Refreshed (repetitively stimulated) delayed light emission (DLE) of cucumber and bell pepper fruit was strongly related to temperature and duration of exposure to chilling temperatures. At the 10th measurement cycle (about 150 ms), DLE of cucumbers exposed to 2.5°C for ≥12 hr or 5.0° for ≥24 hr was greater than that of cucumbers held at higher temperatures (7.5° to 12.5°) for 12 to 264 hr. Similarly, DLE of bell peppers exposed to 2.5° for ≥48 hr was greater than that of peppers held at higher temperatures. For both cucumbers and peppers, however, there was a greater difference in DLE between fruit held at 2.5° or 5.0° and those held at higher temperatures around measurement cycles 400 to 500 (at 6.0–7.5 sec) and this difference increased with increasing duration of exposure. Amount of refreshed DLE around measurement cycles 400 to 500 or the rate of change in DLE around cycles 180 to 300 is proposed as an indicator of chilling exposure for cucumber and bell pepper fruit.
Firmness is a critical quality characteristic in kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson] marketing. The industry seeks a nondestructive method for firmness sorting. We measured sonic vibrational responses of 149 kiwifruit over the range 0 to 2000 Hz and compared them with Magness-Taylor (MT) penetrometer values. Sonic resonant frequencies and mass were combined to calculate a sonic stiffness coefficient. Coefficients of determination (r2) for sonic stiffness coefficients versus MT slope and log of MT maximum force were 0.88 and 0.86, respectively. Sonic stiffness coefficients provided good to excellent classification of kiwifruit into two or three firmness categories based on MT maximum force values. A combination of amplitudes at several specific sonic frequencies selected by stepwise discriminant analysis or regression tree analysis also provided successful sorting algorithms. Identification of soft kiwifruit was 89% to 96% accurate and of firm kiwifruit 83% to 91%. These conclusions are based on a rather small sampling of kiwifruit of a single source and size, but the results clearly indicate the potential of a nondestructive firmness measurement based on sonic frequency vibrations.
A compact automatic system was developed for sampling, analyzing, calculating, and recording rates of carbon dioxide and ethylene production by up to 54 samples. The system consists of rotary stepping valves, microcomputer with printer, cassette tape recorder, and a gas Chromatograph.
The relationships among selected sensory textural attributes and data from modified Instron texture profile analysis (force/deformation curves obtained in compression of tissue cylinders) were examined for ‘Golden Delicious’, ‘Rome Beauty’, ‘York Imperial’, ‘Redspur Delicious’, and ‘Miller Sturdy Spur Delicious’ apples (Malus domestica Borkh.). Sensory crispness, hardness, and toughness were closely related to each other and to Instron texture profile forces at breakpoint (yield), failure, and 75% compression and to work energy in compression and rebound. Correlations of sensory attributes with the best single Instron texture profile variables were similar to those with Magness-Taylor penetration force (measured on an Instron); however, combinations of several texture profile variables in regression equations generally improved prediction of sensory attributes. Experimental Instron texture profile variables, especially force near midcompression, or the experimental variations on the customary variables, such as mean forces around failure and around full compression, were selected for prediction equations more frequently than the customary variables.
Pressure test values obtained on various fruits with 2 manual fruit pressure testers (the Magness-Taylor and the smaller Effe-gi) and the Instron Universal Testing Instrument were compared. Tests were made on 5 apple, 1 nectarine, and 3 peach cultivars on an individual fruit basis. Differences in pressure readings were marked among instruments. Responses to the instruments differed among cultivars. Some apples were classified in different ripeness categories according to different pressure testers. For nectarines and peaches, high correlations, but not complete agreement, were obtained among instruments. For all 3 fruits, differences were sufficient to require specification of instrument and method of measurement when fruit pressure test values are reported and to necessitate compensation when measurements made with different types of instruments are compared. Regression equations such as we report should be used to permit accurate comparisons.