Gerald S. Birth

Use of near infrared analysis for the nondestructive measurement of dry matter in potatoes

Near infrared spectrophotometry in the direct transmittance mode and in the wavelength range of 800 to 1000 nm was used to measure the % dry matter (DM) in sliced and intact potato tubers (cv Russet Burbank). With thin tissue slices, the correlation (r) between spectral and DM data was-0.975 with a standard error of calibration (SEC) of 0.91. With thick slices and intact potatoes the r, SEC, and standard error of prediction (SEP) values were -0.952, 1.28, 1.69 and -0.918, 1.04 and 1.52, respectively.CompendioSe utilizó la espectrofotometría cercana al infrarojo en transmisión directa y en intervalos de longitud de onda de 800 a 1 000 nm, para medir el % de materia seca (MS) en tubérculos de papa cortados en rebanadas, y enteros (cv Russet Burbank). Con rebanadas delgadas de tejido la correlación (r) entre los datos del espectro y la MS fue de -0,975 con un error estándar de calibración (EEC) de 0,91. Con rebanadas gruesas y tubérculos enteros los valores de la r, EEC, y el error estándar de predicción (EEP) fueron -0,952, 1,28, 1,69 y -0,918, 1,04, y 1,52, respectivamente.

A nondestructive technique for detecting internal discolorations in potatoes

SummaryA technique of nondestructively detecting internal discoloration in potatoes by light transmittance has been described. Preliminary investigations with hollow heart indicated that the discolored tissue exhibited a selective absorption of energy at 710 mώ. A measurement of the optical density difference between wavelengths at 800 mώ. and 710 mώ is used as the indication of discoloration. This measurement indicates discolorations associated with hollow heart, blackspot, and greening ; however, the apparatus used in this study was designed to examine potatoes for hollow heart. Results of limited tests showed that the method detected the presence of hollow heart 98 per cent of the time in a group of Irish Cobbler potatoes containing 61 per cent hollow heart. In a test with Katahdin potatoes 81 per cent of all discolored tubers were detected including potatoes with decay, greening, blackspot and hollow heart.

Diffuse Thickness as a Measure of Light Scattering

The concept of diffuse thickness was developed as an alternative method of measuring the light scattering in diffusely reflecting samples. It is defined as the minimum thickness of a diffusely reflecting and transmitting material required to produce complete diffusion. A series of liquid samples with varying concentrations of a green dye differed in light scattering by as much as 7:1 and in reflectance by 8:1. Results showed the diffuse thickness to be independent of absorption. In addition, the diffuse thickness was used with reflectance data to compute an absorption coefficient that correlated linearly with dye concentration despite the differences in light scattering (r = 0.99896). Additional data obtained with samples in which the scattering was varied by changing the proportion of two types of particles showed that a different mathematical procedure was required to obtain an equivalent correlation.

Instrumentation To Measure The Diffuse Thickness Of Scattering Dispersions

An instrument has been developed for measuring the light scattering associated with diffuse reflectance measurements. The instrument measures the sample thickness necessary to bring about diffusion of the transmitted radiation, i.e., the diffuse thickness. This quantity is inversely proportional to the light scattering coefficient as defined by the Kubelka-Munk equations. Results have shown the measurement to be independent of absorption and inversely proportional to particle density in the sample.