Cheese process control

Abstract

The cheese making process at Anchor Products Hautapu was having difficulty reaching the now outdated New Zealand Dairy Board uniformity targets. Even though there is no longer a direct financial benefit in reaching these targets consistently, there is the benefit of being able to show the customer that the product which they are receiving is as consistent as possible. This project was carried out by systematically investigating each section of the cheese making process, looking for variations that were likely to affect the final product. Where variations were found methods for eliminating them or minimising their effect on the final product were developed. The largest source of variation was found to be caused by fluctuations in the curd depths on the belts of the Alf-O-Matic cheddaring machine. Overlapping the ends of consecutive cheese making tanks as well as the re-calculations of the pump out flow rates have been proposed to remedy this problem. Where the curd is drawn off from the end of the Alf-O-Matic cheddaring machine was also found to be causing variation in the product due to particle stratification affecting the salt levels of blocks that were being produced. Recommendations for methods to reduce the level of stratification have been suggested including using a capacitance probe to control the curd level. Further variations were occurring within the cheese making tanks with cutting and stirring speeds differing from tank to tank. The tanks were also being flushed with cold water causing moisture spikes in the product. Both of these problems have been eliminated by changes to the PLC program. Small improvements have been seen in the process with the changes that have already been carried out. Large improvements are expected if the rest of the recommendations are implemented. The largest improvements should be seen with the realisation of an overlapped pump out system.