Effect of multi factor-assisted extraction (pH, ultrasound, and temperature) of protein from Sacha inchi (Plukenetia volubilis) and its protein quality and functional characteristics

Abstract

Seeds are among the most relevant protein sources worldwide. However, the selection of optimum extraction methods is critical to optimize yields and protein quality. This study assessed the effects of ultrasound (US) (15 min, 1 cycle, 100% amplitude) to assist protein extraction of Sacha inchi (SI) at different pH (7, 9 and 11) and temperatures. Protein extracts were characterized in extraction yield, trypsin inhibitors, molecular weight, aminograms, in vitro protein digestibility (IVDP), protein corrected amino acid score (PDCAAS), and techno-functionality. Results indicated that US and temperature did not improve extraction yields and that pH greatly influenced extraction rate. The alkaline extraction of the SI without US performed at room temperature gave the highest extraction yield (66%), IVPD and yielded a protein with improved essential amino acid profile due to a 3.16-fold increment of tryptophan compared to the original source. The US assisted extraction from SI did not improve yields likely due to the high proportion of easily-extracted albumins. Furthermore, the SI protein ranked in the top-tier group in terms of water absorption (3.6 g water/g sample), oil absorption (7.2 g oil/g sample) and foaming capacity (99%). The SI solubility was twice that of soy at pH 4 due to clear differences in the amount of albumins and polarity of amino acids. All experimental treatments achieved at least 80% reduction in trypsin inhibitors. Given these findings, it is inferred that alkaline extracts, independently of the pretreatment with US, yielded SI concentrates with adequate protein quality and techno-functionality.