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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Healthy Processed Foods Research » Research » Publications at this Location » Publication #406125
Research Project: New Technologies and Methodologies for Increasing Quality, Marketability and Value of Food Products and Byproducts

Location: Healthy Processed Foods Research

Title: Upcycling romaine lettuce outer leaves by infrared blanching and hot air drying

Author
item Avena Bustillos, Roberto
item Klausner, Noah
item MILCZAREK, REBECCA - Former ARS Employee
item ALEMAN-HIDALGO, DAVID - Autonomous University Of Sinaloa
item TERAN-CABANILLAS, ELI - Autonomous University Of Sinaloa
item WANG, HONGYE - University Of California, Davis
item WANG, LUXIN - University Of California, Davis
item McHugh, Tara
item Haff, Ronald

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2024
Publication Date: 4/8/2024
Citation: Avena Bustillos, R.D., Klausner, N.M., Milczarek, R., Aleman-Hidalgo, D.M., Teran-Cabanillas, E., Wang, H., Wang, L., McHugh, T.H., Haff, R.P. 2024. Upcycling romaine lettuce outer leaves by infrared blanching and hot air drying. Journal of Food Science. 89(4):1988-2000. https://doi.org/10.1111/1750-3841.16977.
DOI: https://doi.org/10.1111/1750-3841.16977

Interpretive Summary: The study quantified physical parameters, total soluble phenolics, antioxidant activity, cadmium and pesticide residues, and microbial load reduction of powders made using infrared blanching followed by hot air drying of Romaine lettuce hearts and outer leaves and demonstrated that a novel food-grade dried product can be obtained with reduced hot-air drying time to make suitable the upcycling of Romaine lettuce outer leaves that are currently causing environmental soil pollution in the California Salinas Valley.

Technical Abstract: Romaine lettuce (Lactuca sativa L) outer leaves (RLOL), which are typically left in the fields during harvest, provide an excellent opportunity for upcycling. Infrared (IR) blanching of Duquesne RLOL cultivar from a low cadmium soil was used for hot air drying. Drying kinetics and hot air-drying time saving by IR blanching were determined. Physical (moisture, aw, color) and chemical (total soluble phenolics, TSP, and antioxidant capacity, AC) properties of fresh lettuce (outer leaves and heart leaves) were determined. Also, physical (moisture, aw, color, true density, and water vapor isotherms) and chemical (TSP, AC, cadmium, and pesticides residues) properties of dried lettuce powders (outer leaves and heart leaves) were analyzed. TSP, AC, cadmium, and pesticide residues were higher, while moisture content and aw were lower in fresh outer leaves than heart leaves. Hot air-drying reduced TSP and AC to 63.6% and 35.2% respectively while IR dry blanching further reduced TSP and AC to 37.3% and 25.4% respectively in RLOL powders. Otherwise TSC and AC increased 237.2% and 151.3% respectively for not blanched heart leaves powders. Higher increase of TSP than AC in hearts leaves powder may indicate synthesis of phenolics compounds activated by abiotic stresses such as cutting and high temperatures at the initial drying stage. IR blanching resulted in 23% time saving for hot air drying of RLOL. Microbial loads were substantially reduced during drying, although microbial population on outer leaves were more heat resistant. Safe to eat RLOL powders with low cadmium and pesticide residues can be obtained following good agricultural practices.