Questions and Answers
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?
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?
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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?
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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?
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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?
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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
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Polarimetry:
- Measures the rotation of plane-polarized light through a solution, determining carbohydrate concentration against a calibration curve.
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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.
