Supreena Srisaikham, Naoki Isobe and Wisitiporn Suksombat

DOI: 10.14456/sjst-psu.2017.9

pp. 77 - 89

Abstract

Preservation of raw milk quality by activation of lactoperoxidase system (LPs) was studied for the inhibition of microorganism growth. The antimicrobial effects of LPs were examined by measuring thiocyanate (SCN-
) concentration, lactoperoxidase (LP) activity, milk composition, total bacterial count (TBC) and coliform count (CC). All parameters were analyzed at
0 h and at 25°C and 30°C as a control. Thus, the experiment was conducted to evaluate the effect of 2 different temperatures
(25°C vs 30°C) and 4 ratios of NaSCN:2Na₂CO₃
3H₂O₂
 (0:0, 7:15, 14:30 and 21:45 mg/L) on milk samples (both uninoculated raw
milk samples and Escherichia coli (E. coli) inoculated milk samples) with 8 replicates per run using 0-12 h incubation time
in vitro assay. The runs were conducted on the same 4 NaSCN:2Na₂CO₃
3H₂O₂
 ratios and different temperature and time of
incubation were used. The results showed that the milk SCN-
 concentration and LP activity increased with increasing
NaSCN:2Na₂CO₃
3H₂O₂
 ratios. Milk compositions retained the quality of normal milk fat, protein, lactose, solid-not-fat (SNF)
and total solid (TS) contents, and they were not significantly affected by the LPs activation. An obvious effect of the LP
activated milk was the inhibition of TBC in uninoculated raw milk samples for 6 to 12 h both at 25°C and 30°C), and for 6 to
9 h in E. coil inoculated milk samples, whereas CC (6 h at 25°C and at least 3 h at 30°C for both uninoculated and E. coil
inoculated milk samples). It is concluded that improved preservation of milk can be achieved through the addition of 14:30
and 21:45 mg/L of NaSCN:2Na₂CO₃
3H₂O₂
 in uninoculated and E. coil inoculated milk samples respectively, to extend milk
quality during storage.

Keywords

• lactoperoxidase system
• Escherichia coli
• microorganism growth
• raw milk quality