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FDSN 507 Midterm 2
Carbohydrate Analysis
Give three reasons why carbohydrates are important. | Main source of energy, dietary fiber, provides stability properties, sugar lowers water activity. |
Define total carbohydrate. | 100 - (moisture + ash + lipid + protein) |
Define other carbohydrate. | Total carbohydrate - (dietary fiber + sugars) |
T or F: Sugars include polysaccharides. | False |
T or F: Total carbohydrate is always calculated, never measured. | True |
What are the steps in carbohydrate sample preparation? | 1. Dry sample 2. Grind sample to powder 3. Extract lipids via Soxhlet extractor |
80% hot ethanol can be used to extract ____. | mono-/oligo- saccharides |
What method is used to determine total carbohydrate? | Phenol-sulfuric acid method |
In _____ method, carbohydrates are heated in the presence of furan, which condenses with phenol to form compounds quantified with a spectrophotometer. | phenol-sulfuric acid |
Name three colorimetric methods for reducing sugar analysis. | Somogyi-Nelson, Munson-Walker, Lane-Eynon |
Reducing sugar analysis involves reduction of ____ ions in alkaline solution to _____ ions by reducing sugars. | cupric, cuprous |
What method is used to treat a sample before enzymatic analysis? | Carrez treatment |
Describe the Carrez treatment. | Emulsions are broken, proteins precipitated, and colors absorbed; suspension is filtered and used in assay. |
Give two examples of monosaccharides. | Fructose, glucose |
Give two examples of oligosaccharides. | Lactose, maltose, sucrose |
Give two examples of polysaccharides. | Amylose, amylopectin, starch |
Give three advantages to enzymatic methods. | Specific for substance being measured, kits available, low detection limits. |
Give two disadvantages to enzymatic methods. | May have interfering compounds, not always 100% specific |
Name two methods for mono- and oligo- saccharide analysis. | TLC, capillary electrophoresis |
____ can be analyzed by enzymatic methods, degree of gelatinization, or degree of retrogradation. | starch |
Describe the enzyme method for starch analysis. | Starch is converted in D-glucose by enzymes, and then D-glucose is quantified enzymatically; glucose oxidase, peroxidase. |
What are disadvantages to the enzymatic method for starch analysis? | Amylases must be pure, not quantitative for high-amylose starch. |
_____ enzyme is used to determine degree of starch gelatinization and retrogradation. | pullulanase, B-amylase |
How is pectin content determined? | Saponify with NaOH then acidify/precipitate with calcium then weigh pectin; spectrophometric methods |
Define dietary fiber. | The edible parts of plants resistant to digestion and absorption in the human small intestine with partial fermentation in large intestine. |
T or F: Dietary fiber includes monosaccharides. | False |
Name two types of soluble fiber and what foods it is found in. | Pectin, hydrocolloids/gums; beans, fruits and vegetable |
Name two types of insoluble fiber and what foods it is found in. | Cellulose, ligin; wheat bran and whole grains |
T or F: Crude fiber is not used for human food. | True |
What is the advantage to the AOAC method for total dietary fiber? | Includes all fiber components, including resistant starch |
What are the disadvantages to the AOAC method for total dietary fiber? | Time consuming, overestimates fiber content in foods with simple sugars |
Name four physical methods used to analyze carbohydrates. | Microscopy, mass spectroscopy, specific gravity, refractometry |