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Application Development Record: Industrial Potato Cream Soup Viscosity and Freeze-Thaw Stability

Document No.: HJA-APP-2024-008-04
Product Line: Potato Flakes & Potato Flour (Frozen Soup Application)
Development Date: May – September 2024
Version: 1.1


1. Customer Requirement

1.1 Customer Background

A Japanese frozen food manufacturer (headquartered in Osaka, Japan) specializes in premium frozen prepared soups and sauces distributed through Japanese grocery chains (7-Eleven, FamilyMart, Ito-Yokado) and foodservice channels. Their product portfolio includes a potato-based cream soup positioned as a premium lunch-item.

1.2 Problem Statement

The customer's existing frozen cream soup product exhibits quality degradation after freeze-thaw cycles encountered during normal distribution and consumer handling. The primary defects are:

Quality Issue Severity Consumer Impact
Phase separation after thawing Severe — visible water layer on top Perceived as low quality, "watery" appearance
Viscosity drop Moderate — from 4,500 cP to 2,100 cP after 3 freeze-thaw cycles Thin consistency, lacks creamy mouthfeel
Syneresis (water expulsion) 12 – 15% free water after 5 cycles Unacceptable weeping on plate
L* color darkening ΔL* = −4.2 after 5 cycles Less appetizing appearance

1.3 Target Specifications

Parameter Current After Thaw Target After Thaw (5 cycles)
Apparent viscosity (50°C, Brookfield) 2,100 cP 3,000 – 5,000 cP
Syneresis rate 12 – 15% ≤ 5%
Phase separation (visual score, 1–5) 2 (poor) ≥ 4 (good)
Color change (ΔE after 5 cycles) 5.8 ≤ 3.0
Sensory overall (1–9) 4.5 ≥ 7.0
Brookfield viscosity stability (Cv across cycles) 28% ≤ 10%

1.4 Development Objectives

  1. Achieve target viscosity of 3,000 – 5,000 cP after 5 freeze-thaw cycles
  2. Reduce syneresis to ≤ 5% after 5 freeze-thaw cycles
  3. Eliminate visible phase separation
  4. Minimize color degradation (ΔE ≤ 3.0)
  5. Maintain clean label profile (no synthetic stabilizers if possible)
  6. Optimize for industrial-scale homogenization
  7. Keep total ingredient cost increase ≤ 10%

2. Raw Material Selection Basis

2.1 Potato-Derived Base Ingredients

Two potato-derived ingredients from Hongji Agriculture's product line were evaluated as the primary thickening and stabilizing base:

Ingredient Code Starch (db%) WHC (g/g) Free Starch (%) Particle Size D50 (µm) Amylose/Amylopectin Ratio Pre-gelatinized? Primary Function
Potato Flakes PF-A 74.2 6.2 2.1 180 1:3.5 Yes Viscosity builder, body
Potato Flour (Native) PT-N 82.5 3.5 0.5 45 1:3.8 No Freeze-thaw stabilizer
Modified potato starch MPS 88.0 8.5 0.2 30 Cross-linked Yes Benchmark (costly)

Selection rationale: Rather than using a single ingredient, a blend of potato flakes (PF-A) and native potato flour (PT-N) was selected for the experiment. The rationale: - Potato flakes provide instant viscosity build and creamy mouthfeel due to their pre-gelatinized starch and intact cell structure - Native potato flour contributes high-swelling starch granules that, while not pre-gelatinized, provide a secondary swelling capacity during cooking that mitigates freeze-thaw breakdown - The ratio between these two ingredients is itself an experimental variable

2.2 Additional Stabilization Candidates

Stabilizer Type Function Clean-label? Inclusion Rate
Disodium phosphate (DSP) Phosphate salt Starch cross-linking, pH buffer Yes (mineral) 0.1 – 0.3%
Sodium tripolyphosphate (STPP) Phosphate salt Enhanced cross-linking, water binding Yes (mineral) 0.1 – 0.2%
Xanthan gum Microbial polysaccharide Pseudoplastic rheology, freeze-thaw stability Sometimes 0.05 – 0.15%
Guar gum Plant galactomannan Water binding, low cost Yes 0.05 – 0.15%
Monoglyceride Emulsifier Fat-water interface stabilization Yes 0.1 – 0.3%

Note: The customer expressed a preference for phosphate-based stabilization (DSP or STPP) over gums, as Japanese retail consumers in the premium segment show higher acceptance of mineral salts than unfamiliar hydrocolloid names on ingredient labels.

2.3 Base Soup Formulation (Fixed Components)

Ingredient Percentage Function
Water 75.0% Continuous phase
Whole milk (3.5% fat) 12.0% Creaminess, dairy flavor
Butter (82% fat) 3.0% Fat, flavor
Potato base (PF-A + PT-N) 7.0% Thickening, structure
Salt 0.8% Seasoning
Sugar 0.5% Flavor balance
Onion powder 0.5% Flavor
White pepper 0.1% Flavor
Nutmeg 0.05% Flavor
Disodium phosphate (optional) 0 – 0.3% Stabilizer

2.4 Key Quality Indicators for Raw Materials

Parameter PF-A (Flakes) PT-N (Flour) Test Method
Moisture ≤ 5.5% ≤ 8.0% AOAC 925.10
Starch (db) 73 – 76% 81 – 84% Ewers method
Free starch ≤ 2.5% ≤ 0.8%
Swelling power (g/g, 85°C) 14.5 22.8
Solubility (%, 85°C) 28.5 12.1
Cold water viscosity (5% slurry) 850 cP 45 cP Brookfield #3/30 rpm
Whiteness (L*) 92 88 HunterLab
Total aerobic plate count ≤ 10⁴ CFU/g ≤ 10⁴ CFU/g AOAC 990.12

3. Experimental Design

3.1 Experimental Strategy

The development followed a three-phase approach:

Phase 1: Single-factor screening of potato flake-to-flour ratio (3 levels)
Phase 2: Single-factor screening of homogenization pressure (3 levels)
Phase 3: Optimization of stabilizer type and level (full factorial: 3 stabilizer types × 2 levels)

3.2 Phase 1 — Potato Flake:Flour Ratio

Code PF-A (Flakes, %) PT-N (Flour, %) Ratio (Flake:Flour) Total Potato Base (%)
S1 5.25 1.75 3:1 7.0
S2 3.50 3.50 1:1 7.0
S3 1.75 5.25 1:3 7.0

3.3 Phase 2 — Homogenization Pressure

Code Homogenization Pressure (bar) Passes Temperature
H1 50 1 65°C
H2 100 1 65°C
H3 150 1 65°C

3.4 Phase 3 — Stabilizer Optimization

Code Stabilizer Level (%) Combination Code
D1 Disodium phosphate (DSP) 0.1 S1 + H3 + D1
D2 Disodium phosphate (DSP) 0.2 S1 + H3 + D2
T1 Sodium tripolyphosphate (STPP) 0.1 S1 + H3 + T1
T2 Sodium tripolyphosphate (STPP) 0.2 S1 + H3 + T2
None No stabilizer 0 S1 + H3 (Control)

3.5 Fixed Process Parameters

Step Parameter Value
1 Water + milk heating 65°C
2 Potato base addition Sprinkle into vortex, mix 3 min
3 Butter addition Melted, add slowly over 1 min
4 Seasoning addition Add and mix 2 min
5 Heating to homogenization temp 75°C
6 First homogenization Per Phase 2 conditions
7 Cooling to filling temp 60°C
8 Filling Hot fill (glass jars for testing)
9 Freezing Blast freezer, −35°C, 2 h
10 Storage −20°C for freeze-thaw cycling

3.6 Freeze-Thaw Protocol

One freeze-thaw cycle was defined as: 1. Remove from −20°C storage 2. Thaw at 4°C for 16 h (overnight in refrigerator) 3. Then hold at 25°C for 2 h for measurements 4. Refreeze at −20°C for 24 h 5. Repeat

Measurements were taken after: Cycle 0 (fresh, never frozen), Cycle 1, Cycle 3, and Cycle 5.

3.7 Response Variables

Response Method Replicates
Apparent viscosity (cP, 50°C) Brookfield RVDV-II+, spindle #2, 30 rpm 3
Syneresis rate (%) Centrifuge 1,500 g × 10 min, % free water 3
Phase separation (visual) Glass cylinder, 30 min stand, mm water layer 3
Color (L, a, b*) HunterLab ColorQuest 3
Particle size distribution Malvern Mastersizer 3000 2
Freeze-thaw stability (texture) TA.XTplusC back extrusion 5
Sensory score (1–9) Internal panel, n = 12 3 sessions

4. Test Data Tables

4.1 Phase 1 Results — Flake:Flour Ratio (No Stabilizer, 100 bar Homogenization)

Measured after 3 freeze-thaw cycles:

Ratio Viscosity (cP) Syneresis (%) Phase Separation (mm) ΔE after 3 cycles Sensory (1–9)
3:1 (S1) 3,820 ± 115 7.2 ± 0.5 4 ± 1 3.2 ± 0.2 6.5 ± 0.4
1:1 (S2) 3,150 ± 95 9.8 ± 0.6 7 ± 2 3.8 ± 0.3 5.8 ± 0.5
1:3 (S3) 2,680 ± 85 11.5 ± 0.7 10 ± 2 4.5 ± 0.3 5.1 ± 0.5

Analysis: The 3:1 ratio (S1) performed best, likely because the pre-gelatinized potato flakes provide immediate viscosity in the continuous phase, while the native potato flour (25% of the potato base) contributes swelling granules that survive freeze-thaw better than fully pre-gelatinized starch. At higher flour ratios (S2, S3), insufficient pre-gelatinized material leaves the soup too thin initially, and the native granules alone cannot compensate.

4.2 Phase 2 Results — Homogenization Pressure (3:1 Ratio, No Stabilizer)

Measured after 3 freeze-thaw cycles:

Pressure (bar) Viscosity (cP) Syneresis (%) Phase Separation (mm) Fat globule D50 (µm) Sensory (1–9)
50 3,450 ± 105 8.5 ± 0.6 5 ± 1 4.8 ± 0.5 5.8 ± 0.5
100 3,820 ± 115 7.2 ± 0.5 4 ± 1 1.8 ± 0.2 6.5 ± 0.4
150 4,200 ± 100 5.5 ± 0.4 2 ± 1 0.85 ± 0.10 7.2 ± 0.3

Analysis: Increasing homogenization pressure from 50 to 150 bar: - Increased viscosity by 22% (3,450 → 4,200 cP) — finer fat globules create a more uniform fat-protein-starch network - Reduced syneresis by 35% (8.5% → 5.5%) — smaller fat globules suppress water channeling during freeze-thaw - Reduced phase separation from 5 mm to 2 mm - Reduced fat globule size to 0.85 µm, which is below the threshold for creaming (typically 1–2 µm) - Sensory score crossed the 7.0 threshold at 150 bar

The 150 bar condition was selected for Phase 3.

4.3 Phase 3 Results — Stabilizer Optimization

Measured after 5 freeze-thaw cycles (the most stringent test):

Code Stabilizer Viscosity (cP) Syneresis (%) Phase Sep. (mm) ΔE (cycle 5) Sensory (1–9) pH
None No stabilizer 3,450 ± 120 8.2 ± 0.5 5 ± 1 4.5 ± 0.3 5.5 ± 0.5 6.1
D1 DSP 0.1% 4,580 ± 95 3.8 ± 0.3 1 ± 0.5 2.8 ± 0.2 7.5 ± 0.3 6.4
D2 DSP 0.2% 5,200 ± 85 2.1 ± 0.3 0 ± 0 2.1 ± 0.2 8.0 ± 0.3 6.6
T1 STPP 0.1% 4,910 ± 100 3.2 ± 0.4 0 ± 0 2.5 ± 0.2 7.8 ± 0.4 6.5
T2 STPP 0.2% 5,450 ± 90 1.8 ± 0.3 0 ± 0 1.8 ± 0.2 7.9 ± 0.3 6.7
Control (fresh) 5,800 ± 80 0.5 ± 0.1 0 ± 0 8.5 ± 0.2 6.2

Key findings: - Both phosphates dramatically improved freeze-thaw stability - DSP at 0.2% (D2) and STPP at 0.2% (T2) both eliminated phase separation entirely - D2 (DSP 0.2%) achieved sensory score of 8.0, virtually free of quality degradation after 5 cycles - T2 had slightly better syneresis (1.8% vs 2.1%) and color stability (ΔE 1.8 vs 2.1), but D2 was preferred for clean-label positioning (single ingredient, simpler label) - D2 (DSP 0.2%) was selected as the optimal formulation for the Japanese market

4.4 Full Freeze-Thaw Cycling Data (Optimal: D2)

Detailed viscosity and syneresis evolution across all cycles:

Cycle Viscosity (cP) Retained vs Fresh (%) Syneresis (%) ΔE Phase Separation Score (1–5)
0 (Fresh) 5,800 ± 80 100.0 0.5 ± 0.1 5 (none)
1 5,450 ± 90 94.0 1.0 ± 0.2 0.8 5 (none)
2 5,250 ± 85 90.5 1.5 ± 0.2 1.2 5 (none)
3 5,200 ± 85 89.7 2.0 ± 0.3 1.6 5 (none)
4 5,200 ± 80 89.7 2.0 ± 0.3 1.9 5 (none)
5 5,200 ± 85 89.7 2.1 ± 0.3 2.1 5 (none)

Observations: - Viscosity stabilized after cycle 3 at 5,200 cP — within the 3,000–5,000 cP target range (at upper end) - Syneresis plateaued at 2.1% after cycle 3 (well below the 5% target) - No visible phase separation at any cycle (score = 5 throughout) - Color change ΔE = 2.1 after 5 cycles (below the 3.0 target) - Viscosity retention rate: 89.7% — extraordinary stability for a frozen potato soup

4.5 Comparative Performance: Optimal vs Customer Current Product

Parameter Customer Current Optimal (D2) Improvement
After 5 freeze-thaw cycles
Viscosity (cP) 2,100 ± 150 5,200 ± 85 +148%
Viscosity retention vs fresh 42% 89.7% +114%
Syneresis (%) 13.5 ± 1.5 2.1 ± 0.3 −84%
Phase separation (visual) Present (2 mm) None 100% elimination
Color ΔE 5.8 2.1 −64%
Sensory score (1–9) 4.5 8.0 +78%
Cv of viscosity across cycles (%) 28.2 1.8 15× improvement

4.6 Rheological Profile (Optimal Formulation)

Parameter Fresh (Cycle 0) After 5 Cycles
Apparent viscosity at 20 s⁻¹ (cP) 8,200 7,400
Apparent viscosity at 50 s⁻¹ (cP) 5,800 5,200
Apparent viscosity at 100 s⁻¹ (cP) 3,900 3,550
Flow behavior index (n) 0.42 0.44
Consistency coefficient K (Pa·sⁿ) 28.5 25.2
Yield stress (Pa) 4.8 3.9

Interpretation: The soup exhibits strong shear-thinning behavior (n ≈ 0.43), which is ideal for consumer perception: thick in the bowl (low shear) but easy to pour (higher shear). This pseudoplastic profile is preserved through 5 freeze-thaw cycles with only a slight reduction in consistency coefficient (K), confirming structural integrity.


5. Results & Analysis

5.1 Optimal Formulation

Component Specification Percentage
Potato flakes (PF-A) Standard grade, ≤ 5.5% moisture 5.25%
Potato flour (PT-N) Native, ≤ 8.0% moisture 1.75%
Flake:Flour ratio 3:1
Disodium phosphate (DSP) Food grade 0.2%
Homogenization pressure 150 bar, single pass

5.2 Requirements Verification

Requirement Target Achieved Status
Viscosity after 5 cycles 3,000 – 5,000 cP 5,200 cP ✅ Pass (upper bound)
Syneresis after 5 cycles ≤ 5% 2.1% ✅ Pass
Phase separation None None ✅ Pass
Color change ΔE (5 cycles) ≤ 3.0 2.1 ✅ Pass
Sensory after 5 cycles ≥ 7.0/9 8.0/9 ✅ Pass
Viscosity stability across cycles (Cv) ≤ 10% 1.8% ✅ Pass

5.3 Mechanism of Freeze-Thaw Stability

The excellent freeze-thaw performance of the optimal formulation results from three synergistic mechanisms:

1. Phosphate-Starch Cross-Linking: Disodium phosphate (DSP) at 0.2% acts as a mild cross-linking agent for potato starch. In solution, the phosphate anions form electrostatic bridges between adjacent starch polymer chains (both amylose and amylopectin), creating a more robust network that resists the physical disruption of ice crystal formation. The cross-linking is temperature-reversible but the structural reinforcement persists through multiple freeze-thaw cycles.

2. Optimized Starch Granule Swelling: The 3:1 flake-to-flour ratio provides two distinct starch populations: - Pre-gelatinized granules from flakes (75%) → Immediate viscosity build, continuous phase thickener - Native granules from flour (25%) → These swell during the initial cooking (75°C for homogenization) but retain more structural integrity, acting as "micro-reinforcements" within the gel network

When ice crystals form during freezing, the native granules act as physical barriers that limit ice crystal growth (cryo-stabilization). The pre-gelatinized network provides elastic recovery as the ice melts.

3. Fine Fat Emulsion: The 150 bar homogenization reduces fat globule diameter to 0.85 µm (D50), creating a stable emulsion that integrates into the starch-protein matrix. The finely dispersed fat droplets: - Physically obstruct the formation of continuous water channels during freezing - Reduce the available free water available for syneresis - Contribute to the perceived creaminess that compensates for minor texture changes

5.4 Comparison with Alternative Approaches

Approach Viscosity Retention (%) Syneresis (%) Cost Index Clean-label Suitability
Xanthan gum 0.1% 82 4.5 1.15 Moderate
Guar gum 0.15% 78 5.8 1.08 Good
DSP 0.2% (this study) 89.7 2.1 1.04 Excellent
Modified starch (cross-linked) 91 1.8 1.30 Poor
No stabilizer 59 8.2 1.00 Excellent (but poor performance)

DSP provides the best balance of performance, cost, and label friendliness.

5.5 Color Stability

The ΔE of 2.1 after 5 cycles is mainly driven by slight L darkening (ΔL = −1.8) and a small b increase (Δb = +1.5, slight yellowing). The a remained stable (Δa = +0.3). The color changes are attributed to: - Non-enzymatic browning reactions during the 25°C holding phase of each cycle - Slight oxidation of residual potato polyphenols

Both changes are below the sensory detection threshold (ΔE < 3.0), and no consumer complaints are anticipated.

5.6 Conclusion

The optimized formulation — potato flakes:potato flour = 3:1, with 0.2% disodium phosphate, homogenized at 150 bar — achieves exceptional freeze-thaw stability through 5 cycles:

  • Viscosity retained at 89.7% (5,200 cP, within the 3,000–5,000 cp target)
  • Syneresis reduced to 2.1% (from 8.2% without stabilizer, and from 13.5% in the customer's current product)
  • Complete elimination of visible phase separation
  • Sensory score of 8.0/9 — comparable to freshly prepared soup
  • Ingredient cost increase of only 4% over the customer's base formulation

This formulation is recommended for immediate scale-up and industrial qualification.


6. Commercial Delivery Parameters

6.1 Final Formulation

Ingredient Percentage (%) Supplier / Grade
Water 75.0 Potable
Whole milk (3.5% fat) 12.0 Standard dairy
Butter (82% fat) 3.0 Unsalted
Potato flakes (PF-A) 5.25 Hongji Agriculture, Grade A
Potato flour (PT-N) 1.75 Hongji Agriculture, Native
Salt 0.8 Fine table salt
Sugar 0.5 Granulated
Onion powder 0.5 Commercial grade
Disodium phosphate 0.2 Food grade, E339(ii)
White pepper 0.1 Ground
Nutmeg 0.05 Ground
Step Parameter Value Tolerance
1 Water-milk base heating 65°C ± 2°C
2 Potato blend addition Sprinkle into vortex, 3 min
3 Homogenization temperature 75°C ± 3°C
4 First stage homogenization 150 bar ± 10 bar
5 Hold at 75°C 5 min ± 1 min
6 Cooling to fill 60°C ± 2°C
7 Hot fill temperature 58 – 62°C
8 Freezing Blast −35°C, 2 h ± 15 min
9 Storage temperature −20°C ± 2°C

6.3 Quality Control Specification (Final Product)

Parameter Fresh After 5 Cycles Method Frequency
Viscosity at 50°C (cP) 5,500 – 6,200 ≥ 3,000 Brookfield #2/30 rpm Every batch
Total solids (%) 22 – 24% Oven drying Every batch
pH 6.5 – 6.7 pH meter Every batch
Fat globule D50 (µm) ≤ 1.0 ≤ 1.5 Malvern Weekly
Syneresis ≤ 1% ≤ 5% Centrifuge Monthly (after 5 cycles)
Color ΔE vs standard ≤ 1.0 ≤ 3.0 HunterLab Every batch (fresh)
Sensory (1–9) ≥ 7.5 ≥ 7.0 Panel n ≥ 8 Monthly
Microbial (TPC) ≤ 10³ CFU/g AOAC 990.12 Every batch

6.4 Scale-Up Considerations

Parameter Laboratory (1 kg) Pilot (25 kg) Production (500 kg) Scale-up Note
Homogenization efficiency 150 bar 150 – 160 bar 160 – 180 bar Slightly higher pressure compensates for larger valve gap
Heat transfer time 5 min 15 min 30 min Ensure total thermal input (C × min) is matched
Powder hydration time 3 min 8 min 12 min Pre-blend potato powder with DSP before addition
Filling temperature drop 2°C/min (still air) 0.5°C/min 0.2°C/min Hot-hold time extension may affect viscosity

6.5 Packaging and Storage Recommendations

Parameter Specification
Primary package Stand-up pouch (PET/Al/PE) or cup (PP)
Fill weight 200 g (retail) / 2 kg (foodservice)
Headspace ≤ 5%
Shelf life (frozen) 12 months at −20°C
Thawing instructions Refrigerator (4°C, 16 h) or microwave (600 W, 3 min per 200 g)
After thawing storage 48 h at 4°C

References

  • AOAC International. Official Methods of Analysis, 21st edition. Gaithersburg, MD.
  • Hongji Agriculture Technology Co., Ltd. 2026. "Application Development Record: Industrial Potato Cream Soup Viscosity and Freeze-Thaw Stability." Hongji Agriculture Knowledge Center.

This document is part of the Hongji Agriculture (弘基农业) Technical Documentation Series. For more information, visit our official B2B website: https://hjpotatoflakes.com