Annex White book.pdf

A4.1.2.7 Ethereal extractEthereal extract is the aggregate of substances obtained from petroleumether under the conditions defined by in the following method.It can be applied with continuous extraction or with Soxhlet extractionsystem. A paper filter cartridge is placed in the continuous extractionapparatus or in the Soxhlet system and a dried sample fraction of 1 gis accurately weighted (variation 1 mg). The cartridge is placed in theextractor. 50 ml petroleum ether are added in the extraction glass or150 ml in the round bottle of the Soxhlet system. Extraction lasts 1½hour in the continuous extraction apparatus and 8 hours in the Soxhletsystem. Moving forward to the evaporation stage, we place the glass ofthe extraction appliance or the bottle in a drying furnace and heat it for30 minutes at 103 o C ±2 o C. The sample is then cooled in the dryer untilit reaches room temperature and can be weighed.The ethereal extract rendered in mass percentage of the initialdried sample mass is calculated according to following formula: WEE =(P1– Po/ PM) x 100%. P1 is the glass or bottle weight together with theethereal extract, Po is the sole glass or bottle weight, PM is the sampleweight. The outcome is rendered in double decimal percentage (m/m).A4.1.2.8 NitrogenThe procedure for nitrogen determination is described in the ISO1871:1975 “Agricultural food products – General directions for the determinationof nitrogen by the Kjeldhal method”. A sample of 1 g isweighted accurately in the digester tube (variation 10 mg). Three partsof Kjeldhal catalyst (Cu-Se)(1,5% CiSO4 • 5H2O + 2%) are placed ineach tube. 25 ml of acid sulphide is placed in each tube. The sampleis heated at 420oC. When the sample reaches 420oC, the temperatureis held constant for half hour keeping the sample clean and clear. Weremove the tubes from the unit and leave it to for 15 minutes to cool atroom temperature. 50 ml of distilled water are added in each tube. Thecool tube is attached to the distiller and 120 ml of sodium hydroxideare added at 32%. The distiller is set on, concentrating 150 ml extractin a 250 ml Erlenmeyer bottle that contains 25 ml of boric acid at 4%with indicator. 150 ml of the extract are enriched with hydrochloric acid0,25N until red color appears.The nitrogen percentage of the sample is calculated according tofollowing formula: Nitrogen% = (N x v) x (1,4 / P). v is the hydrochloricacid volume 0,25N in ml, P is the weight of the sample in gram. Theoutcome is rendered in double decimal percentage (m/m).151