Comparative study of microbial counts and some volatile compounds of whole milk processed by sonication and high temperature short time (HTST) pasteurization

Document Type

Article

Publication Date

10-24-2012

Abstract

Sonication has the potential to simultaneously homogenize milk and to reduce its microbial load. Raw milk samples were sonicated with horn (diameter 13 mm) set at a maximum acoustic power output of 750 W, frequency 24 kHz with a 100% amplitude for 2 min. Also the raw milk was pasteurized by high temperature and short time (HTST) at 72t,Cfor 16 seconds. Using these settings the coliform count was 0 CFU's/ml in both treatments and total aerobic count was 0 CFU's/ml for sonicated samples and 40 CFU's/ml for HTST pasteurized samples. Since coliform counts and total bacterial counts met the legal requirement, these sonication settings were selected. Sample preparation for gas chromatog-raphy-mass spectrometry (GC-MS) included sample incubation for 30 min at 60°C and drawing of 1 ml of head space. Experiment was replicated 3 times. Trace volatile compounds were analyzed using GC-MS using the NSIT library search software. Dimethyl amine (DMA) and dimethyl sulfide (DMS) were the most significant compounds detected in control (raw). In raw whole milk the coliform count was 160 CFU's/ml and aerobic count was 200,000 CFU's/ml. Using sonication the coliform count and aerobic count were zero. The HTST samples showed no coliform counts, but aerobic counts of 40 CFU's/ml. Compared to HTST, sonication resulted in 20 times less DMA and DMS, compounds that are responsible for the characteristic fish-house like and cow like flavors, respectively.

Publication Source (Journal or Book title)

Milchwissenschaft

First Page

432

Last Page

434

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