Soaking plasma processed chickpea (Cicer arientinum) cultivars

Cold plasma processing has been marched toward becoming one of the proven techno alternatives to thermal food preservation. It was found effective to cause positive alterations in the surface properties of food by etching. The effect of low‐pressure cold plasma on the percent moisture absorption of six chickpea cultivars, namely, Kripa, Virat, Vishal, Vijay, Digvijay, and Rajas, was studied. For plasma treatment, low‐pressure glow discharge plasma with bell‐jar symmetry was employed. The samples were treated with plasma at 40, 50, and 60 W each for 10, 15, and 20 min. These were soaked in distilled water and 1% sodium bicarbonate solution at room temperature for 8 h. The percent moisture absorption changed significantly (p < 0.05) with an increase in plasma power and treatment time. Kripa had the highest percent moisture absorption (102.07 ± 0.28) and (103.31 ± 0.68) at 60 W 20‐min treatment while Rajas had the lowest percent moisture absorption (78.57 ± 0.81) and (79.44 ± 0.26) at 40 W and 10‐min treatment in distilled water and 1% sodium bicarbonate solution soaking, respectively. The samples treated for 20 min with power 60 W showed higher moisture absorption for all the chickpea cultivars. The percent moisture absorption in control samples soaked in 1% sodium bicarbonate solution was higher than in distilled water. The same pattern did not repeat in the plasma‐treated samples. The findings in this research will be useful for designing the soaking process for different cultivars of plasma‐treated legumes.

tion of edible oils, food allergy prevention, inactivation of antinutritional factors, seed germination efficiency adjustment, and effluent control (Ekezie et al., 2017). Effects of cold plasma on the seed moisture absorption have been studied by many authors (Dobrin et al., 2015;Guo et al., 2018;Li et al., 2017;Rahman et al., 2018;Roy et al., 2018;Sera et al., 2010;Sera & Sery, 2018). Ling et al. (2014) showed that plasma treatment had positive effects on seed germination and seedling growth. Physico-chemical properties of low-pressure plasma treated black gram were studied by Sarangapani et al. (2017). However, there is a scarcity of studies on the soaking characteristics of different chickpea cultivars treated with plasma processing.
Grain legumes not only occupy an important place in human nutrition, but these are the indispensable pillars of sustainable agriculture through the mechanism of increasing the fertility of the soil. Chickpea (Cicer arietinum) is the largest food legume produced in South Asia (Gaur et al., 2010). India secured the first position in chickpea production in the world with about 70% area and 67% production (FAOSTAT, 2019). Usually, legumes are soaked then cooked or else soaked then germinated or else soaked, germinated, and cooked to make them edible through softening and increasing the nutrient availability and decreasing antinutrients. Also, chickpea is soaked and cooked before processing into different products in the food industries. During soaking, the water enters into the starch granules and protein fractions of beans. This facilitates gelatinization and protein denaturation and seed gets soften (Siddiq & Uebersax, 2012). Chickpea is known to be a difficult legume to cook.
The soaking is a time-consuming step, and to reduce it, attempts were made (Kon et al., 1973;Rockland & Metzler, 1967). Dried legumes are to be cooked or if they are soaked previous to cooking sodium bicarbonate and also washing soda are sometimes added in small quantities to the soaking or cooking water. This treatment softens the water and so tends to reduce soaking and cooking time (Abel, 1900).
Soaking legumes in water before cooking also takes a long time to cook, while soaking in sodium bicarbonate (NaHCO 3 ) solution causes faster cooking and improves protein digestibility for some legumes (Vijayakumari et al., 2007). Bede (2007) studied the effects of quenching on cook ability of some food legumes.
Plasma processing got much importance nowadays in food processing. The current investigation aimed to research the effects of plasma processing on soaked moisture absorption of six chickpea cultivars with soaking in distilled water and 1% sodium bicarbonate solution. The findings in this research will be further helpful to design the soaking process of plasma-treated legumes.

| Materials
Chickpea samples were procured from Mahatma Phule Krishi Vidyapeeth, Rahuri. The analytical grade chemicals needed were procured from S. D. fine chemicals and Hi-Media, Mumbai, India.
2.2 | Low-pressure glow discharge plasma system and plasma treatment An in-house designed low-pressure glow discharge plasma with belljar symmetry was employed for plasma treatment. The reactor walls were made of 3-mm-thick Pyrex glass, 120 mm in height, and 300 mm in internal diameter. The base of the plasma reactor and the opening lid were made up of stainless steel. The electrodes were made up of aluminum, of 20-cm diameter. Through the Wilson seals on these plates, the electrodes were connected. The electrode distance inside the reactor was maintained at 3 cm during all the plasma treatments. A radio frequency power source with a frequency of 13.56 MHz is capacitively coupled to the device. The system pressure was initially achieved at 0.05 mBar with samples in the system by using HHV vacuum pump ED-20, and the working pressure was adjusted to an optimized value of 0.5 mBar. In this plasma reactor, the plasma glow was observed as shown in Figure 1. The plasma treatment on chickpea cultivars was carried out at 40, 50, and 60 W each having an exposure time of 10, 15, and 20 min.

| Soaking of chickpea cultivars
Approximately 8-g chickpea samples were taken into a beaker. About 50 ml of distilled water or 1% sodium bicarbonate (NaHCO 3 ) solution was added to it and kept at room temperature. After an interval of an hour, chickpea samples were taken out and blotted on a filter paper until the surface moisture gets removed. It was weighed and returned to the beaker. The percentage of moisture absorbed was calculated on a dry basis (Turhan et al., 2002).

| Statistical analysis
The findings were statistically analyzed using SPSS (IBM statistical analysis version 19) using one-way analysis of variance (ANOVA). The significance between the samples was compared at p < 0.05 where the least significant difference was tested by the post hoc and Duncan test. The averages from three different studies were presented in all of the findings.

| Effects of plasma treatment on soaking of chickpea cultivars in distilled water
There was a significant difference (p < 0.05) in moisture absorbed in distilled water soaking by the control sample and plasma treated samples in all the chickpea cultivars (Table 1). In control samples, the increase in moisture absorption was found lowest in Kripa and highest in Virat after 8 h of soaking (Table 1). The contact angle quantifies the wettability of a solid surface by a liquid. Dobrin et al. (2015) worked on the wheat grain; they found that in the case of the plasma untreated grains, the contact angle measured between grain surface and water drop was high, and in the treated grains, it decreased. They reported that after 12 min of plasma treatment, the best water absorption effect was found to be 27% greater than in untreated samples. A major precondition for faster seed wetting and germination is thus surface wetting (Sera & Sery, 2018). The samples exposed to 40-, 50-, and 60-W power for 10, 15, and 20 min found a significant difference (p < 0.05) in moisture absorbed during soaking in distilled water in all the chickpea cultivars.
The percent water absorption was in the range 78.57%-99.78%, 83.78%-102.07%, and 83.93%-102.15%, respectively, for 40, 50, and 60 W in distilled water soaking. The moisture absorption was lowest at power 40 W for 10-min treatment in all the chickpea cultivars during soaking in distilled water, while it was highest at power 60 W for 20-min treatment. The increase in moisture absorption was highest in Kripa with 60 W and 20-min treatment, and it was lowest T A B L E 1 Percent water absorption (db) of plasma-treated chickpea cultivars after soaking in distilled water and 1% sodium bicarbonate (NaHCO 3 ) solution

Cultivar
Time ( Bede (2007) used quenching process in cowpea seeds where those were subjected to different degrees of thermal shock through rapidly cooling them from the boiling point by adding water at lower temperatures. They reported that this has been created cracks in the cowpea seeds. Moreover, they added that this cracking of seeds lead to the facilitation of water permeation into the seed and further it made heat transmission into the core of the seed easier during cooking.
The work carried out by the researchers' states that the nonthermal plasma treatment caused crack formation on the surface of wheat grain, which increased water absorption and subsequently benefited in its germination (Sera et al., 2010). They found the mean water absorption to be 41% in the control sample, while it was 57% in the plasma-exposed sample (Guo et al., 2018). The results in the present investigation are comparable with these findings as well as findings of researchers who worked on the cooking of rice, where in later it was shown that low-pressure plasma was efficient to reduce the time required for cooking brown rice, long-grain brown rice, basmati rice, and parboiled rice and improved the functional properties of basmati rice flour. Reduction in cooking time and cooking properties was due to the significant increase in water uptake due to etching of the surface and increased surface energy of rice (Chen, 2014;Thirumdas et al., 2015;Sarangapani et al., 2015;Thirumdas et al., 2016). Sarangapani et al. (2017) observed scanning electron micro-graphs to confirm that plasma treatment resulted in surface etching and hydrophilization of seed surface, which allowed easy absorption of water in black gram. They showed that plasma treatment decreased the contact angle and increased the surface free energy. The increased water absorption with an increase in plasma power and treatment time in our case also confirms that this might be due to the surface etching and also because of decreased contact angle and increased surface free energy.

| Effects of plasma treatment on soaking of chickpea cultivars in 1% NaHCO 3 solution
There was a significant difference (p < 0.05) in moisture absorbed in 1% sodium bicarbonate solution soaking by the control sample and plasma treated samples in all the chickpea cultivars (Table 1). In control samples, the increase in moisture absorption was found lowest in Digvijay and highest in Virat after 8 h of soaking (Table 1) were compared during soaking in 1% NaHCO 3 solution (Table 1). Rahman et al. (2018) suggested that in wheat grains, which were exposed to the plasma, the surface was much rougher than that of control grains. They further added that after the plasma application, the grain coat becomes eroded and chapped.
The percent water absorption in control samples soaked in 1% sodium bicarbonate solution was higher than in distilled water. The same pattern was not repeated in the plasma treated samples. Plasma treated samples were found lacking in moisture absorption in 1% NaHCO 3 solution as compared to soaking in distilled water. This may be due to the etching, erosion of the surface of treated chickpea samples. In NaHCO 3 solution, there may be more water absorption taken place, but due to the plasma driven seed surface erosion, the absorbed moisture may get leached. It may be due to the surface etching of these samples, which causes leaching loss of moisture absorbed by these plasma treated samples (Thirumdas et al., 2016).
Similar findings were reported by Sabularse et al. (1991) during their studies on the effects of gamma radiation on brown rice cooking efficiency. This suggested that there is an increase in cooking loss in plasma-treated samples compared to control samples, which may be due to the plasma species' degradation of starch molecules. The broken starch particles are easily leached into the surrounding water during the cooking process. Filatova et al. (2014) also shown that active plasma particles produced a change in the seed coat morphology of cereal and legume seeds, which played a significant role in improving the rate of moisture absorption as it occurred in the present experiment.

| CONCLUSION
Looking at the all-round effects of plasma in food processing, the coming era seems to be the era of cold plasma technology. Plasma treatment increased moisture absorption significantly with an increase in plasma treatment power and time for all the six chickpea cultivars in distilled water and 1% sodium bicarbonate solution. The moisture absorption in control samples soaked in 1% sodium bicarbonate solution was found higher as compared to samples soaked in distilled water. The moisture absorption in plasma-treated samples soaked in 1% sodium bicarbonate solution was found less than soaking in distilled water. The major concern in the use of pulses is its long soaking and cooking time. Considering the positive effects of cold plasma on moisture absorption by chickpea, these results will surely help to save time and energy in soaking and consequent cooking of the whole chickpea.

ACKNOWLEDGMENTS
The effort of the Pulses Improvement Project, MPKV, Rahuri, is acknowledged and appreciated for the provision of chickpea cultivars used for this research. The study was self-funded.

CONFLICT OF INTEREST
There is no conflict of interest in the authors.

ETHICS STATEMENT
I hereby declare that this manuscript has not been published elsewhere, there is no conflict of interest, and all co-authors met the criteria for authorship. The study does not require any ethical approval. If any error is subsequently found in the manuscript, I will inform the journal.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author upon reasonable request.