drying process, cracking the dry in-shell nut, separating the shell from the kernel, roasting and grading followed by bulk packaging. The manufacturing process begins with one or more grades of bulk kernel and ends with a retail product. Some of the
Phillip Joy, Rajasekaran Lada, Cameron Fullerton, Brian Williams, and Angus Ells
The quick-frozen (QF) cut and peel processing industry is growing and has significant economical importance. Crack development formation (CDF) and enhancement is a major obstacle in QF carrot processing since it lowers product quality, profitability and consumer preference. Studies were initiated to determine the role of edaphic factors on crack development. Carrot samples (var. Sugarsnax) were collected from nine different fields before processing, after processing, and after 8 weeks of -8 °C freezer storage. Samples were tested for the percent cracked; the length, width, and depth of cracks; and membrane stability using electrical conductivity per gram (EC/g). Membrane injury index (MII) was also analyzed on freezer-stored samples. Very few cracks and low EC readings were observed in treatments prior to processing, with the exception of field VC38. Samples taken at the end of the processing line had a higher percentage of visual cracks and significant differences were found between fields in EC/g and length, but not in width or depth of cracks. Freezer-stored samples had significant differences in all parameters, including EC/g, MII, crack length, width, and depth, indicating that the length of freezer storage time can increase the potential for crack development. Samples from V49 cracked heavily during 8 weeks in freezer storage compared to the samples from other fields. A significant interaction between field and time was also observed in processed samples, indicating that CDF is dependent on both field parameters and freezer storage time. Significant differences were observed among different fields in terms of crack morphology, especially after 8 weeks in freezer storage.
M. Meheriuk, D.-L. McKenzie, and L. Veto
Electron microscopic studies were conducted on `Sue', `Lapins' and `Van' sweet cherry cultivars which have a high, moderate and low resistance to rain cracking, respectively. Epidermal and hypodermal cells showed differences in size and number. Sue, the resistant cultivar, contained an additional thin elongated cell rich in protein matter, in the hypodermal layer. The three cultivars also showed differences in the cell walls and vacuoles. However, mineral content of the epidermal and hypodermal layers showed no relationship to incidence of fruit cracking.
W. R.(Bill) Jester, Charles W. Averre, and Jonathan R. Schultheis
Russet crack-like symptoms have been observed with increasing frequency on Beauregard storage roots in North Carolina and resulted in some crop failures in neighboring states. The objective of this experiment was to determine if this cracking disorder was soil-borne, seed transmissible or transmissible via grafting. Beauregard plants were obtained from cuttings from commercially available virus-indexed micropropagated plants (M), and selected symptomatic roots (culls) originating from 1992 Foundation stocks (R). In a third treatment plants from each source were alternated in a row, then M and R plants were cleft grafted. The planting was made June 30, 1993 and replicated five times (12 plants per rep). Yield was determined and roots from each hill were washed and examined for russet crack-like symptom(s), and interior color on the proximal end. M roots had 82% good color; while R roots had 19%. M plants contained 0.3% symptomatic roots; R plants 65.5%. Similarly, only 1.6% of the M plants contained a symptomatic root, while 95.0% of the R plants had symptomatic roots. One-third of the grafted M plants contained one or more roots with cracking symptoms. M outyielded R. The russet crack-like disorder was determined to not be soil-borne, but was transmissible through the seed or grafting.
W.D. Lane, M. Meheriuk, and D.-L. McKenzie
Fruit were studied to determine if anatomical and physiological features explain the difference in susceptibility to rain-induced cracking of the sweet cherry (Prunus avium L.) cultivars Sue (resistant), Lapins (moderately resistant), and Van (susceptible). Water uptake as a percentage of fruit weight at cracking tended to be high in `Sue', medium in `Lapins', and low in `Van' and was related to the percentage of cherries remaining sound after 4 hours of immersion, suggesting that this trait is a factor in determining resistance. Mesocarp cells of `Sue' were more rectangular in section than those of the other cultivars. Skin elasticity and thickness of the cuticle did not explain resistance of `Sue' to cracking. Magnesium, copper, and phosphorus mineral contents were not related to cracking susceptibility, but the content of calcium, which influences cell wall integrity, in the epidermis of `Sue' was lower than in `Van'. Calcium content was not different in the hypodermal cells of the two cultivars. None of the anatomical features examined in this study explain the resistance to fruit cracking of `Sue'.
Wang Yong, Lu Wangjin, Li Jianguo, and Jiang Yueming
To understand the relationship between fruit cracking and gene expression patterns, we identified two expansin genes from litchi (Litchi chinensis Sonn.) fruit and then examined their expression profiles in pericarp and aril at different stages of fruit development, using the cracking-resistant cultivar Huaizhi and the cracking-susceptible cultivar Nuomici. Two full-length cDNAs of 1087 and 1010 base pairs encoding expansin, named LcExp1 and LcExp2, were isolated from expanding fruit using RT-PCR and RACE-PCR (rapid amplification of cDNA ends) methods. LcExp1 mRNA could be detected from the early stage of fruit rapid growth (59 days after anthesis). The LcExp1 mRNA increased and reached to the highest level at the end of growth phase (80 days after anthesis) in pericarp of `Huaizhi', while the mRNA could be detected at the stage of rapid fruit growth, then increased slightly and finally kept remained almost constant in the pericarp of `Nuomici'. Similar accumulation of LcExp2 mRNA was observed in fruit aril of `Nuomici' and `Huaizhi', whereas LcExp2 accumulated only in pericarp of `Huaizhi' but did not appear in pericarp of `Nuomici'. The results indicate that expression of two expansin genes in litchi pericarp are closely associated with fruit growth and cracking.
Matt Reed, Brie Genter, and J.A. Flore
We have developed a system of automated intermittent salt application above the tree during a rain event that has shown very encouraging results (Washington State Hort Soc. Proc. 1995, Good Fruit Grower, vol. 47; pp. 23-24; Acta Hort. vol. 468 pp. 649 & 683) in Michigan and the Pacific Northwest. In 1998, we significantly reduced rain cracking with the system used in previous years. At the Southwest Michigan Research and Extension Center (SWMREC), on `Ulster', the control averaged 18% while the 0.5% calcium chloride had 6.7% cracks. Similar results were found for `Ulster', `Somerset', and `Rainer' at the Northwest Station. Cracking was greater in the upper part of the tree than the lower part for the control. The calcium chloride had less cracking on the upper part than the lower part indicating that calcium chloride applied from above the tree was not uniformly distributed to the lower part of the canopy in high enough concentrations. Multiple emitters per tree decreased this problem. We determined that there was an interaction with temperature. More fruit cracked at high temperature than low temperature. In the field more fruit cracked during the day than at night. We attribute this to the difference in day and night temperature. Using a bioassay system we able to determine the critical concentration of salt that must be on the fruit to inhibit water uptake and rain splitting up to a 4-h period. It ranged between 0.05% to 0.10 % depending on the variety and stage of development.
R. Thomas Fernandez and James A. Flore
Fruit of sweet cherry (Prunus avium L.) crack during or after rain due, in part, to absorption of water through the fruit surface driven by the water potential gradient. In 1972, J. Vittrup-Christensen suggested that overhead misting of calcium salts during precipitation may be an effective way to prevent cherry cracking by reducing the water potential gradient. We tested this hypothesis by designing a computer-controlled irrigation system to intermittently spray a 10% CaCl2 solution on trees during rain events. Spray emitters were placed in the middle and at the top of the canopy. The program turned the system on for 90 s at each 0.3 mm of rain and monitored daily rainfall and accumulated mist times. Two `Emperor Francis' and two `Ulster' were treated with equal number of controls. Intact and cracked cherries were counted on four branches per tree at three times when cherries were susceptible to cracking. Overall, cracking was reduced from 33% to 11% by the CaCl2 spray at the end of the experiment. Treated `Ulster' had 9% cracked fruit, while control had 43% cracked fruit. Differences for `Emperor Francis' were not significant. Phytotoxicity was estimated at about 15 % of leaf area. This system will be reevaluated in 1995 with the added objective of quantifying and reducing phytotoxicity.
Rémy E. Milad and Kenneth A. Shackel
Irrigation of previously water-stressed French prune trees is known to induce fruit end cracking. The relationships between end cracking, water relations, and mechanical properties of the skin of French prune were studied as a function of irrigation regimes under field conditions. Water stress resulted in the accumulation of solutes in the fruit of nonirrigated trees. A gradient in osmotic potential (ΨS) existed along the vertical axis of fruit from all treatments; ΨS was always lower at the stylar than stem end. Irrigation of previously water-stressed trees (irrigated-dry treatment) resulted in ΨS gradients exceeding those of all other treatments. Moreover, estimated turgor (ΨP) at the stylar end of the fruit increased 2-fold within 24 hours after irrigation. These changes were accompanied by the onset of fruit end cracking, and neither the well-watered controls nor the continuously droughted fruit exhibited such changes. During the 24 hours following irrigation, the overall ΨS of irrigated-dry treatment fruit was diluted by the same amount as the calculated increase in fruit volume. However, during the same period, ΨS at the stem end of the fruit showed more dilution than expected, and ΨS at the stylar end of the fruit concentrated, indicating a redistribution of solutes. There were no differences in skin mechanical properties along the fruit vertical axis and, hence, this could not have accounted for the observed changes in ΨS and ΨP. Thus, when previously stressed French prune trees were irrigated, the overall recovery in water potential (Ψ) and the subsequent movement of solutes to the stylar end of the fruit resulted in apparently excessive turgors in this region and hence the observed pattern of end cracking.
Masahiko Yamada, Akihiko Sato, and Yasuo Ukai
Environmental variance components were estimated for calyx-end fruit cracking in pollination-constant and nonastringent cultivars and selections of Japanese persimmon (Diospyros kaki Thunb.). The cracking value of a tree in a cultivar or selection (genotype) (X) was evaluated as the number of fruit that cracked divided by the total number (25) of fruit evaluated from each tree. Because the mean value of X was correlated with the variance of X, analyses of variance were performed using its square root value. The variance associated with genotyp× year interaction was the largest of environmental variance components. The variances associated among years and among trees within genotypes were very small. The mean percentage of cracked fruit in evaluation for 10 years was 3% for `Fuyu', 11% for `Matsumotowase-Fuyu', and 12% for `Izu'. On the basis of the environmental variance components obtained, it is proposed that all offspring genotypes exhibiting a phenotypic cracking incidence of less than 20% and 11% should be selected in single-year and three-year evaluations, respectively, when those genotypes are evaluated using 25 fruits from a single tree, in order to successfully select all genotypes with an genotypic incidence of less than 3%.