Our main objective is estimation of protein concentration in a given sample of milk by exploiting the relationship between spectral absorptivity and the concentration of protein. We propose to use optical sensors to accurately estimate the concentration of protein in different types of milk. The res
A portable device for estimation of protein concentration through Biuret test
Our main objective is estimation of protein concentration in a given sample of milk by exploiting the relationship between spectral absorptivity and the concentration of protein. We propose to use optical sensors to accurately estimate the concentration of protein in different types of milk. The research objectives under consideration are accuracy, response time, sample size, and portability. We intend to design and fabricate a prototype of a portable spectroscopic device that can determine the concentration of protein within 5 minutes with an accuracy of around 90% in a sample size not greater than 5ml collected from a dairy outlet.
Biuret test is the analytical method in which a protein sample is qualitatively analysed i.e. only tests for the presence of protein in a sample. Followed by a series of reactions with sodium hydroxide (NaOH) and copper (II) sulfate (CuSO4), the conjugate molecule of Cu(II) and NH4 gives blue-violet color combinations. We base our work on the fact that the intensity of color is proportional to protein content in sample. The spectral absorptivity analysis of the color variation, based on Beer-Lambert's law, expressed in equation 1, is the key for estimation of protein content.
Where A, ?, c, and l represent absorbance, absorptivity coefficient, concentration of protein in the sample, and path length through sample, respectively.
such that , ? =c?
where T = transmittance
where
as, Io < I
where Io = is the intensity before transmitted through sample
I = is the intensity after transmitted through sample
Table 1 describes an overview to spectroscopic assays under consideration..
Table 1:
| Source | Wavelengths | Reagents & Indicators | Output Range | Advantages |
| Ultra violet absorption | 240nm - 280nm | 1ml NaOH 2-3 drops copper sulphate (CuS04) | 0.1 โ 100 ????g/ml | Small sample size, low cost |
| Visible light absorption | 540nm โ 560nm | 1ml NaOH 2-3 drops copper sulphate (CuS04) | 20 - 2000????g/ml | Low variability |
| Infra Red absorption | 700 nm onwards | 1ml NaOH 2-3 drops copper sulphate (CuS04) | 10 โ 1000????g/ml | High sensitivity and precision |
Implementation Methodology Flowchart:

Source
Ultra violet absorption
Visible light absorption
Infra Red absorption
Chemicals: Copper (II) sulfate, Sodium hydroxide
Apparatus: Test tubes, Test tube holder, Cuvette, Dropper
Sample Size: 5 ml
Path Length (distance b/w transmitter and receiver): 1 cm
Analysis Mode: Absorbance Mode
Microcontroller: Arduino MEGA 2560
(Programmed in C language using Arduino IDE)
Setup Design:

Transmitters/Sensors:
Table 2 describes an overview to transmitters and sensors...
Table 2:
| S No.. | Transmitters | Cost (PKR) | Receivers | Cost (PKR) | Output |
| 1. | UV Laser Diode (240-280 nm) | 2500/- | UV receiver photodiode | 2000/- | Analog Voltage to ADC value |
| 2.. | White Light LED (380 - 700 nm) | 4000/- | RGB Color sensor (TCS 3200) | 1500/- | Frequency modulated output to ADC value |
| 3. | IR Transmitter (850nm/ 940 nm) | 2500/- | IR receiver photodiode | 2200/- | Analog Voltage to ADC value |
Output:
1.
2..
3.
| S No.. | Transmitters | Cost (PKR) | Receivers | Cost (PKR) | Output |
| 1. | UV Laser Diode (240-280 nm) | 2500/- | UV receiver photodiode | 2000/- | Analog Voltage to ADC value |
| 2.. | White Light LED (380 - 700 nm) | 4000/- | RGB Color sensor (TCS 3200) | 1500/- | Frequency modulated output to ADC value |
| 3. | IR Transmitter (850nm/ 940 nm) | 2500/- | IR receiver photodiode | 2200/- | Analog Voltage to ADC value |
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