Efficiency of N2 Gas Flushing Compared to the Lactoperoxidase System at Controlling Bacterial Growth in Bovine Raw Milk Stored at Mild Temperatures

Abstract

To prevent excessive bacterial growth in raw milk, the FAO recommends two options: either cold storage or activation of the lactoperoxidase system (LPs/HT) in milk with the addition of two chemical preservatives, hydrogen peroxide (H) and thiocyanate (T). N2 gas flushing of raw milk has shown great potential to control bacterial growth in a temperature range of 6–12°C without promoting undesired side effects. Here, the effect of N2 gas (N) was tested as a single treatment and in combination with the lactoperoxidase system (NHT) on seven raw milk samples stored at 15 or 25°C. For the ratio defined as bacterial counts from a certain treatment/counts on the corresponding control, a classical Analyse of Variance (ANOVA) was performed, followed by mean comparison with the Ryan-Einot-Gabriel-Welsch multiple range test (REGWQ). Altogether, the growth inhibition was slightly but significantly higher at 25°C than at 15°C. Except for one sample, all ratios were lower for HT than for N alone; however, these differences were not judged to be significant for five samples by the REGWQ test; in the remaining two samples, N was more effective than HT in one case and less effective in the other case. This study shows that N2 gas flushing, which inhibited bacterial growth in raw milk at 15 and 25°C for 24 and 12 h, respectively, could constitute an alternative to LPs where no cold storage facilities exist, especially as a replacement for adulterating substances.

N2 Gas Flushing Limits the Rise of Antibiotic-Resistant Bacteria in Bovine Raw Milk during Cold Storage

“…At 6°C, the “storage time” factor was preponderant over the “treatment type” under all the conditions (Table 3), in contrast to the study at 15/25°C in which the “treatment type or condition“ factor seemed to be the major determinant of the inhibitory effects for 4 of 7 samples (Munsch-Alatossava et al, 2016). A notable difference between HT and N relied on the observation that at sampling day 3, the activated lactoperoxidase system (HT) reduced TS-resistant bacterial levels to non-detectable levels under four conditions (S1P, S2M, S3M, and S3P) (Figure 1) whereas N experienced a reduction in the L-resistant bacterial types under four conditions (S1M, S2M, S2P, and S3M) (Figure 1).…”

Quality and Safety of Bovine Raw Milk: Present Challenges and Technological Solutions

“…The N 2 gas flushing of raw milk was initially conceived to be applied at earliest possible in farms until the processing site as an additional hurdle to cold storage, such as to preserve the initial microbiological, biochemical and nutritional features of raw milk along the cold chain of raw milk storage and transportation, before its transformation. The recent observation that N 2 gas flushing was about equivalently inhibitory of bacterial growth in raw milk at milder temperatures (15 and 25°C) compared to LPS [62], offers further perspectives for the method and especially as a replacement of numerous adulterating substances, including antibiotics, added to raw milk.…”

“…Impact of N 2 flushing on raw and pasteurised milk-associated bacterial populations, and on some pure strains[24,38,42,[57][58][59][60][61][62].…”

Secondary Sulfonamides as Effective Lactoperoxidase Inhibitors

“…The affinity matrix was synthesised by coupling sulfanilamide as the ligand and l -tyrosine as the spacer arm to CNBr-activated-Sepharose 4B, following the previously published procedure [ 22 ] with a slight modification [ 33 , 34 ]. The protein flow in the column eluates was spectrophotometrically determined at 280 nm [ 35 ].…”

“…Additionally, LPO is released from mucosal glands and can be found in secretions like saliva, milk or tears. The potential of LPO to inhibit bacterial growth in milk has been recognized [ 22 , 23 ]. LPO catalyses the H 2 O 2 -dependent oxidation of thiocyanate (SCN − ) to hypothiocyanite (OSCN − ).…”