WorksheetsExam 2.2.2 Food Analysis
Total questions: 96
Worksheet time: 48mins
Which statement best describes sensory analysis in food evaluation?
Relies solely on instrumental odor detectors
Measures nutrient content using spectrometry
Applies chromatographic separation of flavors
Uses human panels for taste and aroma
Which factor is most critical when selecting an analytical technique for a specific food product?
The number of personnel available
The brand of laboratory instruments
The marketing claims of the product
The analyte or property to be measured
Which source is appropriate for finding validated procedures for food analysis?
Personal blogs by food enthusiasts
Official method repositories like AOAC
Vendor advertisements for reagents
General news articles on nutrition
Which criterion reflects accuracy in analytical method selection?
Closeness of measured values to true values
Ability to detect the lowest analyte concentration
Consistency across different analysts
Repeatability within the same laboratory
A laboratory needs rapid results for safety testing. Which criterion directly addresses this need?
Sensitivity: Lowest analyte concentration detectable
Precision: Repeatability within one laboratory
Simplicity: Ease of use by personnel
Speed: Duration required to achieve results
Why is categorization of food samples essential before analysis?
Guarantees samples never change during extraction
Eliminates the need for cleanup steps entirely
Allows ignoring matrix complexity in measurements
Ensures representative sampling and suitable methods
Which step in sample preparation primarily targets analyte isolation from complex matrices?
Storage maintains cold chain conditions
Cleanup removes interfering substances
Homogenization creates a uniform mass
Extraction isolates the target analytes
A method must detect an analyte present among similar matrix compounds. Which selection criterion applies?
Specificity: Detects analyte despite similar compounds
Safety: Low hazard reagents and procedures
Official approval by ISO and AOAC bodies
Matrix nature like polarity and optical properties
Which formula correctly expresses moisture content by oven drying on a wet basis?
wt of wet sample ÷ wt of dry sample × 100
wt of dry sample ÷ wt of wet sample × 100
wt H2O lost ÷ wt of dry sample × 100
wt H2O in sample ÷ wt of wet sample × 100
In oven drying, which calculation gives total solids on a wet basis?
wt of dry sample ÷ wt of wet sample × 100
wt of wet sample ÷ wt of dry sample × 100
wt H2O in sample ÷ wt of wet sample × 100
wt volatile solids ÷ wt of wet sample × 100
Reflux distillation moisture is computed for a 50 g sample as:
Volume of H2O × 2
Mass of distillate × 2
Volume of solvent × 2
Volume of H2O ÷ 2
Karl Fischer titration requires determining which parameter before sample titration?
KFR water equivalence (KFReq)
Sample response factor
Ashing temperature
Protein conversion factor
Moisture by Karl Fischer is calculated using:
%Moisture = S ÷ KFReq × 100
%Moisture = S × KFReq ÷ Ks × 100
%Moisture = KFReq × Ks ÷ S × 100
%Moisture = Ks ÷ S × 100
In the Goldfish method, fat is determined by:
Sample’s weight loss or fat collected
Ash remaining after incineration
Increase in solvent mass after reflux
Protein nitrogen converted to ammonia
Which expression computes weight of fat in sample during continuous extraction?
beaker ÷ fat
(fat + thimble) − beaker
beaker − (beaker + fat)
(beaker + fat) − beaker
Soxhlet (semicontinuous) fat on dry weight basis is calculated as:
g of fat lost ÷ g of blank residue × 100
g of fat in sample ÷ g of dried sample × 100
g of fat in sample ÷ g of wet sample × 100
g of fat recovered ÷ g of solvent × 100
In discontinuous methods like Mojonnier, percent fat is computed using:
peak area of methyl esters × response factor
100 × {[(wt dish + fat) − (wt dish)] − (avg wt blank residue)} ÷ wt sample
(beaker + fat − beaker) ÷ wt sample × 100
g fat ÷ g dried sample × 100
For GC fat by AOAC 996.06, results are based on:
Peak height or area
Karl Fischer reagent volume
Titrant normality alone
Dry ash weight
Kjeldahl method initially converts sample nitrogen to which compound?
Ammonium sulfate
Nitric oxide
Ammonium nitrate
Urea
In Kjeldahl, moles of HCl used in titration equal:
Moles of NH3
Moles of protein
Moles of sulfuric acid
Moles of NaOH
Kjeldahl percent nitrogen is calculated using:
%N = N HCl × g sample ÷ corrected acid volume × 100
%N = 14 × g sample ÷ corrected acid volume × 100
%N = corrected acid volume ÷ N HCl × 14 × 100
%N = N HCl × corrected acid volume ÷ g sample × 14 g/mol × 100
Which conversion factor is commonly used to express protein from %N?
%N × 2.0
%N × 5.0
%N × 6.25
%N × 0.16
Total carbohydrates for labeling are computed as:
100 − (%Water + %Protein + %Fat + %Ash)
%Protein + %Fat + %Moisture + %Ash
100 − (%Water + %Protein)
%Fiber + %Sugars + %Starch
Ash represents which component in food analysis?
Total minerals
Total moisture
Total nitrogen
Total carbohydrates
Dry ashing typically occurs at which temperature range?
800°C to 900°C
250°C to 300°C
100°C to 150°C
525°C or higher
Percent ash on wet basis is calculated as:
M_wet ÷ M_ash × 100
M_ash ÷ M_dry × 100
(M_dry − M_ash) ÷ M_wet × 100
M_ash ÷ M_wet × 100
Which method is commonly used for declared protein in milk powder batches during nutrition labeling and QC?
Dumas combustion rapid nitrogen screening
Soxhlet crude fat extraction
Kjeldahl (AOAC) total nitrogen determination
HPLC-RID sugar profiling
In high-fat matrices like cheese, what sampling precaution helps prevent nitrogen loss during protein analysis?
Adding antioxidants during extraction
Stratified sampling to reduce heterogeneity
Drying to remove bound moisture
Defatting to minimize nitrogen volatilization
Which technique is used for crude fat in proximate labeling of edible oils and nut products?
Soxhlet continuous extraction
Accelerated Solvent Extraction
GC-FID for fatty acids
NIR rapid screening
For frying oil quality assessment, which combination is applied to determine fatty acid composition?
ICP-MS multi-element screening
GC-FID/FAME analysis workflow
HPLC-RID carbohydrate profiling
UPLC fluorescence vitamin testing
When collecting lipid samples to avoid oxidation, what container recommendation is indicated?
Permeable plastic tubes
Open, clear bottles
Sealed, dark containers
Uncovered metal dishes
Which carbohydrate method is noted for routine QC quantification of sucrose, glucose, and fructose in cereal reformulation?
GC-MS volatile analysis
Colorimetric reducing sugar assay
FT-NIR rapid screening
HPLC-RID sugar profiling
Matrix interferences from fiber during carbohydrate analysis may require which corrective action?
Cleanup or correction steps
Increasing oven drying time
Defatting the sample first
Adding spiking antioxidants
Which moisture method offers more accurate water content in fat-rich or low-moisture matrices like chocolate powders?
Dumas combustion
Oven drying (LOD)
Karl-Fischer titration
NIR rapid screening
During oven drying for shelf-life control in bakery QC, what sampling guidance is emphasized due to moisture heterogeneity?
Apply stratified replicate sets
Use representative sampling
Select dark containers
Perform solvent methylation
Which instrument is applied for multi-element verification of mineral fortification after acid digestion?
ICP-OES/ICP-MS platforms
Atomic absorption spectrometry
HPLC-PDA chromatography
LC-MS/MS tandem analysis
For single-element checks like Fe or Zn, which method is applied routinely?
Karl-Fischer moisture titration
GC-FID fatty acid profiling
UPLC high-resolution testing
AAS single-element analysis
In vitamin analysis of fortified beverages, which approach improves speed and resolution for routine QC?
UPLC with appropriate detectors
GC-MS volatile additive screening
ICP-MS multi-element scanning
Soxhlet solvent extraction
To prevent vitamin degradation during sampling and extraction, what selection is advised?
Microwave digestion protocol
Appropriate solvent and stabilizers
Composite homogenization only
Defatting prior to titration
Which analytical method is employed for volatile additives among processed foods?
HPLC UV absorbance
Karl-Fischer reagent titration
GC-MS targeted analysis
ICP-OES elemental reads
Complex additive matrices may require which sample cleanup technique before LC-MS quantitation of sorbates or benzoates?
Solid-phase extraction (SPE)
Defatting with petroleum ether
QuEChERS partitioning
Microwave acid digestion
For routine multi-residue pesticide monitoring, which pairing is standard after QuEChERS cleanup?
HPLC-RID carbohydrate detection
GC-FID fatty acid workflow
AAS single-element screening
LC-MS/MS tandem detection
Aflatoxins and mycotoxins in grains at low microgram-per-kilogram levels are typically detected using which method?
LC-MS/MS sensitive analysis
UV-Vis dye measurement
ICP-OES elemental profiling
Soxhlet crude fat assay
Heavy metals like Pb and Cd in spices and seafood are measured with which technique?
ICP-MS trace metal analysis
Karl-Fischer titrimetric moisture
HPLC-PDA absorbance assays
GC-MS volatile fractionation
When contamination is heterogeneous, which sampling strategy is recommended to improve representativeness?
Duplicate Soxhlet extraction
Sequential aliquot drying
Single grab sampling
Stratified/composite sampling
What sample preparation step helps reduce matrix suppression in MS-based contaminant analyses?
Robust cleanup using QuEChERS or SPE
Extended oven drying of aliquots
Addition of antioxidants to extracts
Defatting followed by NIR screening
Which statistic best estimates the true value of an analyte from replicate measurements?
Median of replicate values
Mode of replicate values
Mean of replicate values
Range of replicate values
Standard deviation in analytical chemistry primarily measures what aspect of data?
Instrument calibration slope
Central value location
Systematic bias magnitude
Scatter around the mean
Which statement about coefficient of variation (CV) is correct?
CV is mean divided by standard deviation
CV is standard deviation divided by mean
CV equals variance times sample size
CV is range divided by sample size
A low CV in replicate measurements indicates what?
Significant systematic error
High precision of the method
High accuracy of the method
Large random variation
For N replicate results xi, which formula expresses sample standard deviation s?
s = Σ(xi − x̄) / N
s = √[Σ(xi − x̄)² / (N − 1)]
s = Σ(xi)/N
s = (xmax − xmin)/N
Confidence interval around the mean is typically expressed as:
x̄ ± s·t·N
x̄ ± t/(s√N)
x̄ ± N/s·t
x̄ ± t·s/√N
The t-test is used in food analysis to:
Estimate detection limits
Compare variances among groups
Construct calibration curves
Compare means of two groups
ANOVA is appropriate when the goal is to:
Compare three or more group means
Compare two group means
Detect instrument drift over time
Estimate a single population mean
In regression-based calibration, the instrument response y is modeled as:
y = x/b − m
y = b/x + m
y = m·x + b
y = m + x + b
A high R² value close to 1.0 in a calibration curve indicates:
Nonlinear instrument response
Strong linear relationship
Large residual standard deviation
High detection limit for analyte
Which criterion allows rejecting a questionable data point using the Q-test?
Q calculated equal to sample mean
Q calculated less than table value
Q calculated equal to zero
Q calculated larger than table value
For the Q-test, the spread W used in calculation is defined as:
Average of all replicate values
Difference between highest and lowest
Product of extreme values
Sum of all values measured
Interpreting analytical results should include which action when unusually high values appear?
Discard without documentation
Average with other results
Repeat testing and validation
Report with no comment
Which practice strengthens internal validation when explaining final results?
Using certified reference materials
Ignoring blank corrections
Rounding to fewer significant figures
Only reporting nominal values
Percent recovery in external validation is calculated as:
(Conc. unspiked − Conc. spiked)/Spike added
(Conc. spiked − Conc. unspiked)/Spike added
Spike added/(Conc. spiked − Conc. unspiked)
(Conc. spiked + Conc. unspiked)/Spike added
Which statement best describes how an electronic nose generates a “smell fingerprint” for food analysis?
It uses non-selective sensors converting chemical signals to electrical patterns
It measures temperature changes from enzymatic reactions in food
It relies on human tasters to calibrate sensor outputs
It isolates single volatile molecules for targeted detection
Which algorithm is most suitable for reducing dimensionality of complex e-nose signal datasets before classification?
Support Vector Machines for hyperplane separation
Artificial neural networks for deep feature extraction
Linear Discriminant Analysis for group mean separation
Principal Component Analysis for variance-based projection
An e-nose reports a pattern indicating increased amines and sulfur volatiles in stored fish. What is the most appropriate interpretation for quality control?
Spoilage is likely due to microbial degradation
Sensor drift caused random signal variation
Adulteration with non-fish proteins occurred
Freshness has improved during cold storage
Which application best aligns with using e-noses to detect food adulteration rather than spoilage?
Classifying fruit ripeness by ester profiles
Identifying papaya seeds mixed with peppercorns
Predicting shelf-life of packaged bread
Monitoring fermentation consistency in yogurt
Which advantage of e-noses directly contrasts with traditional human sensory panels?
Non-destructive sampling of food matrices
Objective and repeatable measurements
Rapid analysis in minutes
Enhanced aroma intensity perception
A manufacturer needs to decide if incoming wine shipments are authentic. Which workflow is most appropriate for the e-nose system?
Measure pH, compare to supplier certificate, accept shipment
Run GC-MS, manually compare peaks without algorithms
Collect volatile profile, apply PCA, classify with LDA or SVM
Heat samples to increase aroma, rely on operator judgment
Which limitation most likely affects long-term deployment of e-noses in production lines?
Sensor drift requiring recalibration over time
Excessive sample destruction during testing
Lack of any pattern recognition methods
Inability to detect any volatile compounds
Which statement best describes the equilibrium concept in SPME?
Analytes irreversibly bind to fiber coating
Fiber releases analytes to sample continuously
A balance forms between sample and coating
Analytes precipitate out of solution instantly
What is the primary role of the SPME fiber coating during extraction?
Dilute the analytes for easier injection
Increase sample temperature for desorption
Act like a magnet for specific analytes
Catalyze reactions in the sample
Which feature makes SPME considered a greener sample preparation method?
Uses large solvent volumes for washing
Requires extensive sample derivatization steps
Performs sampling and concentration without solvents
Depends on high-pressure liquid flows
During SPME, how do analytes move from the sample to the fiber?
They are electrochemically reduced onto fiber
They crystallize onto the fiber surface
They naturally diffuse toward attractive coating
They are pumped mechanically into coating
After extraction, where is the SPME fiber typically inserted for analysis?
Into a UV-Vis cuvette
Into a lyophilizer chamber
Into GC or HPLC instruments
Into a centrifuge rotor
Which setup is specifically designed to sample volatile analytes above a liquid or solid?
Fiber-in-solution immersion
In-tube microextraction mode
Thin-film microextraction mode
Headspace SPME configuration
Which pair lists adsorbent families commonly used to enhance SPME performance?
Enzymes and phospholipids
CNTs and MOFs
Cellulose and starch
Proteins and peptides
Which statement correctly contrasts fiber-based and thin-film microextraction?
Fibers only work in headspace modes
Thin films offer larger surface area than fibers
Fibers provide larger area than thin films
Thin films require solvents while fibers do not
Which factor does the working approach of SPME depend on?
The price of the instrument
The color of the coating
The pH of laboratory air
The origin of the analyte
In the magnetic SPME method for ascorbic acid by Su et al. (2020), which material served as the adsorbent?
Iron oxide-based magnetic adsorbent
Silver nanoparticle composite
Titanium dioxide-coated fiber
Carbon nanotube thin film
What performance outcome was highlighted for PCB removal from milk using MoS2/RGO fiber coating?
Formation of stable PCB emulsions
Complete solvent dissolution of PCBs
Rapid enzymatic degradation of PCBs
Detection of PCBs at ultra-trace levels
Which technique combination was used to determine selenium after magnetic SPME in food?
GC-MS with derivatization
ETAAS following magnetic SPME
HPLC with fluorescence detection
ICP-OES without preconcentration
Which statement best describes liquid-phase microextraction (LPME) in food analysis?
Uses tiny organic solvent for analyte transfer
Relies on large solvent volumes for extraction
Requires strong heating of aqueous samples
Depends on solid sorbents for analyte capture
In LPME, which phase typically acts as the donor phase?
Membrane polymer phase
Supercritical CO2 stream
Organic acceptor solvent
Aqueous sample matrix
What is the main role of the acceptor phase in LPME?
Remove particulate matter
Stabilize membrane pores
Provide sample dilution
Collect concentrated analytes
Why are membranes with very small pores used in HF-LPME setups?
Accelerate solvent evaporation
Trap proteins as analytes
Permit small target molecules
Increase sample turbulence
Which instrument is commonly used to analyze LPME extracts containing concentrated analytes?
Atomic force microscopes
Gas chromatography systems
Titration burettes
X-ray diffraction units
Which LPME variant uses a single droplet of organic solvent at a syringe tip?
Ionic liquid DLLME
Single-drop microextraction
Membrane-assisted extraction
Hollow-fiber LPME
Which application pairs correctly with its LPME method from recent studies?
Cadmium detection via VA-DES-ELLME
Milk sulfonamides via GC–FID
Cobalt in foods via UV/Vis
Wine catechins via MI-LLME
Which mass spectrometry technique is most widely used for wine polyphenol profiling?
Ambient MS
LC–MS platforms
HRMS only
GC×GC–MS
Which compounds are typically targeted by HPLC–MS or UPLC–MS in wines?
Metal ions
Fat-soluble vitamins
Protein allergens
Catechins and quercetin
What advantage does GC×GC–MS offer in wine polyphenol analysis?
Better differentiation by origin
Lower solvent consumption
Non-contact ionization mode
Real-time fermentation control
Ambient MS techniques in wine analysis are characterized by which feature?
Rapid, solvent-free sampling
High-temperature derivatization
Extensive chromatographic steps
Requirement of vacuum systems
Which benefit aligns with green chemistry goals in supercritical CO2 extraction?
Enhanced protein precipitation
Greater metal chelation capacity
No harmful solvent residues
Higher boiling point solvents
Supercritical CO2 behaves like both a liquid and a gas. What practical outcome does this enable during extraction?
Thermal degradation of pigments
Ionic exchange within membranes
Evaporation-resistant analytes
Efficient penetration and dissolution
Which target compounds are emphasized for SC-CO2 extraction from microalgae?
Inorganic salts and metals
Sugars and organic acids
Polysaccharides and peptides
Carotenoids and fat-soluble vitamins
What was demonstrated by using a design of experiments (DoE) in optimizing SC-CO2 extraction?
High recovery with maintained bioactivity
Need for extreme temperatures
Reduced selectivity and purity
Preference for aqueous donors
Which statement reflects a key advantage of SC-CO2 for heat-sensitive compounds?
Higher boiling points protect analytes
Reactive radicals enhance stability
Gentle conditions minimize degradation
Membrane pores retain pigments
