Peter A.M. Steeneken, Albert J.J. Woortman, A.A.C.M. (Lizette) Oudhuis
Processing stability of cross-linked starches in acid sauce applications and identification of someof the molecular factors involved
21-22 April 2010Starch Convention Detmold2
Starch functionality in sauce applications• The right thickening action
• Thickening action is exerted by swollen granules, not by dissolved starch molecules that have low viscosity and may cause sliminess
• Extended shelf life (≥ 2 yr)• Acetyl or hydroxypropyl groups confer storage stability
• Resistant to processing and media conditions (high shear, retorting, HTST, low pH)
• Cross-linking is applied to protect the swollen starch granules against processing and end-use conditions
• Specialty starches have been developed for optimum performance at specific conditions
• Processing stability• It may be advantageous to use a starch which is insensitive to processing
conditions, i.e. exerts the same thickening action at different processing conditions multi-purpose starch
21-22 April 2010Starch Convention Detmold3
Aims and approach
• Aims• Evaluate the processing stability of modified starches in sauce applications• Identify the factors that contribute to processing stability
• Approach• Development of a simplified and representative small-scale sauce model• Definition and evaluation of processing stability• Study the fate of starch during processing at molecular and supramolecular
(mesoscopic) level
• StarchesStarch Code Adipate
content (ppm)DS
acetylGranule size
(µm)Normal potato starch – acetate – adipate (small granule) NPS-AA 198 0.065 20.0
Normal potato starch – acetate – high adipate (small granule) NPS-AHA 343 0.073 18.8
Amylopectin potato starch – acetate – adipate (small granule) APS-AA 228 0.104 19.6
Waxy maize starch – acetate – adipate WMS-AA 222 0.066 13.2
21-22 April 2010Starch Convention Detmold4
Sauce model: formulation
Component Commercial sauce
Model sauce
Water + +
Modified starch + +
Xanthan + +
Sugar + +
Salt + +
Acid + +
Preservative + +
Protein +/- -
Oil +/- -
Tomato Paste + -
Flavour + -
Spices +/- -
Fruits / vegetables + -
Chicken Tonight Saté Sauce
21-22 April 2010Starch Convention Detmold5
Sauce model: formulation
Zoetzuur met perzik
Kerrie
Pikante tomaten-room
Sate
Ajam pangang
Hawai
Ketjap-tomaat
Zoetzuur met perzik
500
1000
1500
2000
Visc
osity
(cP)
400 800 1200 1600Time (s)
20
40
60
80
Tem
pera
ture
(°C
)
500
1000
1500
2000
Visc
osity
(cP)
400 800 1200 1600Time (s)
20
40
60
80
Viscosity profiles commercial sauces Viscosity profiles virgin model formulations
Tem
pera
ture
(°C
)
Composition of sauce model was derived from label information and best match with commercial sauces (as judged from final RVA viscosity)
21-22 April 2010Starch Convention Detmold6
Sauce model: processing• The RVA is used as the basic sauce making tool
• Standard processing: 25 → 85 (10 min) → 25 °C, 160 rpm, pH 4.0, simulated tap water 10 °DH.
• Processing variables in RVA• Heating time (30 min)• pH (3.6 – 5.0)• Stirring speed (up to 1920 rpm)
• Additional treatments• Standard processing plus:• Heating at 100 – 120 °C (water bath or pressure cooker)• Shear (9500 – 24,000 rpm, Ultra-Turrax T25)• Heating (100 °C) at low pH (3.6)
• Measurement• Standard RVA programme is applied to prepared model sauces. Final
viscosity at 25 °C is taken as the key parameter
• Scale• 1 g starch / 35 g model sauce. A complete test with 14 processing
variations requires < 20 g starch!
21-22 April 2010Starch Convention Detmold7
Sauce model: evaluation14-point spider web plots for 3 starches (final RVA viscosity at 25 °C)
260.0
730.0
1200.085 °C
100 °C
110 °C
115 °C
120 °C
pH 3,7 / 85 °C
pH 3,7 / 100 °C
pH 5 / 85 °C
pH 5 / 110 °C
T-24000 rpm
T-13500 rpm
T-9500 rpm
1920 rpm
960 rpm
← Shear → Standard ← Temp →
←pH
/ Te
mp →
← pH / Temp →
←S
hear
→
←Te
mp →
Yellow: NPS-AARed: NPS-AHAGreen: WMS-AA
21-22 April 2010Starch Convention Detmold8
Sauce model: quantification of processing stabilityProcessing Stability Factor (PSF) = (SD sauce viscosity) / viscosity standard (n=14)
Starch Overall stability(n = 14)
T stability(n = 5)
pH stability(n = 7)
Shear stability(n = 6)
NPS-AA 0.261 0.286 0.140 0.277
NPS-AHA 0.224 0.235 0.230 0.182
APS-AA 0.191 0.184 0.044 0.195
WMS-AA 0.159 0.075 0.023 0.195
ConclusionsStability modified amylopectin starches > modified normal potato starches, especially with regard to T- and pH-stabilityStability modified waxy maize starch > modified amylopectin potato starch, especially with regard to T-stability
21-22 April 2010Starch Convention Detmold9
Molecular factors involvedStability of acetyl and adipate groups to processing conditions
Approach
Conclusion: Substituents are stable
3 % starch / 0.05 M acetate buffer / standard RVA programme+ Ultra-Turrax 13500 rpm 1 min / pH 4.0+ 120 °C 30 min / pH 4.0+ 100 °C 30 min / pH 3.6
Dilute 1:1 Recover and analyse pellet
Starch Processing Adipate content (ppm) DS AcetateUntreated 222 0.066
+ High shear 242 0.067
+ High T 242 0.066
+ Low pH 232 0.067
Untreated 343 0.073
+ High shear 348 0.073
+ High T 337 0.071
+ Low pH 348 0.071
NPS-AHA
WMS-AA
21-22 April 2010Starch Convention Detmold10
Molecular factors involvedStructure of solubilised starch: experimental approach
Dilute 1:1 Recover supernatant Solubility (anthron) Adjust to 0.5 – 1 % carbohydrate Dilute with DMSO Saponification (1 M NaOH)
SEC-MALLS Amylose content Neutralise / dilute with DMSO SEC-MALLS
3 % starch / 0.05 M acetate buffer / standard RVA programme+ Ultra-Turrax 13500 rpm 1 min / pH 4.0+ 120 °C 30 min / pH 4.0+ 100 °C 30 min / pH 3.6
21-22 April 2010Starch Convention Detmold11
Molecular factors involvedStructure of solubilised starch: starch and amylose solubilisation
Results
a: based on total amylose in potato starch (assumed to be 20 %)
ConclusionsOrder of solubilisation: High T > High shear > Low pHOrder of solubilisation: NPS (even at higher DX) > APS > WMSAmylose is solubilised preferentially
Starch Processing Solubility (%) Am content (%) % Am solubiliseda High shear 60.9 25.0 76.1 High T 60.6 29.3 88.8
NPS-AA
Low pH 19.4 68.3 66.0 High shear 13.1 55.0 36.0 High T 38.5 43.8 84.3
NPS-AHA
Low pH 12.1 63.9 38.6 High shear 9.1 n.d. High T 28.8 n.d.
APS-AA
Low pH 6.6 n.d. High shear 7.4 0 High T 13.0 0
WMS-AA
Low pH n.d. n.d.
21-22 April 2010Starch Convention Detmold12
Molecular factors involvedStructure of solubilised starch: molar mass of solubles
Results
ConclusionsOrder of molecular degradation in APS/WMS: High T > Low pH > High shearOrder in NPS: Low pH > High T > High shear because of high amylose contentof Low pH solublesResults suggest different action patterns for High T vs. High shearMolar mass of solubles higher for WMS-AA than for APS-AA
Starch Processing Solubility (%) Am content (%) Mw solublesa High shear 60.9 25.0 50.6 High T 60.6 29.3 10.4
NPS-AA
Low pH 19.4 68.3 0.96 High shear 13.1 55.0 3.3 High T 38.5 43.8 1.3
NPS-AHA
Low pH 12.1 63.9 0.45 High shear 9.1 n.d. 12.7 High T 28.8 n.d. 1.0
APS-AA
Low pH 6.6 n.d. 2.9 High shear 7.4 0 35.5 High T 13.0 0 2.3
WMS-AA
Low pH n.d. n.d. n.d. a: x 106 g/mol
21-22 April 2010Starch Convention Detmold13
Molecular factors involvedStructure of solubilised starch: cross-link degree (DX) of solubles
Results
ConclusionIn all cases, Mw is less than halved by saponification. This indicates ineffective cross-linking of solubilised starch
a: x 106 g/mol; before (BS) and after (AS) saponification
Starch Processing Am content (%) Mw solubles BSa Mw solubles ASa High shear 25.0 50.6 32.4 High T 29.3 10.4 8.6
NPS-AA
Low pH 68.3 0.96 1.0 High shear 55.0 3.3 2.8 High T 43.8 1.3 0.9
NPS-AHA
Low pH 63.9 0.45? 0.9? High shear n.d. 12.7 10.8 High T n.d. 1.0 0.8
APS-AA
Low pH n.d. 2.9 2.2 High shear 0 35.5 24.5 High T 0 2.3 2.0
WMS-AA
Low pH n.d. n.d. n.d.
21-22 April 2010Starch Convention Detmold14
Molecular factors involvedRole of amylose
Why does amylose promote solubilisation and has it a negative effect on processing stability?
Effective cross-linking requires ≥ 1 intermolecular cross-link per molecule (= critical DX)
Reported Mw of potato amylose is ca 106 g/mol (Hizukuri et al. (1984), Carbohydr. Res. 134, 1)
Hence critical DX = 1 cross-link per molecule = 162 / 106 = 0.00016
Actual adipate content of 200 ppm corresponds to DX = 0.00016-0.00018 (assumption: 75 % of adipyl substituents are involved in cross-links)
Quite a number of amylose molecules will have escaped cross-linking
21-22 April 2010Starch Convention Detmold15
Molecular factors involvedRole of amylopectin
What explains the presence of quite large amylopectin fragments (Mw up to 50.106 g/mol) in the solubles of processed starches?
Reported Mw intact amylopectin is ca 108 g/mol critical DX = 1.6.10-6
(Yoo & Jane (2002), Carbohydr. Polym. 49, 307)
This greatly exceeds the estimated DX of 1.6.10-4
However, many cross-links are intramolecular: intra-cluster or inter-cluster
Intra-cluster cross-link
Inter-cluster cross-link
21-22 April 2010Starch Convention Detmold16
Molecular factors involvedAmylopectin potato vs. waxy maize starch
Why has WMS-AA a better processing stability than APS-AA with less solubilisation and higher Mw of its solubles?
Amylopectin from WMS has a 4 times higher Mw than from amylopectinpotato. Hence, critical DX in WMS is lower.
Cross-linking has a greater chance to be effective in WMS
550830Waxy maize
130200Amylopectin potato
94170Normal potato
Mw (x 106 g/mol) bMw (x 106 g/mol) aAmylopectin
550830Waxy maize
130200Amylopectin potato
94170Normal potato
Mw (x 106 g/mol) bMw (x 106 g/mol) aAmylopectin
a: Yoo & Jane, CP 49 (2002) 307b: Sanders & Brunt, unpublished (2002)
21-22 April 2010Starch Convention Detmold17
Impact of processing on mesoscopic structure
120 °C 110 °C 85 °C RVA 1920 rpm 1 min TurraxRVA 160 rpm 13500 rpm
NPS
-AA
APS-
AAW
MS-
AA
Effects at high TNormal starch displays enhanced swelling with high release of solublesAmylopectin starch shows less swelling enhancement with much less solubilisation
Effects at high shearNormal starch displays enhanced swelling with high release of solublesAmylopectin starches are fragmented into tiny swollen particleswith limited solubilisation
21-22 April 2010Starch Convention Detmold18
Impact of processing on mesoscopic structureCSLM optical slices of model sauces subjected to high T or high shear
Bars: 50 μm
WMS-AA NPS-AHA
120
°CH
igh
shea
r
S
21-22 April 2010Starch Convention Detmold19
Impact of processing on mesoscopic structureOrigin of high shear fragmentation
HypothesisPresence of unconnected molecules leads to common swelling and leaching process
Conclusion (tentative)High temperature disrupts at the molecular levelHigh shear disrupts at the mesoscopic level
Starch / process
High temperature High shear
Modified normal
- Bimodal MMD: 106 and 108 g/mol - Incomplete X-link small molecules - Molecular degradation by high T → Leaching and swelling
- Bimodal MMD: 106 and 108 g/mol - Incomplete X-link small molecules - ‘No’ molecular degradation → Leaching and swelling
Modified amylopectin
- Unimodal MMD: 108 g/mol - Effective X-link of molecules - Molecular degradation by high T - Small molecules become un-X-linked → Leaching and swelling
- Unimodal MMD: 108 g/mol - Effective X-link of molecules - ‘No’ molecular degradation - Linking remains effective → Fragmentation
21-22 April 2010Starch Convention Detmold20
ConclusionsA method has been presented for the small-scale testing of starch functionality in sauce applications
This ‘sauce model’ allows the quantitative estimation of the processing stability of starches in sauce-making in terms of a Processing Stability Factor (PSF)
Processing stability decreases in the order: modified WMS > modified APS > modified NPS
High temperature promotes molecular degradation much more than high shear
Major molecular factors involved are incompletely cross-linked amylose and the molar mass of amylopectin, which is lower for APS than for WMS
If molecules are or become unconnected, granule disruption occurs by enhanced swelling and leaching; if molecules remain effectively connected at excess energy input, by granule fragmentation
High T acts primarily at a molecular level, high shear at a mesoscopic level
21-22 April 2010Starch Convention Detmold21
AcknowledgementsThis work was part of Agrobiokon, a collaboration of TNO, AVEBE, Central Arable Farming Marketing Board (HPA) and Northern Netherlands Assembly (SNN)
We thank our colleaguesPeter Sanders for determination of adipate contentsKees de Ruijter for molar mass determinations
