TUGAS 1

Summary

This video provides a detailed guide on protein analysis using the Kjeldahl method. It outlines the process of determining crude protein content in food and feed samples through four main steps: digestion, distillation, titration, and calculation. The procedure involves using specific equipment like a balance, flasks, and a protein analyzer, along with chemicals like sulfuric acid, boric acid, and hydrochloric acid. The video also covers reagent preparation, proper handling, and safety precautions. By following the outlined method, users can accurately determine the nitrogen content and ultimately the protein percentage of the sample.

Takeaways

• 😀 Protein content analysis is a crucial proximate test for food and feed samples, and the Gel Dole method is used for this analysis.
• 😀 The protein analysis procedure includes four main steps: digestion, distillation, titration, and calculation.
• 😀 Essential apparatus for protein analysis includes a balance, acid-proof gloves, various glassware (volumetric flask, pipet, funnel, conical flask), and a protein analyzer (manual or automated).
• 😀 The necessary chemicals for protein analysis are concentrated sulfuric acid, catalyst for digestion, 4% boric acid, 40% sodium hydroxide solution, 0.1 normal hydrochloric acid, and methyl red indicator.
• 😀 Sample digestion involves adding sulfuric acid and catalyst to a homogenized sample, followed by heating at 200-300°C for two hours to obtain a clear, green digestate.
• 😀 After digestion, the sample is diluted with distilled water to prepare it for distillation.
• 😀 Distillation involves adding the diluted digestate, boric acid, sodium hydroxide, and distilled water into a distillation flask and heating at 150-200°C, collecting approximately 100 mL of distillate.
• 😀 Titration is performed by adding 0.1 normal hydrochloric acid to the distillate using a buret, with methyl red as an indicator to determine the endpoint (when the color changes to orange).
• 😀 To calculate the protein content, the volume of hydrochloric acid used in titration is recorded and combined with other known values to find the nitrogen percentage in the sample.
• 😀 The final crude protein content is calculated based on nitrogen percentage, with an example of wheat showing a result of 10.92% crude protein using the Gel Dole method.

Q & A

What is the purpose of the gel doll's method in protein analysis?

The gel doll's method is used to determine the crude protein content in food and feed samples. It involves four main steps: digestion, distillation, titration, and calculation.

What equipment is required for protein analysis using the gel doll's method?

The required equipment includes a balance machine, acid-proof gloves, glassware (such as a 100 ml volumetric flask, pipet, funnel, 50 ml gel doll's flask, and conical flask), and a protein analyzer machine (either manual or automated).

What chemicals and reagents are necessary for this protein analysis test?

The necessary chemicals include concentrated sulfuric acid, a catalyst, 4% boric acid, 40% sodium hydroxide solution, 0.1 normal hydrochloric acid, and methyl red indicator solution.

What is the first step of protein analysis in the gel doll's method?

The first step is to digest the sample by adding concentrated sulfuric acid and a catalyst, followed by heating the mixture on a digester unit at temperatures between 200 to 300°C.

How is the sample prepared for digestion?

The sample is weighed (approximately 2 grams of homogenized sample), placed in a pre-labeled gel doll's flask, and then mixed with the catalyst and concentrated sulfuric acid.

What is the purpose of the distillation step in protein analysis?

The distillation step is used to separate the distillate, which contains nitrogen, from the digested sample. This distillate is then used for titration to determine the nitrogen content.

What is the role of the 4% boric acid in the distillation process?

The 4% boric acid solution is used to collect the distillate during the distillation process. It helps trap the nitrogen released from the sample during distillation.

How is the titration performed in the protein analysis?

Titration is performed by adding 0.1 normal hydrochloric acid to the distillate that has been mixed with methyl red indicator. The endpoint is reached when the color changes from yellow to orange.

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

The nitrogen percentage is calculated using a formula that factors in the volume of hydrochloric acid used in titration, the normality of the acid, the sample weight, the molecular weight of nitrogen, and other factors related to dilution and sample type.

How is the crude protein content calculated from the nitrogen percentage?

The crude protein content is calculated by multiplying the nitrogen percentage by a factor specific to the sample type. For wheat, the factor is 5.70. The final protein content is expressed as a percentage of the sample weight.