ABSTRACT Mitochondrial DNA (mtDNA) fragmentation has been proposed as a time-temperature integrator (TTI) for high-moisture thermal processes using low-acid, high-temperature and high-acid, low-temperature protocols. In this study, dry roasted peanuts were assayed using the same novel molecular TTI. Enterococcus faecium was evaluated as a Salmonella surrogate for process validation and compared to fragmentation of intrinsic peanut mtDNA and Hunter L color, a quality indicator, for dry roasting. Reduction curve data for E. faecium were highly repeatable as similar kinetics were observed when compared to another study which used a commercial, contract laboratory to validate this same surrogate for use with dry roasted peanuts processes (4-log reduction after 10 min at 167 C). Mitochondrial DNA fragmentation was not linear compared to time at a given temperature, but exhibited a long lag time. D and z-values were calculated using E. faecium , threshold cycle (Ct) and Hunter L color values. D values for E. faecium were 2.68, 2.06 and 1.89 min for 138, 153 and 167 C roasting temperatures, respectively. Mitochondrial DNA fragmentation as measured by Ct had a D value of 12.3 min at a roasting temperature of 167 C which was slightly higher than “wet” processes ( ca . 11.5 min). Hunter L values had an inverse, linear relationship with time at a given temperature. Hunter L color, if applied to individual peanuts and empirically validated, could be used as an inexpensive visible method to troubleshoot continuous flow systems. Ct values were not linear or highly correlated to Hunter L values. Dissection of peanuts exhibited a differential heating effect depending on the part of the peanut used for DNA extraction and the type of tissue assayed. Mitochondrial DNA fragmentation as measured by Ct value was deemed too variable for thermal process or quality validation of dry, solid foods such as peanuts. However, it could be used to evaluate penetration of heat through a solid food matrix, to find the coldest spot and test the worst-case scenario.

ABSTRACT A number of outbreaks of salmonellosis since 2006 associated with the consumption of Salmonella -contaminated peanut butter have increased concerns about this food and the associated processing methods. Laboratory studies were conducted to determine the level of Salmonella reduction associated with oil and dry roasting of peanuts. After inoculation with either Salmonella or Enterococcus faecium , peanuts were dry roasted for various time durations at 5 temperatures ranging from 129–163 C and oil roasted at 120–160 C for three different time durations. At each dry roast combination of temperature and time in the study, Salmonella and E. faecium reductions were 2.7 log Colony Forming Units (CFU)/g or greater. Dry roast temperature of 154 C provided 4.6–4.7 log CFU/g reduction of Salmonella at 10 min and greater than 5.4 log CFU/g reduction at15 min. Oil roasting for 1.5 min at 150 C resulted in greater than a 6.0 log CFU/g reduction of S almonella. E. faecium log CFU/g reductions were significantly less than Salmonella reductions in all treatments indicating a greater heat tolerance by E. faecium and documentation that it is an acceptable surrogate for Salmonella on peanuts.

ABSTRACT Studies were conducted to evaluate the effectiveness of industrial peanut dry roasting parameters in Salmonella reduction using a Salmonella surrogate, Enterococcus faecium, which is slightly more heat tolerant than Salmonella . Runner-type peanuts were inoculated with E. faecium and roasted in a laboratory scale roaster simulator in which temperature, airflow, airflow direction and bed depth were highly controlled, allowing for conditions that duplicate industrial dry roasting. Temperature data were collected at the top, middle and bottom of the roasting bed in addition to internal peanut temperature via thermocouples in the bed of peanuts and embedded in a peanut. Regardless of roast conditions, peanuts in the middle of the roasting bed received the least amount of heat and hence, represent the worst case scenario for microbial reduction. E. faecium reductions, reported as the logarithm of colony forming units/g (log CFU/g), followed a linear trend with increasing roasting time when peanuts were roasted at 149, 163, and 177 C, with > 5-log CFU/g reductions occurring at the middle of the peanut bed after 21, 15 and 11 min, respectively, at a bed depth of 75 mm and an air flow of 1.3 m/s. Increased air flow increased E. faecium reduction. At 16 min roast time and a 75 mm bed depth, reduction at the middle of the bed was ≤ 3-log CFU/g at 1 m/s and > 5-log CFU/g at 1.3 m/s. When all other roast parameters were held constant, decreasing bed depth also increased reduction of E. faecium in the middle of the bed. Comparing various samples roasted at 149, 163 and 177 C over a range of times, roast color (Hunter L-value) was positively correlated (R 2 = 0.73) with the log reduction of E. faecium . Most peanuts with an L-value darker than 53, a common threshold for light roast had ≥ 5-log CFU/g reductions; however, further study is required, including roasting peanuts from different origins and maturity, to fully understand the implications of roast color development and microbial reduction. This work provides valuable practical information for manufacturers of roasted peanuts when validating Salmonella reductions under a particular set of roasting parameters.

Peanuts ( Arachis hypogaea L.) are known to be a source of several important B-vitamins, including niacin (Vitamin B3). A total of 39 Florunner and NC7 samples from the 2007 and 2008 Uniform Peanut Performance Test (UPPT) were analyzed to compare their niacin content from 10 different growing locations in the U.S. From the Core of the Core of the peanut germplasm collection, 13 selected samples grown in North Carolina in 2008 were analyzed. Over 2 years and 10 locations, raw Florunner niacin levels ranged from 8.8 to 21.9 mg/100g DW. Mean niacin concentration in 2007 was 15.7 mg/100g DW and 17.8 mg/100g DW in 2008. Raw samples of NC7 averaged 19.0 mg/100g DW in 2007 and 20.3 mg/100g DW in 2008. The varietal difference was statistically significant as were differences among growing locations. The lowest niacin levels were found in the Virginia-Carolina region and the highest in Texas and Oklahoma. Although the 2008 niacin means were higher than 2007, the increase was not statistically significant. Roasting raw 2008 samples caused niacin levels to drop 12% (p = 0.0212) in Florunner and 6% in NC7 (p = 0.0128). Mean niacin concentrations in the Core of the Core samples were found to range from 13.9 to 20.7 mg/100g DW. Levels of niacin in the Core samples tested were found to be higher than Florunner (12.2 mg/100 DW) and NC7 samples (13.8 mg/100g DW) grown at the same location and in the same year. Significant differences in niacin content among NC7 and Florunner UPPT entries across 10 locations indicated a potential for genetic variation that is potentially exploitable by breeders. This is supported by the significant differences found among the Core of the Core entries and NC7 and Florunner samples from the same location and year.

The usefulness of core collections of germplasm collections has been well established. The U.S. germplasm collection for peanuts was selectively reduced based on morphological characteristics to a mini core or “Core of the Core” collection composed of 112 of the 7432 accessions in the whole collection to make it more efficient for study. Of these samples, 108 were available from one location in the same year and were therefore exposed to one set of environmental conditions wherein genetic variability could also be examined. These samples were analyzed for total and individual amino acid content, fatty acid content, tocopherols, and folic acid content. These data provide a starting point for establishing nutrient composition within these accessions and provide an early indication of currently important characteristics in these lines which might be suited for use in random breeding initiatives.

Peanut composition is influenced by several groups of factors: environmental, genetic, and their interaction. This study evaluated the relative contributions of these factors using data from the USDA-ARS quality testing program using samples from the multi-state Uniform Peanut Performance Tests (UPPT). Data were subjected to restricted maximum likelihood estimation of variance components reflecting the main effects of year, production region, location within region, genotype (cultivar or breeding line), and kernel grade (“seed size”) within genotype, and the interactions among these main effects. Genetic variation in oil content was low (9% of total variation); however, fatty acid composition of the oil was highly influenced by genotype (34–77%) with the exception of lignoceric acid (1%). Genetic influence on tocopherols was generally less than that of fatty acids. Environmental variation of tocopherols was greater than the variation attributable to genotype-by-environment interaction. The lowest genetic variation was observed in sugar content; however, environmental variation was high (68%). The magnitude of genetic influence on oil content and fatty acid concentrations suggests that these traits are amenable to improvement through breeding.

Peanut flavor is influenced by several groups of factors: environmental, genetic, and interaction between them. This study evaluated the relative contributions of these factors using data from the USDA-ARS program of sensory quality testing of samples from the multi-state Uniform Peanut Performance Tests (UPPT). Data were subjected to restricted maximum likelihood estimation of variance components reflecting the main effects of year, production region, location within regions, genotype, and kernel grade within genotype, and the interactions among these main effects. Genetic variation was relatively small (0.0 to 9.5% of total variation) while environmental variation, particularly that due to years, was large. Year-by-genotype interaction was large for roast color and intensities of the roasted peanut and sweet aromatic attributes. Estimates of repeatability (R) for sensory attributes were low, even based on means measured across multiple locations and two years, except for that of the sweet attribute (R = 0.10 for a single observation and R = 0.34 for a mean across two years of UPPT testing). Breeders should be able to reliably identify lines with superior sweet attribute intensity, but identification of lines with intense roasted peanut attribute will be more difficult.

Individual peanut seed may develop a fruity fermented (FF) off-flavor if exposed to elevated temperatures after digging. Typically, high moisture, immature peanuts exposed to temperatures above 35°C either in the windrow or during artificial curing may develop the FF off-flavor. Because of the uncertainty associated with sampling and FF measurement, it is difficult to obtain a precise estimate of the true FF intensity within a bulk lot. The objectives of this study were to determine the variability associated with the sampling and measurement steps of the test procedure used to measure FF intensity in a bulk lot and to describe the FF distribution among replicated sample test results taken from the same lot. Twenty test samples of 250 g each were randomly taken from 20 medium grade lots of runner-type peanuts identified by commercial testing as having FF intensities ranging from 0.0 (no FF off flavor) to 4.0. Each test sample was prepared according to published guidelines and the FF intensity of each sample was measured by 8 members of a highly trained descriptive sensory panel. The total variability associated with the FF test procedure was partitioned into sampling and measurement variances for each lot. Each variance was a function of the FF intensity. Using the standard commercial FF test procedure (300 g sample and averaging the score of 5 panel members), the measurement and sampling variances accounted for 31.4% and 68.6% of the total error, respectively. The FF distribution among replicated sample test results tended to be positively skewed and could be described by the compound gamma distribution. The best use of resources to reduce the total variability of the FF test procedure would be to increase sample size to reduce variability of the sampling step.

Peanut cotyledonary cells were observed with transmission and scanning electron microscopy during starch granule formation. Developing starch granules were primarily electron translucent, and both simple and compound granules were observed. Fully developed starch granules were observed during both early and late stages of seed development. Major findings include observation of electron dense materials within the stroma of developing starch granules that may be ultrastructural evidence of the location of enzymes involved in the synthesis of starch.

Experimental methods were used to investigate the effect of microwave energy level on temperature profiles and moisture reduction of farmer stock peanuts (in-shell, uncured) during continuous microwave drying using a planar applicator. Temperature profiles, measured using fiber optic probes, were determined to be dependent on peanut moisture content and microwave power level. Although the maximum temperature in the microwave applicator was a function of power level only, the rate at which that maximum was attained was a function of the dielectric properties and moisture contents of the peanuts. Thermal imaging demonstrated that the temperature of the peanut bed surface at the exit of the microwave curing chamber was uniformly distributed. This study quantifies the relationships among the various parameters that influence the continuous microwave drying process of peanuts. The results provide a foundation for development of optimum process conditions in microwave drying of peanuts and other agricultural commodities.

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 2 nd 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.

Light microscopy staining methods for amino acids and sugars were adapted for glutaraldehyde vapor-fixed, freeze dried, plastic embedded tissue of peanut cotyledons ( Arachis hypogaea L.). These methods revealed the locale of amino acids and sugars, which are regarded as precursors of roasted peanut flavor compounds. Amino acids were localized in the protein bodies and cytoplasmic network by Coomassie Brilliant Blue G-250, Orange G, and diacetylbenzene. Sugars were localized in the protein bodies and cytoplasmic network by Alcian Blue - PAS procedure and an adaptation of the Okamoto method for sugars. Localization of the amino acids and sugars provide further evidence to the importance of the protein bodies in the cotyledon in the production of roasted peanut flavor.

Mesocarp color classification in the Hull Scrape Maturity Method is the most important step in determining peanut maturity and optimum harvest date. This research involved the development of an image acquisition system and a software procedure for color classification. Images of peanut pods that had been sorted manually into color classes and subclasses were used in computer training. After training with sorted color classes, the computer-assisted procedure correctly identified and classified the peanut pods, with a 99% precision for the same sample in different alignment, and with a 95% precision for different size samples taken from the same population. Pod size measurement with a resolution of 0.1 mm was also performed using image processing techniques.

Temperature and relative humidity (RH) in an aerated warehouse in west Texas were monitored during storage of 1994 and 1995 crop farmer stock (FS) peanuts. Temperature and RH were measured at various positions throughout a vertical cross section of the peanut mass in the overspace and outside the warehouse. Data were collected at 1-hr intervals throughout storage. Peanut mass temperatures averaged 9.6 C during storage for the 1994 crop and 10.3 C for the 1995 crop. Relative humidity for the 1994 crop storage averaged 68.3 and 57.9% for the 1995 crop storage. Farmer stock grades were collected at warehouse loading and unloading for 10- to 12-t lots of peanuts stored in the warehouse (Wpnuts) and for samples (Spnuts) positioned at temperature and RH sensor locations. Wpnuts, in approaching equilibrium moisture with ambient RH, lost 2% moisture content both storage years. Spnuts lost 1.4% moisture content during storage of both crops. Percentage sound mature kernels (SMK) from Wpnuts decreased by 3.3% during 1994 crop storage and 6.6% during 1995 crop storage. Percentage SMK from Spnuts decreased 2.2 and 6.2% for the two storage years. Percentage sound splits (SS) for the Wpnuts increased 2.2% during 1994 crop storage and 4.2% during the 1995 crop storage. Percentage SS for Spnuts increased 2.4 and 6.1%, respectively. Changes in other grade factors were not consistent comparing percentage values for Wpnuts and Spnuts. Data indicate that maintaining grade and quality during FS peanut storage in west Texas will require knowledge of moisture content of peanuts placed into the warehouse and environmental monitoring in order to determine storage length. For 3- to 5-mo storage, it is recommended that FS peanuts have a moisture content close to 10% when placed into storage for peanuts to be above 7% when unloaded from the warehouse.

Blanching, seed coat removal, is often a processing step in peanut manufacturing but the general peanut industry consensus is that shelf-life reduction occurs as a result of the process. In order to examine the effects of blanching on shelf-life, runner-type peanuts were blanched using total heating time and final temperature in a 3 × 3 factorial experiment. In each of nine treatments, heating began at 32 C and increased incrementally through six heating zones over a total time of 30,45, or 60 min to a final temperature of either 76.7, 87.8, or 98.9 C. Blanched peanuts from each treatment and nonblanched control samples were stored at 26 ± 1C and ambient RH and were sampled over a 28-wk period. Peroxide value (PV) and oxidative stability index (OSI) of blanched and nonblanched peanuts were similar indicating no meaningful shelf-life differences. Descriptive sensory analysis of peanuts roasted when taken from storage indicated no significant differences in intensity of painty and cardboardy descriptors between blanched and nonblanched peanuts. Mean separations of attributes, including roast peanutty, for which significant differences were noted revealed only a weak, inconsistent relationship between descriptor intensities and final blanching temperature.

Peanut maturity has previously been correlated with the color of the mesocarp of the peanut hull going from light to dark as the peanut matures. In this study, peanuts were sorted into maturity classes of yellow, orange A, orange B, brown and black based on the hull scrape method of Williams and Drexler. The Hunter L * , a * , and b * values were also measured on the dry pods for each class. The color of the mesocarp of freshly harvested peanuts was determined using a Hunter colorimeter. Hunter L * , a * , and b * values on individual peanuts, representative of each class using wet and dry hulls, were reproducibly determined with standard deviations of less than 0.8%. Yellow peanut pods had a median L * value of 70.0, while mature black peanut pods had a median L * value of 51.7 and median values for orange A, orange B and brown pods were, 68.0, 63.7, 57.0, respectively. A similar inverse relationship was observed for the b * value and maturity, while the a * value reached a maximum at orange A. No correlation was observed between the peanut maturity and L * , a * , and b * values acquired with the exocarp intact. Hunter L * and b * values of mesocarps show potential for determining physiological maturity of peanuts.

Medium commercial size, runner-type peanuts were heated in an air flow direction-controlled lab scale oven to simulate an industrial multizone dryer used in peanut blanching. Nine blanching protocols consisting of three heating times (30,45, and 60 min) factorially paired with three final oven set point temperatures (76.7, 87.8, and 98.9 C achieved from 32.2 C over six heating zones) were tested for effects on blanchability, moisture content, and temperature variation within individual seed and within the bed of peanuts. Temperature through the peanut bed varied as air flow (76.2 m/min) was reversed in alternating zones. Bed temperature variation during the heating process was highest in the 30-min protocols where the maximum difference between the top and bottom of the bed reached 17.6 C. Temperature variations decreased in the 45- and 60-min protocols; however, maximum differences as high as 8.1 C were consistently found. Bed temperature variation was related to air flow direction with higher temperatures in the peanuts nearest the air/heat source. Peanuts opposite the air flow direction did not reach the desired maximum temperature in the last zone of any protocol. Seed temperature variation was as much as 5 C between the seed surface and 3.14 mm into the seed. Seed moisture decreased from ca. 5.5% to a low of 2.94% in the 60 min/ 98.9 C protocol. Blanchability reached an upper limit of 71 to 75% in the 45- and 60-min protocols at 87.7 C and all of the protocols at 98.9 C. Blanchability was unrelated to magnitude of temperature variation in either seed or within the bed. Blanchability correlated positively with final oven set point temperature and negatively with final moisture content when moisture content was above 3.8%.

Peanut curing studies utilizing stackpole curing led to the unique observation that extensive potential for post harvest maturation exists during slow curing. In the hull scrape maturity profile the percentage of black maturity class pods increased from 15 to 45% and 21 to 57% in ca. 30 d after stacks were prepared in 2 consecutive years. Simultaneously, the number of pods in less mature classes generally decreased. The weight percentage of black pods increased from 19 to 42% and 37 to 62% after 10 stack d in the 2 yr. A similar but less extensive maturity progression was observed in detached pods in a temperature-relative humidity-controlled environment where drying rate was faster than in stackpoles but much slower than in conventional practices. Because pod and seed sizes did not change during stackpole curing, maturation resulted in large increases in the percentage of mature peanuts (maturity distribution) in all commercial grade sizes. Moisture contents for orange and brown maturity classes related to cessation of color change in pods in both stackpoles and controlled environment treatments were about 29.0 and 22.5%, respectively. Occurrence of physiological seed maturation concurrently with hull color progressions was verified by the consistent oleic acid/linoleic acid ratio in medium grade-size peanuts within each maturity class over curing time.

The biochemical composition of seed collected from six landrace accessions of Arachis hypogaea L. subsp. hypogaea var. hirsuta was investigated. Florida-grown runner- (cv. Florunner) and virginia-type (cv. NC 7) seed were used as comparative controls. Fatty acid methyl esters were prepared from hexane-extracted oil and analyzed by gas-liquid chromatography. Oil stability was determined using oxidative stability instrumentation. Tocopherols, free amino acids, and free sugars were analyzed by high-performance liquid chromatography. Total oil content ranged from 36-45% for var. hirsuta seed as compared to 46 and 45% for Florunner and NC 7, respectively. Oleic acid/linoleic acid ratios ranged from 0.76-0.95 for the var. hirsuta peanuts as compared to runner (1.71) and virginia (2.1) controls. Tocopherol levels for var. hirsuta (295-377 ppm in oil) were similar to NC 7 (30 ppm) and lower than Florunner (425 ppm). Oil quality characteristics were reflected in much shorter oil stability index times for var. hirsuta seed (5.9-8.0 hr) compared to Florunner (11.6 hr) and NC 7 (12.9 hr). In general, var. hirsuta peanuts contained more free sugars (141-178 μmol/g defatted meal) and free amino acids (18.5-37.2 μmol/g defatted meal) than Florunner (127 and 20.2 μmol/g defatted meal free sugars and free amino acids, respectively) or NC 7 (122 and 20.3 μmol/g defatted meal).

High performance anion exchange chromatography and pulsed amperometry were used to separate and quantify peanut sugars extracted with methanol: chloroform:water (60:25:15, V/V/V), a highly polar solvent which solubilizes other seed components including amino acids. Free sugars were separated on an anion exchange column using a sodium hydroxide gradient and detected with a pulsed amperometric detector equipped with a gold electrode. Free amino acids in the seed extract interfered with sugar analysis by causing peak shifting and co-elution of some amino acids with sugars. Free arginine co-eluted with inositol resulting in a peak area which was 42% of the actual total area for both compounds. Proline co-eluted with fructose. Serine eluted on the leading edge of sucrose. Peak areas of these interfering amino acids were either “additive” or “subtractive” to sugar peaks. Altering the gradient elution or using cation syringe filters to remove contaminant amino acids permitted the accurate identification and quantification of peanut seed sugars. Results from this study suggest applications that can be applied in other biological systems containing free amino acids and sugars.