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4/24/17
1
Sensory Quality Measurements
Florence ZakharovDepartment of Plant Sciences
Evaluating Fruit Flavor Quality
• Appearance• Taste, Aroma
• Texture/mouthfeel
Instrumental evaluation / Sensory evaluation
Qualityaspectsforfreshproduce
• Color• Shape• Blemishes• Decay• Affectsinitialdecisionto
purchase• Generallylongershelflife
• Taste/aroma• Texture• Nutrition• Affectsdecisionforrepeat
purchase• Generallyshortershelflife
External characteristics Internal characteristics
Mary Lu Arpaia
Appearance• Shape, size
• Color (uniformity, intensity)
• Gloss (wax)
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Quality Class of compound Examples
Sweet Sugars Sucrose, fructose, glucose
Sour Acids Citric acid, malic acid, tartaric acid
Bitter Alkaloids, Phenolics, Terpenoids, some proteins
Naringin, cucurbitacins, limonoids
Salty Ions Sodium, calcium
Umami Amino acids Glutamate, aspartate
Fruit Composition and Taste Sweet Taste – Rapid Methods
TOTAL Soluble Solids = sugars, organic acids, soluble pectins, anthocyanins, phenolic compounds, ascorbic acid…
Socrative poll– roomnumber:FRUITRIPENING
Sweet Taste – Rapid MethodsEnzyme-based sugar quantification
Fructose
Glucose
Sucrose
Glucose-6-P 6-P-gluconate
NAD+ NADH
Ø More accurate measurement of sweetness-related solutes
Sour Taste – Rapid Methods
• pH
• Titratable acidity
• Enzyme-based acid quantification
• SSC/Acidity meter from ATAGO (citrus, grape, tomato)
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Electronic Tongues
Alpha MOS ASTREE e-tongue St Petersburg Univ. e-tongue
Beullens et al., 2008
Texture
• Penetrometer
• Texture Analyzer
• Aroma (or smell or odor) is the sensation perceived when volatile compounds are drawn into the nose.
n Ripe fruits generally produce tens to hundreds of volatiles. This mixture of volatiles is what we perceive as “aroma”.
Aroma VolatilesWhat is a volatile compound?
• A small molecule which has a high tendency to evaporate.
• Volatiles are naturally produced by plants (from almost all plant organs) and animals.
• Fruit aromas are made up of complex mixtures of volatile compounds (recall strawberry – over 200!).
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What does a volatile compound smell like?
• Each single volatile compound has a distinct smell/odor.
Floral, woody, sweet, fruity, berry, green
Sulfurous, vegetable,
cabbage, onion
b-ionone Dimethyl disulfide Myrcene
Peppery, spicy
Volatile Analysis by GC-MS: the “gold standard”
GCMS
Electronic NosesiSense Colorimetric Sensor Array Airsense Portable Electronic Nose
Gómez et al., 2008Suslick et al., 2010; Askim et al., 2013
Odor Thresholds
• Our olfactory system has different sensitivity levels for different volatiles.
• Some volatiles, like furaneol, we can detect at extremely low levels; while others, like acetic acid (vinegar!), we can detect only at higher levels.
• Even though acetic acid is much more abundant than furaneol in strawberries, it is furaneol that is most important for determining the characteristic aroma of the strawberry (because of its low odor threshold value).
O
OHO
O
OH
OT≈10ppb
OT≈60ppm
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Sensory Attributes and Fruit Composition
• All fruit components (sugars, acids, volatiles, etc…) combine to generate a unique sensory experience for the consumer.
• Physical methods give accurate measurements of fruit composition but it is difficult to relate these measurements to fruit quality without information about sensory perception.
Whatissensoryevaluation?
• ASCIENCE thatmeasures,analyzes,andinterpretsthereactionsofthesensesofsight,smell,sound,tasteandtexturetoproducts
• ItisaPEOPLE science,i.e.peopleareessentialtoobtaininformationaboutproducts
H. Stone, 1999, Food Technology, 53(10):124.
Mary Lu Arpaia
Sensory Evaluation
• Cantelldifferencesb/wproducts
• Cantellwhyandhowmuch
• DoNOTaskpreference• 10-12panelists• Hoursoftraining
• Cantelldifferencesb/wproducts
• Cannottellwhy• Cantellpreferencesbetweenproduct
• 50-100panelists• Logistics
Trained panel (objective)
Consumer panel (subjective)
Mary Lu Arpaia
Your Tools: Panelists• Consumerpanels(notraining)indicatehowmuchaproductisliked
• Donotindicatewhichcomponentoftheproductisthedriverforliking
• Descriptiveanalysis(trainedpanels)todefinedescriptors,traits
• RelateconsumerwithdescriptivePreferencemapping
Mary Lu Arpaia
4/24/17
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Sensory evaluation is no trivial matter!
Beforeyoustart• Knowwhatquestionyouwanttoaskandhowyouaregoingtogettheanswer!
• Makesureyoumakeadjustmentstocommodityneedsforexperiment
• RecognizethatthisisaTIMEintensiveactivity• Workwithsomeonewhohastraininginthisarea
Mary Lu Arpaia
Variability – within tree
Characteristics of the distribution of SSC/TA of
Valencia orange fruit in 5 light Classes Light Class SSC/TA Range Outside 12.56 8.54 – 21.00 Canopy 10.99 4.80 – 16.50 Inside 10.14 5.71 – 14.17 Top outside 12.78 9.69 – 18.47 Top inside 11.50 8.92 – 10.41 All fruit 11.56 4.80 – 21.00
• Outside– fruitonouteredge,max.light• Canopy– fruitembeddedinleafcanopy;partiallyshadedatalltimes• Inside– continuousshade• TopOutside– fulllightallthetime• TopInside– topoftree,embeddedinfoliage;partiallightSitesandReitz,Proc.Amer.Soc.HortSci.,1950
SSC varies in treeLess variation in TA
SSC/TA variation due to SSC
Mary Lu Arpaia
Variability within the fruitSSC (%) Titratable Acidity (%)
SSC Lowest in inner middle of fruit
TA Highest in inner middle of fruit
Mary Lu Arpaia
Does citrus postharvest handling influence eating quality of navel oranges?
M. L. Arpaia and D. Obenland
Mary Lu Arpaia
4/24/17
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Field Bin Washer Waxer Packed Box
1 2 34
Packing House Fruit Sampling Scheme
Does the packing line affect fruit flavor?
6.4 a 6.1 a 6.1 a 6.0 bAverage Acceptability (Hedonic Score)
Mary Lu Arpaia
Fruit stored at 41F for 0, 3, 6 weeks followed by 4 days at 68 F and 3 days at 54 F
Does time in storage affect fruit flavor?
6.4 a 6.2 a 5.7 b
Average Hedonic Score
0 wk 3 wk 6 wk
Mary Lu Arpaia
10 compounds changed significantly due to storage duration
5 compounds changed due to handling
Differences in aroma active compounds and internal ethanol were detected due to
storage and handling
Mary Lu Arpaia
Conclusions• Onegrowerlotoutof3wasdistinctlydifferent• Commercialpacklinehandlinghadaninfluenceoneatingquality
• Eatingqualitydeteriorateswithstorage• Thesedifferencesappeartobeprimarilyrelatedtothefinalstepsoffruithandlingsincewedetecteddifferencesduetoplacementonpackline
• ThealterationineatingqualityisduetochangesinvolatilecharacteristicsratherthanchangesinSSCorTA
Mary Lu Arpaia
4/24/17
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Althoughtherearechallengesweareonlylimitedbyourimaginationonhowtoapplythistooltoourprograms
Thequestionswewillaskneedtobefocusedandspecific
Understandingthatsensoryevaluationisanothertooltobeusedinenhancingourknowledgeofproductquality
Concluding remarks
Mary Lu Arpaia
Questions?Many thanks to Mary Lu Arpaia for sharing her slides on sensory evaluation