See you at 1 pm

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See you at 1 pm
Soluble Protein in Beer Milk

• Lab Quiz Today !!!!!

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FOOD ANALYSIS LAB 2
LABORATORY EXERCISE 3 Determination of Soluble
Protein in Foods
More specifically.BEER
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OVERALL OBJECTIVE

• To measure soluble protein in foods
• To understand the relationship of standard curves
  to food analysis

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Specific Objectives

• To understand the relationship between
  analytical response and concentration
• To perform a standard curve
• To calculate the protein content in beer from
  the label and dilute to appropriate amount for
  detection
• To write a report using appropriate statistical
  techniques to validate which beer has more protein

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• PROTEIN ANALYSIS
• Proteins are important components of food,
  providing biological and structural function.
• There importance for analysis is primarily
  related to their unique biological activities or
  functional properties, and for nutritional
  benefits.

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Protein Methods Soluble Insoluble Protein -
Kjeldahl Dumas (combustion) - measures total
nitrogen (N) Soluble protein - Biuret, Lowry, UV,
Dye binding, Bradford, Ninhydrin
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BIURET METHOD Cupric ions react with peptide
bonds under alkaline conditions Measure color in
SPEC at 540 nm
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BIURET METHOD Advantages - Cheaper and faster
than Kjeldahl - Less problem with color
deviations than other protein methods - Few
substances interfere - Does not measure
non-protein nitrogen (NPN) Disadvantages - not
sensitive, only to 2-4 mg level - bile pigments
interfere (bilirubin) - ammonium salts
interfere - color depends on type of protein -
lipids and carbos can affect clarity of
solution - PROTEIN MUST BE SOLUBLE
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The Biuret Method for Protein

• Going to test soluble protein in beer against a
  standard of BSA.
• The reaction of peptide bonds in protein with
  copper ions in alkaline conditions will produce a
  purple color.
• The intensity of the color is directly
  proportional to the amount of protein.
• Quantify using a spectrophotometer (540 nm)

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Measuring Chemicals with Light

• Spectroscopy - production, measurement, and
  interpretation of spectra from matter interacting
  with EMR (electromagnetic radiation)
• We will apply BEERS LAW (no kidding) to quantify
  our unknowns in, yes, beer.

This could be fun !!
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What if we dont have a STANDARD for what we are
analyzing for?

• How can we possibly do this?

Beers Law States that as concentration
increases, so does concentration. (linear)
A ebc or just A abc
A absorbance e extinction coefficient b
light path distance c concentration
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Fortunately for us.We will use BSA as our
standard

• We will use only the principals of Beers Law as
  applied to a standard curve.
• We will conduct the experiment exactly the same
  on a blank of water, our standard curve of BSA,
  and our unknowns (beer).

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Sample
Poo
P1
A log(Po/P1)
P0
Poo
Reference
What is the proper reference or blank ? How do we
obtain the protein concentration?
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• The solution
• Is there a relationship between color intensity
  and x?
• Sure, color intensity is based on absorbance,
  which is
• related to concentration.

The standard curve
Page 58-60 Linear regression
A mx b m - slope b - y intercept
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First You must calculate the amount of protein
in the beer. The color intensity of your sample
should ideally fall in the center of the standard
curve. We will calculate the estimated protein
from the label to try to make it fall in the
standard curve.
An example a 12 oz serving has 3 g protein
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Second dilution

• Take into account any dilutions you did on the
  beer.
• For example 5 mL of beer diluted with 10 mL of
  water (510) is a 3X dilution of the protein
  present in the beer.
• Always MULTIPLY concentrations and dilution
  factors.
• Calculate the amount of protein in beer.

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Calculate back

• Calculate the concentration of protein in your
  standards using their absorbance.
• Compare the actual values with calculated values