Effect of churning temperature on water content, rheology, microstructure and stability of butter during four weeks of storage
2014
Rønholt, Stine | Madsen, Ann S. | Kirkensgaard, Jacob J.K. | Mortensen, Kell | Knudsen, Jes C.
The effect of churning temperature (10°C vs. 22°C) is evaluated with respect to water content, rheology, microstructure and stability of butter produced using the batch churning method with a temperature ramp of 4°C/min. Using pulsed-nuclear magnetic resonance, an increase in relative solid fat content from 44% to 49.5% was observed when decreasing the churning temperature. Due to lower solid fat content formed upon churning at high temperatures, average water droplet size significantly increased from 5.5μm to 18.5μm and less water could be incorporated into the butter during mixing. Using differential scanning calorimetry, it was observed that water addition as well as churning at low temperatures induced a transition toward more stable crystal structures, as the melting point in the high melting fraction was slightly lower for butter churned at high temperature. This did, however, not reflect in any changes in terms of crystal polymorphism, and all butters contained primarily β′-crystals with traces of α- and β-crystals. Despite the observed changes, small deformation rheology revealed no difference as a function of churning temperature or water content. During isothermal storage at 5°C, the solid fat content increased in all butters, but only butter churned at 10°C showed an increase in hardness during storage. However, no difference in rheological behavior was observed among the butters. Thus it can be concluded that low temperature allows more water to be incorporated in the system without inducing any changes in rheological behavior or crystal polymorphism after four weeks of storage.
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