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

Abstract

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 4.0min to melt cheese. Distilled water (20ml at 57.5°C) was then added and the bottles were centrifuged hot (ca. 57.5°C) for 10min. 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 2min. Bottles were then rocked by hand for 10s, centrifuged for 2min, and a second time rocked by hand for 10s and centrifuged for 2min. Finally, bottles were tempered in 57.5°C water for 5min 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 ranged from 8.8 to 84.9%. Free oil increased with increasing cheese fat on a dry basis.