The time evolution of the oxygen equivalent mean path length shows a similar tendency for all fruits as seen in the figure. During the first days, the value of is found to decrease gradually to a minimum value, and then rise to a second peak. Eventually, it decreases to a very low value. In this process, the fruits are subjected to a series of physiological and biochemical changes. It should be noted that the changes in can be attributed to changes in oxygen concentration or in the path length through the gas, or both phenomena. A reason for the initial reduction of could be attributed to the changes of respiratory rate during fruit ripening. Because the four kinds of fruits are climacteric, the respiratory rate rapidly increases to a peak value (i.e., the climacteric point which is a stage of fruit ripening associated with maximum respiration rate and ethylene production) and then returns to or below the point before the event.23,24 For the climacteric fruits, the climacteric point can be seen as the end point of the fruit ripening period. Then, the fruits are more susceptible to fungal invasion and begin to degrade, ultimately leading to cell death. It can be seen (Fig. 8) that the rises to a secondary peak and then decreases to a very low value after the climacteric point. This can be interpreted as due to the fact that the membrane structure is destroyed and the increasing membrane permeability makes the ambient air penetrate inside the aging fruits. Eventually, the fruits are decaying seriously and are filled with liquid replacing the air.25 We note that the characteristic temporal variation of is useful for assessment of ripeness, regardless of detailed exploration. The day of full ripeness can be inferred from the time evolutions of the oxygen for the fruits, and can be associated with the occurrence of the initial minimum in the GASMAS signal. Also, considering the standard deviation errors, the results are shown in Table 2. We should note that from a practical point of view, on a particular measurement occasion it is not possible to locate the minimum of the curves shown in Fig. 8. However, again, since the GASMAS signal is monotonously falling in the interesting phase of the ripening process, we can again define individual threshold values for each kind of fruit, defining the initiation of full ripeness.