We developed a rapid and sequential analysis system to determine stress marker in the milk. One of the famous stress markers, cortisol, was detected using our method. Quartz crystal microbalance (QCM) method with a twin sensor was used in this study. One channel detected stress marker corresponding to antigen-antibody interaction and the other channel was used as a reference to remove environmental influences. Although nonspecific adsorption was monitored on each channel, frequency difference between them was within a few Hz on the injection of sample solution. One determination cycle including regeneration step could be performed within 10 minutes. The system could detect the cortisol level from 0.1 pg/mL to 100 pg/mL. These results show that our system has a potential to check the daily feeding condition for cows in terms of animal welfare.

Quantitative detection of food allergen is placed considerable emphasis in food factories all over the world. We proposed a quartz crystal microbalance (QCM) method coupled with a passive flow system for the analysis of β-lactoglobulin, as an example. Analytical curves for a passive were comparable on an active flow system, and 1 ppm of β-lactoglobulin was detected. Repeatable detection was achieved by the regeneration of the sensor surface. One detection cycle was completed within 13 min. This proposed system can be used for quantitative analysis without professional skills, only by dropping a liquid sample.