Location: Healthy Processed Foods Research
2022 Annual Report
Objectives
Objective 1: Enable commercially-viable new technologies to detect and mitigate contaminants or defective products from food streams.
• Sub-objective 1A: Investigate x-ray as an alternative to gamma for food irradiation.
• Sub-objective 1B: Detect and mitigate fruit fly infestation in olives.
• Sub-objective 1C: Develop real-time non-destructive analysis of vanilla for adulteration.
Objective 2: Utilize advanced analytical and sensory methods to detect, identify, and quantify desirable and undesirable odors and taste defects in raw and processed foods.
• Sub-objective 2A: Identify compounds in raw and processed specialty crops including peas and grapes that impact flavor and taste. Identify precursors (and eventually pathways) of these compounds and study flavor variation in different varieties.
• Sub-objective 2B: Evaluate almond hulls for use in natural sweeteners or as a supplement to bee diets. Investigate the effects of almond hull phenolics on the acceptability of almond hull sugars in bee diets.
Objective 3: Develop commercially-marketable novel, value-added cereal-based healthy, tasty food products.
• Sub-objective 3A: Utilize oil seed (canola, sunflower and cotton) waste products to produce gluten-free, high protein flatbreads, snacks and pasta and evaluate for consumer acceptance.
Approach
1A: Baby spinach will be used to see if x-ray can replace gamma for food irradiation. The spinach will be inoculated with Shiga toxin-producing E. coli (STEC) strains and irradiated under x-ray and gamma irradiation. Pathogen populations will be monitored by plate count for differences between treatments of dose vs. population reduction. Should spinach not tolerate irradiation well a different commodity will be used. Other pathogens could also be studied, including Salmonella and Listeria.
1B: X-ray imaging and NIR spectroscopy will be evaluated for detection of olives infested with fruit flies. An olive fly colony will be established on-site for generation of infested samples. Film x-ray images will be acquired and digitized, and NIR spectra acquired. Chemometrics, neural network, discriminant analysis, and k nearest neighbor algorithms will be employed.
1C: NIR spectroscopy will be used to quantify coumarin and ethyl vanillin adulterations in vanilla extracts. Vanilla samples will be diluted using CMR, and NIR spectra obtained. Calibration equations for quantitative prediction will be developed. Collaborators will provide samples of vanilla extract processed using the method of green drying which bypasses the traditional curing process. NIR spectra will be acquired and calibrations developed to differentiate between vanilla extract processed under green drying vs. the traditional manner. Should the high ethanol and water concentrations in vanilla extract and concentrate make it impossible to obtain reliable calibrations, evaporation techniques will be developed to remove the ethanol and water and the remaining residue will be used to acquire spectra.
2A: Flavor compounds in peas and grapes will be quantified, precursors identified, and flavor variation studied between varieties. Pea protein will be produced from pea flour under spray drying and drum drying with different time and temperature conditions, and Grosch’s method of flavor analysis will be applied along with identification and quantification of saponins in pea flour and protein. GC-MS spectra will be matched to those in established libraries to identify food constituents. Aroma models will be compared with the food products by sensory panels.
2B: Sugars will be eluted from almond hulls using water and their composition determined by HPLC. Anthocyanins, flavonols, and hydroxycinnamates will be identified by comparison of retention times and UV/Vis spectra of unknown peaks with those of authentic standards. Weight and total phenolic content will be determined for each extract. Bee diet samples will be developed using a 25 °Brix solution of almond hull extract.
3A: Canola, sunflower and cotton seeds will be used to produce gluten-free products with high protein content and consumer acceptance. Various formulations of gluten-free cereal flours, seed meal vegetables and “condiments” will be used to produce pasta, snacks, and flatbread and presented to sensory panels. Proximate analysis will be applied to measure protein, fat, ash and moisture at each stage of processing. Those products that form crust (flatbreads and snacks) will be evaluated for acrylamide levels using LC-MS.
Progress Report
In support of Sub-objective 1A, a new x-ray-based irradiator has been constructed allowing near uniform dose distribution across thin samples. Samples in Ziploc bags or vacuum sealed are attached to the surface of a rotating drum adjacent to two strategically situated line scan x-ray tubes. The novel configuration is ideal for irradiating thin samples such as powders (i.e., vanilla powder), seeds, and leafy greens such as baby spinach. Irradiation experiments with baby spinach inoculated with Shiga toxin-producing Escherichia coli (STEC) are underway.
In support of Sub-objective 1B, x-ray imaging and acquisition of near-infrared (NIR) spectra of infested olives is underway. Maintaining the olive fly colony year-round has been very challenging, as has obtaining fresh olive samples in the off season. With the new season beginning by August, we anticipate processing the rest of the required samples by the end of the season.
In support of Sub-objective 1C, protocols have been investigated for inoculation of vanilla samples to mimic adulteration with coumarin and ethyl vanillin. However, due to lack of on-site staff, the process of acquiring NIR spectra has not yet begun.
In support of Sub-objective 2, a sample preparation method and a high-performance liquid chromatography (HPLC) method were developed to determine the composition of phenolics in almond hull extracts. These methods were developed to determine the efficacy of treatments designed to reduce the amount of phenolics in almond hull extracts. Phenolics reduce the feeding behavior of bees and their concentration must be reduced for product acceptance. Development of almond hull extracts suitable for bee diets will benefit almond growers, apiarists, and farmers.
In support of Sub-objective 3A, various formulations of gluten-free cereal flours and seed meal vegetables were used as basic ingredients for dough processed into flatbread. Proximate analysis on ingredients is largely complete. Sensory panels have been delayed due to maximized telework posture and Covid protocols.
Accomplishments
1. Phenolic composition of table grapes. Grapes are an important source of phenolics in the American diet and an important agricultural product with 1.11 million tons produced in California in 2020, valued at $1.46 billion. ARS researchers in Albany, California, investigated the phenolic composition of three commercial white-skinned table grape cultivars and six white-skinned table grape accessions. Trans-Caftaric acid was the predominant compound in all samples, with some accessions exhibiting much higher concentrations than others. These accessions with high phenolic concentrations represent new commercial, white-skinned table grapes with improved nutritional properties.
Review Publications
Li, X., Kahlon, T.S., Wang, S.C., Friedman, M. 2021. Low acrylamide flatbreads from colored corn and other flours. Foods. 10(10). Article 2495. https://doi.org/10.3390/foods10102495.
Li, X., Kahlon, T.S., Wang, S.C., Friedman, M. 2021. Low acrylamide flatbreads prepared from colored rice flours and relationship to asparagine and proximate content of flours and flatbreads. Foods. 10(12). Article 2909. https://doi.org/10.3390/foods10122909.
