School of Food Science and Engineering, Harbin Institute of Technology, Harbin 150090, China.
Molecules. 2012 Aug 17;17(8):9900-11. doi: 10.3390/molecules17089900.
Certain aldehyde and ketone compounds can be used as indicators, at a molecular level, of the oxidized flavor of milk powder instead of sensory evaluation. This study investigated the formation of aldehyde and ketone compounds as affected by the heat-related processing and storage of milk powder. The compounds were extracted by solid phase microextraction fiber and determined using gas chromatography-mass spectrometry. In the results, higher contents of hexanal, 2-heptanone, octanal and 3-octen-2-one were detected in concentrated milk and fresh milk powders than in raw milk and heated milk. The levels of these compounds increased with increasing time of storage of milk powder. Meanwhile, the DPPH radical scavenging activity decreased and peroxide value increased during the production and storage of milk powder. In addition, the pore volume distribution of milk powder particle was determined by nitrogen isotherm adsorption. The porosity of milk powder was significantly correlated to the changes of aldehyde and ketone compounds during storages periods of 3 months (r > 0.689, p < 0.05) and 6 months (r > 0.806, p < 0.01). Therefore attention should be paid to the detectable aldehyde and ketone molecules to control the oxidized flavor, which was influenced by pre-heating as well as concentration and drying during milk powder production.
某些醛类和酮类化合物可以在分子水平上作为奶粉氧化风味的指示剂，而不是通过感官评估。本研究探讨了奶粉热加工和储存对醛酮化合物形成的影响。采用固相微萃取纤维提取化合物，并用气相色谱-质谱法测定。结果表明，浓缩乳粉和新鲜乳粉中己醛、2-庚酮、辛醛和 3-辛烯-2-酮的含量高于原料乳和加热乳。这些化合物的含量随着奶粉储存时间的增加而增加。同时，在奶粉生产和储存过程中，DPPH 自由基清除活性降低，过氧化物值增加。此外，还通过氮气等温吸附法测定了奶粉颗粒的孔体积分布。在 3 个月（r>0.689，p<0.05）和 6 个月（r>0.806，p<0.01）的储存期内，奶粉的孔隙率与醛酮化合物的变化显著相关。因此，在奶粉生产过程中，应注意预加热、浓缩和干燥对氧化风味的影响，以及可检测的醛酮分子。
