Nondestructive Detection of the Mulberry Quality during Fruit Development and the Research on the Postharvest Classification and Processing Technology of Its Fruit
|School||Zhejiang Normal University|
|Keywords||mulberry nondestructive detection classification sterilization support vector machine|
Mulberry is an increasing important fruit in the word due to its superior nutrition and officinal values. The picking time is crucial for the quality of mulberry. Evaluation of the degree of fruit ripeness and the changes of internal chemical parameters during the development of mulberry can satisfy growers’ selective harvest requirement. In addition, growers can decide real-time watering, fertilizing, and other measures, to achieve precise management of mulberry production according to the testing indexes such as fruit maturity, sugar concentration. The postharvest classification based on the maturity of mulberry can be helpful for transportation and storage of the management as well as its processing and utilization. The nondestructive techniques not only overcome the manual operation’s faults such as complicated operation and high labor intensity, but also have the advantage of rapid, accurate and non-destructivity. In recently, they have been applied to the quality evaluation and grading fruit and are becoming more and more popular. Though there are much high nutrients content in mulberry fruit, it tends to decay and easy to lose nutrient at room temperature. Therefore, this kind of fruit was usually produced to other products such as mulberry juice and dried mulberry. Sterilization is an common process that take place in the mulberry processing field. However, it is often cause serious loss of nutritional value of food. So, it is important to search for the sterilization method that works best for mulberry. To solve the problems above, we have done some researches. The main contents and results can be listed as follows: 1. The use of chlorophyll fluorescence measurements and RGB intensity values to noninvasively evaluate changes of the internal chemical parameters (total flavonoid, total phenols, ABTS cation and DPPH radical scavenging activities and sugars) was investigated during all the development stages (ST) and the last four development stages of mulberry fruits in this study. The appropriately fitted relationships in this study revealed that chlorophyll fluorescence and RGB intensity have high correlations with the internal chemical parameters of mulberry fruits. Especially, each of the internal chemical parameters has higher correlations with chlorophyll fluorescence and RGB intensity during the period of ST4-ST7than during the period of ST1-ST7respectively. High correlations between chlorophyll fluorescence and the internal chemical parameters were found during the period of ST4-ST7, with R2ranged from0.82to0.94. RGB intensity values showed fine correlations with the internal chemical parameters with R2ranged from0.93to0.97during the period of ST4-ST7.2. Develop a new approach for the automatic sorting of mulberry fruit using C-SVM based on chlorophyll fluorescence and RGB intensity color. Our results showed that the best classification accuracy of fruit quality was up to96%using the Linear SVM classifier (C=2, y=0.707) based on combining RGB intensity values and chlorophyll fluorescence. All SVM classifier based on combining RGB intensity values and chlorophyll fluorescence achieved94%accuracy rate except sigmoid.3. The effect of different sterilization methods (thermal, microwave and ultrasonic processing) on the main bioactive compounds and antioxidant activity of mulberry juice during selected storage temperatures (5,15and25℃) was investigated. At all selected storage temperatures, ultrasound sterilized mulberry juice showed higher total phenolics, anthocyanin and antioxidant activity compared to the microwave and conventional thermal processed juice especially at lower temperatures. Anthocyanin level of all treated juices decreased throughout the storage at all storage temperatures, with lower values measured at higher temperature. The antioxidant activity of conventional thermal treated juice depleted with storage time, whilst both ultrasound and microwave treated juices showed transient increase in antioxidant activity during the first2days that later decreased with storage time.In conclusion, chlorophyll fluorescence and RGB values are effective methods to evaluate the quality changes of mulberry, at the same time, The proposed SVM models based on chlorophyll fluorescence and RGB intensity color achieved the best classification accuracy, showing that this method can provide a potential tool for automatically classifying the maturity of not only mulberry but also any other fruit in packing lines. In addition the use of ultrasound sterilization should be preferred over traditional heat pasteurisation and microwave sterilization in order to preserve the antioxidant and other bioactive compounds in mulberry juice.