Predicting powder caking during shelf life with short-term experiments

Think moisture predicts caking? Short-term lab tests accurately predict long-term powder caking with 1% error.

Milk Powder
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Carolina Diaz Quijano | May 13, 2025

Short-term lab tests run under the same conditions as six-month shelf-life tests accurately predict long-term powder caking – with just 1% margin of error. Meanwhile, moisture analysis reflects only the current state of the powder, not its future caking behavior.

In this study, we assess the effectiveness of short-term lab tests – conducted under the same temperature and relative humidity as six-month shelf-life studies (40°C and 75% RH) – to determine their ability to predict long-term milk powder caking behavior.

Predicting caking in days, not months

The results demonstrate that short-term tests can reliably forecast long-term powder caking behavior, showing only a 1% margin of error when compared to six-month data. This indicates the strong predictive capability of quick lab assessments, saving both time and resources in assessing powder stability.

Fitting the data to a GAB model for Type II sorption isotherms yields the following values:

  • Xm2.6±0.6 %
  • C=1.5±0.5
  • K=0.9±0.02 

GAB (Guggenheim–Anderson–de Boer) model for Type II sorption isotherms: 

X= Xm⋅C⋅K⋅aw/(1−K⋅aw)​⋅(1−K⋅aw+C⋅K⋅aw)

Where:

  • X: Moisture content (%)
  • C: Guggenheim constant
  • Xm: Monolayer moisture content
  • K: Factor correcting properties of multilayer molecules relative to the bulk liquid 
  • aw: Water activity (RH/100) 
Figure 1. Sorption isotherm of milk powder, showing moisture uptake across increasing water activity – key for understanding and predicting the onset of caking.

Moisture: A snapshot, not a forecast

Moisture measurements alone cannot predict powder caking. Based on moisture monitoring during both short-term and shelf-life tests, our findings underscore the need to use moisture data as a reference point rather than a predictor of caking behavior.

This is because moisture content reflects the current state of the powder but does not directly correlate with caking behavior. In the case of the milk powder tested, caking begins in the capillary condensation region – above 5% moisture (region above 0.7 aw) – when liquid bridging between particles increases. While moisture is a critical indicator for identifying when a system enters this sensitive range, it cannot predict the extent or severity of caking on its own.

Figure 2. Within just one day of the short test, the powder reaches the critical caking threshold (5% moisture) where capillary condensation begins. Therefore, only data collected after Day 1 were used for further analysis.
Figure 3. Moisture uptake over the six-month shelf-life study, showing that the critical caking threshold is reached just after one month. There is no direct correlation between caking strength and the moisture absorption capacity of the anticaking agent (Omyafood).

Consistent protection from Day 1: The role of Omyafood 

Omyafood is a functionalized calcium carbonate, which prevents caking and improves powder flow. 

Results show that its addition to the milk powder significantly reduces caking under both short- and long-term conditions. In short-term tests, Omyafood reduced caking by 25% after 4 days, while under long-term conditions, a 26% reduction was observed after one month and remained consistent after six months. Importantly, benefits were measurable even before the powder reached the capillary condensation region, indicating that Omyafood offers early-stage protection to moisture-induced caking as well as long-term stability under various conditions.

shelf life graph

Figure 4. Comparison of the caking index – an indicator of the degree of caking in the sample – between untreated milk powder and powder treated with Omyafood in both short-term and six-month shelf-life tests.

Looking ahead: Smarter testing for stronger powder performance

This study confirms the efficacy of Omyafood as a robust anticaking agent and reveals two key insights. First, short-term laboratory tests are highly reliable predictors of long-term caking behavior, with results aligning within just a 1% margin of error compared to six-month data. Second, while moisture content remains a useful indicator for determining when a powder enters the critical capillary condensation range, it is not sufficient on its own to assess the activity of an anticaking agent on powder behavior.

By combining predictive short-term testing with high-performing anticaking solutions like Omyafood, manufacturers can more confidently manage powder stability and performance over time. Want to know more? Please contact us — we’ll be happy to provide further information and discuss how we can support you.

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