In-shell Peanuts Research Articles

Determination of moisture content of in-shell peanuts by parallel-plate impedance measurements in cylindrical sample holder

This paper describes a method to determine the moisture content of in-shell peanuts with a parallel-plate electrode system fitted inside a cylinder by using impedance measurements made on the system. Two parallel-plate electrodes were mounted inside a cylinder, made of acrylic material, and the space between the plates was filled with in-shell peanuts (80–100 g). The impedance measurements were made on the parallel-plate system at 1 and 9 MHz, and the average moisture content (MC) of the peanut pods (in-shell peanuts) was determined from a semi-empirical equation. The calculated MC values were compared with standard oven-determined values and were within 1% of the standard oven values for 90% of the samples tested in the moisture range between 6% and 19%. Two parallel-plate sensors with different plate separations and peanuts from the 2004 and 2005 harvests, were used in these measurements. The method, being rapid and nondestructive, is suitable for the development of a practical instrument for measurement of moisture content in in-shell peanuts.

RF impedance method for nondestructive moisture content determination for in-shell peanuts

A method was developed earlier for estimating the moisture content (mc) in samples of wheat, corn and peanut kernels, nondestructively, by measuring their complex impedance values. In this method, capacitance (C), phase angle (θ) and dissipation factor (D) were measured with an impedance analyser at 1 and 5 MHz on a parallel-plate capacitor holding a few kernels of a particular commodity between the plates. These values were then used in an empirical equation based on the parameters C, θ and D, and the moisture content was calculated. The calculated mc values were within 1% of the air-oven values for about 85% of the kernel samples tested in the moisture range from 6% to 20% for wheat, corn and peanuts. However, it would be useful during drying and processing of peanuts, if the mc could be determined without shelling them. In this work, the feasibility of determining the moisture content of in-shell peanuts (pods) by similar impedance measurements was investigated. Values of capacitance, phase angle and dissipation factor measured at 24 °C and at three frequencies were used in a modified prediction equation and the moisture content was estimated within 1% of the air-oven values for over 90% of the pod samples tested in the moisture range from 6% to 25%. The method is rapid and nondestructive and may be used in the development of a commercial instrument.

The relation between phosphine sorption and terminal gas concentrations in successful fumigation of food commodities

Owing to increased tolerance and the development of resistance in stored product insects to the fumigant phosphine, in recent years there has been a shift in the target terminal concentration from 100 ppm (100 mL m(-3)) to a higher level of 1000 ppm to achieve 100% insect mortality in 7 day commodity treatments. Therefore, there is a need to investigate whether the revised target concentration could be achieved for food commodities fumigated with phosphine at the standard dose of 2 g m(-3) for 7 days under airtight conditions at > or = 25 degrees C. When different types of food commodity (total 74) were fumigated (300 g per replicate) with phosphine at 2 g m(-3) for 7 days, the terminal gas concentrations in the free space of the commodities varied from 0 to > 2000 ppm. In chambers containing no substrate, a 1417 ppm concentration was recorded. Paddy rice, most of the oilseeds, shelled tree nuts, butter beans, cardamom, green gram splits, coriander powder, rice bran and cocoa powder were more sorptive (> or =60%), such that the target concentration of 1000 ppm was not achieved at the end of 7 days. For these commodities, increased doses of 3-6 g m(-3) were required to attain 1000 ppm. In-shell almonds, green cardamom, in-shell peanuts, leaf tea, tamarind pulp and sunflower seeds were exceptionally sorptive (>90%), so that 0, 41, 112, 168, 203 and 217 ppm respectively were noted at the end of 7 days; the dose must exceed 6 g m(-3) for effective fumigation of these commodities.

Validation of Weed Competitive Indices for Predicting Peanut Yield Losses in Oklahoma

Weed interference experiments have not been extensively conducted in Oklahoma peanut. Research was conducted in three environments to evaluate usefulness of single-weed density experiments with the use of several weeds to measure their relative competitive abilities with a crop. These data can be used to validate current competitive indices (CIs) used by a model to predict peanut yield loss due to weeds. This model is used by the Herbicide Application Decision Support System (HADSS) and Pesticide Economic and Environmental Tradeoffs (PEET), two decision-support systems (DSSs) available for Oklahoma peanut. Six weeds common in Oklahoma peanut were used: crownbeard, eclipta, ivyleaf morningglory, johnsongrass, Palmer amaranth, and prickly sida plus two others, barnyardgrass and common cocklebur, as benchmark species. Each weed was planted into peanut uniformly at eight weeds/10 m of row. Dry weed biomass accounted for 77 to 90% of variation in in-shell peanut yield loss; however, model parameters only allow for weed number. Yield losses from these experiments were compared to those predicted by the model to test original CI accuracy. Treatment means were compared to the prediction model with the use of protected LSD. Several significant differences were noted, and the CIs for those weed species were adjusted accordingly. Adjusting CIs improved actual yield data goodness of fit to model predictions specific to environment in question, but not necessarily in different environments. The CI changed at Ft. Cobb were eclipta from 1.8 to 4.5 and ivyleaf morningglory from 3.4 to 5.0. CI adjustments at Perkins were common cocklebur from 10.0 to 5.8 and johnsongrass from 3.0 to 4.6. Collecting data for several weed species at uniform density in a crop provides a more time-efficient method for obtaining accurate relative weed interference data; this method is useful in validating or establishing CI lists in areas and/or crops with limited data.

NONDESTRUCTIVE MOISTURE CONTENT DETERMINATION OF IN-SHELL PEANUTS BY RF IMPEDANCE METHOD

Measuring the moisture content of peanuts without shelling the peanuts, particularly during buying/selling anddrying, would be beneficial to the peanut industry. Previous research has shown that radio frequency (RF) impedancemeasurements of capacitance (C) and phase angle (.) using a parallel-plate system could be used to estimate the moisturecontent (MC) of a single in-shell peanut. This method was extended to determine the average MC of a small sample of peanutpods accommodated between the plates. For both single pods and small samples, the predicted MC values were within 1%of the standard air-oven values for over 85% of the samples tested in the moisture range between 5% and 22%. The currentresearch discusses extending the measurement system to predict the average MC of in-shell peanuts in bulk quantities (about200 g) from similar capacitance and phase angle measurements at 1 and 9 MHz. The parallel-plate system used in previousresearch was modified and fitted into a non-conducting cylindrical sample holder.

Time of Removal of Crownbeard (Verbesina encelioides) on Peanut Yield

Field experiments were conducted in southwestern Oklahoma near Colony in 2000 and near Ft. Cobb in 2001 to quantify the effect of time of removal of a natural population of crownbeard on peanut yield. Weed densities and dry weed weights were measured at eight weed-removal times, and in-shell peanut yields were determined at harvest. Crownbeard was removed at 0 (the weed-free check), 4, 6, 8, 10, 12, 14, and 16 wk (full season) after crop emergence (WAE). Weed density was a poor predictor for dry weed weight and peanut yield; however, dry weed weight and time of removal were good predictors for peanut yield. Weed growth was minimal up to 4 WAE and increased linearly after that time. For each week of weed growth, a 0.52 kg/plot increase in dry weed weight was measured. Peanut yield decreased linearly because of crownbeard competition. For each kilogram per plot increase in dry weed weight, a 129 kg/ha or 5.1% peanut yield reduction took place. For each week of weed interference, a 75 kg/ha or 2.8% peanut yield reduction occurred. Crownbeard removal by or before 4 WAE will minimize losses in peanut yield because of interference.

Moisture Determination in Single Peanut Pods by Complex RF Impedance Measurement

An assessment was made of estimating the moisture content (mc) of single peanut pods (in-shell peanuts) by measuring the complex impedance of a parallel-plate capacitor with a single pod between the plates. Capacitance (C), phase angle (/spl theta/) and/or dissipation factor (D) were measured at 1.0 and 5.0 MHz, and the measured values at these two frequencies were used in a derived empirical equation to calculate the mc. Previous research had determined that the mc of single and small samples of shelled peanuts (kernels) could be determined by similar measurements at 1 and 4.5 MHz. In this paper, the mc of the pods tested was between 5% and 25%. The predicted mc of the pods was within 1% of the standard air-oven values for about 85% of the single pods.

Oil, sugar, and starch characteristics in peanut breeding lines selected for low and high oil content and their combining ability.

Peanut seeds contain approximately 50% oil on a dry weight basis, making them a high fat food. Reduction of the oil content would make peanuts a more desirable food to fat conscious consumers. Removal of existing oil by processing is not feasible for in-shell peanuts, the dominant product of the North Carolina-Virginia area. To reduce oil content in in-shell peanuts, a genetic solution must be found. However, while reduced oil content is a desirable objective, changes in oil must not be accompanied by significant decreases in any of the desirable aspects of peanut flavor. Because the impact of selection for low or high oil on flavor is not known, it would be useful to know in what form dry matter is being stored in the seed, particularly if it is not being stored as oil. Screening of 584 accessions identified two lines (PI 269723 and PI 315608) with high and two (Robusto 2 and Robusto 3) with low oil contents, each pair differing in sugar content. The four parents were crossed in diallel fashion to investigate patterns of inheritance. General combining abilities (GCA) for oil content closely followed values of the parental lines. One low oil parent (Robusto 2) had a correspondingly elevated GCA for sugar content, but neither low oil parent had the effect of elevating starch in progeny. Reciprocal cross differences were found for starch and sugar contents, suggesting influences of cytoplasmic genes on those traits. These lines serve as resource material for researchers interested in the genetic and physiological aspects of the oil-sugar-starch relationship in peanuts.

Improving Shelf Life of Roasted and Salted Inshell Peanuts Using High Oleic Fatty Acid Chemistry

Abstract Major markets for the large-seeded virginia-type peanut (Arachis hypogaea L.) include roasted inshell and salted inshell products with short shelf life being a common consumer complaint. Unlike many other peanut products, it is not economically possible to package these inshell peanuts in nitrogen flushed, oxygen barrier bags. A number of studies have shown that roasted runner-type peanuts with high contents of oleic fatty acid have improved oxidative stability and longer shelf life. A large-seeded, virginia-type peanut cultivar (AgraTech VC-2) with the high oleic trait has been released but no information is available on its shelf life stability. Therefore, this high oleic cultivar and the normal oleic cultivar VA 98R from the 2000 and 2001 crop were used for shelf life evaluations. Peanuts were sized into the fancy inshell grade for roasted inshell and salted inshell products. Peroxide value (PV) results for the roasted inshell peanuts indicated that normal oleic fatty acid (50% range) peanuts reached a PV of 20 meq/kg by the end of 4 wk of storage. On the other hand, the high oleic fatty acid (80% range) peanuts did not reach a value of 20 meq/kg until approximately 32 wk. When salted inshell the normal oleic peanuts exceed a PV of 20 meq/kg before the 2nd wk, whereas the high oleic peanuts still had not reached a PV of 20 meq/kg after 40 wk of storage. These results show a significant advantage of high oleic peanuts for extending shelf life of large-seeded, virginia-type peanuts for either roasted or salted inshell processing.

DIELECTRIC PROPERTIES OF IN-SHELL AND SHELLED PEANUTS AT MICROWAVE FREQUENCIES

Dielectric properties (..,.. ) of ground samples of in-shell and shelled peanuts (Arachis hypogaea L.) weremeasured for several densities, temperatures, and moisture contents in the range of 300 to 3000 MHz. Dielectric mixtureequations were used to correlate the dielectric properties with density. The coefficients of quadratic and linear dielectricmixture equations are tabulated for 915 and 2450 MHz, for different temperatures and moisture contents. The values of thedielectric constant (..) and loss factor (.. ) of bulk in-shell and shelled peanuts were determined by extrapolation of the firstandsecond-order polynomials that relate .. and .. with density. An equation that determines the dielectric properties ofnominal peanut pods (in-shell peanuts) and kernels (shelled peanuts) as a function of their temperature and moisturecontent was determined by using multiple linear regression.

Feasibility Tests for a Two-Stage Batch Dryer for Curing Farmer Stock Peanuts1

Abstract A two-stage batch dryer for farmer stock peanut was developed by a commercial grain dryer manufacturer and tested at a commercial peanut buying point during the 1996 and 1997 harvests. A 7.3-m diameter grain bin provided the superstructure for two peanut curing chambers. Each chamber had an approximate capacity of 18,000 kg of in-shell peanuts. Comparisons between conventional peanut curing wagons and the bin dryer were conducted. Recorded data included temperature and relative humidity in both type dryers, drying time, moisture content throughout curing, farmers stock grades, milling quality, and seed germination. A total of 451,717 kg were cured in the two-stage dryer and 215,460 kg in conventional dryers. The initial moisture content of peanuts averaged 19% wet basis and dried at an average moisture removal rate of 0.45%/hr. The moisture removal rates for the two dryers were not significantly different. The final moisture content averaged 11%. Moisture content at the time of grading averaged 9%. Farmers stock grades and milling quality were not significantly different. The average quota support price, including LSK for peanuts cured in conventional dryers, was $630.47/1000 kg compared to $636.08/1000-kg peanuts cured in the two-stage dryer. Seed germination averaged 75.8 and 76.1% for conventional and bin-dried peanuts, respectively. The twostage batch dryer was comparable to the current wagon-drying system. A single batch in the two-stage dryer was equivalent to three peanut wagons.

Correcting Current Moisture Calculations for Purchasing High Moisture Farmers Stock Peanuts1

Abstract The U.S. peanut industry may eliminate the 10% moisture content threshold for purchasing peanuts to facilitate implementing continuous flow drying systems and to increase the efficiency of the postharvest processing system. Equations based on the theoretical definition of wet basis moisture content were proposed to determine the weight of various components in a load of farmers stock peanuts. These equations more accurately describe and account for the distribution of moisture within a load of peanuts. Accurate descriptions of the amount of loose shelled kernels, foreign material, and in-shell peanuts would enable improved tracking of losses during storage. Compared to the current price structure, the proposed equations predict reduced payments to growers no more than $30 per 5-mt load of peanuts. The maximum reduction of $30 occurred if peanuts were delivered and marketed at 30% w.b. moisture content. A reduction of approximately $8.50 would occur for a 5-mt load delivered at 15% moisture content. The cumulative economic impact warrants adjustment of the peanut support price schedule if accurate accounting of moisture is implemented.

A Laboratory Colorimeter Method to Measure Pod Brightness in Virginia-Type Peanuts

Abstract Pod brightness is an important characteristic that influences consumers to purchase in-shell peanuts. A method is needed to quantitate pod brightness. Studies were conducted to determine whether pod color measurements were related to visual aesthetics rated by a panel representing seven virginia peanut shelling companies and to determine the effect of the optical aperture of the colorimeter on the measurements obtained. Forty-eight virginia-type pod lots were separated into fancy and jumbo fractions using a standard Federal-State Inspection Service grading peanut sizer. Pod color was measured for three subsamples of each fraction using a Hunterlab D25-PC2 colorimeter equipped with the D25-2RAL Reduced Area Viewing for L optical sensor (51-mm diameter sample area). The 96 samples also were rated by 11 Virginia-Carolina area shellers for pod color and size. Sheller ratings for the two traits were highly correlated (r > 0.6, P ≤ 0.01). Hunter L and b scores were strongly correlated with sheller color ratings. The colorimeter is a useful tool for measuring pod brightness as an adjunct to breeding for improved pod brightness. Use of a 95 mm aperture resulted in greater average Hunter L, a, and b scores and significantly reduced the variance among subsamples. The larger aperture should be used when the quantity of pods available for measurement permits.

Anatoxin B1 in Common Egyptian Foods

Samples of common Egyptian foods (17 nuts and seeds, 10 spices, 31 herbs and medicinal plants, 12 dried vegetables, and 28 cereal grains) were collected from markets in Cairo and Giza. A portion of each sample was extracted with chloroform, and the concentrated extract was cleaned by passing through a silica gel column. Aflatoxin B1 was determined by reversed-phase liquid chromatography with UV detection. The highest prevalence of aflatoxin B1 was in nuts and seeds (82%), followed by spices (40%), herbs and medicinal plants (29%), dried vegetables (25%), and cereal grains (21%). The highest mean concentration of aflatoxin B1 was in herb and medicinal plants (49 ppb), followed by cereals (36 ppb), spices (25 ppb), nuts and seeds (24 ppb), and dried vegetables (20 ppb). Among nuts and seeds, the prevalence of aflatoxin B1 was highest (100%) in watermelon seeds, inshell peanuts, and unshelled peanuts. The lowest prevalence and concentrations were in hommos (garbanzo beans). The highest concentrations of aflatoxin B1 were detected in foods that had no potential for field contamination but required drying during processing and storage, such as pomegranate peel, watermelon seeds, and molokhia.

Pod and Seed Size Relation to Maturity and In-Shell Quality Potential in Virginia-Type Peanuts1

Abstract In-shell peanut sales provide a consistent market for large-seeded virginia-type peanuts. In this market, maintenance of a high quality product, which includes fresh roasted peanut flavor, is a recurring challenge. A maturity-seed size-quality relationship has been established for shelled peanuts. To determine if this relationship is true for in-shell peanuts, the relationships of maturity, pod size, and seed size were investigated. In two crop years (1992 and 1993) and on four to five harvest dates, virginia-type peanuts (cv. NC 9) were harvested at Lewiston, NC and sorted into hull scrape maturity classes: black, brown, orange B, orange A, and yellow. After pods were dried, they were screened to obtain the pod size distribution. Sized pods were hand-shelled, and the seed were screened to obtain the seed size distribution from each pod size from each maturity class. Hull scrape pod maturity profiles revealed a decrease of ca. 14% in yellow/orange A and an increase of ca. 14% in brown/black over the 4- to 7-d harvest period. Overall, pod size distribution did not change over time although slight differences were noted between years. Pod size distributions within individual maturity classes were more variable. The data indicated that the Jumbo in-shell grade contained higher percentages of brown and black maturity classes than the fancy grade. Fancy grades contained 26-49% immature pods (yellow and orange A maturity classes).

Susceptibility of Fifth-Instar Indianmeal Moth and Almond Moth (Lepidoptera: Pyralidae) to Cyfluthrin Residues on Peanuts1

Inshell peanuts treated with 10, 14, 18, and 22 ppm cyfluthrin were bioassayed with fifth instar Indianmeal moths, Plodia interpunctella (Hübner) and fifth-instar almond moths, Cadra cautella (Walker), after 0, 2, 4, 6, and 8 months of storage. Emergence of the adult almond moth was greater than Indianmeal moth emergence at residual bioassays of 14, 18, and 22 ppm. Regression of increasing emergence with storage time was significant for the Indianmeal moth at 22 ppm and the almond moth at 14 and 22 ppm. For both species, adult emergence decreased as cyfluthrin concentration increased and was described by quadratic regression.

Interaction of Bracon hebetor (Hymenoptera: Braconidae) and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) in Suppressing Stored-Product Moth Populations in Small Inshell{middle dot}Peanut Storages

Biological control tests in small inshell peanut storages indicated that the release of Bracon hebetor Say as a parasite of moth larvae and Trichogramma pretiosum Riley as a moth egg parasite have considerable potential for suppression of stored-product moth populations. Population suppression of the Indian meal moth, Plodia interpunctella (Hiibner), but not of the almond moth, Cadra cautella (Walker), was dependent on the species of parasite released. Population suppression of Indian meal moth over the storage season was 37.3% of the check treatment for T. pretiosum alone, 66.1% for B. hebetor alone, but 84.3% when parasites were used in combination. For the much more abundant almond moth, reductions averaged 96.7, 97.3, and 98.0% for the three treatments, respectively. Larval feeding damage to peanut kernels was reduced to ≤1.12% by all three parasite treatments as compared with 15.84% in the untreated checks. Thus, B. hebetor and Trichogramma spp. may be useful as parts of an integrated pest control program for lepidopteran pests of stored inshell peanuts.

TWO-COMPONENT THIN-LAYER DRYING MODEL FOR UNSHELLED PEANUTS

ABSTRACT This manuscript describes a thin-layer model for drying of in-shell peanuts which treats the pod as two separate components (kernels and hulls) with moisture movement proportional to a combination of moisture content gradients (liquid diffusion) and vapor pressure gradients (vapor diffusion). Data from the literature were used for model evaluation and the determination of drying parameters. Good fits of experimental data were obtained and the thin-layer model is considered accurate enough for inclusion in a bulk drying model.

The Effect of Loose-Shelled Kernels and Foreign Material on Pirimiphos-Methyl Residues in Stored Farmers Stock Peanuts1

Abstract Farmers stock peanuts containing either 0% loose-shelled kernels (LSK) and 0% foreign material (FM), 5% LSK-10% FM, or 10% LSK-20% FM were sprayed with 20 PPM pirimiphos-methyl. Peanut samples were analyzed for insecticide residues during a 1-year storage period. Significantly lower residues were found on in-shell peanuts with 0% LSK-FM than on either of the 2 LSK-FM combinations. Insecticide residues accumulated in the FM and to a lesser extent in the LSK. Negligible residues were found on sound mature kernels from solid pods.

Interference of Silverleaf Nightshade (Solanum elaeagnifolium) on Spanish Peanuts (Arachis hypogaea)1

Abstract Interference of silverleaf nightshade (Solanum elaeagnifolium Cav.) with Pronto spanish peanuts (Arachis hypogaea L.) was evaluated from 1981 through 1983 in a natural occurring weed population. Treatments consisted of weed-free maintenance or weed interference for 0, 4, 8, 12 weeks and for the full season. Silverleaf nightshade stems were counted as a measure of weed regrowth in treatments maintained weed free for 0, 4, and 8 weeks. Contamination of the harvested in-shell peanuts by silverleaf nightshade berries was determined by counting the number of berries passing through the peanut combine. In-shell peanut yields were reduced by an average of 17% when silverleaf nightshade was allowed to interfere with the crop for 4 weeks. Further yield reductions of 53, 66, and 66% were observed in treatments where interference occurred for 8 and 12 weeks and for the full-season, respectively. Regression analysis conducted on yield data of individual years predicts that each week of weed-free maintenance after crop emergence results in an average of 33 to 38 kg/ha yield increase above the unweeded control. Conversely, analyses of yield data averaged over all years indicated that for each week of weed interference there would be approximately a 103 kg/ha decrease in in-shell yield compared to the weed-free control. When yield data were converted to percent of yield of weed-free controls, there was no interaction among years. Regression analysis of the converted data predicts that for each week of weed-free maintenance after crop emergence there would be a 3.7% yield increase compared to the unweeded control and that for each week of weed interference there would be a corresponding yield loss of 4.5%. Silverleaf nightshade stem counts per plot were reduced an average of 18 and 36 percent for treatments maintained weed free for 4 and 8 weeks, respectively. In 1982 analysis of fruit contamination indicated a significant difference between full-season interference and weed-free maintenance for 4 or more weeks. Differences in fruit contamination between 4, 8, and 12 weeks of weed-free maintenance were not significant. In the second year no differences in fruit contamination were observed between the weedy check and the other treatments; however, fruit production after 4 weeks of weed-free maintenance was significantly higher than after 8 and 12 weeks of weed-free maintenance. Peanut quality, disregarding contamination by silverleaf nightshade berries, was not affected by weed interference.