Extraction of ultra-low gossypol protein from cottonseed: Characterization based on antioxidant activity, structural morphology and functional group analysis

Abstract

Cottonseed can be considered as a potential candidate to act as an important protein source. However, toxic compound “gossypol” is the main hurdle in utilization of this potential source of protein. The current study aims to optimize the extraction of cottonseed protein isolate (CSPI) from defatted cottonseed meal (CSM) using Box-Behnken design (BBD) with ultra-low gossypol concentration (ULGC, <0.1 μg/mg or 100 ppm) which is under the allowable limits of 600 ppm as per United Nations Food and Agriculture Organization and World Health Organization for application in foods. Results indicate that obtained optimal conditions for the recovery of protein from CSM were alkali: sample ratio (33:1), NaCl (0.15 mol/L), Na2SO3 (0.27%) and time (147.5 min) at pH 11 with predicted value of 93.6% protein recovery. Wet-lab confirmed that experimental yield of CSPI was 88.5% with 29.0 ppm of free gossypol concentration. CSPI was analysed for the physicochemical characteristics and found to have balanced ratio of essential and non-essential amino acids using HPLC. Functional group analysis, antioxidant activity, molecular weight distribution and microstructure confirmed various structural features of the isolated protein. Hence, the resultant CSPI can be utilized as a feed supplement for monogastric animals and food supplement for human beings.