Determinação de fibra alimentar

Summary

This script outlines the procedure for determining dietary fiber in a sample, including the necessary equipment like an analytical balance, furnace, and vacuum filtration kit. The process involves preparing the sample, using enzymes to break down starch and protein, and filtering the solution. After multiple washings with ethanol and acetone, the samples are dried and weighed. The analysis includes calculating the fiber content by measuring total residues, ash content, and protein. This method ensures precise measurement, accounting for variables like moisture and fat in the sample.

Takeaways

• 😀 The determination of dietary fiber requires specific equipment like an analytical balance, muffle furnace, vacuum pump with kitassato for filtration, and a water bath with agitation.
• 😀 The sample preparation involves placing one gram of cellulose in four glass crucibles, with one used for blank analysis and the others for the actual sample.
• 😀 The glass crucibles should be placed in a muffle furnace at 550°C for incineration, then removed and weighed after cooling in a desiccator.
• 😀 The sample must be dehydrated and defatted if its fat content exceeds 5%. If necessary, only dehydration in an oven at 105°C is performed.
• 😀 A phosphate buffer solution (pH 6) is prepared for analysis, with 50 ml added to each beaker, followed by enzymatic treatment.
• 😀 Enzymes like alpha-amylase and protease are added sequentially, with the samples being heated in a water bath at 100°C and 60°C, respectively.
• 😀 The pH of the samples is adjusted using sodium hydroxide and hydrochloric acid to maintain optimal enzyme activity.
• 😀 After enzymatic treatment, ethanol and acetone are used for washing and filtering the samples to remove unwanted substances.
• 😀 The samples are then dried overnight in an oven, and one of the triplicates is used to determine protein content via the Kjeldahl method.
• 😀 The remaining triplicates are used for ash determination, which involves heating them in a muffle furnace at 525°C for five hours and then weighing after cooling in a desiccator.
• 😀 The percentage of dietary fiber in the sample is calculated by subtracting the blank's residue weight and factoring in ash, protein content, and sample weight after accounting for moisture and fat content.

Q & A

What is the purpose of the analytical balance in the fiber determination process?

The analytical balance is used to measure the weight of samples and cadinhos with high precision during different stages of the analysis.

Why is it necessary to dry the sample at 105°C in an oven?

The sample must be dried to remove moisture, ensuring accurate weight measurements and preventing interference from water content in the analysis.

What is the role of the muffle furnace in the fiber determination process?

The muffle furnace is used to incinerate the samples at high temperatures (550°C) to remove organic matter, allowing for the measurement of residual fiber content.

Why is a blank sample necessary in the analysis?

A blank sample, which is a cadinho without the sample, is used to account for any potential interference or contamination from the cadinho itself during the analysis.

How does the phosphate buffer contribute to the fiber determination process?

The phosphate buffer, with a pH of 6, is used to maintain the correct pH during the enzymatic digestion of starches and proteins in the sample.

Why is enzyme protease used in the procedure?

Protease is used to break down proteins in the sample, allowing for the accurate determination of the fiber content by isolating it from other macromolecules.

What is the significance of maintaining the pH between 7.3 and 7.7 during the enzyme reaction?

Maintaining the pH between 7.3 and 7.7 ensures that the enzymatic reaction proceeds efficiently, optimizing the breakdown of starches and proteins for accurate fiber analysis.

What is the purpose of washing the sample with ethanol and acetone during the filtration step?

The washing with ethanol and acetone helps to remove any soluble substances, such as fats or impurities, ensuring that only the desired fiber content remains for analysis.

Why must the ethanol concentration be precisely 95% during the process?

A 95% ethanol concentration is necessary because it ensures efficient extraction and removal of non-fiber components, without dissolving the fiber itself.

How is the percentage of dietary fiber in the sample calculated?

The percentage of dietary fiber is calculated using the formula: Fiber percentage = (Residual weight of the sample - Residual weight of the blank) / Sample weight * 100, where the residual weight refers to the weight after incineration.