Effect of Acidified Methanol Modification on Physico Chemical Properties of Black-Eyed Pea (Vigna unguiculata) Starch

Black-eyed pea starch was hydrolyzed using concentrated HCl (36% by weight) at different levels (10-60 mL) in the presence of methanol and the physico-chemical properties of native and acidified methanol modified black-eyed pea starches were compared. Results revealed high recovery (>93%) of acid-alcohol treated black-eyed pea starch upon modification. A drop in swelling power and increase in solubility was also observed during acidified methanol treatment. Acid hydrolysis increased paste clarity and the freeze-thaw stability; however, the trend was found to vary at a specific modification level. Acid thinning of starch revealed significant decrease in gel consistency, sediment volume, water, and oil binding capacity. Disruption of interactions between amylose chains resulted in increased amylose leaching on modification. The X-ray diffraction pattern of black-eyed pea starch was of C-type obtained and with increase in acid concentration the intensity of peak was found to be increased. Increased acid concentration showed significant increase in crystallinity; however, marked loss of crystallinity was observed at an acid level of 40 mL which further increased on acid concentrations of 50 and 60 mL. Also, acid concentration showed significantly improved post-reaction color difference (E) of the modified starches.