble substances; moderately unsaturated fatty acids are easily oxidized by heat. Weight increase. In the absence of a vacuum drying box, it can be dried at 100-105°C for 1.5-3 hours.

(11) If there is no ether or anhydrous ether, it can be extracted with petroleum ether. The boiling point of petroleum ether is 30-60°C.

(12) When using volatile ether or petroleum ether, avoid direct heating. Application of electric sets of electric water baths, light bulbs and so on.