Abstract #M7

# M7
Effect of carbon dioxide on oxidative stability of raw milk.
Jayendra Kumar Amamcharla1, Jia Xin Tang*1, 1Kansas State University, Manhattan, KS.

Sensory attributes play a critical role in the consumer acceptability of pasteurized milk. Any off-flavor present in raw milk is carried onto the pasteurized milk. One such off-flavor is oxidized flavor (OF). This can have a huge economic impact on dairy farmers as well as on milk processors. Raw milk invariably undergoes oxidative changes as soon as the milk leaves the udder. Still, the rate of OF development mainly depends on nature, concentration, and distribution of pro- and anti-oxidants in the milk system. Antioxidants in raw milk play an important role by donating a hydrogen ion to terminate auto-oxidation. In this process, the antioxidant capacity raw milk diminishes during storage. Recent studies showed that the total antioxidant capacity (TAC) of raw milk decreases by 10% after 24 h and 27% after 48 h of storage. The objective of the present work was to mitigate the reduction in TAC of raw milk by using carbon dioxide (CO2). It has been established that CO2 inhibits growth of psychrotrophic bacteria and extends the shelf-life of raw milk but the effect of CO2 treatment on TAC of raw milk has not been established. Approximately one gallon of raw milk was divided into 4 sub-samples and 3 of the sub-samples were injected with CO2 to 3 pH levels (pH 6.65, 6.55, and 6.45) and the remaining fourth subsample was used as a control. Subsequently, each of these 4 sub-samples were divided into 25 equal samples and stored at 4°C. On each experimental day, 5 equal samples were withdrawn and analyzed using a modified ferric reducing ability of plasma (FRAP) assay. Modified FRAP assay was used to determine the TAC of samples on Day 0, 1, 2, 3, and 4. The data were analyzed as repeated measures design using the MIXED procedure in SAS. The presence of CO2, storage time, and their interaction significantly (P < 0.05) influenced the FRAP value of raw milk. It was observed that the TAC of all raw milk samples was gradually reduced during refrigerated storage. However, the drop in TAC was found to be significantly (P < 0.05) lower in CO2 treated milk. Overall, CO2 treatment of raw milk shows potential in reducing TAC loss during storage of raw milk.

Key Words: modified FRAP assay, total antioxidant capacity, raw milk