Journal of Food Processing & Technology

Abstract

Improved Storage of Cold Raw Milk by Continuous Flushing of N2 Gas Separated from Compressed Air: A Pilot Scale Study

Patricia Munsch-Alatossava, Oguz Gursoy and Tapani Alatossava

Nitrogen gas (N2) produced by a gas generator unit from compressed air was continuously introduced in a tank of 170 L, that contained up to 110 L raw milk kept at 5.5±0.4 ºC with an ice-water cooling unit. N2 gas was introduced in the tank at a fixed flow rate ranging from 4 L to 14 L per min, whether flushed in the head space of the raw milk tank or bubbled directly into raw milk. In the tested conditions, the combination bubbling for 6 h followed by continuous flushing of N2, up to seven days, gave the best results, since the bacterial growth in raw milk could be retarded significantly. An increase of one log unit of the total bacteria required about 2.5-fold longer time under the N2 gas flushing compared to the control (no N2 gas treatment). The treatments also reduced phospholipases (PLs)-producing and Bacillus cereus type bacteria. The results obtained at a pilot plant scale demonstrate the potential of this technology, that could be applied in order to improve quality and safety of raw milk, during prolonged storage along the cold chain.