Early-split Nuts Research Articles

Effects of early harvest times on nut quality and physiological characteristics of pistachio (Pistacia vera) trees

Introduction - Pistachio harvesting at the appropriate time is one of the key factors affecting the product quality. The effects of early harvest time on quantitative and qualitative properties of pistachio nuts were investigated. Materials and methods - The 'Ohadi' pistachio cultivar was used as the market reference in Iran. Five harvest times (July 27, August 6, August 16, August 27 and September 6) were studied over four consecutive years (2008-2011) as treatments in the field experiment. Nut weight parameters, hull discoloration, hulling, cracked nuts, early-split nuts, kernel protein, mineral and chlorophyll contents were evaluated at each harvest time. Results and discussion - The fresh and dry nut weights showed the maximum and the minimum nut production rates for the last (September 6) and the first (July 27) harvest times, respectively. Percentages of hull discoloration, cracked nuts and immature nuts were significantly influenced by harvest time. The early-split nut percentage was not significantly different at the various harvest times. The maximum potassium, calcium, magnesium and nitrogen, protein and chlorophyll contents were obtained at the first harvest time. The growth of current year shoots, leaf area, percentages of vegetative and reproductive buds were not influenced by the harvest time, whereas the abscission of reproductive buds was minimum at the first harvest time and significantly different from all other times. Conclusion - Early harvesting of pistachio is preferable in terms of crop health indicators, nutritional value and color of the kernels. However, it is not preferable in terms of yield (nut and kernel production per hectare) for the producers, although potentially more sustainable.

Predicting Nut Damage at Harvest Using Different in-Season Density Estimates of Amyelois Transitella: Analysis of Data from Commercial Almond Production.

Despite decades of research on management tactics for the navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), on almonds, we still do not have an established means of using in-season pest-density estimates to predict damage to nuts at harvest. As a result, hull-split pesticide applications, although timed carefully to coincide with navel orangeworm oviposition and with crop vulnerability, are not tied to pest densities-thus falling short of our goals under modern pest management. Here we use an ecoinformatics approach, analyzing a pre-existing data set collected in commercial almond production in California, to ask: 1) are navel orangeworm density estimates obtained using different sampling methods in strong agreement with one another? and 2) can we use either single density estimates or combinations of density estimates to explain variation in nutmeat damage at harvest? We find that correlations between density estimates of navel orangeworm made over a single growing season are often weak, and suggest that density estimates taken closer to the time of harvest (catches of adult females between hull split and harvest; infestation of early-split nuts) may be most useful for predicting damage at harvest. Single-density estimates explained ≤39.1% of variation in harvest damage, whereas a combination of predictors explained 51.5% of the total variance in nutmeat damage at harvest. Our results suggest that density estimates taken just prior to harvest may, with refinement, be usable within a predictive framework to guide late-season control decisions.

Mathematical approach for sampling plan performance assessment for aflatoxin B1 in pistachios

According to the EU Regulation 165/2010, the level of aflatoxin B1 and total aflatoxins in pistachios must not exceed 8μg/kg and 10μg/kg, respectively. Due to the heterogeneous distribution of this contaminant, the performance of sampling plans highly depends on the way they are designed. So, the sampling plan to be used must be assessed thanks to an OC (Operating Characteristic) curve showing both consumer and producer risks. The first risk is the risk of authorizing pistachios for sale while the contamination level is above the threshold; whereas the second risk is the risk of rejecting a lot having a contamination level under the threshold.The method developed the use of early split contamination levels and incidence in individual pistachios to derive OC curves for various sampling plan designs for aflatoxin B1. Contamination levels in individuals were calculated from small sample contamination levels, thus having a negligible probability of containing more than one contaminated individual. Incidence levels of early split pistachios were derived for each harvest day. Indeed, early split nuts are dubious nuts that were considered to contain all the aflatoxin content found in a global sample. As their percentage increased along the harvesting period, it led to various contamination distributions in 10kg samples. The EU sampling plan (Regulation 178/2010) was found to give a consumer risk with a probability of acceptance at 5% for a lot mean aflatoxin B1 concentration of 75.34μg/kg and a producer risk with a probability of acceptance at 95% for a lot mean concentration of 1.62μg/kg. Finally, the performance of several sampling plan designs was evaluated to demonstrate how to manipulate the number of samples to reduce misclassification of pistachio lots.

Effect of exogenous application of free polyamines on physiological disorders and yield of ‘Kaleh-Ghoochi’ pistachio shoots ( Pistacia vera L.)

Pistachio trees exhibit some physiological disorders such as abscission of inflorescence buds, fruit abscission, the production of blank, non-split, early-split and deformed nuts. Since the occurrence of these disorders is closely related to the yield, the effect of free polyamine treatments on these disorders and the yield was investigated in two consecutive years (“on” and “off” years). Free polyamine treatments were applied one week before and also two weeks after full bloom. Results showed that Spermine (Spm), unlike Putrescine (Put), decreased the physiological disorders of pistachio and also increased the yield. Free polyamine treatments did not affect the percentage of early-split nuts. Spermidine (Spd) decreased the percentage of both fruit abscission and deformed nuts but did not affect the yield. In both the “on” and “off” years the effect of Spm and Spd was greatly dependent on both the time of application and the concentrations used. Results of free polyamine analysis showed that exogenous application of these compounds, especially two weeks after full bloom, increased the free polyamine contents of shoots in both “on” and “off” years confirming the absorption of free polyamines via spray application in pistachio crop. Exogenous application of Spm two weeks after full bloom decreased the abscission of inflorescence buds in “on” year supporting the idea that free polyamines could trigger the abscission process of inflorescence buds. Since Spm decreased the percentage of blank, non-split and deformed nuts, it seems that Spm dominantly plays a key role in the growth and development of pistachio nuts.

Several physical properties of aflatoxin-contaminated pistachio nuts: Application of BGY fluorescence for separation of aflatoxin-contaminated nuts

The primary objective was to evaluate and find a proper method for visual identification of aflatoxin-contaminated pistachio nuts. The feasibility of using bright greenish yellow fluorescence (BGYF) in pistachio nut as a discriminating factor for identification of Aspergillus flavus-infested nuts, at harvest and in post-harvest, is investigated. Results show a strong relationship between BGYF and aflatoxin content at harvest. The factors affecting the application of this method in post-harvest stages are also discussed. The relationship between inside-brown kernels and aflatoxin presence is confirmed. At harvest, the brown kernels are a subdivision of fluorescent fraction. The share of different pistachios based on hull types (with sound hull, growth split and early-split) in contamination is studied. The early-split nuts are the most contaminated nuts, growth split nuts are less contaminated, and pistachios with sound hulls are almost clean. The effect of inappropriate handling on the percentage of fluorescent nuts is studied. The percentage of visible mould in samples is observed which shows a good relationship with the presence of BGY fluorescence.

(474) A Selected Yeast for Control of Aspergillus flavus in Pistachio Orchards

Aspergillus flavus produces aflatoxin, a cancer-causing contaminant of pistachio in many production areas. A superior yeast strain of Pichia anomala has been demonstrated to inhibit the growth of A. flavus in the laboratory. It was selected for further study and potential release based on tests of durability and ability to inhibit A. flavus growth. This strain has been tested in the field for the past two years to evaluate its ability to survive in a field environment and to inhibit A. flavus production. The yeast was evaluated in the field to determine if: 1) the biocontrol yeast can survive in pistachio orchards; 2) the yeast has no phytotoxic effects on the pistachio trees or nuts; and 3) the yeast can be demonstrated to control A. flavus in the field. Studies during 2003 were conducted using a replicated experiment with three yeast concentrations and a water control. Treatments applied later in the season were found to be most effective. Highest yeast concentrations were observed just prior to harvest. Three spray concentrations and a water control were applied to evaluate possible phytotoxic effects on pistachio during 2004. No differences in leaf or nut appearance, in nut percent splits, or dry weight were observed for any of the treatments when compared to the water control. Artificial wounding experiments were also conducted during 2003 and 2004 to simulate the occurrence of early split nuts, the primary repository for A. flavus contamination. A 5× reduction in A. flavus colonization was observed on treated wounded nuts vs. untreated wounded nuts. A 5× reduction in A. flavus sporulation was also observed on treated wounded nuts vs. untreated wounded nuts.

Insufficient spring irrigation increases abnormal splitting of pistachio nuts

Abnormal pistachio nuts, known as “early-split nuts,” have both the hull and shell split while still on the tree, exposing the kernel to invasion by insects and molds. Deficit irrigation of pistachio trees in April and May resulted in substantial increases in the formation of early-split nuts in late summer, while extreme deficit irrigation in July and August resulted in decreased formation. However, deficit irrigation during the period of shell hardening, mainly in June, did not affect early-split formation.

Relationship Between Shell Discoloration of Pistachio Nuts and Incidence of Fungal Decay and Insect Infestation.

Shell discoloration of pistachio (Pistacia vera) nuts collected from commercial orchards and processing plants was related to fungal decay and insect infestation of the kernel. Nuts with ruptured hulls (early split nuts and nuts with cracked hulls) varied considerably in the amount of shell discoloration, ranging from none to extensive. For both types of hull rupture, as shell discoloration increased, kernel decay also increased. Nuts with no discoloration had little or no fungal decay and navel orangeworm (Amyelois transitella) infestation. Processed nuts with an oily-shell appearance had the highest incidences of fungal decay and navel orangeworm infestation; nuts with a crinkled shell, nuts with extensive dark brown discoloration, and nuts with moderate dark brown discoloration along the suture had relatively high levels of decayed and infested kernels; while nuts with yellow discoloration, nuts with moderate dark brown discoloration not along the suture, and nuts with no discoloration had little or no decay and infestation. Also, as shell discoloration of processed nuts increased, kernel decay increased. Our results suggest that shell characteristics may be used by processors to identify poor quality nuts and to improve the quality of pistachio nuts sold to consumers.

Machine Vision Detection of Early Split Pistachio Nuts

Computer vision was used to detect early split lesions on the hull of pistachio nuts. Gray scale intensity profiles were computed across the width of the nut (perpendicular to the suture along the longitudinal axis). If the profile crossed an early split lesion, a deep and narrow valley on the profile at the early split location was observed. Profiles were computed every 0.5 mm along the longitudinal axis of the nut and the number of adjacent profiles with deep and narrow valleys was recorded. Early split nuts contained a significantly higher count of these adjacent profiles than normal nuts. Combining unhulled nut cross-sectional area with the adjacent profile data, 100% of the early split nuts and 99% of the normal nuts were correctly classified of the total of 180 nuts tested.

Hull Adhesion Characteristics of Early-split and Normal Pistachio Nuts

The hull adhesion properties of early-split and normal pistachio nuts were studied to determine the feasibility of separating early-split nuts from normal nuts by their hulling characteristics. The hulls of pistachio nuts were found to adhere more tightly to the shells of early-split nuts than to normal nuts. Laboratory hulling tests on pistachio nuts harvested in 1993 indicated that under controlled conditions, 98% of the normal nut hulls were removed while only 9% of the early-split hulls were removed.

Physical Properties of Pistachio Nuts

Physical properties of pistachio nuts were evaluated to determine distinguishable characteristics of early split pistachio nuts. The hulls of early split pistachios abnormally split open several weeks before harvest, making the kernel more vulnerable to the aflatoxin producing mold Aspergillus flavus. The most distinguishing features of early split pistachio nuts were found to be shell staining and hull adhesion tendencies. Using shell stain characteristics and shell dimensions, an algorithm was developed that correctly classified 90% of the early splits, and 97% of the normal nuts. When unhulled nuts were placed into a tumbler, 98% of the early split nuts kept their hulls while 95% of the normal nuts were hulled. A mechanical separation device was constructed that successfully separated 90% of the early split nuts and only 5% of the nonsplit nuts from the rest of the samples. Nut mass, length, width, and height are significantly different between early split nuts and normal nuts, however, these properties cannot be used to accurately classify the nuts into split types.