a. The biggest and most common cause of artificially high crude fat results is an incomplete drying in the pre-extraction phase. Because our technique uses the indirect method of determining fat (weighing what is left over after the fat has been extracted), it is vital that all the moisture in the sample is removed before the extraction.

You should regularly check your moisture (dry matter) values when performing fat extraction using ANKOM instrumentation. This can be done by simply weighing and recording the weight of the Filter Bag prior to filling it with sample.  After the three hour drying step with the oven set at 100° - 105 ° C, place the bags in a desiccant pouch, allow to cool, and re-weigh the bags plus sample and use the following formula to calculate the moisture value:

100 x ((Filter Bag Weight + Sample Weight) - Weight After Drying) / Sample Weight)

Low moisture values tend to be due to:

  • Not using or incorrectly using a desiccant pouch

  • Incorrect oven temperature settings

  • Hot or cold spots in the oven

  • The oven is being over loaded with other samples or glassware 

We would suggest each lab regularly test this analysis by utilizing a check sample or lab standard.

As indicated above, all samples should be dried at 100 ° - 105 ° C for three hours. Most samples can be placed directly into the oven on a tray, in an ANKOM Multi-bag holder (part #H37), or any other device that will keep the bags in place during the drying process. However, the pre-extraction drying of high fat samples (meat > 20%, plants > 40%) requires the use of weigh tins. These sample types tend to have oil that begins to liquefy during the drying process. This oil can seep to the outside surface of the bag and/or drip from the bag. By placing each high fat sample in a pre-weighed weigh tin, the samples can be isolated from touching other bags and transferring oil.  In addition, any oil that drips from the bag will be captured by the weigh tin.

At the end of the drying process, the weigh tins are placed in a Weigh Tin Desiccator (part # X49), allowed to cool, and weighed back with the XT4 Filter Bags still in the weigh tins.  The tins are then discarded and the samples are extracted in the XT Extractor.

b. Yes, all samples should be treated the same during the drying process.