Apples were selected as the test medium to provide information about the relative value of physical-chemical measurements as predictors of sensory appraisal of texture. Sensory, shear force, moisture, pH and protopectin/total pectin measurements of textural parameters for five variety-lots, after various storage periods, were treated by multiple regression, analysis of variance, and covariance and path analyses. Statistical treatments revealed relationships that were clearcut and certain trends that appear to be meaningful. Panel scores were not well predicted by objective measurements with one exception. Shear force was an excellent predictor for crispness of Colorado Red Delicious. Tenderness of Golden Delicious increased as storage increased and protopectin/total pectin decreased, whereas losses of crispness and juiciness were small and inconsistent. Overall results of sensory and physical-chemical tests for Winesap and Red Delicious were rather consistent in that tenderness increased and juiciness decreased linearly with the length of storage. Texture Studies 3 (1972) 478-491. All Rights Reserved Copyright Journal of
The appearance of a black or blue-black discoloration in potatoes after they are cooked and exposed to the air is a fault common in tubers grown in certain regions during certain seasons. It has been possible to reduce the discoloration in potatoes having this tendency by boiling them in acidified aqueous solutions (1, 2? 4, 6, 9, 11, 2.2, 14). The favorable effect of many acids could be reversed by a change in hydrogen ion concentration ; however, this was not true f o r two acids, boric and benzoic ( I ? 2).Ross (10) stated that browning in dehydrated potatoes was accompanied by the development of an ultra-violet fluorescence of the extracts. Lewis and Doty (7) obtained a blue fluorescent precipitate from tuber extracts and suggested that the blue fluorescent material was a precursor of the substance causing some cooked potatoes to turn black.This study was undertaken to investigate further the relation of duorescence to darkening. The investigations included an examination of both darkening and non-darkening potatoes and of potato extracts as well as the effect of various reagents on both darkening and fluorescence. EXPERIMENTALPROCEDUREUnless otherwise specified, the potatoes were grown in Wisconsin, some being obtained on the retail market and some grown on the Agricultural Experiment Station farms and stored a t 38" t o 42°F. until used. Since it was never possible t o predict whether a given tuber would turn dark after it was cooked nor which areas of the darkening tuber would show the discoloration, careful sampling and cooking techniques were necessary. For some comparisons, the potatoes were cubed, mixed, and portions taken f o r the various treatments; f o r other comparisons, halves, quarters or eighths cut lengthwise from the same tubers were used for the treatments to be compared. All cooked potatoes were exposed to the air for one hour a t room temperature t o permit maximum development of color before they were observed for blackening.Whenever fluorescence and degree of blackening were to be correlated, tubers were bisected radiallly from bud t o stem ends thus giving matching halves. One half of each tuber was cooked and discoloration noted. The other half was used for an extract on which the determination of fluorescence equivalent was made. Clear extracts wew prepared from a slurry made by slicing the potato, then blending for one minute in a Waring Blendor with acidified alcohol ( 2 ml. per gmm of potato; 400 ml. of 95% alcohol t o 25 ml. of concentrated hydrochloric acid). For certain experiments, the raw half was fitted against the cooked half and the areas on the raw half corresponding to the black areas were selected for extraction, Fluorescent regions were observed in the ultra-violet irradiation from a 100-watt Mazda B1 Mercury Arc, using a filter of black glass transmitting light waves ranging a
Electromagnetic (microwave or radio frequency) field-induced heating is used in industrial, medical, and domestic applications. In most cases, efficient, rapid, and controllable heating is needed. A problem with this heating modality is the difficulty in gaining an accurate measurement of temperature in the presence of a strong electromagnetic field. A simple infrared fiber-radiometer system has been developed for thermometry in the presence of these strong electromagnetic fields. The radiometer was used to measure temperatures in the range 0–70 °C, with an accuracy of ±0.5 °C. The signal obtained varied almost linearly with temperature.
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