The protein content of any part of rice can be estimated by estimating the total Nitrogen % present in them. This can be done by using a widely used method Kjeldahl.

Some materials have substantial amounts of non-protein nitrogen. Be aware of that!

Using calibrated Near infrared spectroscopy (NIRS)

The protein content in rice bran can be determined from the organic Nitrogen content by Kjeldahl method. Ideally the protein content of food stuff is calculated by multiplying its total nitrogen content by the conversion factor. For different grains it vary. Since rice bran fat content is high so usually we use defatted sample for protein estimation. This method you can find in below reference:

1. Pearson’s Composition and Analysis of Foods, 9th edn, page 17.

2. Standard AOAC method no. 920.87 (AOAC, 2000).

3. MANUAL OF METHODS OF ANALYSIS OF FOODS-FSSAI

1- The protein concentration in the extracted rice bran solution was measured using a UV-Vis spectrophotometer, based on the Bradford method (Bradford Citation 1976). The amount of protein in each sample was evaluated by measuring the absorbance at 595 nm and comparing the samples to bovine serum albumin.

2: There are two main methods used for crude protein analysis: the Kjeldahl and Dumas methods.

Kjeldahl method can be used to determine the total Nitrogen content of the rice which can then be multiplied with the rice conversion factor to obtain the protein content

Determining the total protein content of a plant sample such as rice bran typically involves using methods such as the Kjeldahl method, the Dumas method, or the Bradford assay. The Kjeldahl method involves digestion of the sample with concentrated sulfuric acid, distillation, and titration to determine the total nitrogen content, which is then multiplied by a conversion factor to estimate the protein content. The Dumas method utilizes combustion to measure nitrogen content, and the Bradford assay is a colorimetric protein assay that can be used to quantitate protein concentration based on protein-dye binding. Each method has its advantages and limitations, and the choice of method depends on factors such as available equipment, sample size, and required sensitivity.