Quiz Flashcards
(248 cards)
1
Q
What is the purpose of a rotary evaporator?
A
To concentrate a solution by evaporating solvents
It uses heat and reduced pressure to achieve rapid evaporation.
2
Q
What components are involved in a rotary evaporator system?
A
A, B, C, D, E
* A: Round-bottom flask
* B: Condensate collection flask
* C: Condenser
* D: Motor
* E: Water bath
3
Q
How does evaporation occur in a rotary evaporator?
A
Evaporation occurs from a thin film on the walls of the flask due to reduced pressure, large surface area, and elevated temperature
4
Q
What is a key advantage of the Kjeldahl method for protein measurement?
A
It is an official method for crude protein content
It has been modified to measure microgram quantities of proteins.
5
Q
What is a significant disadvantage of the Kjeldahl method?
A
Measures total organic nitrogen, not just protein nitrogen
6
Q
What is the principle of the Dumas method?
A
Samples are combusted at high temperatures with pure oxygen, converting carbon to CO2 and nitrogen components to N2
7
Q
What are the applications of the Dumas method?
A
Suitable for all types of foods and requires no hazardous chemicals
8
Q
What are the disadvantages of the Dumas method?
A
Expensive equipment is required and measures total organic nitrogen, not just protein nitrogen
9
Q
What is dietary fiber primarily composed of?
A
Polysaccharide molecules
Includes components like cellulose, hemicelluloses, and lignin.
10
Q
What are components of insoluble dietary fiber?
A
Cellulose, microcrystalline cellulose, lignin, hemicelluloses, resistant starch
11
Q
Fill in the blank: Dietary fiber is essentially the sum of the _______ components of a foodstuff.
A
[nondigestible]
12
Q
What are some methods for quantitating ammonia or nitrogen?
A
Nesslerization, pH measurement, direct measurement using ion chromatography
Nesslerization involves a color change based on ammonium ion concentration.
13
Q
What does the nitrogen to protein conversion factor depend on?
A
The type of food being analyzed
14
Q
True or False: The Dumas method is less time-consuming than the Kjeldahl method.
A
True
15
Q
What is the temperature range for combustion in the Dumas method?
A
700–1000 °C
16
Q
What happens to nitrogen oxides in the Dumas method?
A
They are reduced to nitrogen in a copper reduction column at 600 °C
17
Q
List the components of soluble dietary fiber.
A
- Other polysaccharides
- Native pectin
- Hydrocolloids/food gums
18
Q
What is the formula for calculating the percentage of nitrogen in a sample?
A
%N = (N H C l x (Corrected acid volume) / (g of sample)) × (14 g N) / mol x 100
19
Q
What does N H C l represent in the nitrogen calculation?
A
Normality of HCl, in mol/1000 ml
20
Q
How is the corrected acid volume calculated?
A
(ml std. acid for sample) – (ml std. acid for blank)
21
Q
What is the atomic weight of nitrogen used in the nitrogen calculation?
A
14
22
Q
What is the conversion factor to convert percent nitrogen to percent crude protein?
A
6.25
23
Q
What is the formula for calculating protein from nitrogen percentage?
A
%N × 6.25 = %protein
24
Q
What is the importance of protein analysis?
A
To determine total protein content, protein composition, and nutritional value
25
What is the Kjeldahl method used for?
To analyze total organic nitrogen in food samples
26
What occurs during the digestion step of the Kjeldahl procedure?
Proteins are digested with sulfuric acid and catalysts to form ammonium sulfate
27
What is formed from the reaction of nitrogen and sulfuric acid during digestion?
Nonvolatile ammonium sulfate
28
What is the purpose of neutralization in the Kjeldahl method?
To neutralize sulfuric acid and prepare for distillation
29
What indicators are used in the boric acid solution during distillation?
Methyl blue and methyl red
30
What is titrated in the Kjeldahl method?
Borate anion with standardized HCl
31
True or False: Dietary fibers are digestible and supply calories.
False
32
What are some sources of dietary fiber?
Vegetables, fruits, whole grains, legumes
33
What are the health benefits of dietary fiber?
Reducing the risk of heart disease and diabetes
34
What components are included in dietary fiber?
* Cellulose
* Hemicellulose
* Lignin
* Pectin
* Mucilage
* Gum
35
What does crude fiber measure?
The quantity of indigestible cellulose, pentosans, lignin, and other components in foods
36
What type of dietary fiber does crude fiber refer to?
The type that remains as indigestible
37
What does crude fiber refer to?
Crude fiber refers to the type of dietary fiber that remains as a residue after food receives a standardized laboratory treatment with dilute acid and alkali.
## Footnote
The treatment dissolves all soluble fiber and some insoluble fiber in a food.
38
What is the primary composition of crude fiber?
Crude fiber is primarily composed of cellulose and lignin.
39
Is the determination of crude fiber content mandatory worldwide?
Yes, the determination of crude fiber content of food and animal feed is mandatory worldwide.
40
Why is the measurement of insoluble fiber important?
Measurement of insoluble fiber is important for calculating the caloric content of food.
41
What is one method allowed to calculate calories in food?
One method involves subtracting the amount of insoluble dietary fiber from the value for total carbohydrate before calculating the calories based on protein, fat, and carbohydrate content.
42
What are the approximate calorie values per gram for protein, fat, and carbohydrates?
Approximately 4, 9, and 4 Calories per gram, respectively.
43
What is dry ashing?
Dry ashing refers to the use of a muffle furnace capable of maintaining temperatures of 500–600 °C to vaporize water and volatiles and burn organic substances.
44
What happens to most minerals during dry ashing?
Most minerals are converted to oxides, sulfates, phosphates, chlorides, and silicates.
45
What are some volatile elements that may be lost during dry ashing?
* As
* B
* Cd
* Cr
* Cu
* Fe
* Pb
* Hg
* Ni
* P
* V
* Zn
46
What is an advantage of conventional dry ashing?
It is a safe method that requires no added reagents or blank subtraction.
47
What is a disadvantage of dry ashing?
The length of time required (12–18 hours or overnight) and loss of volatile elements.
48
What is wet ashing sometimes called?
Wet ashing is sometimes called wet oxidation or wet digestion.
49
What is the primary use of wet ashing?
Preparation for specific mineral analysis and metallic poisons.
50
What is one advantage of wet ashing?
Minerals usually stay in solution with little or no loss from volatilization.
51
What is a disadvantage of wet ashing?
It requires virtually constant operator attention and uses corrosive reagents.
52
What type of samples are generally used for ash determination?
A 2–10 g sample is generally used for ash determination.
53
What should always be used for ash determination?
Distilled-deionized water should always be used.
54
What is the recommended drying method for fresh stem and leaf tissue?
They should be dried in two stages: first at a lower temperature of 55 °C, then at a higher temperature.
55
What type of water should be used in plant material analysis?
Distilled-deionized water
## Footnote
This is crucial to avoid contamination and ensure accurate results.
56
How should fresh stem and leaf tissue be dried?
In two stages:
* First at a lower temperature of 55°C
* Then at a higher temperature
## Footnote
This method helps prevent artifact lignin.
57
What is the maximum moisture content for plant material to be ashed without prior drying?
15% or less
58
What does ash content represent in foods?
The total mineral content
59
Why is determining ash content important?
For several reasons:
* It is part of proximate analysis for nutritional evaluation
* It is the first step in preparing a food sample for specific elemental analysis
* Certain foods are high in particular minerals
## Footnote
Understanding ash content helps in nutritional labeling and quality control.
60
What is ash in the context of food analysis?
The inorganic residue remaining after ignition or complete oxidation of organic matter
61
What are the two major types of ashing methods?
* Dry ashing
* Wet ashing (oxidation)
## Footnote
Dry ashing is primarily for proximate composition and some mineral analyses, while wet ashing is for specific mineral analysis.
62
On what basis can ash content of foods be expressed?
On either a wet weight or a dry weight basis
63
What is the typical ash content of most fresh foods?
Rarely greater than 5%
64
What is the ash content of pure oils and fats?
Little or no ash
65
What is the ash content of cured bacon and dried beef?
* Cured bacon: may contain 6% ash
* Dried beef: may be as high as 11.6% (wet weight basis)
66
How is dietary fiber often determined?
Gravimetrically
67
What materials are selectively solubilized during dietary fiber analysis?
Digestible carbohydrates, lipids, and proteins
68
What enzymes are used in starch analysis?
* Alpha-amylase
* Debranching enzymes (pullulanase and isoamylase)
* Glucoamylase (amyloglucosidase)
69
What does α-Amylase catalyze?
Hydrolysis of unbranched segments of 1,4-linked α-D-glucopyranosyl units
70
What do debranching enzymes hydrolyze?
The 1,6 linkages that constitute the branch points
71
What does Glucoamylase (amyloglucosidase) do?
Starts at the nonreducing ends of starch chains and releases D-glucose one unit at a time
72
What temperature and duration are used to gelatinize starch granules in fiber methods?
95–100°C for 35 minutes
73
What remains unhydrolyzed in dietary fiber analysis?
Resistant starch molecules
74
How are lipids treated in fiber analysis?
Removed easily with organic solvents
75
What must be corrected for during fiber analysis?
Protein and minerals not removed during solubilization
76
Why are methods for fiber determination continually researched?
Because:
* Labeling of dietary fiber content is required
* Dietary fiber is a complex heterogeneous material
* Its physiological importance
77
What does A.O.A.C. method 991.43 determine?
Soluble, insoluble, and total dietary fiber in various food products
78
What are the steps involved in the A.O.A.C. method for dietary fiber determination?
Treating the sample with:
* Thermostable α-amylase
* Protease
* Glucoamylase
## Footnote
This method helps isolate insoluble and soluble dietary fiber.
79
What is the importance of protein analysis?
* Nutrition labeling
* Pricing based on protein content
* Functional property investigation
## Footnote
Proteins have unique functional properties that are vital in food science.
80
What basic principles are involved in protein analysis methods?
* Determinations of nitrogen
* Peptide bonds
* Aromatic amino acids
* Dye-binding capacity
* Ultraviolet absorptivity of proteins
* Light scattering properties
81
What factors must be considered in the selection of an appropriate method for a particular application?
sensitivity, accuracy, precision, speed, cost of analysis
82
Why is the analysis of proteins complicated?
Some food components possess similar physicochemical properties
83
What are sources of nonprotein nitrogen in food?
free amino acids, small peptides, nucleic acids, phospholipids, amino sugars, porphyrin, vitamins, alkaloids, uric acid, urea, ammonium ions
84
What does total organic nitrogen in foods primarily represent?
nitrogen primarily from proteins and to a lesser extent from all organic nitrogen-containing nonprotein substances
85
What major food components may interfere with the analysis of food proteins?
lipids and carbohydrates
86
What is the matrix assisted laser desorption time-of-flight (MALDI-TOF) technique useful for?
analysis of a homologous series of oligosaccharides
87
What is the most abundant component of food after water?
starch
88
Where is starch found in plants?
leaves, stems, roots, tubers, seeds
89
What types of starches are commercially available as food additives?
corn (maize), waxy maize, high-amylose corn (amylo maize), potato, wheat, rice, tapioca (cassava), arrowroot, sago
90
What is the principle for determining total starch?
complete conversion of starch into D-glucose by purified enzymes specific for starch
91
What potential problems can arise when determining total starch?
Contamination from other enzymic activity releasing D-glucose, e.g., cellulases, invertase, β-glucanase, and catalase
92
What enzyme oxidizes D-glucose in the GOPOD method?
glucose oxidase
93
What does the GOPOD method involve for measuring D-glucose?
oxidation of a colorless compound to a colored compound which is measured spectrophotometrically
94
What is the method of choice for the determination of starch?
The combination of enzymes in sequential enzyme-catalyzed reactions
95
What does gas-liquid chromatography (GLC) provide for carbohydrates?
qualitative and quantitative analysis
96
What must sugars be converted into for gas chromatography?
volatile derivatives
97
What are the commonly used derivatives for gas chromatography?
alditol peracetates, aldonic acid pertrimethylsilyl ethers
98
What is the detector of choice for peracetylated carbohydrate derivatives?
flame ionization detector
99
What is a significant problem with GC for carbohydrate analysis?
involvement of two preparation steps: reduction of aldehyde groups and conversion to a volatile derivative
100
What is oxidation in the context of chemical reactions?
Oxidation is a loss of electrons.
101
What is reduction in the context of chemical reactions?
Reduction is a gain of electrons.
102
What are reducing sugars?
Reducing sugars are those sugars that have an aldehydo group (aldoses) that can give up electrons to an oxidizing agent.
103
What is produced when the aldehydo group is oxidized?
A carboxylic acid group is produced.
104
Under what conditions do ketoses behave as weak reducing sugars?
Under alkaline conditions.
105
What is the most often used method to determine amounts of reducing sugars?
The Somogyi–Nelson method.
106
What does the Somogyi–Nelson method measure?
It measures the reduction of Cu(II) ions to Cu(I) ions by reducing sugars.
107
What complex is reduced in the Somogyi–Nelson method?
An arsenomolybdate complex.
108
What is the visual indicator of the reaction in the Somogyi–Nelson method?
An intense, stable blue color.
109
What is the absorbance measured at in the Somogyi–Nelson method?
520 nm.
110
What is the Dinitrosalicylic Acid method used for?
To measure reducing sugars naturally occurring in foods or released by enzymes.
111
What does the Munson–Walker method measure?
It measures the precipitate of cuprous oxide.
112
How can the cuprous oxide precipitate be determined in the Munson–Walker method?
Gravimetrically, by titration with sodium thiosulfate, potassium permanganate, or electrolytically.
113
What is required when using methods that measure reducing sugars?
Standard curves because each reducing sugar reacts differently.
114
What is the method of choice for analysis of mono- and oligosaccharides?
High-Performance Liquid Chromatography (HPLC).
115
What types of analysis does HPLC provide?
Qualitative analysis and quantitative analysis.
116
What is the general solubility characteristic of lipids?
Lipids are soluble in ether, chloroform, and other organic solvents, but sparingly soluble in water.
117
What is the widely accepted definition of lipids based on?
Solubility.
118
What do the terms lipids, fats, and oils refer to?
They are often used interchangeably to refer to the collection of food molecules that meet the definition of lipids.
119
What is the difference between fats and oils?
Fats are solid at room temperature, while oils are liquid at room temperature.
120
What are lipids that are solid at room temperature generally referred to as?
Fats
121
What are lipids that are liquid at room temperature generally referred to as?
Oils
122
Why is accurate analysis of lipids in foods important?
For accurate nutritional labeling and to ensure product meets manufacturing specifications
123
What can inaccuracies in lipid analysis result in?
Costly errors for manufacturers and undesirable product quality
124
What is the Folch extraction method used for?
Extracting lipids from small samples
125
What is the Bligh and Dyer extraction method used for?
Extracting lipids from large samples of high moisture content
126
What is added to minimize oxidative degradation of fatty acids during analysis?
Pyrogallic acid
127
What are fatty acid methyl esters (FAMEs) used for in lipid analysis?
Quantitative measurement by capillary gas chromatography
128
Total fat is calculated as the sum of individual fatty acids expressed as what?
Triglyceride equivalents
129
What type of fats includes only the cis form of fatty acids?
Monounsaturated fats
130
True or False: Trans fats can be quantified using established identification criteria.
True
131
What method involves the addition of H2SO4 to a known amount of milk for fat quantification?
Babcock method
132
What is the principle of the Gerber method for milk fat analysis?
Uses sulfuric acid and amyl alcohol to digest proteins and release fat
133
What are proteins composed of?
Hydrogen, carbon, nitrogen, oxygen, and sulfur
134
How many α-amino acids are the building blocks of proteins?
Twenty
135
What is the most distinguishing element present in proteins?
Nitrogen
136
What is the Mojonnier method primarily applied to?
Dairy foods
137
What is the method used for fat extraction in pet food?
Acid hydrolysis with HCl followed by extraction with ethyl ether and petroleum ether
138
Fill in the blank: The combination of chloroform and methanol is commonly used to extract _______.
Lipids
139
What method is used to extract fat in the Mojonnier method?
A mixture of ethyl ether and petroleum ether
## Footnote
The extracted fat is dried to a constant weight and expressed as percent fat by weight.
140
Does the Mojonnier test require removal of moisture from the sample?
No
## Footnote
It can be applied to both liquid and solid samples.
141
What is a disadvantage of the Mojonnier method compared to continuous methods?
It requires more time
## Footnote
The continuous method is faster and more efficient.
142
What is the principle behind the Soxhlet method?
Continuous solvent extraction
## Footnote
The solvent continuously flows over the sample held in a ceramic thimble.
143
What is one advantage of microwave ashing?
Reduces sample preparation time to minutes
## Footnote
This has led to widespread use in analytical and quality control laboratories.
144
What type of digestion may be performed safely in a closed-vessel microwave system?
Microwave wet ashing
## Footnote
The choice of system depends on sample amount and required temperatures.
145
What is the common acid used in microwave wet ashing?
Nitric acid
## Footnote
It is often the acid of choice for digestion.
146
What is the key factor affecting the accuracy of direct solvent extraction methods?
The solubility of the lipids in the solvent used
## Footnote
It also depends on the ability to separate lipids from complexes with other macromolecules.
147
True or False: Acid hydrolysis eliminates some matrix effects exhibited by solvent extraction methods.
True
148
Fill in the blank: The total lipid content of food is commonly determined by _______.
[organic solvent extraction methods]
149
What is the disadvantage of the Goldfish method?
It may cause channeling, resulting in incomplete extraction
## Footnote
This can affect the accuracy of the fat content measurement.
150
What type of method is the Soxhlet method categorized under?
Semi-continuous solvent extraction method
## Footnote
AOAC Method 920.39 for cereal fat and AOAC Method 960.39 for meat fat are examples.
151
What does the Mojonnier extraction equipment eliminate in the hydrolysis process?
Some matrix effects
## Footnote
This is particularly relevant for multicomponent food products.
152
What is a characteristic of continuous solvent extraction methods?
Faster and more efficient extraction
## Footnote
They are more effective than semi-continuous extraction methods.
153
What is the main purpose of total fat determination in food?
Nutrition labeling
## Footnote
Total fat is most commonly determined by gas chromatography (GC) analysis.
154
In microwave digestion, what can closed-vessel systems process at a time?
Up to 40 samples
## Footnote
This allows for significant throughput in laboratories.
155
What are two types of ashing that can utilize microwave instrumentation?
Wet ashing and dry ashing
## Footnote
This method provides a faster alternative to conventional techniques.
156
What is the definition of viscosity?
Viscosity is the measure of a substance's resistance to motion under an applied force.
157
What is the viscosity measuring range of the VISCOMETER digital rotational viscometer?
1~100,000 mPa.s
158
What is the accuracy of the VISCOMETER digital rotational viscometer?
±2%
159
What is the typical expression for viscosity measurement?
Centipoise (cP)
160
Fill in the blank: The phenol-sulfuric acid procedure is often used as a qualitative test for the presence of _______.
carbohydrate
161
What are the three states of water in food products?
* Free water
* Adsorbed water
* Water of hydration
162
What does water activity (Aw) determine?
How much water is available for microbial growth.
163
True or False: Water activity is the same as water content.
False
164
What major components does proximate analysis of foods determine?
* Moisture
* Ash (total minerals)
* Lipids
* Protein
* Carbohydrates
165
What is a pycnometer used for?
Measuring specific gravity by comparing the weights of equal volumes of a liquid and water.
166
What is the water activity value for pure water?
One
167
What are the effects of temperature on viscosity?
Temperature can easily affect the viscosity of certain foods.
168
What is the importance of accurate temperature measurement in food safety?
It is an important indicator of food safety and food quality.
169
What is the standard curve used for in the phenol-sulfuric acid method?
It must be prepared using mixtures of the same sugars present in the unknown.
170
What is the role of calibration in temperature measurement?
Calibration is important to keep thermometers accurate.
171
Fill in the blank: The ease of water removal from foods depends on how it exists in the food _______.
product
172
What is the significance of the food matrix in analytical methods?
The food matrix often presents the greatest challenge to the analyst.
173
What types of foods can cause different types of interferences in analysis?
* High-fat foods
* High-sugar foods
174
What does the term 'food matrix' refer to?
The nutrient and non-nutrient components of foods and their molecular relationships.
175
Fill in the blank: The density of the sample is calculated as follows: weight of sample-filled pycnometer - weight of empty pycnometer / weight of water-filled pycnometer - weight of empty pycnometer = _______.
density of sample
176
What are the water activity levels for fresh meat and fish?
>0.98
177
What is an alcoholometer used for?
Estimating the alcohol content of beverages.
178
What is a Brix hydrometer used for?
A Brix hydrometer is a type of saccharometer used for sugar solutions such as fruit juices and syrups, reading the percentage of sucrose at 20°C.
179
What is the purpose of alcoholometers?
Alcoholometers are used to estimate the alcohol content of beverages.
180
What type of liquids is the Twaddell hydrometer specifically for?
The Twaddell hydrometer is only for liquids heavier than water.
181
List the reasons why food analysis is important.
* Food safety
* Quality control
* Nutritional value
* Product development
182
What does food analysis help detect?
Food analysis helps detect adulterants, such as expired ingredients, harmful compounds, and deceptive labels.
183
What is proximate analysis in food analysis?
Proximate analysis involves the determination of carbohydrates, lipids, crude protein, crude fiber, dietary fiber, ash, and mineral content.
184
What does Brix measure?
Brix measures the soluble solids in a liquid and is equivalent to the percentage by weight of sugar.
185
What is the minimum soluble solids percentage required for jams and jellies?
At least 65 percent for jams and jellies.
186
True or False: The higher the Brix, the more water is available for microorganisms to grow.
False. The higher the Brix, the less water available for microorganisms to grow.
187
What is the refractive index (RI)?
The refractive index (RI) is a dimensionless constant used to describe the nature of a food.
188
What principle is used to measure specific gravity?
Archimedes’ principle states that a solid suspended in a liquid will be buoyed by a force equal to the weight of the liquid displaced.
189
What is the formula for density?
Density (ρ) = mass (m) / volume (V).
190
What is specific gravity?
Specific gravity is the density of a liquid compared to the density of another material, usually water.
191
Fill in the blank: The direct method for moisture determination involves _______.
[oven drying, desiccation, distillation, extraction, and other physicochemical techniques]
192
What are the two methods for moisture determination?
* Direct method
* Indirect method
193
What does the indirect method of moisture determination involve?
Continuous measurement and automatic control of moisture content in food processing.
194
What are the main types of vitamin assays?
* Bioassays
* Microbiological assays
* Physicochemical assays
195
What is the reference standard method for vitamin analysis?
The line test, based on bone calcification.
196
True or False: Bioassays are currently used for the analysis of all vitamins.
False. Bioassays are used primarily for vitamins B12 and D.
197
What is the reference standard method of analysis for vitamins B1, B12, and D?
The line test, based on bone calcification.
198
Why is the determination of vitamin D limited to animals?
It involves deficiency studies and sacrificing test organisms.
199
Which vitamins can be analyzed using microbiological assays?
Water-soluble vitamins such as C, B6, B12, Thiamin, Riboflavin, Niacin.
200
What is critical for accurate results in microbiological assays?
Strict adherence to the analytical protocol.
201
What organisms are typically used in microbiological assays?
Bacteria, yeast, or protozoans.
202
How is growth measured in microbiological assays?
In terms of turbidity, acid production, gravimetry, or respiration.
203
What factors affect the stability of vitamin A?
Ultraviolet light, air, high temperatures, and moisture.
204
What method is considered the only acceptable for measuring vitamin A activity?
High-performance liquid chromatography (HPLC).
205
What is the role of vitamin analysis in nutrition?
Determining nutritional requirements and assessing diet adequacy.
206
How are vitamins defined?
As relatively low-molecular weight compounds required in small quantities.
207
What deficiency disease is caused by a lack of ascorbic acid?
Scurvy.
208
What deficiency disease is due to the lack of niacin?
Pellagra.
209
What is a significant advantage of microwave muffle furnaces over conventional dry ashing?
They can ash samples in minutes, decreasing analysis time by as much as 97%.
210
What is the moisture content range of fresh fruits?
81-93%.
211
What is the moisture content range of vegetables?
90-95%.
212
What is the moisture content of nuts?
1.5-3%.
213
What is the significance of knowing mineral levels in food?
Minerals are of nutritional and functional importance.
214
How is calcium content affected in direct acid cottage cheese?
Low calcium due to acid action freeing calcium bound to casein.
215
What methods are used for specific separation of minerals?
Colorimetry, ion-selective electrodes (ISE), atomic absorption spectroscopy, or inductively coupled plasma-atomic emission spectroscopy.
216
What is the extraction method for vitamin E in general food products?
Saponified under reflux, extracted with hexane, and analyzed by HPLC.
217
What is the extraction method for oils in HPLC analysis?
Dissolved in hexane and injected directly onto the HPLC column.
218
What is thiamin also known as?
Vitamin B1
219
What does the thiochrome fluorometric procedure measure?
The fluorescence measurement of the oxidized form of thiamin, thiochrome
220
What must be done under subdued light during the thiochrome method?
All analytical steps following the oxidation
221
What is the impact of temperature and time on moisture loss during analysis?
Moisture loss is a function of time and temperature
222
At what temperature do carbohydrates decompose?
100°C
223
What is the chemical reaction for the decomposition of glucose?
C6H12O6 → 6C + 6H2O
224
What is the boiling point of water at which moisture is typically evaporated?
100°C
225
How does the presence of solute affect the boiling point of water?
The boiling point is raised by 0.512°C for 1 mol of solute in 1.0 L of water
226
What influences the rate and efficiency of moisture removal?
Particle size, particle size distribution, sample sizes, and surface area
227
What is the principle of the oven drying method?
The loss of weight is used to calculate the moisture content of the sample
228
List the typical extraction procedures for vitamins.
* Ascorbic acid: Cold extraction with metaphosphoric acid/acetic acid
* Vitamin B1 and B2: Boiling or autoclaving in acid plus enzyme treatment
* Niacin: Autoclaving in acid (noncereal products) or alkali (cereal products)
* Folate: Enzyme extraction with α-amylase, protease and γ-glutamyl hydrolase
* Vitamins A, E, or D: Organic solvent extraction, saponification, and re-extraction with organic solvents
229
What is the principle of the dichloroindophenol titrimetric method?
L-ascorbic acid is oxidized to L-dehydroascorbic acid by the oxidation-reduction indicator dye
230
What does the microfluorometric method measure?
Both ascorbic acid and dehydroascorbic acid
231
What is the caloric contribution of carbohydrates to the human diet?
More than 70%
232
What are nondigestible polysaccharides primarily composed of?
All those other than starch
233
What are some attributes contributed by carbohydrates?
* Bulk
* Body
* Viscosity
* Stability to emulsions and foams
* Water-holding capacity
* Freeze-thaw stability
* Browning
* Flavors
* Aromas
* Textures
234
What is the principle of the phenol-sulfuric acid method?
It is a condensation reaction used for determining carbohydrates
235
What is essential for reliable results in riboflavin determination?
Exact adherence to the permanganate oxidation process
236
What treatments are included in extraction methods for vitamins?
* Heat
* Acid
* Alkali
* Solvents
* Enzymes
237
What is the common extraction requirement for fat-soluble vitamins?
Saponification
238
What must be done for the extraction of mono- and oligosaccharides?
Specific extraction procedures designed to stabilize the sugars
239
What is saponification?
A chemical reaction typically occurring overnight at room temperature or by refluxing at 70°C
## Footnote
Saponification is often used in the production of soap from fats and oils.
240
What types of saccharides can be determined in extraction?
Mono-, di-, tri-, tetra-, and oligosaccharides
## Footnote
Examples include glucose (mono), sucrose (di), raffinose (tri), stachyose (tetra), and maltodextrins (oligo).
241
What method is used for carbohydrate extraction?
Hot 80% ethanol extraction of dried, lipid-free sample
## Footnote
This method helps to isolate various types of saccharides for analysis.
242
What happens to carbohydrates under strong acids and high temperatures?
They are destroyed and undergo a series of complex reactions
## Footnote
These reactions include dehydration and produce various furan derivatives.
243
What are the products of continued heating of carbohydrates in the presence of acid?
Brown and black substances
## Footnote
These substances form as a result of condensation reactions with other products.
244
Which phenolic compounds can condense with carbohydrate products?
Phenol, resorcinol, orcinol, α-naphthol, naphthoresorcinol
## Footnote
These reactions produce colored compounds useful for carbohydrate analysis.
245
Which aromatic amines can react with carbohydrate products?
Aniline, o-toluidine
## Footnote
These reactions also contribute to the formation of colored compounds for analysis.
246
Fill in the blank: The extraction of saccharides typically uses _______.
hot 80% ethanol
247
True or False: Oligosaccharides include maltodextrins.
True
248
What is the significance of the phenol-sulfuric acid method?
It is used for carbohydrate analysis by producing colored compounds
## Footnote
The method relies on the reactions of carbohydrates with phenolic compounds and aromatic amines.
