The water content of a food product is an important factor in determining its quality and stability. Inappropriate moisture content in food may result to microbial contamination and food spoilage. Every food product has its corresponding water activity range. Water activity, (aw), is an indicator of food stability. It corresponds to the vapour pressure present in food and the partial pressure of pure water, given that temperature of the vapour pressure in food is the same as the temperature when the pure water’s partial pressure is measured. Water activity can also be determined by dividing the equilibrium relative humidity of the sample in which the water present is no longer absorbed or lost, with 100.

Since water activity of a sample is important in all food products, different ranges for corresponding food products were given as standards. High moisture foods with 0.97 to 1 aw, low moisture food (less than 0.6), and intermediate moisture food with aw ranging from 0.6 to 0.9. Liquid milk falls under the high moisture foods since it is susceptible to deterioration. On the other hand, milk products like cheese can be classified as intermediate moisture food since they are stable without refrigeration, yet may have browning reaction during shelving.

The moisture content of a sample can be computed using the formula below. First, the sample is analytically weighed in an aluminum container. Afterwards, the sample is subjected to drying. Cheese sample was tested through Oven-dried method, in which it was dried under 102oC for 3 to 4 hours. On the other hand, the butter was dehydrated through heating and boiling until light brown color was achieved. Both of the samples were cooled and weighed afterwards.

%Moisture= Weight lossWeight of sample

×100

The results showed that the cheese sample had a moisture content of 59.0512%, as seen in Table 1. This value is near to the approximate moisture content of “kesong puti” being produced in DTRI, UPLB. According to UPLB Research, Development and Extension, soft cheese of “kesong puti” in DTRI contains moisture of approximately 60%. The explanation why cheese, despite of its solidity even in room temperature, has high moisture content is due to the production itself. The milk is allowed to clot in order to produce cheese. During clotting, the casein micelles forms clusters as they aggregate. This aggregation will trap fat and moisture inside the cheese (Johnson, 2003).

Table 1. Average moisture content of cheese or “kesong puti” and butter.

Milk Product Average % Moisture“Kesong Puti” 59.0512 %

Butter 33.0502 %

On the other hand, butter sample had a moisture content of 33.0502%. Butter is produced through the process of churning. It is an emulsion process in which fat globules in milk were mixed in such a way that they will stick together, forming the butter. After churning, buttermilk will be formed, which is a watery liquid produced that floats above the butter chunk (Oklahoma Department of

Agriculture, n.d.). Buttermilk, as well as water is removed from the butter by draining or pressing the butter into a solid mass. This process makes the butter to be low in moisture content.

References:

Johnson, M. (June 2003). Moisture Migration in Cheese- Gauging the Effects of Moisture Loss and Moisture Gain. Dairy Pipeline, 12(2), 1-12. Retrieved from https://www.cdr.wisc.edu/sites/default/files/pipelines/2003/pipeline_2003_vol15_02.pdf. September 13, 2015.

Oklahoma Department of Agriculture. (n.d.). Chemistry of Butter. Oklahoma: Oklahoma Cooperative Extension Service. Retrieved from http://lib.dr.iastate.edu/cgi/viewcontent.cgi?filename=6&article=1020&context=ag_researchbulletins&type=additional on September 13, 2015.

"UPLB-DTRI Soft Cheese or “Kesong Puti”/ Probiotic Soft Cheese." ovcre.uplb. UP Los Baños, 2013. Web. 13 Sept. 2015.

Computation:

Cheese T1 T2 T3Before After Before After Before After

Crucible 23.8182 23.8182 18.0466 18.0466 20.0950 20.0950Crucible +

sample25.2771 24.4013 19.8024 18.7765 22.1421 20.9406

Sample 1.4589 0.5831 1.7558 0.7299 2.0471 0.8456%

Moisture60.0315 58.4292 58.6928

Average % Moisture

59.0512

Butter T1 T2Before After Before After

Aluminum beaker

50 50 49.37 49.37

Aluminum beaker + sample

60.26 56.97 59.36 55.96

Sample 10.26 6.97 9.99 6.59%

Moisture32.0663 34.0340

Average % Moisture

33.0502