Protective role of ascorbic acid in the decontamination of cow milk casein by gamma-irradiation.
OBJECTIVE
The aim of this work was to investigate the protective role of ascorbic acid on irradiation-induced modification of casein.


METHODS
Casein stock solutions were irradiated with increasing doses 2-10 kGy using (60)Co Gamma rays at a dose rate D• = 136.73 Gy/min at room temperature. The total viable microorganism content of cow milk casein was evaluated by Plate Count Agar (PCA) incubation for 48 h at 37°C. Sodium dodecylsulfate gel electrophoresis (SDS-PAGE) and Matrix-Assisted Laser Desorption-Ionization Time-of-Flight mass spectrometry (MALDI-TOF-MS) analysis were used to evaluate the effect of gamma irradiation on casein integrity.


RESULTS
Gamma irradiation reduced the bacterial contamination of casein solutions at a lower irradiation dose when performed in the presence of ascorbic acid. The irradiation treatment of casein in the absence of ascorbic acid with a dose of 4 kGy could reduce 99% of the original amount of bacterial colonies. However, in the presence of ascorbic acid the irradiation treatment of casein with a dose lower than 2 kGy could reduce 99% of the original amount of bacterial colonies which suggested that the irradiation dose lower than 2 kGy achieved almost the entire decontamination result. SDS-PAGE and MALDI-TOF-MS analysis showed that ascorbic acid protected cow milk casein from degradation and subsequent aggregation probably by scavenging oxygen and protein radicals produced by the irradiation.


CONCLUSIONS
It is demonstrated that the combination of gamma irradiation and ascorbic acid produce additive effects, providing acceptable hygienic quality of cow milk casein and protects caseins against Reactive Oxygen Species (ROS) generated, during the irradiation process.
Unité de recherche de Biochimie des lipides et interactions avec les macromolecules, Laboratoire de Biochimie et de Biologie moléculaire, Faculté des sciences de Bizerte, Zarzouna, Tunisia. kouasssahbanisaloua@rocketmail.com
Saloua
S
Kouass Sahbani
Klaus
K
Klarskov
Amine
A
Aloui
Salah
S
Kouass
Ahmed
A
Landoulsi
D000818:Animals; D001205:Ascorbic Acid / Q000737:chemistry* / Q000528:radiation effects; D018407:Bacterial Physiological Phenomena / Q000528:radiation effects*; D002364:Caseins / Q000737:chemistry* / Q000528:radiation effects*; D002417:Cattle; D003666:Decontamination / Q000379:methods; D005503:Food Additives / Q000737:chemistry / Q000528:radiation effects; D005720:Gamma Rays; D008892:Milk / Q000737:chemistry* / Q000382:microbiology*; D011829:Radiation Dosage; D011837:Radiation-Protective Agents / Q000737:chemistry; D013242:Sterilization / Q000379:methods*
D002364:Caseins; D005503:Food Additives; D011837:Radiation-Protective Agents; D001205:Ascorbic Acid