Effects of Flash Evaporation Conditions on the Quality of UHT Milk by Changing the Dissolved Oxygen Content in Milk

Abstract

This study assessed the impact of reducing dissolved oxygen (DO) content on the quality of UHT milk using a flash deoxygenation treatment. Flash deoxygenation was designed based on preheated milk reaching boiling early under low-pressure conditions to remove DO from the milk. Two parameters were designed for flash deoxygenation: preheating temperature 65 °C, −0.08 Mpa, and 70 °C, −0.06 Mpa. The flash conditions were applied to two UHT sterilization conditions (135 °C for 10 s and 145 °C for 5 s). After deoxygenation, the total oxidation (TOTOX) value of UHT milk was reduced by 1.4~1.71, and the protein carbonyl (PC) value was reduced by 1.15~1.52 nmol/mg of protein. The maximum inhibition rates of furusine and 5-HMF were 33.23 ± 1.72% and 25.43 ± 3.14%, respectively. The particle size was reduced by 0.141~0.178 μm. The ketones and stale aldehydes causing oxidized taste in the UHT milk were significantly reduced. This study showed that the oxidation and Maillard reactions of UHT milk were significantly inhibited, stability was improved, and the content of undesirable volatile flavor substances was reduced after flash deoxygenation. Therefore, reducing DO content was beneficial to improving the quality of UHT milk.

Comparative Study of Nanofiltration and Evaporation Technologies on the Milk Concentration

“…From the obtained data in table, the statistically analyzed results show that although (RM) obtained the significant highest scores at all parameters (P≤0.05) among all treatments, but there was no significant difference at (P<0.05) compared to (CM) at all parameters and also total score, this is in agreement with [54], who stated that concentrating milk by membrane filtration preserves its sensory qualities. On the contrary, the scores obtained by (EM) differed with a significant difference among all the treatments at (P<0.05), where obtained a significant lowest values for individual parameter, as well as for the total scores of sensory evaluation, it was recorded 83.5 while (RM) and (CM) was recorded 95.6 and 92.8 respectively and this is in agreement with [55,56], who decided that the heat treatment negatively affects the sensory properties of evaporated milk due to the occurrence of partial caramelization, which causes browning and a change in taste and flavor and can be avoided by reducing the oxygen in the milk by conducting the treatment under vacuum. But looking closely, it can be seen that (EM) obtained a non-significant lower value than (CM) at body and texture parameter, this is due to that both of them contain the same percentage of moisture and total solids, which means that they have almost the same concentration and texture approximately [57].…”