Calcium in raclette cheese<<. importance of pH value and complexing

Among other topics dealt with in a previous ALP paper was the effect of citric acid on the melting properties of raclette. The citric acid extracted a lot of calcium from the casein matrix and improved melting. A further study was carried out in order to examine the importance of the type, extent and time of pH reduction during production. The pH-reducing measures applied were pre-ripening of the milk and addition of different concentrations of citric acid and lactic acid to the wash water. This study showed that the time and pattern of pH reduction are crucial to the extent of calcium loss with the whey. Good calcium extraction from the casein matrix was obtained when the pH value was reduced dramatically after curdling, i.e. between cutting the curd and filling it into the molds. Significantly less calcium was extracted with lactic acid than with citric acid, although the pH values obtained in the whey were comparable. The complexing of the citric acid with the calcium seems to be a key effect favouring the extraction of calcium. On the other hand, pre-ripening of the milk resulted in better calcium retention compared with standard production. The state of the calcium played an important role in the ripe cheese: a low pH and complexing with calcium increased the proportion of dissolved calcium, an important factor for the melting properties of raclette cheese.