# Optimal Storage Temperature for Maintaining the Solubility of Micellar Casein Powder

## TL;DR

This study finds that storing micellar casein powder at 4°C maintains its solubility better than higher temperatures.

## Contribution

The study identifies optimal storage conditions for preserving micellar casein powder solubility.

## Key findings

- Solubility of micellar casein powder is preserved at 4°C and −20°C for 30 days.
- Higher storage temperatures cause decreased solubility and visible precipitation.
- Structural changes like surface cross-linking are suppressed at lower storage temperatures.

## Abstract

Maintaining the solubility of micellar casein (MC) powder during storage is a major practical challenge. This study investigated the effects of storage temperature (−20 to 37 °C) on solubility and structure of MC powder. Results showed that solubility of MC powder was well preserved at 4 °C and −20 °C over 30 d, whereas higher storage temperatures led to a marked decline. Correspondingly, particle size and stability of rehydrated solution from powders stored at lower temperatures remained unchanged but increased significantly at elevated temperatures, alongside visible precipitation. Structural analysis indicated that surface cross-linking and reduced porosity occurred during storage, resulting in decreased solubility, which were effectively suppressed at 4 °C and −20 °C. These findings demonstrate that refrigerated storage at 4 °C is sufficient to maintain the solubility of MC powder, with no clear additional advantage observed at −20 °C under the tested conditions. This work provides practical guidance for optimizing MC powder storage.