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Quiz Flashcards

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.

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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

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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

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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.

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5
Q

What is a significant disadvantage of the Kjeldahl method?

A

Measures total organic nitrogen, not just protein nitrogen

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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

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7
Q

What are the applications of the Dumas method?

A

Suitable for all types of foods and requires no hazardous chemicals

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8
Q

What are the disadvantages of the Dumas method?

A

Expensive equipment is required and measures total organic nitrogen, not just protein nitrogen

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9
Q

What is dietary fiber primarily composed of?

A

Polysaccharide molecules

Includes components like cellulose, hemicelluloses, and lignin.

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10
Q

What are components of insoluble dietary fiber?

A

Cellulose, microcrystalline cellulose, lignin, hemicelluloses, resistant starch

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11
Q

Fill in the blank: Dietary fiber is essentially the sum of the _______ components of a foodstuff.

A

[nondigestible]

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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.

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13
Q

What does the nitrogen to protein conversion factor depend on?

A

The type of food being analyzed

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14
Q

True or False: The Dumas method is less time-consuming than the Kjeldahl method.

A

True

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15
Q

What is the temperature range for combustion in the Dumas method?

A

700–1000 °C

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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

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17
Q

List the components of soluble dietary fiber.

A
  • Other polysaccharides
  • Native pectin
  • Hydrocolloids/food gums
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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

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19
Q

What does N H C l represent in the nitrogen calculation?

A

Normality of HCl, in mol/1000 ml

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20
Q

How is the corrected acid volume calculated?

A

(ml std. acid for sample) – (ml std. acid for blank)

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21
Q

What is the atomic weight of nitrogen used in the nitrogen calculation?

A

14

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22
Q

What is the conversion factor to convert percent nitrogen to percent crude protein?

A

6.25

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23
Q

What is the formula for calculating protein from nitrogen percentage?

A

%N × 6.25 = %protein

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24
Q

What is the importance of protein analysis?

A

To determine total protein content, protein composition, and nutritional value

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25
Q

What is the Kjeldahl method used for?

A

To analyze total organic nitrogen in food samples

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26
Q

What occurs during the digestion step of the Kjeldahl procedure?

A

Proteins are digested with sulfuric acid and catalysts to form ammonium sulfate

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27
Q

What is formed from the reaction of nitrogen and sulfuric acid during digestion?

A

Nonvolatile ammonium sulfate

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28
Q

What is the purpose of neutralization in the Kjeldahl method?

A

To neutralize sulfuric acid and prepare for distillation

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29
Q

What indicators are used in the boric acid solution during distillation?

A

Methyl blue and methyl red

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30
Q

What is titrated in the Kjeldahl method?

A

Borate anion with standardized HCl

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31
Q

True or False: Dietary fibers are digestible and supply calories.

A

False

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32
Q

What are some sources of dietary fiber?

A

Vegetables, fruits, whole grains, legumes

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33
Q

What are the health benefits of dietary fiber?

A

Reducing the risk of heart disease and diabetes

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34
Q

What components are included in dietary fiber?

A
  • Cellulose
  • Hemicellulose
  • Lignin
  • Pectin
  • Mucilage
  • Gum
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35
Q

What does crude fiber measure?

A

The quantity of indigestible cellulose, pentosans, lignin, and other components in foods

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36
Q

What type of dietary fiber does crude fiber refer to?

A

The type that remains as indigestible

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37
Q

What does crude fiber refer to?

A

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.

The treatment dissolves all soluble fiber and some insoluble fiber in a food.

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38
Q

What is the primary composition of crude fiber?

A

Crude fiber is primarily composed of cellulose and lignin.

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39
Q

Is the determination of crude fiber content mandatory worldwide?

A

Yes, the determination of crude fiber content of food and animal feed is mandatory worldwide.

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40
Q

Why is the measurement of insoluble fiber important?

A

Measurement of insoluble fiber is important for calculating the caloric content of food.

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41
Q

What is one method allowed to calculate calories in food?

A

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.

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42
Q

What are the approximate calorie values per gram for protein, fat, and carbohydrates?

A

Approximately 4, 9, and 4 Calories per gram, respectively.

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43
Q

What is dry ashing?

A

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.

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44
Q

What happens to most minerals during dry ashing?

A

Most minerals are converted to oxides, sulfates, phosphates, chlorides, and silicates.

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45
Q

What are some volatile elements that may be lost during dry ashing?

A
  • As
  • B
  • Cd
  • Cr
  • Cu
  • Fe
  • Pb
  • Hg
  • Ni
  • P
  • V
  • Zn
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46
Q

What is an advantage of conventional dry ashing?

A

It is a safe method that requires no added reagents or blank subtraction.

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47
Q

What is a disadvantage of dry ashing?

A

The length of time required (12–18 hours or overnight) and loss of volatile elements.

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48
Q

What is wet ashing sometimes called?

A

Wet ashing is sometimes called wet oxidation or wet digestion.

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49
Q

What is the primary use of wet ashing?

A

Preparation for specific mineral analysis and metallic poisons.

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50
Q

What is one advantage of wet ashing?

A

Minerals usually stay in solution with little or no loss from volatilization.

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51
Q

What is a disadvantage of wet ashing?

A

It requires virtually constant operator attention and uses corrosive reagents.

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52
Q

What type of samples are generally used for ash determination?

A

A 2–10 g sample is generally used for ash determination.

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53
Q

What should always be used for ash determination?

A

Distilled-deionized water should always be used.

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54
Q

What is the recommended drying method for fresh stem and leaf tissue?

A

They should be dried in two stages: first at a lower temperature of 55 °C, then at a higher temperature.

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55
Q

What type of water should be used in plant material analysis?

A

Distilled-deionized water

This is crucial to avoid contamination and ensure accurate results.

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56
Q

How should fresh stem and leaf tissue be dried?

A

In two stages:
* First at a lower temperature of 55°C
* Then at a higher temperature

This method helps prevent artifact lignin.

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57
Q

What is the maximum moisture content for plant material to be ashed without prior drying?

A

15% or less

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58
Q

What does ash content represent in foods?

A

The total mineral content

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59
Q

Why is determining ash content important?

A

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

Understanding ash content helps in nutritional labeling and quality control.

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60
Q

What is ash in the context of food analysis?

A

The inorganic residue remaining after ignition or complete oxidation of organic matter

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61
Q

What are the two major types of ashing methods?

A
  • Dry ashing
  • Wet ashing (oxidation)

Dry ashing is primarily for proximate composition and some mineral analyses, while wet ashing is for specific mineral analysis.

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62
Q

On what basis can ash content of foods be expressed?

A

On either a wet weight or a dry weight basis

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63
Q

What is the typical ash content of most fresh foods?

A

Rarely greater than 5%

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64
Q

What is the ash content of pure oils and fats?

A

Little or no ash

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65
Q

What is the ash content of cured bacon and dried beef?

A
  • Cured bacon: may contain 6% ash
  • Dried beef: may be as high as 11.6% (wet weight basis)
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66
Q

How is dietary fiber often determined?

A

Gravimetrically

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67
Q

What materials are selectively solubilized during dietary fiber analysis?

A

Digestible carbohydrates, lipids, and proteins

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68
Q

What enzymes are used in starch analysis?

A
  • Alpha-amylase
  • Debranching enzymes (pullulanase and isoamylase)
  • Glucoamylase (amyloglucosidase)
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69
Q

What does α-Amylase catalyze?

A

Hydrolysis of unbranched segments of 1,4-linked α-D-glucopyranosyl units

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70
Q

What do debranching enzymes hydrolyze?

A

The 1,6 linkages that constitute the branch points

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71
Q

What does Glucoamylase (amyloglucosidase) do?

A

Starts at the nonreducing ends of starch chains and releases D-glucose one unit at a time

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72
Q

What temperature and duration are used to gelatinize starch granules in fiber methods?

A

95–100°C for 35 minutes

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73
Q

What remains unhydrolyzed in dietary fiber analysis?

A

Resistant starch molecules

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74
Q

How are lipids treated in fiber analysis?

A

Removed easily with organic solvents

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75
Q

What must be corrected for during fiber analysis?

A

Protein and minerals not removed during solubilization

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76
Q

Why are methods for fiber determination continually researched?

A

Because:
* Labeling of dietary fiber content is required
* Dietary fiber is a complex heterogeneous material
* Its physiological importance

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77
Q

What does A.O.A.C. method 991.43 determine?

A

Soluble, insoluble, and total dietary fiber in various food products

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78
Q

What are the steps involved in the A.O.A.C. method for dietary fiber determination?

A

Treating the sample with:
* Thermostable α-amylase
* Protease
* Glucoamylase

This method helps isolate insoluble and soluble dietary fiber.

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79
Q

What is the importance of protein analysis?

A
  • Nutrition labeling
  • Pricing based on protein content
  • Functional property investigation

Proteins have unique functional properties that are vital in food science.

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80
Q

What basic principles are involved in protein analysis methods?

A
  • Determinations of nitrogen
  • Peptide bonds
  • Aromatic amino acids
  • Dye-binding capacity
  • Ultraviolet absorptivity of proteins
  • Light scattering properties
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81
Q

What factors must be considered in the selection of an appropriate method for a particular application?

A

sensitivity, accuracy, precision, speed, cost of analysis

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82
Q

Why is the analysis of proteins complicated?

A

Some food components possess similar physicochemical properties

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83
Q

What are sources of nonprotein nitrogen in food?

A

free amino acids, small peptides, nucleic acids, phospholipids, amino sugars, porphyrin, vitamins, alkaloids, uric acid, urea, ammonium ions

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84
Q

What does total organic nitrogen in foods primarily represent?

A

nitrogen primarily from proteins and to a lesser extent from all organic nitrogen-containing nonprotein substances

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85
Q

What major food components may interfere with the analysis of food proteins?

A

lipids and carbohydrates

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86
Q

What is the matrix assisted laser desorption time-of-flight (MALDI-TOF) technique useful for?

A

analysis of a homologous series of oligosaccharides

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87
Q

What is the most abundant component of food after water?

A

starch

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88
Q

Where is starch found in plants?

A

leaves, stems, roots, tubers, seeds

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89
Q

What types of starches are commercially available as food additives?

A

corn (maize), waxy maize, high-amylose corn (amylo maize), potato, wheat, rice, tapioca (cassava), arrowroot, sago

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90
Q

What is the principle for determining total starch?

A

complete conversion of starch into D-glucose by purified enzymes specific for starch

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91
Q

What potential problems can arise when determining total starch?

A

Contamination from other enzymic activity releasing D-glucose, e.g., cellulases, invertase, β-glucanase, and catalase

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92
Q

What enzyme oxidizes D-glucose in the GOPOD method?

A

glucose oxidase

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93
Q

What does the GOPOD method involve for measuring D-glucose?

A

oxidation of a colorless compound to a colored compound which is measured spectrophotometrically

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94
Q

What is the method of choice for the determination of starch?

A

The combination of enzymes in sequential enzyme-catalyzed reactions

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95
Q

What does gas-liquid chromatography (GLC) provide for carbohydrates?

A

qualitative and quantitative analysis

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96
Q

What must sugars be converted into for gas chromatography?

A

volatile derivatives

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97
Q

What are the commonly used derivatives for gas chromatography?

A

alditol peracetates, aldonic acid pertrimethylsilyl ethers

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98
Q

What is the detector of choice for peracetylated carbohydrate derivatives?

A

flame ionization detector

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99
Q

What is a significant problem with GC for carbohydrate analysis?

A

involvement of two preparation steps: reduction of aldehyde groups and conversion to a volatile derivative

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100
Q

What is oxidation in the context of chemical reactions?

A

Oxidation is a loss of electrons.

101
Q

What is reduction in the context of chemical reactions?

A

Reduction is a gain of electrons.

102
Q

What are reducing sugars?

A

Reducing sugars are those sugars that have an aldehydo group (aldoses) that can give up electrons to an oxidizing agent.

103
Q

What is produced when the aldehydo group is oxidized?

A

A carboxylic acid group is produced.

104
Q

Under what conditions do ketoses behave as weak reducing sugars?

A

Under alkaline conditions.

105
Q

What is the most often used method to determine amounts of reducing sugars?

A

The Somogyi–Nelson method.

106
Q

What does the Somogyi–Nelson method measure?

A

It measures the reduction of Cu(II) ions to Cu(I) ions by reducing sugars.

107
Q

What complex is reduced in the Somogyi–Nelson method?

A

An arsenomolybdate complex.

108
Q

What is the visual indicator of the reaction in the Somogyi–Nelson method?

A

An intense, stable blue color.

109
Q

What is the absorbance measured at in the Somogyi–Nelson method?

A

520 nm.

110
Q

What is the Dinitrosalicylic Acid method used for?

A

To measure reducing sugars naturally occurring in foods or released by enzymes.

111
Q

What does the Munson–Walker method measure?

A

It measures the precipitate of cuprous oxide.

112
Q

How can the cuprous oxide precipitate be determined in the Munson–Walker method?

A

Gravimetrically, by titration with sodium thiosulfate, potassium permanganate, or electrolytically.

113
Q

What is required when using methods that measure reducing sugars?

A

Standard curves because each reducing sugar reacts differently.

114
Q

What is the method of choice for analysis of mono- and oligosaccharides?

A

High-Performance Liquid Chromatography (HPLC).

115
Q

What types of analysis does HPLC provide?

A

Qualitative analysis and quantitative analysis.

116
Q

What is the general solubility characteristic of lipids?

A

Lipids are soluble in ether, chloroform, and other organic solvents, but sparingly soluble in water.

117
Q

What is the widely accepted definition of lipids based on?

A

Solubility.

118
Q

What do the terms lipids, fats, and oils refer to?

A

They are often used interchangeably to refer to the collection of food molecules that meet the definition of lipids.

119
Q

What is the difference between fats and oils?

A

Fats are solid at room temperature, while oils are liquid at room temperature.

120
Q

What are lipids that are solid at room temperature generally referred to as?

A

Fats

121
Q

What are lipids that are liquid at room temperature generally referred to as?

A

Oils

122
Q

Why is accurate analysis of lipids in foods important?

A

For accurate nutritional labeling and to ensure product meets manufacturing specifications

123
Q

What can inaccuracies in lipid analysis result in?

A

Costly errors for manufacturers and undesirable product quality

124
Q

What is the Folch extraction method used for?

A

Extracting lipids from small samples

125
Q

What is the Bligh and Dyer extraction method used for?

A

Extracting lipids from large samples of high moisture content

126
Q

What is added to minimize oxidative degradation of fatty acids during analysis?

A

Pyrogallic acid

127
Q

What are fatty acid methyl esters (FAMEs) used for in lipid analysis?

A

Quantitative measurement by capillary gas chromatography

128
Q

Total fat is calculated as the sum of individual fatty acids expressed as what?

A

Triglyceride equivalents

129
Q

What type of fats includes only the cis form of fatty acids?

A

Monounsaturated fats

130
Q

True or False: Trans fats can be quantified using established identification criteria.

A

True

131
Q

What method involves the addition of H2SO4 to a known amount of milk for fat quantification?

A

Babcock method

132
Q

What is the principle of the Gerber method for milk fat analysis?

A

Uses sulfuric acid and amyl alcohol to digest proteins and release fat

133
Q

What are proteins composed of?

A

Hydrogen, carbon, nitrogen, oxygen, and sulfur

134
Q

How many α-amino acids are the building blocks of proteins?

A

Twenty

135
Q

What is the most distinguishing element present in proteins?

A

Nitrogen

136
Q

What is the Mojonnier method primarily applied to?

A

Dairy foods

137
Q

What is the method used for fat extraction in pet food?

A

Acid hydrolysis with HCl followed by extraction with ethyl ether and petroleum ether

138
Q

Fill in the blank: The combination of chloroform and methanol is commonly used to extract _______.

A

Lipids

139
Q

What method is used to extract fat in the Mojonnier method?

A

A mixture of ethyl ether and petroleum ether

The extracted fat is dried to a constant weight and expressed as percent fat by weight.

140
Q

Does the Mojonnier test require removal of moisture from the sample?

A

No

It can be applied to both liquid and solid samples.

141
Q

What is a disadvantage of the Mojonnier method compared to continuous methods?

A

It requires more time

The continuous method is faster and more efficient.

142
Q

What is the principle behind the Soxhlet method?

A

Continuous solvent extraction

The solvent continuously flows over the sample held in a ceramic thimble.

143
Q

What is one advantage of microwave ashing?

A

Reduces sample preparation time to minutes

This has led to widespread use in analytical and quality control laboratories.

144
Q

What type of digestion may be performed safely in a closed-vessel microwave system?

A

Microwave wet ashing

The choice of system depends on sample amount and required temperatures.

145
Q

What is the common acid used in microwave wet ashing?

A

Nitric acid

It is often the acid of choice for digestion.

146
Q

What is the key factor affecting the accuracy of direct solvent extraction methods?

A

The solubility of the lipids in the solvent used

It also depends on the ability to separate lipids from complexes with other macromolecules.

147
Q

True or False: Acid hydrolysis eliminates some matrix effects exhibited by solvent extraction methods.

A

True

148
Q

Fill in the blank: The total lipid content of food is commonly determined by _______.

A

[organic solvent extraction methods]

149
Q

What is the disadvantage of the Goldfish method?

A

It may cause channeling, resulting in incomplete extraction

This can affect the accuracy of the fat content measurement.

150
Q

What type of method is the Soxhlet method categorized under?

A

Semi-continuous solvent extraction method

AOAC Method 920.39 for cereal fat and AOAC Method 960.39 for meat fat are examples.

151
Q

What does the Mojonnier extraction equipment eliminate in the hydrolysis process?

A

Some matrix effects

This is particularly relevant for multicomponent food products.

152
Q

What is a characteristic of continuous solvent extraction methods?

A

Faster and more efficient extraction

They are more effective than semi-continuous extraction methods.

153
Q

What is the main purpose of total fat determination in food?

A

Nutrition labeling

Total fat is most commonly determined by gas chromatography (GC) analysis.

154
Q

In microwave digestion, what can closed-vessel systems process at a time?

A

Up to 40 samples

This allows for significant throughput in laboratories.

155
Q

What are two types of ashing that can utilize microwave instrumentation?

A

Wet ashing and dry ashing

This method provides a faster alternative to conventional techniques.

156
Q

What is the definition of viscosity?

A

Viscosity is the measure of a substance’s resistance to motion under an applied force.

157
Q

What is the viscosity measuring range of the VISCOMETER digital rotational viscometer?

A

1~100,000 mPa.s

158
Q

What is the accuracy of the VISCOMETER digital rotational viscometer?

A

±2%

159
Q

What is the typical expression for viscosity measurement?

A

Centipoise (cP)

160
Q

Fill in the blank: The phenol-sulfuric acid procedure is often used as a qualitative test for the presence of _______.

A

carbohydrate

161
Q

What are the three states of water in food products?

A
  • Free water
  • Adsorbed water
  • Water of hydration
162
Q

What does water activity (Aw) determine?

A

How much water is available for microbial growth.

163
Q

True or False: Water activity is the same as water content.

A

False

164
Q

What major components does proximate analysis of foods determine?

A
  • Moisture
  • Ash (total minerals)
  • Lipids
  • Protein
  • Carbohydrates
165
Q

What is a pycnometer used for?

A

Measuring specific gravity by comparing the weights of equal volumes of a liquid and water.

166
Q

What is the water activity value for pure water?

A

One

167
Q

What are the effects of temperature on viscosity?

A

Temperature can easily affect the viscosity of certain foods.

168
Q

What is the importance of accurate temperature measurement in food safety?

A

It is an important indicator of food safety and food quality.

169
Q

What is the standard curve used for in the phenol-sulfuric acid method?

A

It must be prepared using mixtures of the same sugars present in the unknown.

170
Q

What is the role of calibration in temperature measurement?

A

Calibration is important to keep thermometers accurate.

171
Q

Fill in the blank: The ease of water removal from foods depends on how it exists in the food _______.

A

product

172
Q

What is the significance of the food matrix in analytical methods?

A

The food matrix often presents the greatest challenge to the analyst.

173
Q

What types of foods can cause different types of interferences in analysis?

A
  • High-fat foods
  • High-sugar foods
174
Q

What does the term ‘food matrix’ refer to?

A

The nutrient and non-nutrient components of foods and their molecular relationships.

175
Q

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 = _______.

A

density of sample

176
Q

What are the water activity levels for fresh meat and fish?

A

> 0.98

177
Q

What is an alcoholometer used for?

A

Estimating the alcohol content of beverages.

178
Q

What is a Brix hydrometer used for?

A

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
Q

What is the purpose of alcoholometers?

A

Alcoholometers are used to estimate the alcohol content of beverages.

180
Q

What type of liquids is the Twaddell hydrometer specifically for?

A

The Twaddell hydrometer is only for liquids heavier than water.

181
Q

List the reasons why food analysis is important.

A
  • Food safety
  • Quality control
  • Nutritional value
  • Product development
182
Q

What does food analysis help detect?

A

Food analysis helps detect adulterants, such as expired ingredients, harmful compounds, and deceptive labels.

183
Q

What is proximate analysis in food analysis?

A

Proximate analysis involves the determination of carbohydrates, lipids, crude protein, crude fiber, dietary fiber, ash, and mineral content.

184
Q

What does Brix measure?

A

Brix measures the soluble solids in a liquid and is equivalent to the percentage by weight of sugar.

185
Q

What is the minimum soluble solids percentage required for jams and jellies?

A

At least 65 percent for jams and jellies.

186
Q

True or False: The higher the Brix, the more water is available for microorganisms to grow.

A

False. The higher the Brix, the less water available for microorganisms to grow.

187
Q

What is the refractive index (RI)?

A

The refractive index (RI) is a dimensionless constant used to describe the nature of a food.

188
Q

What principle is used to measure specific gravity?

A

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
Q

What is the formula for density?

A

Density (ρ) = mass (m) / volume (V).

190
Q

What is specific gravity?

A

Specific gravity is the density of a liquid compared to the density of another material, usually water.

191
Q

Fill in the blank: The direct method for moisture determination involves _______.

A

[oven drying, desiccation, distillation, extraction, and other physicochemical techniques]

192
Q

What are the two methods for moisture determination?

A
  • Direct method
  • Indirect method
193
Q

What does the indirect method of moisture determination involve?

A

Continuous measurement and automatic control of moisture content in food processing.

194
Q

What are the main types of vitamin assays?

A
  • Bioassays
  • Microbiological assays
  • Physicochemical assays
195
Q

What is the reference standard method for vitamin analysis?

A

The line test, based on bone calcification.

196
Q

True or False: Bioassays are currently used for the analysis of all vitamins.

A

False. Bioassays are used primarily for vitamins B12 and D.

197
Q

What is the reference standard method of analysis for vitamins B1, B12, and D?

A

The line test, based on bone calcification.

198
Q

Why is the determination of vitamin D limited to animals?

A

It involves deficiency studies and sacrificing test organisms.

199
Q

Which vitamins can be analyzed using microbiological assays?

A

Water-soluble vitamins such as C, B6, B12, Thiamin, Riboflavin, Niacin.

200
Q

What is critical for accurate results in microbiological assays?

A

Strict adherence to the analytical protocol.

201
Q

What organisms are typically used in microbiological assays?

A

Bacteria, yeast, or protozoans.

202
Q

How is growth measured in microbiological assays?

A

In terms of turbidity, acid production, gravimetry, or respiration.

203
Q

What factors affect the stability of vitamin A?

A

Ultraviolet light, air, high temperatures, and moisture.

204
Q

What method is considered the only acceptable for measuring vitamin A activity?

A

High-performance liquid chromatography (HPLC).

205
Q

What is the role of vitamin analysis in nutrition?

A

Determining nutritional requirements and assessing diet adequacy.

206
Q

How are vitamins defined?

A

As relatively low-molecular weight compounds required in small quantities.

207
Q

What deficiency disease is caused by a lack of ascorbic acid?

A

Scurvy.

208
Q

What deficiency disease is due to the lack of niacin?

A

Pellagra.

209
Q

What is a significant advantage of microwave muffle furnaces over conventional dry ashing?

A

They can ash samples in minutes, decreasing analysis time by as much as 97%.

210
Q

What is the moisture content range of fresh fruits?

A

81-93%.

211
Q

What is the moisture content range of vegetables?

A

90-95%.

212
Q

What is the moisture content of nuts?

A

1.5-3%.

213
Q

What is the significance of knowing mineral levels in food?

A

Minerals are of nutritional and functional importance.

214
Q

How is calcium content affected in direct acid cottage cheese?

A

Low calcium due to acid action freeing calcium bound to casein.

215
Q

What methods are used for specific separation of minerals?

A

Colorimetry, ion-selective electrodes (ISE), atomic absorption spectroscopy, or inductively coupled plasma-atomic emission spectroscopy.

216
Q

What is the extraction method for vitamin E in general food products?

A

Saponified under reflux, extracted with hexane, and analyzed by HPLC.

217
Q

What is the extraction method for oils in HPLC analysis?

A

Dissolved in hexane and injected directly onto the HPLC column.

218
Q

What is thiamin also known as?

A

Vitamin B1

219
Q

What does the thiochrome fluorometric procedure measure?

A

The fluorescence measurement of the oxidized form of thiamin, thiochrome

220
Q

What must be done under subdued light during the thiochrome method?

A

All analytical steps following the oxidation

221
Q

What is the impact of temperature and time on moisture loss during analysis?

A

Moisture loss is a function of time and temperature

222
Q

At what temperature do carbohydrates decompose?

A

100°C

223
Q

What is the chemical reaction for the decomposition of glucose?

A

C6H12O6 → 6C + 6H2O

224
Q

What is the boiling point of water at which moisture is typically evaporated?

A

100°C

225
Q

How does the presence of solute affect the boiling point of water?

A

The boiling point is raised by 0.512°C for 1 mol of solute in 1.0 L of water

226
Q

What influences the rate and efficiency of moisture removal?

A

Particle size, particle size distribution, sample sizes, and surface area

227
Q

What is the principle of the oven drying method?

A

The loss of weight is used to calculate the moisture content of the sample

228
Q

List the typical extraction procedures for vitamins.

A
  • 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
Q

What is the principle of the dichloroindophenol titrimetric method?

A

L-ascorbic acid is oxidized to L-dehydroascorbic acid by the oxidation-reduction indicator dye

230
Q

What does the microfluorometric method measure?

A

Both ascorbic acid and dehydroascorbic acid

231
Q

What is the caloric contribution of carbohydrates to the human diet?

A

More than 70%

232
Q

What are nondigestible polysaccharides primarily composed of?

A

All those other than starch

233
Q

What are some attributes contributed by carbohydrates?

A
  • Bulk
  • Body
  • Viscosity
  • Stability to emulsions and foams
  • Water-holding capacity
  • Freeze-thaw stability
  • Browning
  • Flavors
  • Aromas
  • Textures
234
Q

What is the principle of the phenol-sulfuric acid method?

A

It is a condensation reaction used for determining carbohydrates

235
Q

What is essential for reliable results in riboflavin determination?

A

Exact adherence to the permanganate oxidation process

236
Q

What treatments are included in extraction methods for vitamins?

A
  • Heat
  • Acid
  • Alkali
  • Solvents
  • Enzymes
237
Q

What is the common extraction requirement for fat-soluble vitamins?

A

Saponification

238
Q

What must be done for the extraction of mono- and oligosaccharides?

A

Specific extraction procedures designed to stabilize the sugars

239
Q

What is saponification?

A

A chemical reaction typically occurring overnight at room temperature or by refluxing at 70°C

Saponification is often used in the production of soap from fats and oils.

240
Q

What types of saccharides can be determined in extraction?

A

Mono-, di-, tri-, tetra-, and oligosaccharides

Examples include glucose (mono), sucrose (di), raffinose (tri), stachyose (tetra), and maltodextrins (oligo).

241
Q

What method is used for carbohydrate extraction?

A

Hot 80% ethanol extraction of dried, lipid-free sample

This method helps to isolate various types of saccharides for analysis.

242
Q

What happens to carbohydrates under strong acids and high temperatures?

A

They are destroyed and undergo a series of complex reactions

These reactions include dehydration and produce various furan derivatives.

243
Q

What are the products of continued heating of carbohydrates in the presence of acid?

A

Brown and black substances

These substances form as a result of condensation reactions with other products.

244
Q

Which phenolic compounds can condense with carbohydrate products?

A

Phenol, resorcinol, orcinol, α-naphthol, naphthoresorcinol

These reactions produce colored compounds useful for carbohydrate analysis.

245
Q

Which aromatic amines can react with carbohydrate products?

A

Aniline, o-toluidine

These reactions also contribute to the formation of colored compounds for analysis.

246
Q

Fill in the blank: The extraction of saccharides typically uses _______.

A

hot 80% ethanol

247
Q

True or False: Oligosaccharides include maltodextrins.

A

True

248
Q

What is the significance of the phenol-sulfuric acid method?

A

It is used for carbohydrate analysis by producing colored compounds

The method relies on the reactions of carbohydrates with phenolic compounds and aromatic amines.

Food Analysis (2 decks)

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