Research Project: Reducing Postharvest Loss and Improving Fresh Produce Marketability and Nutritive Values through Technological Innovations and Process Optimization

Location: Food Quality Laboratory

2021 Annual Report

Objectives
Objective 1. Enhance key organoleptic and nutritional qualities of major horticultural crops using emerging production and post-harvest handling practices. Sub-obj. 1A. Improve food quality and nutrition, and harvesting efficiency for vegetables grown via controlled environment agriculture (CEA). Sub-obj. 1B. Develop novel technologies to support NASA’s mission in growing microgreens in space. Objective 2. Reduce post-harvest loss and waste and enhance marketability of fresh produce. Sub-obj. 2A. Non-destructive monitoring of produce quality and maturity via a paper sensor. Sub-obj. 2B. Improve quality and shelf life of fresh produce through collaborative breeding and cultivar selection. Objective 3. Improve product quality and sustainability through novel fresh-cut processing technologies and process optimization. Sub-obj. 3A. Develop novel fresh-cut produce wash and disinfection technologies for comprehensive improvement in food quality and safety. Sub-obj. 3B. Determine chemical profile of fresh-cut produce wash water in support of cost-effective water treatment and reuse. Objective 4. Enable new or refine commercial viscometry, spectroscopic imaging, and physical technologies that integrate indicators of wheat endosperm integrity.

Approach
This project takes an integrated and holistic approach to tackle major food security problems by supporting efficient growth and harvesting of nutrient-dense food products and reducing post-harvest food loss and waste. This project consists three objectives. In objective 1, we will investigate the effect of light wavelength, intensity, and photoperiod on the growth, sensorial quality, and phytonutrient content of specialty vegetables. We will develop mechanical devices to facilitate harvesting of microgreens while minimizing tissue damage. We will also develop and/or evaluate soil mixes and soil-less growth media for seed fixation in microgravity. In objective 2, our team of scientists will collaborate with ARS breeders to identify lettuce cultivars resistant to enzymatic browning and having improved post-harvest quality and shelf life. We will continue collaborating with our university partner (and co-inventor) to advance our patent-pending paper sensor array for nondestructive quality evaluation. In objective 3, we will work with our industry partners to further develop, optimize, and commercialize our patented produce washing and disinfection technology. We will develop and optimize a novel in-flight washing system to improve the food quality and safety of fresh-cut products. This will be a continuation and expansion of the patented in-flight washing technology developed under a previous project. We will also investigate the major chemical components of fresh-cut produce wash water and develop approaches to support safe and cost-effective water reuse. Specifically, we will identify major compounds present in produce; their release during cutting; their reactivity with free chlorine during different washing stages; how such reaction contributes to the loss of free chlorine in wash water, and to difficulties in maintaining adequate chlorine levels; the type and amount of harmful disinfectant byproducts thus produced during washing; and effective methods to remove or mitigate the chemical oxygen demand (COD) and chlorine demand (CLD) in wash water during fresh-cut processing.

Progress Report
In light of the pandemic-related facility access restriction to the fresh-cut processing pilot plant (essential for Objective 3), we creatively shifted the research focus to Objectives 1 and 2. We completed some of these milestones ahead of schedule. We developed a novel hydrogel-based "artificial soil" and demonstrated the feasibility of growing microgreens to full maturity (up to 14 days) without frequent watering. The following are major items achieved in FY2021: 1) Conceptualized and developed a novel hydrogel-based growth substrate for microgreen production (up to 14 days) without ongoing watering. In addition, we also investigated the effect of dynamic lighting conditions on the quality and nutrition of vegetables. We conducted phenotypic characterization and inheritance of browning of lettuce stem and ribs. See accomplishment reports for details. 2) Established a close partnership with leading urban vertical farming industry members (AeroFarms, Sensei Farms, and Plenty) and provide a preliminary assessment of product quality and nutrition of leafy vegetables grown in a commercial setting using controlled environment agriculture (CEA) practices. The nutritional aspects we evaluated include an abundance of health-promoting compounds (ascorbic acid, glucosinolates, and flavonoids) of a diversity of aeroponically grown micro-and baby greens (arugula, watercress, mustard, and kale, etc.). Results revealed significant dry weight and vitamin C contents variations between plant species, growth stages, and CEA conditions. Since data comparing sensorial qualities and phytochemical composition of CEA growth conditions is lacking, our findings will support the CEA industry in evidence-based marketing and product improvement and inform consumer understanding of these products. 3) Enzymatic browning is a major postharvest quality defect of romaine lettuce and is pervasive on the cut surfaces of leaf ribs and stems. A Food Technologist in Beltsville, Maryland, and a Geneticist in Salinas, California, collaboratively investigated the relationship between the browning of leaf ribs and stems across major cultivars. Research findings revealed, for the first time, a strong correlation between stem and leaf browning, which led to the development of a new way to predict browning in leaf ribs (difficult to measure) via measurement on the stems (easier to measure). The new method simplifies the lettuce cultivar screening procedure, thus allowing researchers to breed browning resistant cultivars and decipher the genetics of lettuce browning more efficiently. Moreover, quantitative trait locus broad sense heritability analyses indicated that both genetic and non-genetic factors contribute to the variation of browning among the cultivars studied. Such findings lay the groundwork for further investigation on the interplay of genetic and environmental factors during lettuce breeding. Information on browning resistant cultivars is also used by the CEA industry to select optimum lettuce cultivars for indoor and hydroponic production of ready-to-eat baby leafy vegetables. 4) Designed and fabricated a 2D clinostat with unique features to accommodate microgreen growth under simulated microgravity. This system is currently used by a colleague at FQL. It has significantly advanced the unit's research capacity in addressing major challenges in microgreen growth on the international space station, a key challenge encountered by NASA and one of the main tasks in our ARS-NASA interagency MU.

Accomplishments
1. A Novel Hydrogel-based Artificial Soil to Support Microgreen Growth without Frequent Watering. Feeding the increasing world population with shrinking arable land and water resources requires novel alternatives to soil-based cultivation systems and creative solutions to minimize water usage. Our ARS research team in Beltsville, Maryland, developed a biodegradable, hydrogel-based "artificial soil" that contributed to water conservation and labor reduction. By improving water retention/delivery and root zone aeration, this new technology supports a full 14-day growth cycle for red cabbage microgreens, yielding a growth rate comparable to conventional methods without ongoing watering, a significant improvement over current practice. Enthusiastic feedback from the urban farming industry suggested additional potential applications, including facilitating live plant shipping and user-friendly vegetable growth kits for health-conscious consumers and novice urban farmers.

2. Enhancing key organoleptic and nutritional qualities of leafy vegetables by manipulating LED lighting. Red or purple leafy vegetables have high market demand as they visually complement other salad greens and are rich in anthocyanins, a family of health-promoting flavonoid phytochemicals. However, due to the uncontrolled lighting conditions. In collaboration with our industry partner, ARS scientists in Beltsville, Maryland, investigated the effect of the LED lighting conditions on the growth profile of red cabbage microgreens and ruby-red mustard and showed a significant increase in red color in red cabbage and a 200 percent increase in anthocyanin concentration in red mustard microgreens. We also found that manipulating artificial lighting during different growth stages precisely controlled the plant's morphological development, increased the nutrients, and produced desirable taste quality. Our findings lay out the knowledge base critical for future light recipes for leafy vegetables' targeted quality and nutrition traits while minimizing energy consumption.

4. A new way to conduct sensory evaluations. Traditionally, food quality is evaluated by human inspection, complemented by physical (texture)-chemical analyses. This multi-dimensional and comprehensive approach is ideal; however, it is time-consuming, labor-intensive, and expensive. Our recent research found that by examining a well-constructed digital image of a fruit, consumers could qualitatively determine the actual, authentic physical appearance of the same fruit with only a small quantitative score difference. This finding revealed the significance of utilizing digital images for sensory panels. This new method will further allow our investigators to use artificial intelligence (machine learning) by generating a vast amount of data, enabling an automation for predicting consumers' choices and guiding the marketability of fresh produce. To strengthen this work across all the objectives of the projects, our team acquired a 3-D Robot image capture system with photo/lightbox and image processing software.

Review Publications
Lu, Y., Dongg, W., Yang, T., Luo, Y., Chen, P., Wang, Q. 2021. Pre-harvest UV-B applications increases glucosinolate contents and enhances the postharvest quality of broccoli microgreen. Molecules. 26:3247. https://doi.org/10.3390/molecules26113247.
Huang, R., Vaze, N., Soorneedi, A., Moore, M., Luo, Y., Poverenov, E., Rodov, V., Demokritou, P. 2020. A novel antimicrobial technology to enhance food safety and quality of leafy vegetables using engineered water nanostructures. Environmental Science: Nano. 8:514-526. https://doi.org//10.1039/D0EN00814A.
Zhen, J., Luo, Y., Wang, D., Dinh, Q., Lin, S., Sharma, A., Block, E.M., Yang, M., Gu, T., Pearlstein, A.J., Yu, H., Zhang, B. 2021. Nondestructive multiplex detection of foodborne pathogens with background microflora and symbiosis using a paper chromogenic array and advanced neural network. Biosensors and Bioelectronics. 183:113209. https://doi.org/10.1016/j.bios.2021.113209.
Mei, L., Zhang, F., Zhang, J., Li, Y., Liu, Y., Luo, Y., Wang, Q. 2020. Alkynyl silver modified chitosan as a novel antimicrobial coating material for potential food applications. Carbohydrate Polymers. 254:117416. https://doi.org/10.1016/j.carbpol.2020.117416.
Nong, W., Guan, W., Yin, Y., Lu, C., Wang, Q., Luo, Y., Zhang, B., Wu, J., Guan, Y. 2021. Photothermal metal-organic framework nano-generators for non-contact microorganism inactivation. Advanced Functional Materials. https://doi.org/10.1016/j.cej.2021.129874.
Teng, Z., Luo, Y., Zhou, B., Wang, Q., Hapeman, C.J. 2021. Characterization and mitigation of chemical oxygen demand and chlorine demand from fresh produce wash water. Food Control. 127:1008112. https://doi.org/10.1016/j.foodcont.2021.108112.
Brecht, J., Xie, Y., Abrahan, C., Bornhorst, E., Luo, Y., Monge-Brenes, A., Vorst, K., Brown, W. 2020. Improving temperature management and retaining quality of freshcut leafy greens by retrofitting open refrigerated retail display cases with doors. Journal of Food Engineering. https://doi.org/10.1016/j.jfoodeng.2020.110271.
Liu, X., Yang, M., Luo, Y., Wang, S., Zhou, B., Teng, Z., Dillow, H., Gu, T., Reed, K., Sharm, A., Jia, Z., Yu, H., Zhang, B. 2021. Machine learning-enabled non-destructive paper chromogenic array detection of multiplexed viable pathogens on food. Nature Food. 2:110-117. https://www.x-mol.com/paperRedirect/1362513694001762304.
Zhou, B., Luo, Y., Teng, Z., Millner, P.D., Pearlstein, A. 2020. A novel in-flight washing system on bacterial reduction and quality of fresh-cut lettuce. Food Control. https://doi.org/10.1016/j.foodcont.2020.107538.
Zhou, B., Luo, Y., Teng, Z., Nou, X., Millner, P.D. 2022. Factors impacting water quality and microbiota during simulated dump tank wash of grape tomatoes. Journal of Food Protection. 84:695-703. https://doi.org/10.4315/JFP-20-343.