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Francisco Javier López-Escudero, Miguel Ángel Blanco-López, Carmen Del Río Rincón and Juan Manuel Caballero Reig

technique for evaluating resistance in olive, because it reliably reproduces the infection process incited by V. dahliae ( Blanco-López et al., 1998 ; López-Escudero et al., 2004 ). Nevertheless, other works have revealed that stem puncture inoculation

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Yu Sung, Daniel J. Cantliffe and Russell Nagata

Temperature is an important environmental factor that affects lettuce (Lactuca sativa L.) germination. The present research was conducted to determine the role of seed coverings on lettuce seed germination at high temperature. Five lettuce genotypes were primed in order to bypass thermoinhibitional effects on germination. During germination of primed and nonprimed seeds, imbibition followed a normal triphasic pattern. Primed seeds had higher final water content, a decreased imbibitional phase II, and germinated at 36 °C compared to nonprimed seeds of thermosensitive genotypes, which did not germinate at 36 °C. Puncture tests were conducted to determine the force required to penetrate the whole seed or endosperm of the five genotypes at 24 and 33 °C. `Dark Green Boston', a thermosensitive genotype, had the highest mean resistance (0.207 N) and PI 251245, a thermotolerant genotype, had the lowest (0.139 N). Resistance to penetration of the endopserm of the five genotypes was different at both temperatures. However, three thermotolerant genotypes had lower endosperm resistance than two thermosensitive types. At 36 °C, the penetration force for primed and nonprimed seeds was compared after the first hour of imbibition and 1 hour before radicle protrusion. The force required to penetrate the seed was affected by genotype, seed priming, and duration of imbibition. Puncture force decreased as imbibition time at 36 °C increased in primed and nonprimed seed of each thermotolerant genotype but not in the thermosensitive genotypes. Priming reduced the initial force necessary to penetrate the seed and endosperm in all genotypes. Thus, for radicle protrusion to occur, there must first be a decrease in the resistance of the endosperm layer as evidenced by priming or thermotolerant genotype. Then, the pericarp and integument are sufficiently weakened so that tissue resistance is lower than the turgor pressure of the expanding embryo, allowing germination to be completed.

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Catherine Belisle, Uyen T.X. Phan, Koushik Adhikari and Dario J. Chavez

have been reported as softer and juicier in texture, compared with non-melting types that have been reported as harder and less juicy ( Brovelli et al., 1999 ). The use of different textural tests, such as compression, puncture, and Kramer shear, have

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R.L. Jackman, A.G. Marangoni and D.W. Stanley

Flat-plate compression, constant area compression, and puncture tests were examined for their sensitivity in differentiating the firmness of previously chilled (6C, 85% RH, 15 days) and nonchilled mature-green tomato (Lycopersicon esculentum Mill cv. Caruso) fruit during 10 days of ripening at 22C. Firmness, as measured by each of the three methods, progressively decreased (P < 0.001) with ripening. Previously chilled tomatoes were initially softer (P < 0.01) than nonchilled tomatoes, as measured by puncture of whole fruit and constant area compression of pericarp tissue sections, but not by flat-plate compression of whole fruit. Flat-plate compression was therefore found to be a relatively insensitive method by which to measure differences in tomato firmness that are characteristic of slightly chilling-injured fruit.

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Richard K. Volz, F. Roger Harker and Sandy Lang

Puncture force was measured in `Gala'apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit from 16 to 175 days after full bloom over 2 years using a range of circular flat-tipped probes (1 to 11 mm diameter) to test the firmness of each fruit. The area-dependent (Ka) and perimeter-dependent (Kp) coefficients of puncture force were determined and were used to calculate the indicative puncture force approximating a standard 11.1-mm-diameter Effegi/Magness-Taylor probe for even the smallest fruit. Ka declined exponentially throughout fruit development with much greater changes occurring closer to bloom. In contrast, maximum Kp occurred at 107 to 119 days after full bloom before declining progressively. Estimated firmness (using a 11.1-mm-diameter probe) declined constantly from 16 days after full bloom. Ka was associated with developmental changes in cortical tissue intercellular air space, cell volume and cell packing density although relationships changed throughout fruit growth. However seasonal change in Kp was not associated with any obvious anatomical change in the cortex.

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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.

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F.R. Harker, J.H. Maindonald and P.J. Jackson

Flesh firmness is a characteristic used to indicate fruit quality. Experimental design and data analysis are important when comparing devices that measure fruit firmness. We compared the Effegi penetrometer operated by hand, mounted in a drill press and then operated by hand, and mounted on a motorized drive and operated remotely; the hand-operated EPT pressure tester; the Instron with an Effegi probe; and a hand-operated prototype of the twist tester. Devices varied in operator differences and precision. Comparisons between devices were at the within-fruit level of variability and, therefore, more precise than comparisons where different device-operators used different fruit. We demonstrate statistical methods that are appropriate for making the comparisons of interest and discuss the possible cause of differences between operators and between devices. We also discuss how the mechanical properties of the devices may affect results and consider implications for their practical use. In this study, we found the precision of discrimination between soft and hard apples was best using the Instron in 1992, while the Instron and hand-held Effegi penetrometer were comparable in 1991. For kiwifruit, the hand-held Effegi penetrometer consistently gave the most precise measurements of softening in 1991, while the twist test was the most precise in 1992.

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Hong Chen, Greg McCollum, Elizabeth Baldwin and Jinhe Bai

arrangement, and cell wall structure etc.) and material composition of fruits have an effect on their mechanical properties. Puncture, compression, cutting, tensile, shear, and TPA tests are usually used to estimate the maturity or resistance of fruit to force

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Timothy M. Spann, Luis V. Pozo, Igor Kostenyuk and Jacqueline K. Burns

. Our objective was to determine if fruit treated with CMNP and subjected to mechanical harvesting have reduced peel integrity, measured as peel puncture force and fruit crush force, or are more susceptible to postharvest decay within the commercial

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Hyun-Gyun Yuk, Benjamin R. Warren and Keith R. Schneider

purpose of this study was to determine the survival and infiltration of Salmonella spp. inoculated on laser-etched, puncture wounded, and untreated tomato surfaces during 14 d of storage at 25 °C/60% relative humidity (RH). Materials and methods