Effects of processing on the concentration of lead in Manchego-type cheese.

Variations in lead content were determined throughout the process of manufacturing cheese, using graphite furnace atomic absorption spectrophotometry and taking samples of natural, pasteurized milk, with additions of rennet, curd whey, pressed curd, pressing whey and cheese. The mean content of lead in cheese was 211 micrograms/kg on dry weight. Statistically significant differences (p < 0.001) were found in the lead levels in the products from cheese-making, expressed both on wet weight and dry weight. Certain differences were observed in the groups formed on using a Scheffe homogeneity test (p < 0.05) depending on whether the lead content was expressed on wet weight or on dry weight. Slight rises in the lead content based on dry weight were shown to be mainly due to the retention of lead by curd and, secondly, by possible contamination occurring during the process.