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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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Melkizedek O. Oluoch and Gregory E. Welbaum

We thank Kent J. Bradford for providing the seeds for this experiment and James H. Wilson for assistance with Instron analysis. This research was funded in part by USDA research project W-168. Use of trade names does not imply endorsement of

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D.A. Smith, J.B. Fitzgerald and G.E. Meyer

Vitalization is a process whereby senescence is retarded and refrigerated storage can be extended. The process involves hyperhydration of plant materials with selected aqueous solution, thereby flooding interstitial spaces and vascular tissues. Microscopic examination revealed increased size of interstitial spaces and expansion and increased roundness to cells. No disruption of tissues was detected. Turgidity was measured with an Instron Universal Testing Machine equipped with a Kramer Shear Cell. Color was measured with a Minolta color difference meter. Leaves were evaluated for color and turgidity changes during storage. Vitalized leaves did not change significantly in color or turgidity during a 10-week storage period. Untreated leaves lost turgidity and yellowed in storage.

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A. Akinbolu, D.J. Huber, G.J. Hochmuth and O.C. Aworh

The influence of potassium (K) on respiratory behavior, flesh firmness, and internal color of watermelon (Citrullus lanatus) was studied. Two cultivars (Crimson Sweet and Sangria) were planted at the Univ. of Florida research station, Gainesville. The fruits from both cultivars were harvested at two different stages of maturity (25 days and 35 days after anthesis). Respiration and ethylene production were measured using gas chromatography under a static system. The internal color was measured by a colorimeter, while the flesh and rind firmness were measured by a instron Universal pressure tester. Carbon dioxide and ethylene production were non-climacteric in behavior and were not greatly affected by K treatment or cultivar.

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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.

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William S. Conway, Carl E. Sams, Chien Yi Wang and Judith A. Abbott

`Golden Delicious' apples (Malus domestics Borkh.) were treated with heat or CaCl2 solutions or a combination thereof to determine the effects of these treatments on decay and quality of fruit in storage. Heat treatment at 38C for 4 days, pressure infiltration with 2% or 4% solutions of CaCl2, or a combination of both, with heat following CaCl2 treatment affected decay and firmness during 6 months of storage at 0C. The heat treatment alone reduced decay caused by Botrytis cinerea (Pers.:Fr.) by ≈30%, while heat in combination with a 2% CaC12 solution reduced decay by ≈60 %. Calcium chloride solutions of 2% or 4% alone reduced decay by 40 % and 60 %, respectively. Heat treatments, either alone or in combination with CaC12 treatments, maintained firmness (80 N) best, followed by fruit infiltrated with 2% or 4% solutions of CaCl2 alone (70 N) and the nontreated controls (66 N). Instron Magness-Taylor and Instron compression test curves show that heat-treated fruit differed qualitatively and quantitatively from nonheated fruit. Heat treatment did not increase the amount of infiltrated Ca bound to the cell wall significantly, and a combination of heat treatment after CaCl2 infiltration increased surface injury over those fruit heated or infiltrated with CaCl2 solutions alone.

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F. Mencarelli, L. Lanzarotta, R. Massantini and R. Botondi

Kiwifruits were picked by hand and gently placed in pulp trays. Impact tests were conducted by dropping the fruits from heights of 30 cm onto different sandpapers to provide a uniform abrasion surface. Abrasion tests were conducted by compressing the fruits with a fixed load of 3.5 N (Instron equipment) onto different sandpapers and pulling out the fruits. Compression test was performed by using the previous procedure with a fixed load of 4.5 N for different period of time (minutes). Increase of transpiration rate and ethylene production was observed in fruits abraded with sandpaper which slight wounded the peel. Impact onto sandpaper, caused the appearance of white lignifted filaments in the flesh. Increase in soluble solids and softness of flesh and core was observed in injured fruits. Healing process and polyamines effect will be discussed.

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J. Anthony Hopfinger, Donald W. Shaffner and Eric D. Cubberley

Both Cacl2 and Nutrical (a trihydroxyglutarate chelate) were foliarly applied at rates of 1.8 and 5.5 Cacl2/ha/season and 1.5 and 4.5 l/ha/season, respectively. Applications were made starting at shuck split and repeated at 2 week intervals until harvest. Neither calcium treatment had an effect on fruit size and size distribution. Fruit size was directly related to crop load. Calcium chloride application had the most pronounced effect on increasing the red over-color of `Cresthaven' peaches with Nutrical intermediate compared to the control. The high rate of Nutrical increased flesh calcium levels at harvest by 75-100 PPM. Instron Texture Profile Analysis indicated that any calcium treatment significantly increased the hardness of the peach. Nutrical at 4.5 l/ha/season improved hardness 2-fold compared to the controls. The improved hardness was maintained throughout the 6 week storage period.

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Judith A. Abbott and D. R. Massie

Firmness is a critical quality attribute for kiwifruit, as it is for most commodities. Firmness is related to flesh elasticity and rigidity which, along with geometry and density, determine vibrational behavior. Firmness changes in kiwifruit were followed during storage at 0C by three methods: sonic vibrational spectra from 0 to 2000 Hz, dynamic force/deformation (F/D) in the range 40 to 440 Hz, and Magness-Taylor puncture (MT) on an Instron. Frequencies of sonic resonances and dynamic F/D peaks, as well as MT maximum force, decreased as storage time increased. Sonic resonance frequencies were highly correlated with MT maximum force and apparent elasticity (r=0.79 and 0.88). Frequencies of peaks in the dynamic F/D traces were correlated with MT maximum force and apparent elasticity (r=0.68 and 0.72) and with resonance frequency (r=0.81). Further data processing improves the ability of the nondestructive vibrational measurements to estimate the destructive MT test values.

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Niels O. Maness, Gerald H. Brusewitz and T. Gregory McCollum

Variability in mesocarp firmness for peach (Prunus persica L. Batsch) fruit halves cut either parallel or perpendicular to the suture was determined for three cultivars (Halehaven, Ranger, and Topaz). Firmness evaluations were conducted using an Instron Universal testing instrument with a 3.2-mm rounded tip probe. Firmness of the inner, middle, and outer regions of the mesocarp at four angular positions around each peach half was determined at four maturity stages. Average mesocarp firmness declined with advanced stages of fruit maturity. Inner mesocarp was firmest for fruit from all three cultivars. Internal variation in firmness for the middle and outer regions of the mesocarp was highly cultivar dependent. Firmness decreased longitudinally from the stem end to the blossom end and latitudinally from the suture to the cheeks.