. Factors contributing to splitting in cherries include cultivar differences, water temperature, period of wetting, soluble solids, fruit firmness and turgor, and elasticity of the skin ( Ackley and Krueger, 1980 ; Bullock, 1952 ; Davenport et al., 1972a
Donna A. Marshall, James M. Spiers, and Stephen J. Stringer
Kareen Stanich, Margaret Cliff, and Cheryl Hampson
., 1980 ); although some exceptions exist ( Clarke, 1990 ; Judd et al., 1989 ), they appear to be tolerated statistically ( Zhang and Robson, 2002 ). Although fruit weight distributions are frequently reported in the literature, fruit firmness
Fruit firmness is one of the most important quality aspects in the production of pickling cucumbers (Cucumis sativus) for industry. This study compared the fruit firmness of different cultivars and evaluated the usability of different firmness variables. Firmness of fruit of five to six cultivars from a cultivar experiment was measured penetrometrically over 3 years. The maximum load needed to penetrate the skin, distance at maximum load, load at the end of the measurement, and the mean work during the whole measurement were recorded. Different variables gave a versatile impression of the fruit texture. Although there were some differences in the measured values each year, the ranking of the cultivars was similar each year. Cultivars Celine and Servus had the firmest skin and overall texture. `Aubade' and `Carine' had lower skin firmness but the inner part of the fruit of `Aubade' was very firm. `Etude' was similar to `Carine'. `B2590', measured in only 2 years, had lowest firmness both in skin and flesh. The results show that penetrometric measurement of fruit firmness is a suitable method for analyzing the texture of cucumbers intended for pickling.
Thomas E. Marler and Philip W. Marler
The eyecare industry has used various instruments and methods for determining intraocular pressure. Some of the methods may be applicable for measurement of fruit firmness in the horticultural industry. We determined fruit firmness with an applanation tonometer, currently one of the most popular instruments in the eyecare industry. We then measured firmness of the same sample using a penetrometer with an 8-mm probe. Kiwi, mango, peach, strawberry, tomatillo, and tomato fruit were included in the study. With the exception of mango, tonometer and penetrometer measurements within a species were significantly correlated. The contact area of the tonometer probe was 1.5 mm2, which was less than 3% of the contact area of the penetrometer probe. The heterogeneous nature of mango mesocarp due to fibers and this large difference in contact area between the two instruments may have caused the lack of correlation for that species. The data indicate that tonometry may be useful for determining firmness of fruit, and further development may lead to a nondestructive method of obtaining these data.
Tarja Hietaranta and Minna-Maria Linna
The firmness of five strawberry (Fragaria×ananassa Duch.) varieties was determined by penetrometric method using a motorized materials testing device equipped with a 100-N load cell and a probe 6.4 mm (0.252 inches) in diameter. Maximum and mean forces and instant of yield point were recorded with the aim of testing the suitability of these three parameters for the assessment of fruit firmness, i.e., handling and transportation tolerance. The maximum and mean force data revealed significant differences among varieties, but instant of yield point was not reliable measurement in this test arrangement. Maximum force was the best parameter for the assessment of firmness.
E.J. Mitcham, M. Clayton, and W.V. Biasi
The performance of three relatively new nondestructive cherry firmness devices and a penetrometer were evaluated and compared with the firmness testing performance of an Instron Universal Testing Machine. The inherent variability of the nondestructive devices was estimated by repeated measurement of a uniform, symmetrical, and resilient rubber ball. Analysis of residuals from correlations between each device and the Instron from firmness testing on common samples of sweet cherries (Prunus avium L.) confirmed the relative variability of the nondestructive devices, and estimated measurement reliability of the penetrometer. Subjective firmness sensing by compression of cherries between the fingers of human evaluators proved to be less reliable than the devices tested. Sweet cherry firmness correlated reasonably well with skin color, with the strength of the correlations from each device agreeing with device ranking in terms of firmness measurement reliability. Firmness correlated poorly with soluble solids, titratable acidity, and specific gravity; soluble solids correlated well with specific gravity; and skin color correlated reasonably well with both soluble solids and specific gravity. Fruit surface pit volume, induced by a specific impact force from a ball bearing, correlated relatively well with fruit firmness measured by the penetrometer, but poorly or inconsistently with measurements from the remaining firmness devices.
Patrick P. Moore
Strawberry fruit of 16 clones was harvested from 45 plots in 1997. Fruit from 35 plots, 12 of the clones sampled in 1997 plus four additional clones, was harvested in 1998. Fruit was harvested on three to five dates in 1997 and three to seven dates in 1998 with 160 samples in 1997 and 165 samples in 1998. Fruit firmness was determined for five fruit from each plot at each harvest with a penetrometer and fruit from the same harvest was sliced, sugared, and frozen. Drip loss was determined later for the frozen, sliced samples. There were statistically significant correlations between firmness and drip-loss (r = -0.27, n = 160, P < 0.01 in 1997 and r = -0.44, n = 165, P < 0.001 in 1998); however, firmness did not adequately predict drip-loss. There was considerable variation in drip loss from harvest to harvest, which was associated with weather conditions or precipitation/irrigation. The drip loss in 1997 was not significantly correlated with the drip loss for the same plots in 1998 (r = -0.26, n = 24, ns); however there was a significant correlation between firmness in 1997 and 1998 (r = 0.52, n = 24, P < 0.05). These findings have implications for evaluation of fruit in a strawberry breeding program for a processing industry.
Todd C. Einhorn, Yan Wang, and Janet Turner
Instrument, Bohemia, NY); 2) average fruit diameter (at the widest point of the fruit opposite the suture) and fruit firmness were determined nondestructively (Firmtech; Bioworks, Stillwater, OK); 3) skin color was rated on a scale of 1 to 7, where 1 is
Kevin L. Cook, August C. Gabert, and James R. Baggett
One concern that has restricted the use of parthenocarpic pickling cucumber cultivars in the United States has been firmness of fruit processed by brining. Selection for mesocarp and endocarp firmness, in addition to morphological traits associated with firmness, such as fruit length, length: diameter ratio, seed cavity size, and seed cavity: fruit diameter ratio, may produce parthenocarpic cultivars with improved quality. Combining ability of a set of parthenocarpic and nonparthenocarpic parents for fruit firmness and these related morphological characteristics were investigated using a factorial mating design grown in 1992 and 1994 at Brooks, Ore. General combining ability was greater than specific combining ability for all traits before and after processing. Fruit firmness, mesocarp firmness, endocarp firmness, length, and length: diameter ratio were positively correlated phenotypically and genetically to one another. Seed cavity diameter and seed cavity: fruit diameter ratio were positively correlated phenotypically and genetically, but were negatively correlated to all other traits.
Mark K. Ehlenfeldt and Robert B. Martin Jr.
Eighty-seven highbush blueberry and species-introgressed blueberry cultivars were evaluated for fruit firmness in the 1998-2000 growing seasons with a FirmTech 1 automated firmness tester. Significant differences were observed among cultivars. An average firmness of 136.1 g·mm-1 of deflection (g·mm-1 dfl) was observed across all studied cultivars, and a range of 80.4 g·mm-1 dfl (`Herbert') to 189.0 g·mm-1 dfl (`Pearl River'). Species ancestry was not consistently related to firmness; however, cultivars with higher firmness values often possessed a higher percentage of Vaccinium darrowi Camp and V. ashei Reade ancestry. Conversely, cultivars with softer than average fruit often possessed a higher percentage of lowbush (V. angustifolium Ait.) ancestry. This information may help to identify sources of breeding material for increased firmness in highbush blueberry hybrids.