Journal of Food, Agriculture and Environment

Comparison of inactivation effects of pressurized CO₂ and thermal pasteurization on natural microorganisms in raw milk 

Author(s):

Chunyan Yao ^{1, 2, 3}, Xiaodong Li ^{1, 2}*, Weiwei Bi ^{1, 2}, Shudong He ^{1, 2}

Recieved Date: 2013-01-27, Accepted Date: 2013-04-23

Abstract:

The inactivation effects of pressurized CO₂ and thermal pasteurization on natural microorganisms in raw milk were investigated comparatively. The stability of natural microorganisms in the treated raw milk during storage was also investigated comparatively. The effects of pressurized CO₂ treatment parameters on the inactivation results were investigated by changing CO₂ pressure (4.5, 7.5 and 10.5MPa), pressurized time (20, 40 and 60 min), temperature (4, 15 and 25°C) and pressurized modus (continuous treatment and intermittent treatments). The results indicated that CO₂ pressure, pressurized time and temperature had more profound effects on the inactivation degree of natural microorganisms in raw milk, but the effect of pressurized modus was less profound relatively. The Gram-positive bacteria in raw milk were more resistant to the pressurized CO₂ treatment than gram-negative bacteria. Pressurized CO₂ treatment at 7.5 MPa, 4°C, under continuous treatment for 40 min could decrease the viable count of Pseudomonas, Enterobacteriaceae and the total bacterial count in raw milk to the levels lower than thermal pasteurization (63°C, 30min), could decrease the viable count of Staphylococcus aureus to the level undetectable, but the viable count of Lactic Acid Bacteria (LAB) was more than thermal pasteurization. Compared with thermal pasteurization, at the optimal conditions, the effect of pressurized CO₂ treatment on the storage stability of natural microorganisms in raw milk was investigated at 4°C. The results indicated that during the whole storage period, the storage stability of Pseudomonas and Enterobacteriaceae in the samples treated by pressurized CO₂ was better than thermal pasteurization, the storage stability of LAB was worse than thermal pasteurization, Staphylococcus aureus was undetectable, the total bacterial count in the samples treated by pressurized CO₂ was all lower than thermal pasteurization. Compared with thermal pasteurization, as for the aspect of total bacterial count, the storage time of the raw milk samples treated by pressurized CO₂ was extended for two days.

Keywords:

Pressurized CO₂, thermal pasteurization, raw milk, natural microorganisms, inactivation effect, storage stability

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Journal: Journal of Food, Agriculture and Environment
Year: 2013
Volume: 11
Issue: 2
Category: Agriculture
Pages: 767-772

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