NON-DESTRUCTIVE EVALUATION OF INTERNAL QUALITY OF RADISH TUBERS USING SPECIFIC GRAVITY, X-RAY ANALYSIS AND NEAR INFRARED SPECTROSCOPY

Up to now the degree of sponginess has been determined by visually comparing the transversely cut tuber with a series of photographs of spongy tubers. This method is subjective, destructive and time-consuming. Therefore, an objective, non-destructive and rapid method is desired to determine the degree of sponginess. In this preliminary study some of these methods were tested, including (1) measurement of specific gravity, (2) X-ray analysis and (3) near infrared spectroscopy. Two batches of 50 tubers were analysed by all three methods. Finally, the degree of sponginess was determined visually by comparing the transversely cut tubers with a standard series of photographs. The visually estimated relative area of spongy tissue was highly correlated with specific gravity (R=-0.92) as well as X-ray analysis (R=0.87) and correlated reasonably well with near infrared reflectance (R=0.73) and transmittance (R=0.66). When sponginess led to hollowness of the tubers the specific gravity was reduced, but the X-ray technique did not discriminate between spongy tissue with and spongy tissue without hollows, while the near infrared spectroscopy tended to predict a lower degree of sponginess when the spongy tissue showed hollows. Advantages and disadvantages of each method are discussed.

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