Determination of Crude Protein Content (Part-1)_A Complete Procedure (AOAC 2001.11)

Summary

This video provides a comprehensive guide to analyzing protein content in food and feed samples using the gel dolls method. It outlines the essential equipment, chemicals, and step-by-step procedures including sample digestion, dilution, distillation, and titration. Key calculations for determining nitrogen and crude protein percentages are also explained, emphasizing safety and accuracy throughout the process. Viewers will gain valuable insights into laboratory practices and the importance of protein analysis in quality assessment.

Takeaways

• 🔬 The determination of protein content is a crucial proximate test for analyzing food and feed samples.
• 🧪 The gel dolls method involves four main steps: digestion, distillation, titration, and calculation.
• ⚗️ Essential equipment includes a balance, acid-proof gloves, and various glassware like volumetric and conical flasks.
• 🧫 Key reagents for digestion include concentrated sulfuric acid and a catalyst, while boric acid and sodium hydroxide are used for distillation.
• 📏 The sample preparation begins with weighing 2 g of the homogenized sample and catalyst, followed by mixing with sulfuric acid for digestion.
• 🔥 Digestion is performed at 200-300°C for two hours, resulting in a clear green-colored digested juice.
• 💧 After digestion, the sample must be diluted with distilled water to reach a final volume of 100 ml.
• 🌡️ The distillation process involves adding the diluted digested juice to a distillation flask with boric acid and sodium hydroxide.
• 📊 Titration is carried out using 0.1 N hydrochloric acid, with methyl red as an indicator to determine the endpoint.
• 🔢 The final calculation of crude protein content is based on the titration results, sample weight, and specific factors, yielding a result of 10.92% for the tested wheat sample.

Q & A

What is the primary objective of the protein analysis discussed in the video?

The primary objective is to determine the crude protein content in food and feed samples using the Kjeldahl method.

What are the four main steps involved in the Kjeldahl method for protein analysis?

The four main steps are digestion, distillation, titration, and calculation.

What equipment is necessary to perform the protein analysis?

Necessary equipment includes an analytical balance, acid-proof gloves, various glassware (such as volumetric flasks and conical flasks), and a protein analyzer (manual or automated).

What chemicals are required for the digestion process?

The chemicals required for digestion are concentrated sulfuric acid and a catalyst.

How is the sample prepared before digestion?

The sample is homogenized, weighed (2 g), and added to a pre-labeled Kjeldahl flask along with the catalyst and concentrated sulfuric acid.

What temperature and duration are recommended for the digestion step?

The sample should be heated at a temperature of 200 to 300°C for a duration of 2 hours.

What is the purpose of diluting the digested sample with distilled water?

Dilution with distilled water is necessary to prepare the sample for the distillation step, ensuring that the analysis can be performed accurately.

What is the role of boric acid in the distillation process?

Boric acid acts as a collecting agent for the nitrogen released during distillation, allowing for accurate measurement during the titration step.

How is the end point of the titration identified?

The end point of the titration is identified by a color change in the distillate from transparent to orange after adding methyl red indicator.

What formula is used to calculate the nitrogen percentage in the sample?

The nitrogen percentage is calculated using the formula: Nitrogen % = (V1 × N1 × F1 × MW_N) / (WS × 10), where each variable represents specific measurements taken during the process.

What safety precautions should be taken when performing the protein analysis?

Safety precautions include wearing protective gloves and masks when handling chemicals, especially concentrated sulfuric acid, and ensuring proper ventilation.

Why is it important to wash the glassware during the dilution step?

Washing the glassware ensures that no residual digested material is left, which could affect the accuracy of the final results.

What factor is used to convert nitrogen percentage to crude protein content?

A specific conversion factor based on the sample type is used to calculate crude protein content from the nitrogen percentage.