Cold Plasma Processing of Chickpeas and Lentils Increases Water Transport Into Grains and Results in Softer Texture After Cooking

ABSTRACT Dried legumes require processing before they are soft enough for consumption. This study investigated the use of cold plasma pre‐treatments on chickpea and lentil grains to improve their textural properties after cooking. Low temperature plasma treatments were conducted in a rotating plasma reactor. After plasma treatment, graphs of water uptake showed greatly changed hydration, with quantitative measures of water transport modeled to show substantial increases to both the rate of water entry into the grains and the total amount of water imbibed. When cooked, the measured textural properties (hardness, cohesiveness, chewiness, and resilience) had also changed. Softening of cooked grains after plasma treatment can be explained by the improved water penetration pre‐cooking caused by plasma's ability to etch the outer seed coat of legumes. Surface analysis by scanning electron microscopy (SEM) and x‐ray photoelectron spectroscopy (XPS) indicated changes to the physicochemical properties of the seed coat, with notable removal of waxes, exposure of tissue layers, and surface oxidation. Identical plasma treatments affected the hydration properties of chickpeas and lentils differently. This evidence suggests that the different biological makeup of chickpeas or lentils is important to consider, because the way in which plasma interacts with the outer surfaces (seed coats) of grains can be quite different for different foods. Future studies where plasma is used as a food processing technology will benefit from detailed surface analysis and quantification of water transport coefficients as a robust methodology for understanding how to apply effective plasma treatments.