The bioavailability of Calcium in Milk

Abstract

Calcium is an important mineral which the body uses to maintain strong bones and carry out many important bodily functions. According to the Dutch nutrition center people in the Netherlands consume 80-90% of their calcium through milk and other milk products. Often times people will further ’process’ milk for other food products. Examples of these include boiling milk to make hot chocolate or freezing it for ice-cream. These temperature changes can have great influence on the bio-availability of the Calcium. The goal of this thesis was to find the effect of temperature on the bio-availability of Calcium in milk. This was done through 2 experiments. Dialysing skim bovine milk at temperatures between 4-90°C and heating or cooling the bovine milk to temperatures between -18°C-95°C and then dialysing at room temperature. The dialysis separates the soluble and insoluble phase of milk allowing for the calculation of percentage soluble calcium which is a good indicator for bio-availability of calcium in milk. It was found that there is a linear relationship between the temperature of the milk and the percentage soluble Calcium, the higher the temperature of the milk the lower the amount of bio-available calcium in the milk. Furthermore when looking at the heated milk it was found that heating to 60°C and above all showed a similar drop in percentage soluble calcium indicating some permanent loss of bio-available calcium. This permanent loss is however lower than what can be observed to be lost in the milk whilst hot indicating that a portion of the calcium that becomes insoluble upon heating returns to the soluble phase once returned to its original temperature.