"Prosky" Fiber Video Method (AOAC 985.29 / AACC method 32-05.01) with K-TDFR

Summary

The video tutorial outlines the Prosky method for measuring total dietary fiber, emphasizing its focus on high molecular weight non-digestible polysaccharides like cellulose and pectins. Developed in the 1980s, this method has become widely adopted despite its limitations, such as not measuring resistant starch and non-digestible oligosaccharides. The process involves enzymatic hydrolysis followed by ethanol precipitation, filtration, and residue analysis. Detailed instructions are provided for sample preparation, reagent use, and calculations, along with a recommendation to use the MegaCalc spreadsheet for simplified data processing.

Takeaways

• 😀 Dietary fiber consists of complex organic substances, including polysaccharides and non-digestible oligosaccharides.
• 😀 The Prosky method (AOAC Method 985.29) measures total dietary fiber, focusing primarily on high molecular weight polysaccharides.
• 😀 This method was developed in the 1980s and is widely used despite only measuring the polysaccharide fraction, often referred to as 'Prosky fiber.'
• 😀 The definition of dietary fiber was updated in 2009 to include resistant starch and non-digestible oligosaccharides.
• 😀 The Prosky method uses enzymatic treatments to hydrolyze starch and proteins, mimicking digestion.
• 😀 After enzymatic digestion, high molecular weight soluble dietary fiber is precipitated using ethanol or IMS.
• 😀 Samples must be prepared properly, including drying and potentially defatting samples with high fat content.
• 😀 The method involves measuring residue weights after filtration and washing, followed by ash and protein analysis.
• 😀 Calculations of dietary fiber can be performed using detailed methods or simplified using the MegaCalc Excel application.
• 😀 Enzyme purity is crucial for accurate measurement of dietary fiber content.

Q & A

What is dietary fiber composed of?

Dietary fiber is a mixture of complex organic substances, including hydrophilic compounds like soluble and insoluble polysaccharides, non-digestible oligosaccharides, and less hydrophobic compounds such as cutins, suberins, and lignins.

What is the Prosky method used for?

The Prosky method (AOAC Method 985.29) is used to measure total dietary fiber, specifically targeting high molecular weight non-digestible polysaccharides like cellulose, beta-glucan, and pectins.

What are the limitations of the Prosky method?

The Prosky method only measures the polysaccharide fraction of dietary fiber and does not account for non-digestible oligosaccharides or resistant starch, leading to potentially incorrect values.

When was the Prosky method developed?

The Prosky method was developed in the 1980s and contributed to the then-definition of dietary fiber.

How does the Prosky method prepare samples?

Samples are treated with thermostable α-amylase, protease, and amyloglucosidase to hydrolyze starch and protein, mimicking digestion before being precipitated with ethanol or IMS.

What is the importance of the CODEX Alimentarius in relation to dietary fiber?

The CODEX Alimentarius published an updated definition of dietary fiber in 2009, which includes resistant starch and non-digestible oligosaccharides as recognized components.

What steps are involved in the sample analysis process?

The process includes drying samples, hydrolyzing proteins and starch, precipitating dietary fiber, filtering, and analyzing residues for protein and ash content.

How is the final dietary fiber content calculated?

Final calculations for dietary fiber content can be performed as detailed in the kit data booklet or simplified using the MegaCalc Excel application, which automates the calculation process.

What precautions should be taken when conducting the Prosky method?

Precautions include ensuring proper pH levels during incubations, accurately measuring reagent volumes, and handling samples carefully to avoid contamination.

Why is enzyme purity important in dietary fiber measurement?

Enzyme purity is crucial because impurities can interfere with the enzymatic reactions, affecting the accuracy of dietary fiber measurements.