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Questions and Answers
Which method primarily relies on enzyme catalysis to achieve specificity in measuring carbohydrate concentrations?
Which method primarily relies on enzyme catalysis to achieve specificity in measuring carbohydrate concentrations?
What is the primary disadvantage of using α-glucosidase for the determination of sugar concentrations in mixed carbohydrate solutions?
What is the primary disadvantage of using α-glucosidase for the determination of sugar concentrations in mixed carbohydrate solutions?
In the enzymatic method for measuring D-glucose conversion, what role does NADP+ play in the process?
In the enzymatic method for measuring D-glucose conversion, what role does NADP+ play in the process?
Which physical method measures the concentration of carbohydrates based on the rotation of polarized light?
Which physical method measures the concentration of carbohydrates based on the rotation of polarized light?
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What does an increase in the refractive index of a carbohydrate solution indicate?
What does an increase in the refractive index of a carbohydrate solution indicate?
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Which enzyme is responsible for converting maltose and sucrose into their monosaccharide components?
Which enzyme is responsible for converting maltose and sucrose into their monosaccharide components?
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What is a key characteristic of enzymatic methods compared to physical methods in carbohydrate concentration measurement?
What is a key characteristic of enzymatic methods compared to physical methods in carbohydrate concentration measurement?
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In which scenario would you likely need to use liquid water to prepare a sample for analysis?
In which scenario would you likely need to use liquid water to prepare a sample for analysis?
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What physical property increases as the concentration of carbohydrates in an aqueous solution increases?
What physical property increases as the concentration of carbohydrates in an aqueous solution increases?
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What is a common application for determining sugar concentrations using the refractive index method?
What is a common application for determining sugar concentrations using the refractive index method?
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Study Notes
Introduction
- Filtrate treatment involves clarifying agents and ion-exchange resins to eliminate minor components.
- Clarifying agents, such as heavy metal salts, form insoluble complexes for removal via filtration or centrifugation.
- Mono-, di-, and oligosaccharides are polar and can be separated using positively and negatively charged ion-exchange columns.
Methods of Analysis
- Key characteristics of mono-, di-, and oligosaccharides include their reducing properties, which allow for specific chemical reactions that yield precipitates or colored complexes.
- Non-reducing carbohydrates can be analyzed post-hydrolysis.
- Chemical methods encompass titration, gravimetric, and colorimetric techniques.
Chemical Titration Methods
- The Lane-Eynon method determines the concentration of reducing sugars.
- Disadvantages include:
- Results vary with reaction time, temperature, and reagent concentration.
- Cannot distinguish between types of reducing sugars.
- Inability to directly measure non-reducing sugars.
- Susceptibility to interference from other reducing agents.
- Procedure involves boiling copper sulfate and observing a color change from blue to white.
Englyst-Cummings Procedure
- A defatted food sample undergoes heating to gelatinize starch, followed by enzyme digestion.
- Ethanol precipitates fiber, which is separated by centrifugation, washed, and dried.
- After hydrolysis with sulfuric acid, monosaccharide concentrations are measured.
- Assumes total mass of fiber equals total monosaccharides, enabling determination of soluble and insoluble dietary fiber, though lignin content remains unaddressed.
Conclusion
- Mono-, di-, and oligosaccharides dissolve in ethanol; polysaccharides require enzymatic or chemical hydrolysis for measurement.
- Indigestible polysaccharides (fiber) typically undergo precipitation methods due to their resistance to digestion.
Enzymatic Methods
- Enzymatic analysis capitalizes on specific enzyme reactions, offering rapid, sensitive measurements with minimal preparation.
- Liquid foods can be analyzed directly; solid foods must be dissolved in water.
Enzymatic Analysis Techniques
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D-glucose/D-Fructose Method:
- D-glucose is converted to glucose-6-phosphate (G6P) using hexokinase and ATP, then oxidized by NADP+ via G6P-dehydrogenase.
- The amount of NADPH formed corresponds to G6P concentration, measured at 340 nm.
- Fructose must first transform into glucose for analysis.
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Maltose/Sucrose Method:
- Maltose and sucrose are broken down into monosaccharides through α-glucosidase enzyme action.
- Concerns arise as oligosaccharides are also converted, complicating analysis.
Physical Methods
-
Polarimetry:
- Measures the rotation of plane-polarized light through a solution, determining carbohydrate concentration against a calibration curve.
-
Refractive Index (RI):
- RI varies with carbohydrate concentration, useful for syrup, honey, and jam analysis.
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Density Measurement:
- Increased carbohydrate concentration raises the density of aqueous solutions, commonly employed for concentration determination in various food industries.
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Description
This quiz covers the processes of treating filtrate with clarifying agents or ion-exchange resins to remove minor components in carbohydrate analysis. Learn about the functions of heavy metal salts and ion-exchange resins in sample preparation.
