Enzymatic-Gravimetric Dietary Fiber Analyzer

What is the Enzymatic-Gravimetric Dietary Fiber Analyzer?

An enzymatic-gravimetric dietary fiber analyzer removes starch and protein with enzymes, precipitates soluble fiber with alcohol and weighs the residue. It provides the total dietary fiber value used for nutrition labelling of foods and beverages.

Overview

The sample is treated sequentially with heat-stable alpha-amylase, protease and amyloglucosidase at controlled temperatures and pH to digest starch and protein. Ethanol is then added to precipitate soluble fiber together with the insoluble fraction, and the mixture is filtered through a fritted crucible. The residue is dried and weighed, and duplicate portions of the residue are analysed for protein and ash, which are subtracted to give total dietary fiber. Some procedures separate insoluble and soluble fractions by filtering before precipitation and by precipitating the filtrate separately. Runs take about one to two working days, and each batch needs enzyme blanks and internal control samples because enzyme activity varies between lots and affects the result.

How does it work?

Fiber is a family of carbohydrate polymers and lignin that resist digestion, so methods measure an operationally defined residue. The Weende crude fiber method digests the sample sequentially with dilute acid and alkali, then filters, dries, ignites and weighs the residue, capturing cellulose and part of the lignin. Detergent methods use neutral or acid detergent solutions to isolate neutral detergent fiber, which includes hemicellulose, cellulose and lignin, or acid detergent fiber, which excludes hemicellulose. Enzymatic-gravimetric dietary fiber methods treat the sample with amylase, protease and amyloglucosidase to remove starch and protein, then precipitate soluble fiber with alcohol and weigh the total residue, correcting for ash and protein. HPLC-based methods quantify individual fiber fractions after enzymatic digestion, which supports labelling of specific fiber types.

What are the key features?

• Sequential enzyme digestion of starch and protein
• Alcohol precipitation of soluble fiber
• Fritted crucibles for filtration and weighing
• Optional separation of insoluble and soluble fractions
• Residue protein and ash correction
• Batch capacity of six or more samples

What are the technical specifications?

A typical enzymatic-gravimetric dietary fiber analyzer configuration offers enzymes of Alpha-amylase, protease, amyloglucosidase, incubation temperature of 60 °C and 95 °C stages, pH control of Phosphate buffer, pH 6.0 and 7.5, precipitation of Ethanol to 78 percent, 1 h, filtration of Fritted crucible, vacuum and corrections of Residue protein and ash subtracted. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Enzymatic-Gravimetric Dietary Fiber Analyzer is used in total dietary fiber for nutrition labelling, soluble and insoluble fiber claim verification, cereal, legume, fruit and vegetable fiber testing and fiber-enriched product development. Across the wider Fiber Analyzers class, laboratories also deploy it for dietary fiber declaration for nutrition labelling, crude fiber compliance for feed and export and NDF and ADF values for ration formulation.

Which standards and certifications apply?

Relevant standards and methods include ISO 5498, ISO 6541, ISO 6865, ISO 16472, AOAC 991.43, AOAC 985.29, AOAC 2011.25 and ISO/IEC 17025. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Fiber analysis is sensitive to filtration and transfer losses, so crucibles, fritted glassware and filter bags must be prepared, dried and weighed consistently, and residues must be handled without spillage. Enzyme activities vary between lots, so incubation times, temperatures and pH buffers must follow the method exactly, and each batch should include a blank and a control sample. The ashing step requires a muffle furnace at 525 to 550 °C with a stable, calibrated controller. Drying and cooling to constant mass before weighing are essential for gravimetric accuracy. Because results are operationally defined, laboratories should state the method, the corrections applied and participate in proficiency-testing schemes for dietary fiber.

How do I select the right Enzymatic-Gravimetric Dietary Fiber Analyzer?

Choose this method when total dietary fiber must be reported for labelling and your products contain starch and protein that enzymes remove. Confirm that the procedure follows the accredited standard for your matrix and that enzyme blanks and controls are routine. Consider the fractionation option if soluble and insoluble fiber claims are needed.

How does it compare with other Fiber Analyzers variants?

Choose the method according to the fiber value you must report. Crude fiber is an older, inexpensive measure still used for feed regulation and some export certificates, but it underestimates total fiber considerably. Detergent fiber methods give NDF and ADF values used in feed formulation and ruminant nutrition, and they are rapid with filter bag systems. For human nutrition labelling, enzymatic-gravimetric methods such as AOAC 991.43 give total dietary fiber and, with additional steps, insoluble and soluble fractions. HPLC-based methods are needed when individual fiber components, such as beta-glucan or inulin, must be declared or studied. Always check that the accredited method applies to your matrix and that ash and protein corrections are included.