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Potato sloughingandand
instrumental methodsfor its assessment
Anna Hejlová, Jiří Blahovec
• Cooked potato quality and texture profile
• Sensory methods for texture assessment
• CPM/CPW (cooked potato mass/weight) tests for sloughingassessment
Potato sloughingand
instrumental methodsfor its assessment
assessment
• CPEM (cooked potato effective mass) method as modification ofCPM tests
• CT (cooking time) and disintegration rate - new sloughingparameters
• Sloughing
in different varieties
in different cultivation conditions
in relation to tuber density and starch content
Cooked potato quality
A – Salad potatoB – Fairly firm all-purposeC – MealyD – Very mealy
Cooking/utilization
types:
saladmash
AB
C
• Mealiness
• Hardness/softness
• Visually when crushed with a fork, 1= non-mealy, 7= very mealy
• The force necesssary to cut thewedges with a fork, 1=firm, 7=soft
Potato texture profile
Sensory methods for its evaluation:Texture attributes:
• Sloughing
• Moisture/dryness
• Graininess/structure
wedges with a fork, 1=firm, 7=soft
• Visually according to pictures, 1=remaining whole, 7=completelydisintegrated
• Orally, 1=moist, 7=dry
• Orally, 1=fine, 7= coarse
Potato sloughingflaking and disintegration of the outer layers of
potato tubers cooked in water
Sensory methodsvisually according to pictures of cooked tubers
1 = remaining whole, 7 = completely disintegrated
• separating in water
bath• remaining on the
cooked sample
Instrumental methodsdetermination of cooked potato tissue amount
1 = remaining whole, 7 = completely disintegrated
Standard CPM/CPW test(cooked potato mass/weight)
potato sloughing assessment
Potato samplecut from inner parenchyma
100 g, 10x10x1.5 mm
Cooked and stirreddecanted
CPM value recordedcooking curve: CPM ~ t
EAPR (European Association of Potato Research), Wageningen,1977
CPM cooking curves120
115
110
105
95 po
tato
ma
ss
(g
) NicolaCT = 32 min100
CT = 11 min100
Panda
Direct correlation between CT100
and cooking type was not found
CT100< 4 min … very sloughed
CT100> 12 min … non-sloughed
EAPR: recommends as a
complement to sensory tests
85
90
420 14121086 2422201816 32302826
cooking time (min)
co
ok
ed
CT = 14 min100
CT = 11 min100
Javor
CPM cooking curve – result of 10-20 measurements
(Vacek, 1997)
100 g – mass of the raw potato sampleCT100 (characteristic time) – resistance against sloughing
Modification: CPEM method
• Sample cooked and stirred on the sieve
• Cooked potato effective mass CPEM recorded continuously during cooking
• The whole cooking curve obtained in one test
• The sloughing can bestudied in relation to tuber density
Sample preparation
3-4 tubers of the samesize and density ρ (kg/m3)
potato sample = 100 gflakes 10x10x1.5 mm
estimated by double weighing in air (m) and in water (muww)
ρ = ρwater m / (m – muww)
CPEM experimental set-up
1 – glass beaker (5l, dia 180 mm) with a
round metal sieve 2x2 mm placed 5 mm
above the beaker bottom
2 – polystyrene desk3 – screen basket (dia 150 mm, height
190 mm, diamond mesh 3x5 mm, part of a
pasta cooker)
4 – laboratory stand
5 – analytical balance SCALTEC
6 – immersion heater (≈ 1 kW)
7 – stirring apparatus with metal propeller
(VEB Prüfgeräte-Werk, Dresden, 1967)
8 – metal propeller9 – NTC thermistor10 – digital multimeter11 - stopwatch
Time schedule of the CPEM test
s ted
Pre-Heating120 s
working temperature
Init
ial
Sc
reen
Eff
ecti
ve M
as
s
Heating30 s
Calming30 s
Bala
nce D
ata
:00
:10
Heating30 s
Bala
nce
Dat a
Calming40 s
:00
:10
:45
Sa
mp
le i
ns
ert
ed
Heating30 s
Calming30 s
Ba
lan
ce D
ata
:00
:10
t = -1 t = 0 t = 1Experiment time (min)
:05
:05
:05
148
149
150
151
152
153
154
155
-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24
Recorded cooking curve and temperature
Sample insertion
SEM initial screen effective mass
t (min)Reco
rded
bala
nce d
ata
m
bal(g
)
96,5
97,0
97,5
98,0
98,5
99,0
99,5
100,0
-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24
Initial test temperature
t (min)
T (°° °°C
)
-2
-1
0
1
2
3
4
5
6
7
0 2 4 6 8 10 12 14 16 18 20 22 24
transformed CPEM curve= initial screen effective mass SEM
subtracted
change in SEM
final CPEM curve= change in SEM compensated
CP
EM
(g
)
t (min)
Calibration and final CPEM cooking curve
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Sample includedm = 0.0395 t - 0.9532, R2 = 0.9673
Calibration test without samplem = 0.0339 t + 0.1645, R2 = 0.9584
t (min)
Ch
an
ge
of
SE
M (
g)
3
4
5
6
7
CPEM cooking curve and parameters
SBP - Slope of the Breaking Part
Breaking Part
Cooking Part
CP
EM
(g
)
0
1
2
3
0 2 4 6 8 10 12 14 16 18 20 22 24
CT - Cooking Time
t (min)
CP
EM
(g
)
CT … cooking time required to start disintegration (min) SBP … disintegration rate (g/min)
Sloughing in different cultivars
0,40
0,60
0,80
1,00
1,20S
BP
(g
.min
-1)
Nicolacooking type BAsalad
Agriacooking type Bcrispscultivation regimes
Saturna
Sloughed
0,00
0,20
4 6 8 10 12 14 16 18 20 22
CT (min)
salad
Saturnamealystarch Salad
CT … cooking time required to start disintegration
SBP … disintegration rate 0
1
2
3
4
5
6
7
0 2 4 6 8 10 12 14 16 18 20 22 24
SBP (g/min)
CT (min)C
PE
M (
g)
t (min)
Different cultivation regimes
0.005
0.010
0.015
0.020
SB
P (
g.s
-1)
4
6
8
10
12
CT
(m
in)
Agria 2004+2005F Fertilization, W Irrigation
0.000
F0 F1 W0 W1
0
2
F0 F1 W0 W1
0
1
2
3
4
5
6
7
0 2 4 6 8 10 12 14 16 18 20 22 24
SBP (g/min)
CT (min)C
PE
M (
g)
t (min)
CT … cooking time required to start disintegration
SBP … disintegration rate
Fertilization ≈ lower degree of sloughingIrrigation … no significant influence on sloughing
CPEM parameters in relation to tuber density
0,20
0,40
0,60
0,80
1,00
1,20
1,40
4
6
8
10
12
14
16
18
Nicola
Agria
Saturna
Agria
Saturna
Nicola
SB
P (
g.m
in-1
)
CT
(m
in)
0,00
0,20
1060 1070 1080 1090 1100 1110 1120
2
4
1060 1070 1080 1090 1100 1110 1120
ρρρρ (kg.m-3) ρρρρ (kg.m-3)
Nicola
higher degree of sloughing ≈ higher tuber density
0
1
2
3
4
5
6
7
0 2 4 6 8 10 12 14 16 18 20 22 24
SBP (g/min)
CT (min)C
PE
M (
g)
t (min)
CT … cooking time required to start disintegration
SBP … disintegration rate
correlation between tuber density, dry matter and
starch content
• Maercker´s tables (1880)
• Scheele´s formulas (1937)
2
4
6
8
10
12
14
16
18
1060 1070 1080 1090 1100 1110 1120
ρρρρ (kg.m-3)
CT
(m
in)
Nicola
Agria
Saturna
CT ~ CTMV - b (ρρρρ – ρρρρMV)
Linear model of cooking stage I
b (min.m3.kg-1)
• CT-sensitivity to tuber densityand starch content
• Cooking parameter typical for variety, independent ofgrowing conditions
R2 … 0.5 – 0.92
ρρρρ (kg.m-3)
ρρρρMV (kg.m-3)
• Density mean value of testedtubers
• Correlates closely with starchcontent
growing conditions
CTMV (min)
• Cooking time mean value
• Characteristic of potatovariety
Why does the cooked potato tissuedisintegrate?
• Biological plant material
• Parenchyma cells
Starch – starchswelling pressure dueto gelatinisation, comparable with turgor
• Parenchyma cells
• Disintegration = potato cell ruptureand/or separation
comparable with turgor pressure
Cell wall and middlelamella – degradationof pectic polymers
2
4
6
8
10
12
14
16
18
1060 1070 1080 1090 1100 1110 1120
ρρρρ (kg.m-3)
CT
(m
in)
Nicola
Agria
Saturna
CT ~ aCT0 - b (ρρρρ – ρρρρ0)
Linear model of cooking stage II
b (min.m3.kg-1)
• CT-sensitivity to tuber densityand starch content
• Cooking parameter typical for variety, independent ofgrowing conditions
R2 … 0.5 – 0.92
ρρρρ (kg.m-3)
ρρρρ0
(kg.m-3)
• Density of hypothetical potatotissue without starch
• Estimated as 1005 kg.m-3
(empirical formulas betweendensity, dry matter and starchcontent - von Scheele)
growing conditions
aCT0 (min)
• Time of cooking necessary to start disintegration of fictivepotato tissue without starch
• Characteristic related to cell wall and middle lamellaproperties
2
4
6
8
10
12
14
16
18
1060 1070 1080 1090 1100 1110 1120
ρρρρ (kg.m-3)
CT
(m
in)
Nicola
Agria
Saturna
CT ~ aCT0 - b (ρρρρ – ρρρρ0)
Linear model of cooking stage III
b (min.m3.kg-1)
• CT-sensitivity to tuber densityand starch content
aCT0 (min)• Time of cooking necessary to
1060 1070 1080 1090 1100 1110 1120
ρρρρ (kg.m-3)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
18 19 20 21 22 23 24 25 26 27 28 29 30
aCT0 (min)
b (
min
.m3.k
g-1
)
Nicola
Agria+Saturna+Samantana
start disintegration of fictivepotato tissue without starch
• Characteristic related to cell wall and middle lamellaproperties
The most varieties followed a commoninner mechanism of cell tissuedisintegration
Divergent behavior of salad
cultivar Nicola was observed
Conclusions
• objective instrumental method for potato sloughingassessment
• reduces experimental material and operational time
• potato cooking properties can be studied in detail in relationto tuber density
CPEM method
to tuber density
• CT cooking time – main parameter• less than 6 min – sloughed (type C)
• 6 – 14 min – moderately sloughed (type B)
• more than 14 min – slightly and non-sloughed (type A)
• improvement of experimental set-up possible
PublicationsHejlová A., Blahovec J., Vacek, J. (2006) Modified test for potato sloughingassessment. Journal of Food Engineering 77(3), 411-415.
Blahovec J., Hejlová A. (2006) Role of Tuber Density in Potato Sloughing. Journal ofTexture Studies 37,165-178.
Hejlová A., Blahovec J. (2008) Sloughing in potatoes induced by tuber density and affected by variety. Czech Journal of Food Sciences, 26(1): 41-50.
Blahovec J. and Hejlova A. (2010). Simple Kinetic Models of Potato Sloughing, International Journal of Food Properties, 13(1): 51-64.
Hejlová, A. and Blahovec, J. (2010). The Modified CPEM (Cooked Potato Effective Mass) Method: an Instrumental Assessment of Potato Sloughing. Czech Journal of Food Sciences, 28(5): 407-411.
Current research:Blahovec, J., Hejlová, A., Čopíková J. and Novák, M. (2011). Tensile Properties ofMicrobial β-Glucan Films. Polymer Engineering and Science, 51:2564-2570.
Hejlová A., Blahovec J. (2015). Stress Relaxation and Activation Volume in Tension in β-Glucan and Chitosan Films. Polymer Engineering and Science, 55 (3): 624-633.
Thank you for your attention
