A plant-based beverage may be stable without heat but become unstable once heated because heat can change the starch, protein, and microbial survival in the beverage, leading to thickening, phase separation or spoilage during storage. Therefore, validate plant-based beverage stability across formulation, homogenization, and shelf life—not infer it from a stable bench sample. For UAE and wider GCC distribution, validation should also reflect the intended ambient storage, packaging and distribution conditions, supported by FRL’s plant-based beverage stability testing services before scale-up.
Why a "Stable" Plant-Based Beverage Can Fail After Heat Treatment: Controlling Starch Gelation, Phase Separation and Microbial Shelf Life Before UAE Scale-Up
Dr. Shreya Iyer, PhD (Food Science) — Director of New Product Development, Food Research Lab
Specialization: Food formulation, beverage development, and culinary innovation
Quick Answer
A plant-based beverage may be stable without heat but become unstable once heated because heat can change the starch, protein, and microbial survival in the beverage, leading to thickening, phase separation or spoilage during storage. Therefore, validate plant-based beverage stability across formulation, homogenization, and shelf life—not infer it from a stable bench sample. For UAE and wider GCC distribution, validation should also reflect the intended ambient storage, packaging and distribution conditions, supported by FRL’s plant-based beverage stability testing services before scale-up.
1. Why a Beverage Can Look Stable Before Heat Treatment
A plant-based beverage can pass every bench check — clean taste, consistent colour, and absence of any layer after 48 hours — and still fail six weeks later, a pouch thickened into a spoonable gel, or chalkiness forming along the bottom. The formula wasn’t wrong in the bench tests; it was never put to the test for how it would behave in the process.
“Stability” in the raw slurry is generally defined in one way: lack of visible separation for a brief period. That masks at least four forms of plant-based beverage stability that are particularly challenged by thermal processing:
- Physical — resistance to sedimentation, creaming, flocculation and aggregation.
- Rheological — control of viscosity, yield stress, and flow behaviour.
- Chemical — pH and oxidation-sensitive components.
- Microbiological — control of relevant microorganisms through shelf life.
Although a bench sample may score highly on criteria one to three, it may yet have a spore load that is not fully controlled by a full-scale process. A 2026 systematic review on the technology of plant-based milk alternatives cites phase instability as a consistent technical problem associated with the composition of raw materials and processing history. [1]
Whereas stability testing for a product to be marketed in the UAE needs to consider its intended commercial storage, transport, and packaging conditions, rather than bench storage alone, starches show this point quite effectively in beverage product development. An unheated oat slurry contains intact, ungelatinized granules that contribute relatively little to viscosity, while thermal processing can cause substantial starch swelling and viscosity development—one reason “oat milk thick after heating” is a recurring formulation complaint. [2]
2. What Heat Does to a Starch-Rich Plant Matrix
Starch granules of native origin are semi-crystalline, largely insoluble in cold water, and do not contribute much viscosity before gelatinization. During heating through the gelatinization range, water enters the granule, the crystallinity breaks down, and the granule swells; if heated further with applied shear, it bursts and liberates amylose into the serum. Cooling results in gel formation, whereby amylose and swollen particles form a network—called gelation—which occurs after gelatinization but should not be confused with it. Even formulations with identical starch levels may yield different viscosities after heating because of different history of hydrolysis or shear, and the key for discrimination between a process-related effect and structural change lies in comparing pre-heat → post-heat → storage viscosity to distinguish an immediate process response from longer-term structural change. For UAE scale-up, extend this comparison to storage conditions representing the intended commercial distribution pathway. [2] [3]
Formulators Guidance
If viscosity continues rising after heat treatment or during storage, compare pre- and post-process rheology with particle-size changes. A large viscosity increase with little particle-size change suggests starch-driven thickening or retrogradation, while a large particle-size increase points more toward aggregation or flocculation. Identify the mechanism before increasing hydrocolloid levels, which may mask rather than resolve the underlying instability.
3. Why Rising Viscosity Is More Than a Sensory Problem
An unexpected viscosity rise is more than a sensory issue since it can also impact pumping and process efficiency through alteration of fluid flow in heat exchangers and retention tubes. Thus, rheology can play a role in thermal-process validation and not merely finished product quality control.
The increase in viscosity might also obscure the root cause of instability since rising viscosity of the continuous phase may fail to solve problems like large oil droplets, protein precipitation, coarse particles, and improper homogenization. Therefore, a flow curve conducted under process shear conditions needs to become an integral part of the beverage product development process from the very beginning. [1] [2]
4. Why “Add More Stabiliser” Can Be the Wrong Fix
The first reaction to the problem of stability after heating is an attempt to add more hydrocolloid and/or emulsifier, which can help with one issue while causing another. Hydrocolloid stabilizer selection should match the mechanism; low acyl gellan gum stabilizer allows for creating a loose network able to suspend particles from sedimentation; xanthan gum will increase the viscosity of the continuous phase but will not prevent creaming or sedimentation; and lecithin and other emulsifiers work at the oil-water interface rather than correcting starch gelation in beverages or proteins’ aggregation. Concentrations validated in one matrix, such as soy milk, should therefore be treated as guidance rather than specifications transferable to oat, pea or almond beverages. [1] [2]
Formulator’s Guidance
Identify the failure mechanism before increasing hydrocolloid levels: assess particle size and viscosity for sedimentation, droplet size and homogenization for creaming, pH and zeta potential for flocculation, and starch behaviour for post-heat thickening. Increasing viscosity may mask visible separation without correcting the underlying cause.
Formulation Troubleshooting
Request a Plant-Based Beverage Formulation Review
FRL’s food science team determines whether the problem is starch behaviour, protein aggregation, emulsion instability or process control — before engaging a new hydrocolloid supplier.
5. Enzymatic Hydrolysis as a Viscosity-Control Tool
When gelatinization of starch leads to viscosity after heating, an enzymatic hydrolysis process can be more specific compared to adding a stabilizer. Amylase, alone or in combination with a debranching enzyme, such as pullulanase or isoamylase, breaks down starch chains during the processing stage, thus decreasing the molecular weight and degree of branching, which will limit the retrogradation process due to excessive gelatinization. According to 2025 Foods research, the combination of amylase and debranching enzymes lowered starch molecular weight and size as well as improved emulsification properties [4]. The number of enzymes needs to be optimized based on rheological and sensory properties since their activity depends on temperature, time and pH. For UAE-bound products, the treatment should also be reproduced at pilot scale, with enzyme activity, treatment time, pH and downstream thermal inactivation controlled through the commercial process. [5]
6. Thermal Process Optimisation: Time, Temperature, Cooling, Filling and Hold Time
UHT systems typically apply temperatures above 135°C for seconds; retort holds lower peak temperatures for longer. Both interact with starch and protein differently and are influenced by upstream homogenization pressure, which sets particle and droplet size entering the heat exchanger. Fill temperature affects whether the product is still metastable entering aseptic filling and hold time in intermediate tanks — often overlooked — is where much unplanned thickening develops. For a UAE-bound ambient beverage, process validation should therefore extend beyond the heat exchanger to cooling, intermediate holding, aseptic filling and package integrity, followed by storage testing under the intended commercial distribution conditions. [6] [7]
Figure 1. Plant-Based Beverage Post-Heat Stability Diagnostic Decision Tree
7. Separate the Failure Modes: Sedimentation, Creaming, Flocculation and Protein Aggregation
Phase separation” is too broad to guide formulation. Sedimentation involves downward movement of dense particles, creaming involves upward migration of oil droplets, flocculation involves particle association without complete fusion, and protein aggregation results from processing-induced protein association. Each mechanism requires different measurements and formulation or process responses. [1] [2]
Table 1. Plant-Based Beverage Failure-Mode Diagnostic Matrix
Failure mode | Likely mechanism | What to measure | Formulation/process response |
Sedimentation | Dense particles settle under gravity as viscosity drops post-heat | Particle size D, settling volume | Suspending gellan gum or reduced particle size |
Creaming | Fat droplets rise from poor stabilisation or coalescence | Droplet size D, creaming index | Emulsifier optimisation, higher homogenization pressure |
Flocculation | Particles cluster near the protein isoelectric point or via depletion | Zeta potential, pH, microscopy | pH adjustment, hydrocolloid dose/type change |
Protein aggregation | Heat-induced unfolding binds protein into larger complexes | Soluble protein pre/post-heat, turbidity | Temperature/hold-time adjustment, pH control |
Starch-driven thickening | Granule swelling then amylose retrogradation on cooling | Viscosity pre/post-heat, RVA profile | Enzymatic hydrolysis, lower-gelling starch |
Sedimentation, creaming, flocculation and protein aggregation are often grouped as “separation,” but their mechanisms and diagnostic measurements differ. This distinction matters during troubleshooting because a process change such as homogenization can influence multiple mechanisms simultaneously, while syneresis and sedimentation require different corrective approaches.
8. FRL Technical Insight: What FRL Measures During Troubleshooting
When a client brings a post-heat stability complaint, our sequence compares the same sample before and after the client’s actual thermal process, not a bench approximation:
(1) viscosity and flow curve pre/post-heat at process-relevant shear rates;
(2) particle/droplet size distribution to distinguish sedimentation from creaming;
(3) pH and buffering capacity, since small shifts can trigger flocculation not seen at bench pH;
(4) separation assessment over a real-time storage window; and
(5) microbiological indicator testing to rule out microbial activity behind changes otherwise misread as physical.
A useful troubleshooting dataset captures changes across processing rather than a single final value: initial → post-heat → storage viscosity, particle size, pH and microbial counts. A large viscosity increase with limited particle-size change indicates a different mechanism from a small viscosity change with a large particle-size increase — the basis of a scientifically useful plant-based beverage stability testing services programme. For UAE-bound products, the selected pilot batch should then be followed under storage conditions representing the intended commercial distribution pathway, helping distinguish instability created during thermal processing from changes that develop during storage.
9. Shelf-Life and Microbial Stability Must Be Revalidated After Reformulation
While UHT processing greatly reduces the microbial content, UHT plant-based milk stability and reformulation can alter microbial risk. Meta-analyses on D-values in 3,563 D-value measurements showed heat stability of spores present in raw materials from plants with values ranging from ~87.7°C for non-proteolytic Clostridium botulinum to ~124.8°C for Geobacillus stearothermophilus [6]. A 2026 study on 5 different types of autoclaving processes done on pea protein beverages (105–115°C, 5–20 minutes) showed that none of the products had any microbial growth at time zero; however, yeast and mold growth was seen in those samples which were subjected to milder temperature ranges of 105–110°C after 14 days of storage at 22°C, showing that safety at time zero does not predict storage behaviour. [8] [9] For UAE scale-up, storage studies should represent the actual commercial pathway, including temperature exposure, storage duration, package configuration and predefined sampling intervals, with physical and microbiological stability assessed together.
10. UAE Scale-Up: Ambient Distribution, Packaging and Commercial Process Constraints
Validated formulations under temperate storage conditions do not automatically transfer to UAE and GCC distribution due to higher ambient temperatures, which may speed up temperature-dependent chemical reactions, such as retrogradation, residual enzyme action and growth of surviving microorganisms; these need to be considered within the validation process. The same applies to the integrity of packaging, since an aseptic process adequate under moderate conditions can be more susceptible to failures during regional distribution. According to a study on 158 plant-based ingredient samples, spore and viable counts ranged from about 1 to 8.5 log10 CFU/g, with measurable spores remaining in UHT-treated syrup, showing that ingredient sourcing as well as thermal processing influences microbial load [9]. The UAE Federal Law No. 10 of 2015 governs food safety issues in the country, whereas GSO 9:2022 covers labelling of foods at the GCC level. [10] [11] For manufacturers evaluating food formulation services UAE providers or planning a beverage scale-up UAE launch, climate-adjusted stability, packaging and microbiological testing should therefore be integrated into the development and validation pathway.
Table 2. Shelf-Life and Stability Testing Plan for UAE Scale-Up
Test | Condition | Parameters tracked | Purpose |
Real-time storage | Regional ambient range, full shelf life | Viscosity, pH, sedimentation, sensory, microbial count | Confirms performance under distribution climate |
Accelerated storage | Elevated temperature, correlated to real-time | Same physical/chemical parameters | Early indication of shelf-life-limiting reactions |
Microbial challenge | Defined inoculum, raw material flora | Log-reduction, post-process growth | Confirms lethality against relevant organisms |
Package integrity | Simulated regional handling/cycling | Seal strength, barrier, leak detection | Confirms aseptic barrier under logistics stress |
A flow curve run at one low shear rate often misses a process-relevant instability. Pumps, heat exchangers and filling valves each impose a different shear regime, and a thickened system can behave very differently at process shear than on a single-point bench reading — test across a range spanning your actual equipment.
11. Pre-Scale-Up Stability Checklist
Before commercial scale-up, formulation, thermal processing, packaging, microbiological controls and shelf-life performance should be validated as one system. The checklist below provides a practical final review of these critical parameters before production release.
12. Illustrative Case Study: When the Fix Was the Enzyme Step, Not the Stabiliser
Diagnosing Post-Heat Thickening in an Oat-Based Beverage
Brief: An oat-based beverage appeared stable during bench testing but developed progressive thickening during ambient storage after thermal processing. The stabiliser system had been selected for physical suspension, but the failure suggested heat-induced starch transformation rather than simple sedimentation or creaming.
Diagnostic approach: Pre-heat and post-heat samples were compared using viscosity, flow behaviour, particle-size analysis and storage rheology. A viscosity increase without significant particle-size growth would support a starch-driven mechanism.
Formulation response: Instead of increasing hydrocolloid concentration, a controlled amylase/debranching enzyme treatment was evaluated upstream of thermal processing. The trial was assessed for post-heat viscosity, storage rheology, physical stability and sensory performance.
✓ Pre-heat → post-heat rheology used to identify viscosity change
✓ Particle-size analysis used to distinguish starch effects from aggregation
✓ Amylase/debranching treatment evaluated as a mechanism-specific intervention
✓ Pilot-scale processing and storage validation required before scale-up
Scale-Up Readiness
Request a Plant-Based Beverage Feasibility Review
Diagnose the mechanism — starch, protein, emulsion or microbial — before your next scale-up trial.
Conclusion
A beverage that looks stable on the bench has not been tested against what determines commercial shelf life: the thermal process, the shear it imposes, and the climate it will be distributed into. Diagnosing the mechanism—starch, protein, emulsion or microbial—before choosing a fix is what separates a durable plant-based beverage formulation from a repeated complaint.
Food Research Lab provides Beverage Product Development Services covering formulation, process optimisation, stability testing and scale-up validation. Work with our food science team to identify the failure mechanism, optimise the formulation and validate your beverage before commercial production.
Frequently Asked Questions
UHT heat can denature plant proteins and destabilize the emulsion, so proteins and oil droplets aggregate and separate over time. An underdosed or mismatched hydrocolloid system, or insufficient homogenization, makes creaming and sedimentation much more likely during shelf life.
When starch-containing ingredients such as oats are heated in water, the granules swell and gelatinize, which raises viscosity sharply and can set the drink into a gel. Processors control this with enzymatic hydrolysis (for example, amylase) before heat treatment or by selecting less gel-prone ingredients.
No. UHT reduces the microbial load, but heat-resistant spore-formers, post-process contamination or weak aseptic filling can still cause spoilage. Shelf life should be confirmed with microbial challenge testing and stability studies on the final package, not assumed from the heat process alone.
Run real-time and accelerated storage studies at temperatures that reflect hot-climate distribution, and track viscosity, sedimentation, pH and microbial counts at set intervals. Doing this on pilot-scale batches gives results that translate to commercial production far more reliably than bench samples.
References
- Kuksal, K., Sharma, A., Sharma, A., et al. (2026). Techno-functional properties of plant-based milk alternatives and beverages: A systematic review. Comprehensive Reviews in Food Science and Food Safety, 25(3), e70460. https://doi.org/10.1111/1541-4337.70460
- Patra, T., Axel, C., Rinnan, Å., & Olsen, K. (2022). The physicochemical stability of oat-based drinks. Journal of Cereal Science, 104, 103422. https://doi.org/10.1016/j.jcs.2022.103422
- Punia Bangar, S., Ashogbon, A. O., Singh, A., Chaudhary, V., & Whiteside, W. S. (2022). Enzymatic modification of starch: A green approach for starch applications. Carbohydrate Polymers, 287, 119265. https://doi.org/10.1016/j.carbpol.2022.119265
- Zhan, X., Zhang, J., Xing, J., Xu, J., Ouyang, D., Wang, L., Wan, Y., & Luo, X. (2025). Synergistic amylase and debranching enzyme catalysis to improve the stability of oat milk. Foods, 14(7), 1271. https://doi.org/10.3390/foods14071271
- Huang, Y., Li, L., Hong, Y., Cheng, L., & Gu, Z. (2025). Enzymatically modified starch: Structure, digestibility, energy supply, and applications. Carbohydrate Polymers, 367, 123959. https://doi.org/10.1016/j.carbpol.2025.123959
- Karamcheti, S. T., Beekmann-Metselaar, K. I., Eijlander, R. T., Wells-Bennik, M. H. J., Zwietering, M. H., & den Besten, H. M. W. (2025). Heat resistance of bacterial spores isolated from plant-based matrices: Consequences for food safety and quality. International Journal of Food Microbiology, 443, 111426. https://doi.org/10.1016/j.ijfoodmicro.2025.111426
- Codex Alimentarius Commission. (1993). Code of Hygienic Practice for Aseptically Processed and Packaged Low-Acid Foods (CXC 40-1993). FAO/WHO. Official Codex reference / PDF
- Plocina, L., & Beitane, I. (2026). Microbiological safety and pH stability of autoclaved pea protein-based beverages during short-term storage. Frontiers in Nutrition, 13, 1795658. https://doi.org/10.3389/fnut.2026.1795658
- Gleissle, A., Schmidt, H., & Hinrichs, J. (2025). Prevalence of spore-forming bacteria in plant-based raw materials used for plant-based milk alternatives. International Journal of Food Microbiology, 439, 111255. https://doi.org/10.1016/j.ijfoodmicro.2025.111255
- United Arab Emirates. (n.d.). Food legislation and regulations. UAE Legislation – Food Regulations
- Gulf Cooperation Council Standardization Organization. (2022). GSO 9:2022—Labelling of prepackaged foods. GSO 9:2022
📑 Table of Contents
- Why a Beverage Can Look Stable Before Heat Treatment
- What Heat Does to a Starch-Rich Plant Matrix
- Why Rising Viscosity Is More Than a Sensory Problem
- Why "Add More Stabiliser" Can Be the Wrong Fix
- Enzymatic Hydrolysis as a Viscosity-Control Tool
- Thermal Process Optimisation: Time, Temperature, Cooling, Filling and Hold Time
- Separate the Failure Modes: Sedimentation, Creaming, Flocculation and Protein Aggregation
- FRL Technical Insight: What FRL Measures During Troubleshooting
- Shelf-Life and Microbial Stability Must Be Revalidated After Reformulation
- UAE Scale-Up: Ambient Distribution, Packaging and Commercial Process Constraints
- Pre-Scale-Up Stability Checklist
- Illustrative Case Study: When the Fix Was the Enzyme Step, Not the Stabiliser
- Conclusion
- Frequently Asked Questions
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