Determination of mango physiological indices by mechanical wave analysis

Maturity indicators in mango are softening of the flesh, decreased acidity, increased contents of sugars, soluble solids and total solids, and increased carotenoid pigments. Tissue firmness is known to be the factor most closely related to the stage of maturity in mango fruit, and it can be sensed by a trained person. High quality demand by consumers calls for a reliable, rapid, non-destructive, non-invasive technique for maturity determination. A technique based on a nondestructive ultrasonic method to determine quality parameters of fruits and vegetables was suggested in previous research. The objectives of the present study were to evaluate ultrasonic wave analysis and the physiological properties of cv. 'Tommy Atkins' mango fruit and to establish relationships between the nondestructive ultrasonic measurements and the major physiological quality indices of mango fruit. The passage of ultrasonic waves through the flesh of whole mango fruits was successfully measured by means of ultrasonic probes in contact with the fruit peel. Fast Fourier transforms (FFT) of the ultrasonic wave created frequency domain spectra. A partial least squares (PLS) regression model related the FFT spectra with storage time, firmness, sugar content and acidity. The coefficient of determination (r(2) = 0.64-0.87) between the parameters predicted by ultrasonic spectral models and the measured values were relatively high for storage time and fairly low for firmness. The standard error of calibration (SEC) represents the sensitivity of prediction and was found to be between 12 and 18% of the total range. It was shown that by using the non-destructive ultrasonic measurement system in the appropriate frequency domain, it is possible to assess components of mango fruit maturity and to estimate shelf life.