Modification of Moth Bean Starch Using Mixture of Organic Acids under Dry Heating

Abstract

Moth bean (Vigna aconitifolia) starch is modified in its dry state (110 °C for 8 h, 14% moisture) using various ratios of organic acids (citric acid and stearic acid) in solvent free (solid–solid) reaction mode. Apparent amylose content is observed to increase in organic acid treated starches. Modified starches show lower swelling power than native starch. Scanning electron micrographs display rough granules surface for treated starches. Crystalline polymorphic pattern of moth bean starch is unaffected by organic acid treatment and dry heating. However, relative crystallinity increases after dry modification. Pasting properties indicate reduction following hydrolysis and loss of granular strength. Resistant starch (RS) content increases as an effect of the modification. This novel modification provides different functionality as compared to aqueous protocols and also provides a clean alternative to replace acid hydrolysis process with concentrated mineral acids.

Preparation of Starch Citrates Using Solvent Free Reaction and Comparison with Aqueous and Ethanol Mediated Reactions

“…Starch and citric acid (2.5% w/w) mixture [ 3,18 ] was kneaded and kept in preheated oven at 110 °C for 8 h. Starch was collected as described for the AQ sample and termed DH for dry heating.…”

“…The procedure for the measurement of swelling power and solubility of native and modified starches as mentioned in ref. [3] was utilized.…”

“…Furthermore, such modification can also have additional effects including derivatization and cross‐linking by esterification reactions. [ 3,4 ] So far, treatment of starch with citric acid has been carried out at varying concentrations of citric acid (5–60% w/w), reaction temperatures (30–140 °C), pH (3–6), and reaction times (0.5–16 h). [ 5,6 ] Specifically, high reaction temperatures lead to dehydration of the citric acid to yield anhydride, which has high capability of forming a starch citrate complex resulting in cross‐linking reactions.…”

“…The effects of starch dry heating depend upon a variety of parameters including starch type, granule size and strength, starch chain molecular profiles, crystalline polymorph type, and moisture content. [ 3 ] Among other effects, dry heating can introduce cross‐links and depolymerize the starch [ 14 ] thereby improving the starch process stability.…”

“…[ 17 ] This work is a sequel to our previous work on moth bean starch modification with organic acids under dry heating conditions in solvent free reaction mode. [ 3 ] We carried out reaction of citric acid in solid state dry conditions in direct comparison with modification in alcoholic and aqueous media to assess possible differences in reaction patterns directly head‐to‐head.…”