Relationship Between Electrical Parameters And Physio-biochemical Attributes Of 'huoshi' Persimmon And 'red Bartlett' Pear Fruit

The relationship between fruit electrical properties and quality attributes of persimmon fruit variety'Huoshi'(Diospyros kaki L. Huoshi) and'Red Bartlett'(Pyrus communis L., Red Bartlett) pear fruit were studied through the combined research of micro-electric nondestructive techniques and physio-biochemical destructive test. Synchronism sampling and parallel assessment for electrical and physio-biochemical test were conducted by the cross-discipinary study of electrobiology, physio-biochemical, postharvest physiology, biomathematics research, and regression models were set for fruit quality prediction. The techniques of fruit quality prediction in this research provided basis for online nondestructive assessment of fruit quality by electrical properties. The main results of this thesis were as follows:(1) The persimmon fruit variety'Huoshi'could be de-astringent by constant temperature short duration (CTSD) technique, and 1-Methylcyclopropene (1-MCP) had no significant affect on de-astringency process. 500 nL?L-11-MCP treatment suspended ethylene climactic and fruit firmness for CK and CO2 treated'Huoshi'fruit, slowed down the decrease of fruit firmness, soluble solids content (SSC) and titratable acidity (TA) for CK fruit, decreased the POD activity and MDA content for CK and CO2 treated fruit, depressed the activity of SOD for CO2 treated fruit. The shelf-life of CK/de-astringent fruit was extended by 1-MCP treatment from 25 d/5 d to 37 d/20 d, respectively.(2) With the voltage increasing from 0.2 to 5 V, the impedance (Z) and inductance (Lp) of'Huoshi'decreased, while capacitance (Cp) and conductance (G) increased. Over the frequency 100 Hz~3.98 MHz, the impedance and inductance of'Huoshi'were declined on power function with the increasing of frequency; the capacitance varied on wave manner; the conductance increased on power manner (f≤15.8 kHz) or varied irregularly (f>15.8 kHz). With the rising of fruit temperature from 10℃to 40℃,fruit impedance and inductance were linearly decreased, while low frequency conductance and capacitance were linearly increased.(3) With the maturation of'Huoshi'fruit, the impedance and inductance decreased, while the capacitance and conductance (f<6.31 kHz or f>1 MHz) significantly increased (P<0.01). Fruit impedance and inductance were significantly decreased during the storage at (20±1)℃, while the capacitance and conductance were significantly increased (P<0.01). The variation of electrical properties were accelerated for de-astringent'Huoshi'fruit, 1-MCP treatment delayed the variation of electrical parameters for both CK and de-astringent fruit.(4) The firmness of'Huoshi'was positively correlated with impedance and inductance, while negatively correlated with the capacitance and inductance. The correlation coefficient (r) increased with the tested frequencies. Best correlation of impedance, capacitance and inductance with firmness attained at 1 MHz, with the r values of 0.867,-0.65 and 0.867, respectively; while best correlation between firmness and conductance obtained at 100 kHz with the r value of -0.613. The impedance and inductance were positively correlated with SSC for CK and 1-MCP treated fruit, while negatively correlated for CO2 and CO2+1-MCP treated fruit. The correlation of fruit electrical parameters with fruit firmness and SSC were better fitted in power function, and the regression coefficient of Z, Cp, Lp and G with fruit firmness was 0.906,-0.902,0.909 and -0.879, respectively, and with SSC was 0.682,-0.690,0.683,-0.649, respectively.(5) The firmness of'Huoshi'persimmon could be successfully predicted by electrical parameters. The determination coefficient (r2) was 0.803,0.747,0.810 and 0.692 when predicted by Z, Cp, Lp and G, respectively; r2=0.824 when predicted by multiple linear regression model with inductance and capacitance as independent variable; r2=0.823 and 0.829 when predicted by segment model composed by impedance and inductance, respectively. The determination coefficient for SSC predicting was not high enough for precise prediction.(6) With the increasing of tested frequency from 100 Hz to 3.98 MHz, the impedance and inductance of'Red Bartlett'fruit decreased in exponential form, while the capacitance and conductance varied irregularly. Fruit impedance and inductance decreased significantly with fruit ripening (P<0.01), while capacitance and conductance changes had an increasing trend, Within 100 Hz~1 MHz frequency, the correlation coefficient between fruit impedance, inductance, capacitance and fruit firmness increased from 0.45, 0.45 and 0.37 at 100 Hz to 0.84, 0.83 and 0.73 at 1 MHz, respectively; while decreased or not changed significantly at the frequencies above 1 MHz. The impedance, capacitance and inductance can be taken as the sensitive electrical attributes for fruit ripeness, and 1 MHz is the optimum test frequency for'Red Bartlett'fruit. At the frequencies lower than 4 kHz, SSC of'Red Bartlett'fruit is negative correlated with impedance and inductance, and positive with the capacitance, while the correlation reversed at the frequencies higher than 4 kHz. The correlation was not significant between electrical parameters and SSC for'Red Bartlett'pear fruit (P>0.05).Main creations:1) 1-MCP was the first time to be utilized for the storage of de-astringent Chinese persimmon variety, and the shelf-life of'Huoshi'was extended from 5 d to 20 d, which is important for the extension of fresh astringent persimmon fruit in China.2) The variations of physio-biochemical properties and electrical parameters for'Huoshi'were parallel studied, effect of external factors such as voltage, frequency, different treatment, and internal factors like fruit temperature, maturation and storage durations to electrical parameters were studied, and the electrical properties were analyzed by electromagnetism theories and physiology principles. The sensitive electrical parameters to quality attributes and optimum test frequency were validated. The techniques, data and principles in this research provided important information for further study on fruit electrical properties.3) The temperature dependency of electrical properties for intact fruit were firstly be studied, and the linearly correlation equations were set between electrical parameters and fruit temperatures for'Huoshi'fruit, which could be used for electrical parameters prediction at different temperatures.4)'Huoshi'firmness was successfully predicted by electrical parameters. The accuracy is prior to most nondestructive techniques at present.