Reduction of Flocculation in Potato-Based Milk Analogues

Abstract

This study investigates the mechanisms driving flocculation in potato-based milk analogues, a critical quality defect arising during long-term storage. Initial hypotheses implicated starch retrogradation as the primary destabilization mechanism, given its well-documented role in plant-based systems. However, enzymatic treatment with α-amylase successfully hydrolyzed amylose (confirmed via iodine staining) and reduced viscosity, but failed to prevent aggregation, therefore excluding starch recrystallization as the dominant factor. Comparative analysis with potato-based cooking cream, which exhibited no flocculation despite higher fat content (13% vs. 3% in milk), provided another assumption. Potato milk’s higher protein-to-fat ratio (0.528 vs. 0.085 in cream) promotes protein-protein bridging and network formation.
Combining the findings from SAXS/WAXS, centrifugation, and microscopy helped us understand the main reasons behind flocculation in potato milk analogues. SAXS/WAXS data demonstrated no detectable retrogradation-induced crystallinity in flocs, which indicated that starch wasn't the primary reason for flocculation. TD-NMR data showed non-enzyme treated samples centrifuged bottom had very low mobile water compared to the top phase, and enzyme-treated samples showed no bottom phase, which indicates the removal of starch structures. However, the top phase of milk persisted. Microscopy images of both enzyme-treated and non-enzyme-treated potato milk analogues revealed similar oil droplet distributions, with no clear evidence of major aggregation in either group after 150 days of storage. Occasional small clusters were observed, but overall, both types of milk showed comparable results, suggesting that enzymatic treatment did not significantly alter the droplet morphology or reduce flocculation compared to non-enzyme-treated samples. In sharp contrast, cooking cream displayed uniformly dispersed oil droplets without visible aggregation, regardless of storage conditions, confirming its superior emulsion stability. Instead, protein-driven aggregation was suggested as the dominant factor: excess pea protein formed interfacial bridges between fat droplets, as evidenced by persistent surface flocs in centrifuged enzyme-treated samples. In contrast, cooking cream exhibited exceptional stability across all conditions, maintaining uniform droplet dispersion (D(0.9) smaller than 5 µm, while the potato milk analogue showed bigger than 15 µm after 130 days. The stability difference was attributed to cooking cream’s optimized protein-to-fat ratio (0.085 vs. 0.528 in milk), which minimized interfacial overcrowding and prevented bridging. These findings collectively shift the focus from starch modification to protein-oil balance as the critical lever for improving potato milk stability.
Enzymatic starch hydrolysis reduced viscosity but did not address protein overcrowding at the oil-water interface, as evidenced by persistent surface flocs in centrifuged enzyme-treated samples.
As a conclusion, the results focus on protein-oil ratio optimization as a key way to control milk quality. Reducing pea protein content is expected to mitigate bridging without compromising emulsification.

Popular Abstract

Imagine pouring a glass of creamy potato-based milk into your coffee, only to find grainy clumps floating on the surface. This unappetizing phenomenon, common in plant-based milks, has puzzled consumers and scientists alike. For companies like DUG Foodtech AB, creators of the potato milk "DUG Barista," these clumps, called flocs, are more than a nuisance, they indicate a decline in product quality. But what causes these flocs, and how can they be stopped? This thesis provides a method to reduce flocs and explains the science underlying the clumping.
As one of the ingredients in potato-based milk, potato starch was suspected to be the cause of flocs. When heated, starch granules swell and release molecules called amylose and amylopectin (Lovegrove et al., 2015). As the milk cools, these molecules can rearrange into orderly structures, a process called retrogradation, which was suspected to make clumps (Kaper et al., 2004)
To test this, α-amylase was added, an enzyme that breaks down starch. The enzyme worked, partially. It made the milk smoother and thinner (reducing viscosity). But to everyone’s surprise, the clumps still appeared. This meant starch wasn’t the main villain.
Further experiments revealed a hidden factor: protein. Potato milk contains pea protein, as one of the emulsifiers. But compared to potato-based cooking cream, another product from DUG Foodtech AB, potato milk has much more protein relative to fat. This excess protein acts like glue, sticking particles together (Guan, Zhao & Thaiudom, 2022).
Under the microscope, flocculation was observed both for non-enzyme-treated potato milk and enzyme-treated milk, regardless of storage condition, stored in the fridge, room, or temperature cycle (shifting from fridge to room weekly). However, not many clusters were observed for cooking cream.
Cooking cream, a potato-based product with 13% fat (vs. potato milk’s 3%), never formed clumps. Why? Its protein-to-fat ratio was much lower (0.085 vs. 0.528). With less protein, there weren’t enough "glue molecules" to bind particles.
Therefore, potato-based milk needs the right balance of ingredients. Cooking cream’s ultimate stability comes from a low protein-to-fat ratio: Less protein means fewer bridges between particles.
The simplest fix is to use less pea protein. This prevents overcrowding at the oil-water interface, reducing bridging.
Plant-based milks are a $22.53 billion industry, estimated to reach about $43.63 billion in 2034 (Precedence Research, 2024). For this skyrocketing industry, clumping remains a major barrier to consumer acceptance. By shifting focus from starch to protein, this research opens a new path for longer shelf life. Clump-free milk stays appealing for months. Lessons from potato milk could therefore improve oat, almond, and other plant-based drinks.
Excess protein, not starch, is the hidden culprit behind clumpy potato milk. By rebalancing ingredients and learning from other plant-based products, we can create plant-based milks that are smooth, stable, and satisfying, no shaking required.

• author: Kwon, Seohyun
• supervisor: Eva Tornberg; Tobias Halthur
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLTM02 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: food engineering nutrition and food chemistry, flocculation, potato-based milk analogues, plant-based milk, emulsion stability, protein-to-fat ratio, pea protein, starch retrogradation, emulsification, particle size distribution, protein bridging, shelf life, product quality, food engineering, storage conditon, viscosity, microscopy, NMR, SAXS, WAXS
• language: English
• id: 9203400
• date added to LUP: 2025-06-23 11:14:21
• date last changed: 2025-06-23 11:14:21