Rapid Quantitative Test for Free Oil (Oiling Off) in Melted Mozzarella Cheese

A test for free oil in melted Mozzarella cheese using standard Babcock equipment was developed and evaluated.Eighteen grams of whole milk or part skim Mozzarella were weighed into 50 or 20% Paley-Babcock bottles, respectively.Bottles were immersed in boiling water for 4.0 min to melt cheese.Distilled water (20 ml at 57SC) was then added and the bottles were centrifuged hot (ca.57SC) for 10 min.A portion of 1:1 distilled water:methanol (21°C) was added to a final level in the upper region of the calibrated neck and then centrifuged for 2 min.Bottles were then rocked by hand for 10 s, centrifuged for 2 min, and a second time rocked by hand for 10 s and centrifuged for 2 min.Finally, bottles were tempered in 57.5°C water for 5 min and the fat column then measured with glymol.This procedure gave a clear, defined fat column.Free oil was expressed as percentage in cheese and percentage in cheese fat.A series of recovery trials in which low moisture and low moisture.part skim Mozzarellas were spiked with butter oil gave recoveries ranging from 97.3% to 104.5%.Eighteen replicates of a low moisture and low moisture, part skim Mozzarella gave coefficients of variation of 3.3 and 6.2%, respectively.Free oil was measured in 64 Mozzarella cheese obtained from local supermarkets and two industrial cheese plants.Free oil as a percentage of total cheese fat