What can cause HIGHER than expected Dietary Fiber results?
Static electricity during the weighting process: The largest contributor to poor results is the effect of static electricity on the weighing process. Because plastic gloves can contribute to static electricity, only use anti-static gloves. To eliminate static electricity while the bag is being weighed, you MUST use the Bag Weigh Holder (Part #: TDF52) during the weighing process.
Moisture control: The MoistureStop Desiccant Pouches (Part #: X45) should be used to minimize the effect of moisture on the weighing process. Verify that the desiccant pouches are in good condition (no holes and the zipper is functioning) and the packets within the desiccant pouches are still working (they should be a blue color).
BLANK values: BLANK values are used in the IDF, SDF, and TDF calculations. If you're not using the BLANK values provided by ANKOM, try using them in your calculation.
Chemicals: Because the MES-TRIS buffer can degrade in performance due to bacteria growth, making this solution daily is important. Clean all containers daily and refill them with fresh solutions. Make sure that each container is securely connected to the appropriate supply tube on the instrument.
Protein and Ash Determinations: Because protein and ash values are part of the IDF, SDF, and TDF calculations, verify that your protein and ash systems are working properly and providing the expected results.
Protein and Ash Preparation: See the procedures detailed in the TDF Operator's Manual (Ash Determination section) for preparing the bags for ashing. To prepare the ANKOM Filter Bags for protein analysis via Kjeldahl, refer to the TDF Operator’s Manual.
To prepare the ANKOM Filter Bags for analysis via combustion methods, cut open the Filter Bag and lightly scrape or brush the particles of sample residue and DE into a small mortar. Grind the mixture with the pestle until homogenous. Take several aliquots of the mixture and run them through your dumas. Use the average protein value of the aliquots for the TDF calculation.
Various manufacturer options are available for nitrogen determination using the combustion method. Contact your combustion/dumas manufacturer for further information regarding specific settings and recommendations regarding N2 determinations that involve DE.
Drying: Bags must be dried at 105° C to constant weight (90 minutes).
Acetone rinses: See the procedure detailed in the TDF Operator's Manual (IDF/SDF Analysis section) for performing the acetone rinses.
Sample size: Using sample sizes larger than the recommended size can cause higher results. ANKOM recommends using a sample size of 0.5 g (+ / - 0.05g) however a larger sample up to 1g is acceptable.
Digestion times: For demonstration and diagnostic purposes, you can set the digestion times to non-standard values through the Touch Screen Display. Results will be inaccurate if the instrument is run using non-standard digestion times.
Technician variability: Confirm that all technicians are following the procedures detailed in the TDF Operator's Manual to avoid any variation in results associated with different operators.
pH: Typically, the pH reading should be between 3.5 and 6 before correction. If the pH reading is outside of these values check the acid and buffer solutions, and check that tubing is connected to the proper containers.
Enzyme delivery: View the enzyme containers while the enzymes are being delivered. The fluid level should go down. If the enzymes are not being delivered properly, contact ANKOM at https://www.ankom.com/contact/technical-services or (315) 986-8090.
Temperature control: To verify that the temperature is being properly controlled, follow the procedure detailed in the TDF Operator's Manual (QC / Calibration section).
Mixing: To verify that the mixing is being properly controlled, follow the procedure detailed in the TDF Operator's Manual (QC / Calibration section).
Sample with bound fat: Certain highly processed samples, such as dried pet food, contain fat that is complexed in the matrix. Defatting prior to TDF analysis, as described in the methods, does not sufficiently remove complexed fat. Residual fat interferes with the enzymatic digestion in TDF analysis, resulting in artificially higher fiber results. We recommend the following two methods: (i) Grind the sample to 0.3-0.5mm (to improve penetration of the solvent during defatting). Then, extract the sample three times with hexane (25ml/g sample) at 50C for 10min, while stirring. Record the loss of weight due to fat removal and make the appropriate correction to final value for dietary fiber; or (ii) defat samples in XT4 bags with hexane (see attached procedure).