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WorksheetsExam 2.2.1 Food Analysis
Total questions: 150
Worksheet time: 1hrs 15mins
Which statement best defines food analysis in scientific practice?
Marketing strategies to increase consumer demand
Routine cooking methods to enhance flavor and texture
Application of analytical procedures to characterize food properties
Environmental assessments of agricultural land use
Which is a primary use of food analysis for manufacturers?
Boost sales via social media promotional campaigns
Reduce packaging costs by minimizing materials used
Increase crop yields with genetic modification programs
Verify product and facility safety through regular testing
Which aspect is commonly characterized through food analysis?
International trade tariffs and quotas
Corporate governance and shareholder reporting
Composition, structure, and physico‑chemical properties
Climate variability across farming regions
Which outcome aligns with maintaining overall food quality and safety under regulation?
Eliminating all imported food from local markets
Mandating uniform packaging colors for all brands
Lowering prices by cutting inspection personnel
Ensuring the food supply is safe, wholesome, high quality
Which practice supports prevention of economic fraud in food production and labeling?
Use of larger fonts and brighter label colors
Seasonal promotion of premium product lines
Analytical verification of authenticity and composition
Outsourcing distribution to third‑party vendors
Under RA 10611, which body coordinates Philippine food safety regulation across agencies?
Regional Agricultural Standards Committee
National Food Defense Strategy Council
Food Safety Regulation Coordinating Board
Philippine Consumer Protection Task Force
Which agencies are listed under the DOH food safety regulatory group?
Bureau of Plant Industry and Fertilizer Authority
National Dairy Authority and Sugar Regulatory Administration
Department of Trade and Industry and DOST
Food and Drug Administration and Bureau of Quarantine
Which agencies fall under the Department of Agriculture for food safety?
Bureau of Animal Industry and National Meat Inspection Service
Department of Health and Department of the Interior
Department of Science and Technology and DTI
Food and Drug Administration and Bureau of Quarantine
Which statement describes Good Manufacturing Practices in the context of food safety?
Procedures ensuring harmful substances are eliminated before consumption
Marketing guidelines for brand placement in supermarkets
Financial auditing standards for food companies
International trade rules for exporting food products
Which analytical capability is emphasized for detecting contaminants in food safety programs?
High sensitivity to detect low levels of contaminants
Energy efficiency in refrigeration equipment
Automated scheduling of delivery logistics
Rapid color changes to improve product aesthetics
Which statement best distinguishes a Standard of Identity from a Standard of Quality in food regulation?
Identity sets required composition; quality sets minimum attributes
Identity defines packaging weight; quality defines shelf life days
Identity sets labeling format; quality sets serving size rules
Identity sets factory hygiene; quality sets inspection frequency
Which is a key role of the Codex Alimentarius Commission?
Setting globally harmonized food safety standards
Enforcing national retail price controls
Auditing individual factory production lines
Issuing product-specific trademarks
Under mandatory standards, what do Standards of Fill-of-Container ensure?
Manufacturers disclose country of origin
Labels list all micronutrients per serving
Containers are properly filled to prevent deception
Packaging uses recyclable materials only
Which agency develops technical standards to ensure quality, safety, and market access for products and systems in the Philippines?
Bureau of Philippine Standards (BPS)
Food and Drug Administration (DOH)
Bureau of Fisheries and Agriculture
Codex Alimentarius Secretariat
HACCP is best described as which of the following?
A legal definition of nutrient content claims
A voluntary grading program for prime meat cuts
A systematic approach to identify and control food hazards
A container fill measurement protocol
The Nutritional Labeling and Education Act (NLEA, 1990) primarily requires what?
Mandatory organic certification for produce
Daily menu disclosure for restaurants
Front-of-pack traffic-light labeling
Standardized nutrition labels on food products
Which list best reflects nutrients typically required on standardized nutrition labels?
Calories, moisture, ash, fiber fractions, total solids
Water activity, pH, titratable acidity, specific gravity
Pesticide residues, mycotoxins, heavy metals, allergens
Calories, fat, sodium, carbohydrates, protein, vitamins, minerals
Which consumer benefit is directly linked to nutritional labeling?
Ensuring identical taste among brands
Making informed dietary choices
Guaranteeing lowest retail prices
Eliminating all foodborne pathogens
What is the typical analytical tolerance for energy, fat, and carbohydrate values on nutrition labels when no related claims are made?
Within 5% above and 5% below declared value
Within 50% above and 50% below declared value
Within 20% above and 20% below declared value
Exactly equal to declared value only
Health claims in Philippine labeling adopt guidelines from which body?
European Food Safety Authority
International Organization for Standardization
World Trade Organization
Codex Alimentarius Commission
Which agency establishes and enforces mandatory food safety standards and conducts laboratory analyses for compliance?
Bureau of Philippine Standards
Food and Drug Administration - DOH
Department of Trade and Industry
Bureau of Fisheries and Agriculture
Which statement about voluntary standards of grade is most accurate?
They define required ingredient composition
They regulate fill levels for containers
They mandate nutrient lists on all packages
They classify foods based on quality categories
Authenticity testing in food analysis primarily ensures what?
Every batch meets identical sensory scores
All labels use the same font and format
All packages are filled to identical net weights
Product claims on origin, ingredients, or variety are truthful
Which characteristic is required of official analytical methods used in food inspection and grading?
Accurate, reliable, simple, and cost-effective
Proprietary, confidential, and expensive
Subjective, non-reproducible, and narrative
Experimental, complex, and unvalidated
Quality control in food manufacturing mainly aims to achieve which outcome?
Consistent products that meet safety and nutritional value
Maximize advertising exposure across media channels
Increase product novelty over consistency
Eliminate the need for any government oversight
Which statement best describes the role of food analysis in quality control for incoming materials?
Predicts processing behavior for desired results
Focuses only on final product sensory tests
Eliminates the need for supplier specifications
Replaces documentation of test performance entirely
During processing, why are on-line analytical techniques preferred?
Eliminate the need for trained personnel
Guarantee complete absence of defects
Rapid, precise, non-destructive measurements
Lower equipment maintenance requirements
In HACCP, what is the primary purpose of identifying critical control points?
Reduce marketing costs of new products
Specify tests and corrective actions for safety
Replace legal labeling requirements entirely
Improve flavor without measuring parameters
Which question aligns with raw material evaluation in a quality assurance program?
Is the label information already developed?
Do they meet required legal specifications?
How can we develop new products from it?
Will it have the appropriate shelf life?
Which critical question best fits process control samples?
Did a specific step yield acceptable composition?
Are materials safe and authentic for purchase?
What are competitor product characteristics?
How do complaint samples differ in quality?
For finished product analysis, which aspect is directly evaluated?
Potential to develop entirely new products
Compliance with legal requirements and claims
Supplier capability for future deliveries
Need to modify a processing parameter
Which action follows if a finished product is unacceptable and cannot be salvaged?
Freeze distribution and extend shelf life
Immediately change raw material suppliers
Conduct consumer panel testing first
Decide on trash, rework, or seconds
In research and development, food analysis primarily supports which activity?
Evaluates physical, chemical, sensory traits
Eliminates need for fundamental studies
Focuses solely on marketing preferences
Ignores interactions between ingredients
Which statement correctly links composition analysis to labeling?
Labels remove the need for compositional tests
Accurate quantification supports nutrition labels
Structural analysis determines label wording
Only vitamins require quantification for labels
Which structural level is correctly matched with its description?
Molecular: >100 mm, air cells and particles
Microscopic: 10–100 mm, visible inclusions
Molecular: 1–100 nm, shapes and interactions
Macroscopic: 10–100 nm, crystal aggregates
Which physicochemical property category focuses on deformation and flow affecting texture?
Rheological properties and behavior
Optical properties and appearance
Flavor properties and aroma release
Stability properties and shelf life
Why are objective analytical methods used alongside sensory evaluation?
Ensure testing is subjective and resource-free
Correlate measurable parameters to attributes
Replace all consumer testing entirely
Avoid evaluating texture and flavor together
Which statement best describes Good Laboratory Practices (GLP) in a food lab?
A set of principles for non-clinical study integrity
A marketing guideline for consumer communication
A single safety rule for handling food samples
An informal checklist used by individual analysts
Which is a key objective of GLP?
Ensure accuracy and reproducibility of test data
Prioritize speed over method validation
Eliminate the need for documentation entirely
Increase sample throughput at any cost
Which element of GLP focuses on detailed protocols for all tests?
Quality Control Checks
Organization and Personnel
Facilities and Equipment
Standard Operating Procedures
In GLP, proper collection, labeling, storage, and disposal relate primarily to which component?
Sample Handling processes
Audit and Review cycles
Calibration and Maintenance
Data Management systems
Which activity is part of Quality Assurance (QA) rather than just GLP?
Planned and systematic activities to meet standards
Single-study protocol writing for one experiment
Informal peer discussions about results
Unrecorded trial runs to explore methods
Which practice most directly enhances safety in food laboratories?
Proper handling of samples and chemicals
Increasing test speed through fewer steps
Outsourcing data review to vendors
Skipping labeling to reduce complexity
Which statement distinguishes Quality Control (QC) from QA?
QC uses routine operational checks with control samples
QC focuses on long-term process improvement cycles
QC is only about documentation management and archiving
QC eliminates the need for staff training and competency
Why is regular calibration and maintenance part of QA systems?
To guarantee precision of equipment results
To reduce the number of documented procedures
To replace training and competency needs
To limit audit requirements permanently
Which GLP element ensures accurate recording, reporting, and archiving?
Audit and Review policies
Facilities and Equipment
Sample Handling steps
Data Management protocols
Which outcome reflects the importance of GLP in food laboratories?
Repeated tests yield consistent results
Analysts may skip validation steps
Regulatory compliance becomes optional
Credibility relies solely on marketing
Which benefit is most associated with QA in food testing?
Reduced need for calibration and audits
Consistent quality through standardized processes
Greater variance across different analysts
Faster testing by removing documentation
Which difference between GLP and QA is highlighted in the Venn diagram?
GLP provides framework; QA ensures ongoing improvement
GLP focuses on marketing; QA handles equipment purchase
GLP removes traceability; QA increases subjectivity
GLP prevents audits; QA discourages compliance
Which statement best distinguishes random errors from systematic errors in analytical measurements?
Random errors arise from instruments; systematic errors arise from people
Random errors are large in magnitude; systematic errors are negligible
Random errors affect accuracy only; systematic errors affect precision only
Random errors fluctuate unpredictably; systematic errors are consistent
Gross errors in food analysis are most accurately described as:
One-time blunders often due to human mistakes
Small unavoidable fluctuations around a mean
Consistent deviations from true values
Bias introduced by calibrated instruments
Which source is commonly associated with gross errors?
Slow or incomplete reactions
Instrumental drift over long runs
Matrix effects in complex samples
Transposition and transcription during recording
Random errors primarily impact which aspect of measurements?
Precision of repeated measurements
Trueness of the final result
Calibration function definition
Indicator color selection
Which situation best represents a systematic error?
A transcription slip during data entry
A sample spill leading to one incorrect result
A vibration causing occasional reading spikes
An uncalibrated instrument giving consistently high readings
Personal systematic errors can arise from which factor?
Blank variability between runs
Random environmental temperature changes
Variable gains and losses bias in electronics
Operator bias affecting judgment consistently
An instrumental systematic error is best exemplified by:
Glassware delivering volumes slightly off graduation
Sample heterogeneity across aliquots
Observer’s inconsistent judgment under fatigue
Unpredictable mechanical vibrations during weighing
Which description fits method systematic errors in analysis?
Introduced by transcription mistakes in calculations
Due to instability of instrument power supplies
Caused by careless reading of the instrument scale
Arising from non-ideal chemical behavior of the system
Outliers are most often linked to which error type in food analysis datasets?
Random errors from indeterminate variables
Systematic errors from instrument drift
Method errors from side reactions
Gross errors from one-time mistakes
Which is a typical source of random error listed for analytical work?
Matrix effects altering analyte response consistently
Environmental fluctuations causing unpredictable changes
Operator bias influencing color endpoint repeatedly
Uncalibrated volumetric glassware biasing results
When are random errors considered unavoidable in measurement?
They arise solely from analyst inattention
They are always present to a small extent
They happen only when using new instruments
They occur only during poor reagent control
Which practice is part of error control through quantification methods?
Using non-ideal reagents to stress-test methods
Ignoring blank corrections in calibration curves
Relying on single unverified sample measurements
Comparison with standards such as direct titration
In external standard calibration, the primary goal is to:
Detect and remove one-time transcription mistakes
Eliminate all random fluctuations during analysis
Match sample matrix exactly with the standard
Establish instrument response versus analyte concentration
Which statement about systematic errors is accurate?
They shift results consistently in one direction
They cannot affect measurement accuracy
They are easily identified by brief inspection
They are larger than all random errors by default
Which assumption underlies external standard calibration in instrumental analysis?
Instrument cannot distinguish similar signals
Matrix effects are negligible across samples
Standards must be chemically different from analyte
Analyte response varies unpredictably with matrix
Which issue is a common error source in external standard calibration?
No contamination during sample preparation
Unlimited number of standards available
Perfect matching of standards to analyte
Matrix effects altering the analyte response
In standard addition, why is the sample spiked with known analyte?
To change the chemical form of the analyte
To reduce instrument sensitivity permanently
To avoid using blanks during calibration
To compensate for matrix effects in complex samples
Which statement best describes internal standard methodology?
Calibrate with blanks instead of standards
Add a known reference species to all solutions
Use only external standards for comparison
Spike samples with multiple analytes randomly
A suitable internal standard should provide a signal that is:
Similar yet distinguishable from analyte
Identical and indistinguishable from analyte
Completely unrelated to analyte chemistry
Invisible to the instrument response
Which requirement must an internal standard meet regarding the sample matrix?
Reactive with analyte to enhance signal
Variable concentration across samples
Present naturally in high concentration
Absent from the matrix before addition
Which step helps ensure accurate apparatus performance?
Skipping calibration to avoid bias
Relying solely on operator experience
Calibration with a standard and external calibration
Using only replication without calibration
What is the main purpose of blank determination?
Estimate errors from reagent impurities
Measure instrument resolution limits
Increase analyte concentration in samples
Eliminate the need for internal standards
Replication in measurements primarily aims to:
Remove the need for recovery experiments
Increase matrix effects intentionally
Change the analyte chemical form
Reduce likelihood of unintentional errors
Recovery experiments involve:
Adding known analyte standard to sample
Subtracting blank signal from response
Using multiple additions without spiking
Diluting standards to match matrix
For addition or subtraction of independent quantities, the propagated error ΔZ equals:
Average of ΔX and ΔY
Product of ΔX and ΔY values
Sum of ΔX and ΔY directly
Square root of ΔX² plus ΔY²
For multiplication or division of independent quantities, the relative error az/z equals:
Difference of ΔX and ΔY over Z
Square root of (ΔX/X)² plus (ΔY/Y)²
Sum of ΔX and ΔY divided by Z
Square of ΔX plus square of ΔY
Which statement about the purpose of error propagation is accurate?
Replaces the need for replication entirely
Quantifies precision and identifies error sources
Proves the instrument is perfectly calibrated
Eliminates all random and systematic errors
If the observed value minus literature value is much greater than ΔZ, the error is likely:
Systematic rather than random
Random rather than systematic
Instrumental noise only
Due to rounding alone
Which analyst practice supports reliable food analysis results?
Maintaining focus and scientific attitude
Skipping questions to save analysis time
Avoiding reference samples entirely
Relying on single trial measurements
Which statement best distinguishes direct from indirect moisture determination methods in food analysis?
Direct measures a property correlated with water
Direct removes water and measures mass change
Indirect yields higher accuracy without calibration
Indirect removes water and measures gravimetrically
Which major purpose of proximate analysis relates to consumer information requirements?
Legal and labeling compliance
Microbial stability evaluation
Food processing control
Nutritional quality estimation
During sample handling for moisture analysis, which practice minimizes moisture gain from ambient air?
Increase friction during grinding
Delay weighing until room dries
Use larger headspace containers
Limit open-air exposure time
In drying methods, moisture percentage is calculated primarily from which measurement?
Sample volume change
Infrared absorbance value
Water activity reading
Initial minus dried mass
Which statement about total solids in drying-based moisture analysis is correct?
Sum of bound and free water
Mass lost before heating begins
Material remaining after evaporation
Only volatile non-water compounds
Why are forced draft ovens often preferred for general drying when no standard method exists?
Shortest constant-rate period
Built-in vacuum control
Highest infrared penetration
Small temperature differential
Which caution applies when using a forced draft oven on high-carbohydrate samples?
Prefer vacuum drying below 70°C
Use steam bath to prevent splatter
Increase temperature to compensate
Add calcium sulfate as indicator
Vacuum oven drying enhances removal of water primarily due to which condition?
Microwave energy excites dipoles
Reduced pressure lowers boiling points
Desiccant traps absorb liquid water
Higher airflow raises temperature
Which device in a vacuum oven setup monitors the gas flow rate to ensure consistent drying?
Rotameter measuring airflow
Digital analytical balance
Calcium sulfate indicator
Thermocouple probe
When drying in vacuum, why should you avoid increasing temperature to offset cooling?
Evaporation is endothermic
Moisture migrates to warmer areas
Viscosity decreases linearly
Air trap saturates quickly
Which factor most increases drying time in vacuum oven moisture analysis?
Use of sand as dispersant
Higher forced ventilation rate
Lower surface area per unit weight
Presence of metal shelving
Which product category is commonly analyzed for total solids using infrared drying?
Processed tomato products
Fresh leafy vegetables
Carbonated beverages
Raw fish fillets
Which key control factor is critical in infrared drying to avoid overheating?
Distance between source and sample
Ambient relative humidity
Container headspace volume
Sample color uniformity
Microwave drying ovens measure moisture content primarily through which approach?
Karl Fischer titration volume
Water activity at equilibrium
Infrared transmittance ratio
Weight loss after microwave heating
Which is a principal advantage of microwave drying for moisture analysis?
Least affected by sample thickness
Best for low-sugar fruits only
Highest precision without calibration
Rapid analysis reduces degradation
Which precaution improves accuracy when using microwave drying?
Use larger samples to reduce error
Avoid weighing between cycles
Increase oven temperature gradients
Uniform distribution of microwave energy
Which statement best characterizes Karl Fischer titration compared with drying methods?
Uses infrared radiation for direct heating
Requires vacuum to remove water physically
Reports total solids on dry weight basis
Chemical titration measures water stoichiometrically
Which distinction between direct and indirect moisture methods affects routine analysis feasibility?
Indirect methods favor routine use
Direct methods avoid calibration steps
Indirect methods remove water gravimetrically
Direct methods require less labor overall
Which statement best describes the principle of the Dean and Stark reflux distillation method for moisture determination?
Moisture reacts with iodine to form HI quantified by titration
Water’s capacitance change is read from dielectric sensors
Water evaporates under vacuum and is weighed as loss of mass
Water codistills with an immiscible solvent and is measured by volume
In direct distillation (e.g., Brown–Duvel), what feature distinguishes it from reflux distillation?
Water distills directly from the liquid without solvent codistillation
Water is measured by electrical impedance change
Water is inferred from refractive index readings
Water separates after cooling with an immiscible solvent
Which solvent is most commonly used in reflux distillation for moisture?
Acetone as polar solvent
Toluene as immiscible solvent
Ethanol as drying solvent
Benzene as miscible solvent
Which advantage is associated with distillation methods over oven drying?
Less thermal decomposition during analysis
Faster than Karl Fischer titration
No use of organic solvents at all
Applicable to all high‑moisture foods
Which is a common source of error in distillation moisture analysis?
Emulsions between water and solvent hinder separation
Incomplete mixing of titrant and analyte
Calibration curve misfit for hydrometry
Pressure effects on refractive index
Which application is typical for distillation moisture measurement approved by AOAC?
Fresh milk solids under AOAC 932.14B
Raw leafy vegetables under AOAC 967.19
Wine alcohol using AOAC 930.17
Spices using AOAC Method 986.21
Which limitation of distillation methods can reduce accuracy compared with weight‑based methods?
Assumption of constant atmospheric pressure
Water measured by volume rather than weight
Requirement for a dielectric standard curve
Dependence on refractive index of solutes
Karl Fischer titration is based on the reduction of iodine by sulfur dioxide in the presence of water. What indicates the endpoint?
Disappearance of milky emulsion in solvent trap
Stable refractive index equals calibration value
Appearance of dark red color due to excess iodine
Plateau in weight loss on digital balance
Which composition correctly lists classic Karl Fischer reagent components?
Silver nitrate, ammonia, acetone as solution
Iodine, sulfur dioxide, pyridine in specified ratio
Iodine, hydrochloric acid, ethanol in equal parts
Bromine, sulfuric acid, methanol in mixture
Which food type is especially suited to Karl Fischer due to erratic results from heat methods?
High‑moisture fresh vegetables
Low‑moisture foods like roasted coffee
Carbonated beverages with sugars
Fermented dairy with live cultures
Which difficulty can affect Karl Fischer measurements?
Requirement for hydrometer temperature baths
Moisture adhering to walls of the unit
Necessity of toluene reflux at high temperatures
Need for binary clear solutions only
What principle underlies the dielectric method for moisture?
Quantifying iodine consumption during titration
Measuring electrical properties such as capacitance or resistance
Observing mass loss during controlled heating
Reading refractive index changes in clear solutions
Which basis value supports dielectric moisture estimation in foods?
Water’s dielectric constant around 80 at 20°C
Sucrose’s refractive index around 1.33 at 20°C
Toluene’s boiling point near 110°C
Iodine’s endpoint colorless in ethanol
What is a key requirement for reliable dielectric moisture measurements?
Calibration with samples of known moisture
Use of hydrometer for density checks
Maintaining vacuum during extraction
Cooling condensate to separate water
Hydrometry most accurately measures solutions that are:
Highly turbid with suspended solids
Simple with one solute in a medium
Supercritical fluids under pressure
Multicomponent emulsions and gels
Which is a common application of hydrometry in food analysis?
Moisture in honey by AOAC 969.38B
Protein in milk by Kjeldahl method
Fat in meat by Soxhlet extraction
Solids in sugar syrups by AOAC 932.14B
What physical principle does refractometry rely on?
Electrical impedance proportional to moisture
Change in mass from heating to constant weight
Redox reaction consuming iodine reagent
Bending of light between media of different optical densities
Which limitation applies to refractometry for food solutions?
Cannot produce % solids or °Brix outputs
Requires distillation before any measurement
Restricted to clear, binary solutions without suspended solids
Unaffected by temperature or pressure variations
Which statement best describes the principle of the Soxhlet method for fat extraction?
Condensed solvent drips through sample during heating
Chloroform phase partitions lipids from aqueous phase
Solvent continuously siphons over sample in thimble
Acid digest releases fat measured volumetrically
In the Goldfish method, how is solvent applied to the sample?
Added once and allowed to soak sample without reflux
Heated, vaporized, condensed, then drips through sample
Mixed with acid to digest proteins before extraction
Continuously flows over sample from boiling flask
Which is a key advantage of semi‑continuous solvent extraction?
Uses nonflammable solvents exclusively
Measures fat by volumetric rise of fat layer
Builds solvent in chamber to fully surround sample
Requires no drying of high‑moisture samples
What is a common limitation of continuous solvent extraction techniques?
Possible channeling leads to incomplete extraction
Requires centrifugation at 55–60°C
Cannot determine phospholipids in milk
Only suitable for dairy products
Which set lists good solvent characteristics for lipid extraction?
Reactive, oxidizing, and miscible with water
Inexpensive, low boiling point, nonflammable
High boiling point and high toxicity
High polarity and strong hydrogen bonding
During solvent extraction, which interactions are broken while covalent bonds remain intact?
Ionic and metallic bonding
Covalent and hydrogen bonds
Van der Waals and electrostatic interactions
Peptide and glycosidic bonds
Why is drying a sample often necessary prior to solvent extraction?
Water accelerates solvent evaporation
Organic solvents cannot penetrate water‑rich foods
Acids hydrolyze lipids only in dry samples
Drying prevents oxidation during centrifugation
Which step releases lipids bound to proteins or carbohydrates before extraction?
Addition of nonpolar solvent
Acid hydrolysis with 3N HCl
Grinding at high temperature
Cold nitrogen atmosphere
What determines solvent selection efficiency for lipid extraction?
Molecular weight of analyte only
Ambient light intensity
Color of solvent and sample
Polarity of both lipids and solvents
Which statement about polar versus non‑polar lipids is correct for solvent choice?
Polar lipids dissolve in hexane solvents
Non‑polar lipids dissolve in alcohol solvents
Both dissolve equally in water
Polar lipids dissolve in alcohol solvents
Which method uses sulfuric acid to digest proteins and release fat for volumetric measurement in milk?
Mojonnier method
Folch extraction
Babcock method
Gerber method
What temperature range is typical during Babcock centrifugation?
55–60°C
80–95°C
35–45°C
20–30°C
Which is a limitation of the Babcock method?
Requires drying high‑moisture samples
Cannot determine phospholipids; remain in aqueous phase
Needs chloroform partitioning for accuracy
Only applicable to solid food matrices
How does the Gerber method differ from the Babcock method?
Employs chloroform–methanol mixture
Replaces water with KCl solution
Requires Mojonnier flask and ethers
Uses isoamyl alcohol with sulfuric acid
Which procedure partitions lipids into a chloroform bottom phase while aqueous top contains non‑lipids?
Mojonnier ether extraction
Babcock volumetric method
Folch/Bligh and Dyer extraction
Soxhlet semi‑continuous reflux
In Mojonnier method, which solvents are used to extract fat?
Hexane and ethanol
Ethyl ether and petroleum ether
Sulfuric acid and isoamyl alcohol
Chloroform and methanol
Which factor should be carefully controlled to prevent oxidation during preparation of lipid samples?
High light exposure and warm temperatures
Cold temperature, low light, antioxidants
Alkaline pH and high humidity
Strong stirring and large headspace
Which advantage is associated with the Soxhlet method?
Simultaneous extraction due to full immersion
No solvent needed for lipid isolation
Non‑destructive and rapid IR measurement
Measures fat by rise in graduated neck
Which step improves solvent contact by reducing particle size before extraction?
Centrifugation at warm temperature
Grinding or comminution at low temperature
Oxidation under nitrogen atmosphere
Addition of isoamyl alcohol
Which statement distinguishes Soxhlet from Goldfish methods?
Soxhlet partitions into chloroform; Goldfish into methanol
Goldfish applies acid digestion; Soxhlet uses alcohol
Both use volumetric fat measurement in bottles
Soxhlet immerses sample; Goldfish uses condensing drip
In the enhanced Dumas method, which gas is primarily measured by a thermal conductivity detector after CO2 and H2O are removed?
Ammonia gas produced by alkali treatment
Carbon monoxide formed during pyrolysis
Nitrogen gas from combustion products
Oxygen gas from the carrier stream
Which statement best describes the principle of the Kjeldahl method for protein determination?
Strong acid digestion releases nitrogen for titration
UV absorption at 280 nm estimates protein content
Combustion quantifies nitrogen via conductivity
Copper ions form a violet complex with peptides
What is the typical nitrogen-to-protein conversion factor used in the Kjeldahl method for mixed food proteins?
5.70 adjusted for cereal proteins
7.50 for high-lysine proteins
6.25 as grams protein per gram nitrogen
4.38 specific to collagen samples
During Kjeldahl neutralization, adding NaOH converts ammonium sulfate into which gas that is distilled into boric acid?
Carbon dioxide released by neutralization
Nitrous oxide formed by reduction
Hydrogen gas produced by base
Ammonia gas liberated from solution
Which advantage is associated with the enhanced Dumas method compared to Kjeldahl?
Faster, automated operation without corrosive acids
Greater specificity for true protein nitrogen
Better precision for microgram protein assays
Lower equipment cost than titration setups
A sample measured at 280 nm relies mainly on absorption by which amino acids?
Lysine and arginine residues
Glycine and alanine residues
Tryptophan and tyrosine residues
Serine and threonine residues
Which is a major limitation of direct UV measurement at 280 nm for proteins?
Nucleic acids absorb and cause interference
Requires complex chemical reagents
Cannot be used on clear solutions
Only detects proteins with copper binding
In the Biuret method, what produces the characteristic violet-purple color under alkaline conditions?
Zinc ions reacting with histidine side chains
Iron ions chelating with heme groups
Silver ions binding to cysteine residues
Cupric ions complexing with peptide bonds
Which wavelength is typically used to measure Biuret assay absorbance?
At 500 nm for high proteins
Near 750 nm for low proteins
Exactly 280 nm in UV range
Around 540 nm after incubation
The Lowry method increases sensitivity by combining Biuret chemistry with which reagent?
Ninhydrin color reagent
Folin–Ciocalteu phenol reagent
Bradford Coomassie dye reagent
Ortho-phthalaldehyde reagent
Compared to Biuret, the Lowry method is approximately how much more sensitive?
50–100 times greater sensitivity
2–5 times greater sensitivity
5–10 times greater sensitivity
150–200 times greater sensitivity
Which statement about UV-visible protein methods is accurate?
Chemical modification is always required
Only scattering is used for quantification
Proteins absorb or scatter light in UV-visible
Absorption occurs only above 600 nm
For Biuret assay standardization, which protein is commonly used as a reference?
Gelatin from collagen as standard
Lysozyme solution as standard
Bovine Serum Albumin as calibrant
Casein micelles as reference
Which interference can falsely increase absorbance in direct 280 nm measurement, and what is a common mitigation?
Turbidity from particulates; use multiple wavelengths
High ammonium; increase alkalinity
Bile pigments; add Folin reagent
Lipid opalescence; switch to 750 nm
Which disadvantage is common to the enhanced Dumas method?
Slow manual titration steps
High initial cost for specialized equipment
Requires corrosive sulfuric acid reagents
Measures only true protein nitrogen
In Kjeldahl titration, the endpoint is detected after forming which borate species in the receiving flask?
Boric acid trimerization complex
Sodium borate from NaOH excess
Potassium borate precipitate
Ammonium borate from absorbed NH3
