1. Introduction
Aurora black is a new and original breed grape of Okayama Prefecture. Special characteristics of this grape are its large grain, seedless, high sugar content, and its fine look. It is also suitable to export since it has excellent characteristics for transportation such as it is difficult to berry drop and long-lasting after harvest. Therefore, it is recommended as a next-generation grape.
A cultivation method is not fully optimized since it is still not fully known. To find its biological information, fruits on several parts of a vine were harvested and physical quantities related to ripeness were measured.
2. Materials and Methods
In Okayama, many vines are shaped as a H or double H style as shown in Fig. 1. Usually, a double H style is 8 branches but due to a space limit, it was 6 branches in this house. A total of 6 grape bunches were sampled from branch 1 and 2, and it was located close, middle, and far from the trunk respectively. Brach 2 was sampled on the second week of September 2021, and branch 1 on the following week.
From each grape bunches, 6 berries were sampled based on its location like top, middle or bottom of the bunch. Measured quantities were weight, solidity, sugar content, and acidity as freshness and anthocyanin content, and Lab as a color information.
3. Results and Discussion
Based on the location of the grape bunches on a vine, all the measured quantities were different. For weight, there was significant difference between middle bunches of branches 1 and 2. Solidity showed the most variation with other grape bunches as far grape bunches from branch 1 had variation with all samples from branch 2. Sugar content difference was notable for far grapes from different branches. There was no significant difference in acidity, however, in average, branch 2 had higher in acidity average than branch 1. For the appearance measurement, there were no significant difference in anthocyanin, L, and b value, however, there was a remarkable difference to the far grape from the branch 1 to middle and far grape on branch 2. There were no significant differences among each grape bunches, however, there were difference in average of three grape bunches from each brunch 1 and 2 for anthocyanin, L and b value.
By comparing all the data, it was found out that the wight increase, solidity decrease, with increase in sugar content to the branch 1 samples than branch 2. Those factors may cause the ripeness. It is possible to say the difference is due to not only 1 week delay but also the direction of the grape bunches since the sunlight would affect the ripening speed of the grapes on a vine. Branch 2 was located at the middle of the vine, and it was hard for this branch to get enough sunlight compared to branch 1 and 3. Branch 3 was fully ripened so that it was already harvested by the time of the experiment.
Fig. 1 Layout of a vine and samples
Table 1 Physical quantities of the Aurora black grape by location of a vine
