Location: Healthy Processed Foods Research
2017 Annual Report
Objectives
The long-term goal of this project is to develop novel methods, and define measure and mitigate attributes that adversely impact the quality of foods. Specifically, during the next five years we will focus on the following objectives:
Objective 1: Enable novel commercial methods for prevention or removal of defects and contaminants in foods.
• Subobjective 1A: Develop techniques for detection and removal of potatoes affected by Zebra Chip disorder from the processing line.
• Subobjective 1B: Develop X-ray based alternatives to radioisotopes for irradiation.
Objective 2: Integrate physical, chemical, sensory, and biological changes from raw and commercially processed food products, including, olives and grapes.
• Subobjective 2A: Pinpoint and identify impact aroma compounds of raw materials and commercially processed products from specialty crops including grapes and olives using gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Identify precursors (and eventually pathways) of such impact aroma compounds and study flavor variation in different varieties.
• Subobjective 2B: Isolate and characterize phytonutrients in raw materials and food products from grapes, olives, and other specialty crops. Determine the effects of processing on the levels of these constituents and also monitor changes in biological activity (i.e., antioxidant activity).
Objective 3: Integrate measurable allergenic properties with methods to mitigate food allergens in nuts and dairy.
• Subobjective 3A: Identify, characterize, and develop methods for the detection of food allergens in tree nut and other foods.
• Subobjective 3B: Investigate and differentiate allergen cross-reactivity and multi-sensitization and study the effects of processing methodologies on allergenicity.
Approach
1A: Acquire x-ray images and NIR spectra from whole potatoes (reflection) and through slices (transmission). Analyze slices for moisture and sugar, followed by frying and color evaluation. Develop calibration equations for prediction of Zebra Chip (ZC), moisture content, sucrose, and glucose and investigate correlations between ZC and moisture and/or sugar. Isolate appropriate subsets of NIR absorbance values as input features for standard statistical classification techniques. Test appropriate optics that can measure absorption at the determined wavelengths for the ability to evaluate ZC. Observe x-ray images for differences between potato classes and develop detection algorithms. 1B: Design, build, and test x-ray based irradiation units was alternatives to traditional gamma based units using two technologies: traditional x-ray tubes and a higher power prototype x-ray emitter system.
2A: Extract aroma compounds from grapes and olives using GC. Identify precursors and study flavor variation in plant varieties. Have judges evaluate ability to detect odor from each compound’s effluent from a GC column, with compounds detected in the most dilute sample considered to be impact aroma compounds. Identify acquired capillary GC-MS spectra using established libraries to identify food constituents. Quantify food constituents by GC-MS by comparing the areas of characteristic mass fragment ions of the compounds with that of 2-undecanone (m/z 170). Calculate odor activity values by dividing the determined concentrations by their odor thresholds. For confirmation, compare synthetic blends of identified odorants with those of the original raw and processed products using sensory panels.
2B: Extract homogenates from processed and unprocessed food components and analyze using an HPLC-diode array detector. Identify constituents by comparison of retention times and UV/Vis spectra of unknown peaks with those of authentic standards and verify by HPLC-MS, NMR or IR if necessary. Determine weight and total phenolic content for each homogenate. Evaluate antioxidant activity by the DPPH and ABTS procedures. Determine effects of processing by comparison.
3A: Isolate 2S albumins from nuts and express recombinantly to assess their allergenicity using sera from allergic patients. Isolate and express profilin protein for comparative studies. Develop protocols to purify 2S albumin allergens in other nuts including almond, pine nut, coconut, macadamia nut, and optionally chestnut. Determine the peptide sequences by N-terminal peptide sequencing and mass spectrometry. Develop antibody based methods for detecting food allergen and allergic food.
3B: Isolate and clone hazelnut allergens following established protocols. Assay association with serum IgE from patients known to react to peanut and/or hazelnut. Frequency of IgE recognition of allergens will reflect cross-reactivity and multi-sensitization. Process samples by extrusion to investigate processing effects on allergenicity.
Progress Report
Under Subobjective 1A, classification models have been developed with greater than 95% accuracy in identifying affected potatoes based on chemometric analysis of the entire spectra. Statistical models have been applied to the near infrared (NIR) spectra to identify specific discreet wavelengths or wavebands that contribute significantly to the classification. The correlation between Zebra Chip (ZC) and sugar content has been quantified.
In support of Subobjective 1B, X-ray tube based irradiation units have been constructed and their efficacy as a suitable replacement to gamma irradiation for insect sterilization has been demonstrated. The x-ray emitter system is operational and x-ray dose experiments are underway.
Under Subobjective 2A, aroma compounds from various rice varieties were isolated using solid-phase microextraction. Different sample:water ratios and sampling times were studied to maximize extraction of volatiles. Gas chromatography conditions were optimized to achieve desired resolution of aroma compounds.
Related to Subobjective 2B, the phenolic composition of the pomace of four grape varieties, Carignan, Merlot, Cabernet Sauvignon, and Syrah was investigated. Carignan pomace had the highest concentrations of caftaric acid, rutin, quercetin 3-glucoside, kaempferol 3-glucoside and resveratrol. These compounds are important because they have antioxidant properties. Syrah pomace had the highest concentration of gallic acid, while Cabernet Sauvignon pomace had the highest concentration of catechin.
Finally, under Subobjectives 3A and 3B, the coding sequence of 2S albumin from all economically important tree nuts have been synthesized, cloned in a cloning vector and shuffled in the final expression vector and confirmed by DNA sequencing. Two of the 2S albumin have been purified. These experiments will help us identify and characterize tree nut allergens important for human health.
Accomplishments
1. Mesquite flour phenolics identified. Mesquite is the common name in North America for leguminous desert plants of the genus Prosopis that has about 44 species native to North America, South America, Africa, and south Asia. The plant has attracted attention due to its ability to tolerate high temperatures and low rainfall, its capacity to grow in saline soil and its ability to fix nitrogen. Consumption of mesquite-derived foods has been linked to antibacterial, cardioprotective and anti-inflammatory health effects. To better study these health effects there is a need for reliable analytical methods for the characterization of compounds found in mesquite flour-based foods. Researchers in Albany, California successfully employed a liquid chromatography–mass spectrometry method in conjunction with reversed phase and aqueous normal phase chromatography to separate and identify phenolic compounds in mesquite flour. The characterization of phenolics in mesquite flour will be useful for elucidating the beneficial health effects of their consumption.
2. X-ray based insect irradiation. Sterile Insect Technique, in which sterile insects are released into the environment to compete with the wild population, is one important aspect of some Integrated Pest Management programs. Traditional methods for insect irradiation involve the use of radioisotopes, with subsequent complications in terms of dose uniformity, and serious security and environmental issues. Researchers in Albany, California, developed methods allowing irradiation of Navel Orangeworm, a major agricultural pest, with relatively high throughput and dose uniformity using simple x-ray tube based technology. This provides the means for safer and more environmentally friendly insect sterilization, with the potential to increase the use of this valuable tool for insect control.
3. NIR based determination of astringency in persimmons. Different persimmon varieties have different properties in terms of astringency, with some always astringent, some never, and some rather unpredictable. When eaten, astringent foods can cause an unpleasant feeling in the mouth. ARS researchers in Albany, California, developed NIR calibrations that can classify persimmons according to their level of astringency. This allows producers to separate the unpredictable varieties before going to market. This provides the means to construct optical sorting devices based on reflection of light from a limited set of wavelengths that can sort persimmons at high speed.
4. A new walnut allergen (Jug n 4) officially identified. Tree nut (including walnut) allergies are equally as common and dangerous as peanut allergies, affecting millions of Americans and negatively impacting tree nut utilization. Thus, there is an urgent need to define, measure, and mitigate the allergenicity of tree nut (as well as other food) allergens. ARS researchers in Albany, California and their collaborators have identified a new walnut allergen which is now officially designated as Jug n 4 by the World Health Organization and International Union of Immunological Societies Allergen Nomenclature Sub-committee. The identification and characterization of this allergen increases understanding of the allergenicity of foods.
Review Publications
Zhang, Y., Du, W., Fan, Y., Jiang, Y., Lyu, S., Nadeau, K.C., McHugh, T.H. 2016. Identification, characterization, and initial epitope mapping of pine nut allergen Pin k 2. Food Research International. 90:268-274. doi.org/10.1016/j.foodres.2016.10.043.
Young, J.E., Pan, Z., Teh, H., Menon, V., Modereger, B., Pesek, J.H., Matyska, M.T., Dao, L.T., Takeoka, G.R. 2017. Phenolic composition of pomegranate peel extracts using an LC-MS approach with silica hydride columns. Journal of Separation Science. 40(7)1449-1456. doi:10.1002/jssc.201601310.
Zhang, Y., Du, W., Fan, Y., Yi, J., Lyu, S., Nadeau, K.C., Thomas, A.L., McHugh, T.H. 2016. Purification and characterization of black walnut (Juglans nigra) Allergen, Jug n 4. Journal of Agricultural and Food Chemistry. 65(2):454-462.
Young, J.E., Nguyen, T., Ly, C., Jarman, S., Diep, D., Pham, C., Pesek, J.J., Matyska, M.T., Takeoka, G.R. 2017. LC-MS characterization of constituents of mesquite flour. LC GC Europe. 1:18-21.
Sunmonu, M., Chukwu, O., Haff, R.P. 2016. Development of wind operated passive evaporative cooling structures for storage of tomatoes. Arid Zone Journal of Engineering, Technology and Environment. 12:94-102.
Light, D.M., Grant, J., Haff, R.P., Knight, A.L. 2017. Addition of pear ester enhances disruption of mating by female codling moth (Lepidoptera: Tortricidae) in walnut orchards treated with meso dispensers. Environmental Entomology. 46(2):319-327.
Liang, P., Moscetti, R., Massintini, R., Light, D.M., Haff, R.P. 2017. Detection of pits and pit fragments in fresh cherries using near infrared spectroscopy. Near Infrared Spectroscopy Journal. 25(3):196-202. https://doi.org/10.1177/0967033517712130.
Isenberg, S.L., Carter, M.S., Hayes, S.R., Graham, L., Johnson, D., Matthews, T.P., Harden, L.A., Takeoka, G.R., Thomas, J.D., Pirkle, J.L., Johnson, R.C. 2016. Quantification of toxins in soapberry (Sapindaceae) arils: Hypoglycin A and Methylenecyclopropylglycine. Journal of Agricultural and Food Chemistry. 64(27):5607-5613. doi:10.1021/acs.jafc.6b02478.
Fan, Y., Yi, J., Zhang, Y., Wen, Z., Zhao, L. 2016. Physicochemical stability and in vitro bioaccessibility of ß-carotene nanoemulsions stabilized with whey protein-dextran conjugates. Food Hydrocolloids Journal. 63:256-264. doi:10.1016/j.foodhyd.2016.09.008.
Chaiya, J., Slaughter, D., Liang, P., Siwalak, P. 2017. Nondestructive determination of dry matter and soluble solids content in dehydrator onions and garlics using a handheld visible and near infrared instrument. Postharvest Biology and Technology. 133:98-103. doi: 10.1016/j.postharvbio.2017.07.007.
