Location: Food Science and Market Quality and Handling Research Unit
2022 Annual Report
Objectives
1. Improve peanut flavor, flavor consistency and nutritional composition through integration of novel peanut genetic/genomic resources.
1A. Investigation of peanut composition using targeted and non-targeted analyses to identify compounds and metabolomic pathways of formation related to peanut flavor formation.
1B. Evaluate the flavor and quality characteristics of specific peanut varieties or breeding lines in cooperation with U.S. peanut breeders.
2. Identify commercially-viable bioactive compounds from raw/roasted peanuts and characterize their functional food attributes. [NP306, C1 PS1B]
2A. Evaluate peanut skins as an antimicrobial ingredient in livestock feed.
2B. Determination of the effectiveness of extracts from peanut skins as a natural antioxidant in preventing the onset of rancidity in peanut butter.
3. Enable the commercial use of whole high-oleic peanuts and/or by-products as a livestock (poultry, swine, and aquaculture) feed ingredient.
Approach
The United States peanut industry generates approximately $4.4 billion annually in economic activity. With a value of over one billion dollars at the farm level, the peanut crop ranks twelfth among USA food crops, grown on approximately 7,500 farms with 1.4 billion acres producing over five billion pounds of peanuts in the shell. In addition, the peanut industry is composed of producers, shellers, and manufacturers. These manufacturers produce peanut butter, candies, confections, bakery goods and ingredients for other foods, in addition to snack peanuts. The USA peanut industry is vibrant, but the private sector relies on the USDA-ARS to increase and expand markets through continual improvement of peanuts and peanut products across all segments of the industry, from farm to processors and consumers. This project is one of only two public research programs dedicated to improving the value of the crop by enhancing flavor, nutrition, and post harvest processing using modern food science technology. The specific objectives are: Objective 1, improvement of peanut flavor, flavor consistency and nutritional composition through integration of novel peanut genetic/genomic resources; Objective 2, the identification of commercially-viable bioactive compounds from raw/roasted peanuts and peanut processing waste materials and to characterize their functional food attributes; Objective 3, to enable the commercial use of whole high-oleic peanuts and /or bi-products as a livestock feed ingredient. This research will be accomplished using chemical and molecular biological techniques and methodology as well as sensory analytical techniques.
Progress Report
ARS scientists at Raleigh, North Carolina, believe that with a value of over 1 billion dollars at the farm level, the peanut crop ranks as second only to soybeans in terms of oilseed value. In addition, the peanut industry is composed of producers, shellers, and manufacturers. ARS scientists at Raleigh, North Carolina are focused on addressing issues of flavor, nutrition, processing, and value-added products that are critical to delivering optimized peanut products across all peanut industry segments.
Objective 1A. Samples of peanut cultivars from two of the four market types currently in commercial cultivation were grown, harvested, cured, shelled, and sorted at the USDA-ARS, National Peanut Research Laboratory (NPRL) in Dawson, Georgia. The samples were roasted to a specific roast color. The flavor of the samples was evaluated by the descriptive sensory panel composed of ARS scientific personnel. Using gas chromatography coupled to mass spectroscopy, the volatile and semi-volatile compounds produced by roasting were determined and quantified. This information proved the relationship between roasted peanut flavor impact and specific chemical compounds formed. The precursors to these compounds can now be identified for a possible link to specific genes for maintenance and improvement of roast peanut flavor. This information is a priority of the Peanut Foundation Genomic Initiative, Part II.
Objective 1B. Samples of peanut cultivars in development for seed release during the crop year 2020 were evaluated by ARS scientists in Raleigh, North Carolina. The samples were grown in the United States by public plant breeders participating in the Uniform Peanut Performance Trials and sent to the USDA-ARS, National Peanut Research Laboratory (NPRL) in Dawson, Georgia. After shelling and sizing, the samples were forwarded to ARS scientists in Raleigh, North Carolina. The samples were analyzed for total fat, total protein, moisture content, fatty acid and sugar profiles, and tocopherol content. In addition, the samples were roasted, and the sensory characteristics were determined by a trained sensory panel. The data set was processed and reported to the cooperators and to the program website at the USDA-ARS, NPRL.
Objective 2A. Salmonella is the leading cause of bacterial foodborne zoonoses in humans, making strategies to control bacterial pathogens in poultry essential. Peanut skins, a waste by-product of the peanut blanching industry, contain polyphenolic compounds possessing antimicrobial properties. A poultry feeding trial with broiler chickens using peanut skins as an antibacterial feed additive in the diets of broilers to prevent the proliferation of Salmonella enteritidis (SE) was conducted. One hundred sixty male hatchlings (Ross 308) were randomly assigned to, (1) peanut skin diet without SE inoculation; (2) peanut skin diet and SE inoculation; 3) control diet without SE inoculation; and (4) control diet with SE inoculation. There were no significant differences (P > 0.05) in weekly average pen body weight, total feed consumption, bird weight gain, feed conversion ratio and in SE colony forming units (CFU)/g for the fecal or litter samples or in the feed conversion ratio between the treatment groups, the control fed group inoculated with Salmonella or the peanut skin fed group inoculated with Salmonella. However, for both fecal and litter samples, the group fed the peanut skin diet and inoculated with Salmonella tended (P = 0.1) to have a lower Salmonella CFU/g compared to the control fed group inoculated with Salmonella. Peanut skins may have potential application as an antimicrobial feed additive to reduce the transmission or proliferation of SE in poultry environments or flocks.
Objective 2B. Extracts from peanut skins were encapsulated with maltodextrin to create a free-flowing powder according to methodology previously developed by ARS scientists at Raleigh, North Carolina. Freshly roasted peanuts were obtained within hours of production from an industry cooperator and used to create peanut butter. The peanut skin powder was incorporated into the peanut butter at levels of 0, 0.5, 1.0, 1.5 and 2.0% (w/w). Another set of samples was created in the same way with the addition of peanut skin extracts that had not been encapsulated with maltodextrin. As the controls, untreated peanut butter and peanut butter created with unblanched peanuts (skins on) were prepared. The samples were packed into glass jars, sealed, stored in incubators at 30°C, then removed and sampled at 1-month intervals over a period of 6 months. Each sample, including a control at zero time were analyzed for fatty acid profiles, tocopherols, moisture, peroxide value, hexanal and pentanal content. The samples were also evaluated by a descriptive sensory panel using the standard peanut lexicon. The study was completed, and the resulting data evaluated. A publication was submitted for peer review. This completes this subobjective for the project plan.
Objective 3. Poultry Feeding Trial 1: A layer feeding trial to determine the utilization of whole-in-shell high-oleic peanuts (WPN) and/or unblanched high-oleic peanuts (HOPN) as an alternative feed ingredient for poultry was conducted. Layer hens were randomly assigned to four dietary treatments: a conventional control diet (C1); a diet containing 4% WPN; an 8% HOPN diet; and a conventional control diet containing soy protein isolate (C2). There were no significant differences in body weights or egg weights after 6 weeks. Hens fed the C2 diet produced more total dozen eggs relative to C1 hens over the feeding trial (P < 0.05). Hens fed the C1 diet consumed less total feed relative to the other treatments with the best feed conversion ratio (P < 0.05). There were no differences in egg quality, with the exception of yolk color, with significantly higher yolk color scores in eggs produced from the C1 and C2 treatments relative to the other treatments (P < 0.05). Eggs produced from the HOPN treatment had significantly reduced stearic and linoleic fatty acid levels relative to the other treatments (P < 0.05). Eggs produced from hens fed the WPN diet had significantly greater beta-carotene content relative to eggs from the other treatment groups (P < 0.05). This study suggests that WPN and/or HOPN may be a suitable alternative layer feed ingredient and a dietary means to enrich the eggs produced while not adversely affecting hen performance.
Poultry Feeding Trial 2: The search for locally grown alternative feed ingredients has become a priority over the years to recapture nutrients that could be used for animal feed. This study used 48 Shaver hens aimed to examine feeding an 8% inclusion of HOPN, or a 4% inclusion of whole-in-shell peanuts (WPS), compared to a conventional control (Control) in a 6-week feeding trial using Celite as an indigestible marker. Bodyweights, total feed consumed, total dozens of eggs, and feed conversion ratio were not significantly different between treatments. The apparent metabolizable energy corrected for nitrogen showed significant differences (P < 0.0001) between treatments with the Control and HOPN being higher than WPS. There were no differences between the apparent nitrogen retention of the Control and HOPN groups, however, the WPS apparent nitrogen retention percentage was significantly less than all the other two treatments (P < 0.05). When analyzing the fat digestibility, WPS treatment had the highest fat with the Control being the lowest (P < 0.0001). The apparent protein digestibility of hens fed the Control diet was significantly greater (P < 0.0001) than either treatment, with HOPN being the next highest. The WPS resulted in the lowest digestible protein percentage compared to the other treatments analyzed (P < 0.0001). Feeding HOPN could be beneficial because they have comparable apparent metabolizable energy, apparent nitrogen retention, as well as both apparent fat and protein digestibility to a conventional control diet. It may not be beneficial to feed WPS without supplemental protein and/or energy added to the feed due to lower digestibility values. The impact of this study is the additional validation of peanuts as a viable nutrient rich alternative feed ingredient for layers while opening the potential for greater utilization of peanuts in poultry production with positive economic outcomes for the peanut industry.
Poultry Feeding Trial 3: Peanut skins are a waste by-product generated in the peanut blanching industry. The effect of peanut skins in the diet of egg-producing hens was compared to an unblanched high-oleic peanut diet or an oleic acid oil supplemented diet on performance, egg quality and chemistry. Two hundred commercial hens were randomly assigned to four dietary treatments with five replicates/treatment. The dietary treatments consisted of a conventional control diet, diet containing 24% unblanched high-oleic peanut (HO PN), diet containing 3% peanut skin (PN Skin), and a diet with 2.5% oleic acid fed for 8 weeks. At week 8, hens fed the HO PN diet had significantly reduced body weights relative hens in the control and PN Skin treatments (P < 0.05), while producing fewer total dozen eggs over the 8-week period (P < 0.05). There were no significant differences in the feed conversion ratios between the treatment groups (P > 0.05). Eggs weights were similar between the control and PN Skin treatments at week 2 and 4, while eggs from the PN Skin treatment group were heavier than other treatment groups at week 6 and 8 (P < 0.0001). Eggs from the HO PN treatment group had reduced palmitic and stearic saturated fatty acid in comparison to the other treatment groups, while the fatty acid profile was similar between PN Skin and Control eggs at week 8 (P < 0.0001). This study suggests that feeding egg-producing hens a PN skin supplemented diet does not adversely affect hen performance, shell egg quality or lipid profile.
Accomplishments
1. Phenotyping the composition of heirloom peanut cultivars. It has been suggested that older “heirloom” peanut cultivars have better roasted peanut flavor than those under commercial production at this time. Reintroducing these lines into limited production will provide higher economic value to small producers of peanuts for specific culinary applications. Phenotyping of chemical composition and the sensory characteristics of several peanut cultivars no longer in commercial production was performed by ARS scientists in Raleigh, North Carolina. These lines were found to possess favorable nutrient profiles and higher flavor impact than some cultivars current being produced on the commercial level. This information will aid in bringing some older lines to the attention of specialty users and provide incentives for peanut breeders to reintroduce these cultivars.
2. Value added uses of waste peanut skins. Peanut skins are a waste material from the peanut blanching industry with hundreds of thousands of pounds produced each year with little or no economic value. Their current use as animal feed is limited due to their bitter flavor and astringency. ARS scientists at Raleigh, North Carolina, removed the phenolic compounds responsible for these negative responses using food grade solvents. The resulting material was high in protein and fiber, but without bitter flavors. Studies done in cooperation with Fort Valley State University at Macon, Georgia (an HBCU) showed that the material after extraction was palatable to sheep and that feeding peanut skins increased the quality of the meat and the incorporation of antioxidants.
3. Extracts of peanut skins as functional food ingredients. Phenolic rich extracts from peanut skins that had been encapsulated with maltodextrin to mitigate the bitter flavor and astringency were incorporated into freshly made peanut butter to determine their suitability as a natural source of antioxidants. Although previous research by ARS scientists at Raleigh, North Carolina, had demonstrated that there is little negative flavor impact from the extract when used in foods and that the extracts were able to reduce glycemic response to peanuts in human subjects, the extracts were not able to retard the onset of rancidity in the peanut butter when compared to controls without the additive.
4. Inclusion of peanut skins in the diets of layer hens improves egg fatty acid profiles. The addition of peanut skins to the diet of layer hens at a level of 3% was compared with conventional layer hen diets and those containing 24% skin on (unblanched) high oleic peanuts and those with the addition of 2.5% of high oleic peanut oil. ARS scientists at Raleigh, North Carolina, suggest the inclusion of the peanut skins resulted in heavier egg weights. The inclusion of the whole peanuts in the diets resulted in eggs with lower levels of saturated fatty acids than the other diets. Eggs with lower saturated fatty acid levels would be a healthier alternative than conventional eggs.
5. Inclusion of peanut skins in the diets of newly hatched broiler chickens. The addition of peanut skins to the diets of chickens being raised for meat were compared by ARS scientists at Raleigh, North Carolina, to conventional broiler chicken diets that had been inoculated with Salmonella. The amount of feed consumed, the bird weight, the feed conversion rate and the bacteria load were not different between the study groups. The chickens fed peanut skins did have lower Salmonella levels than the control. Peanut skins may be considered as an antimicrobial feed additive.
Review Publications
Chamberlin, K.D., Grey, T.L., Puppala, N., Holbrook, C.C., Isleib, T.G., Dunne, J., Dean, L.O., Hurdle, N.L., Payton, M.E. 2021. Comparison of field emergence and thermal gradient table germination rates of seed from high oleic and low oleic near isogenic peanut lines. Peanut Science. 48:131-143.
Toomer, O.T., Vu, T.C., Wysocky, R., Moraes, V., Malheiros, R., Anderson, K.E. 2021. The effect of feeding hens a peanut skin-containing diet on hen performance, and shell egg quality and lipid chemistry. Agriculture. 11:894. https://doi.org/10.3390/agriculture11090894.
Toomer, O.T., Vu, T.C., Sanders, E.A., Redhead, A.K., Malheiros, R., Anderson, K.E. 2021. Feeding laying hens a diet containing high-oleic peanuts or oleic acid enriches yolk color and beta-carotene while reducing the saturated fatty acid content in eggs. Agriculture Journal. 11:771. https://doi.org/10.3390/agriculture11080771.
Harding, K.L., Vu, T.C., Wysocky, R., Malheiros, R., Anderson, K., Toomer, O.T. 2021. The effects of feeding whole-in-shell peanut-containing diet on layer performance and the quality and chemistry of eggs produced. Agriculture. 11(11):1176. https://doi.org/10.3390/agriculture11111176.
Redhead, A.K., Azman, N., Nasaruddin, A., Vu, T.C., Santos, F., Malheiros, R., Hussin, A.M., Toomer, O.T. 2021. Peanut skins as a natural antimicrobial feed additive to reduce the transmission of Salmonella in poultry meat produced for human consumption. Journal of Food Protection. 85(10):1479-1487. https://doi.org/10.4315/JFP-21-205.
