Preparation of zein—soy protein isolate composites by pH cycling and their nutritional and digestion properties

Enhancement of functional properties, digestive properties, and in vitro digestion product physiological activity of extruded corn gluten meal by enzymatic modification

BACKGROUND

Enzymatic modification is an effective means of improving the functional properties, digestive properties, and in vitro digestion product physiological activity of proteins, thus significantly expanding protein uses in various food applications.

RESULTS

In this study, the addition of chymotrypsin (CT) at pH 9.0 and 11.0 was found to significantly improve the functional properties (solubility, foaming properties, water holding capacity, oil holding capacity, etc.) and digestive properties of extruded corn gluten meal (ECGM). Similar changes were observed when treating ECGM with glutaminase, protein glutaminase, and papain. These changes were likely due to the increase in number of carboxyl groups and the multiple effects of change in protein net charge and conformation caused by enzymatic deamidation. Of note, ECGM deamidated by CT showed the highest degree of deamidation, solubility, and gastrointestinal digestibility at pH 11.0, up to 44.92%, 43.75%, and 82.22%, respectively. In addition, CT-ECGM digestion product exhibited strong antioxidant activity and potential to promote alcohol metabolism in both a static digestion model and dynamic digestion model, even comparable to commercial corn peptides (CCP), while being inexpensive and of low bitterness compared to CCP. Meanwhile, the physiological activity enhanced as the molecular weight of digestion product decreased with the digested component having strongest activity.

CONCLUSION

This study may promote the application of ECGM as a food component in the food industry or even as a substitute for CCP. © 2023 Society of Chemical Industry.

Antioxidant capacity and antitumor activity of the bioactive protein prepared from orange peel residues as a by-product using fungal protease

Agricultural and industrial residues (AIR) are renewable biomass sources present in large quantities causing pollution. Converting AIR to eco-friendly products (bioactive materials) reduces their quantity and impact on the environment, in addition to reducing production costs. Therefore, orange peel (OP) protein degradation, antioxidant capacity, and antitumor activity were investigated using Aspergillus niger WA 2017 protease. The highest value of the protein hydrolysate with the highest antioxidant using the DPPH method was obtained after 24 h. The single-factor method boosted the protein hydrolysate and the DPPH antioxidant activity by 3.7 and 1.7-fold, respectively. Statistical optimized conditions (Central Composite Method) increased the hydrolysate value and the DPPH antioxidant activity by 1.6 and 1.1-fold, respectively. The central trial samples exhibited the highest DPPH antioxidant activity (62.37 %), while the control sample recorded 20 %. All antioxidant tests in vitro (DPPH, reducing power, ABTS, and FRAP) confirmed the superiority of the potent hydrolysate as a good antioxidant. In vitro antitumor activity, the potent hydrolysate exhibited the highest effect on the Ehrlich Ascites Carcinoma Cells viability as it recorded 60.62 % dead cells. In vivo antitumor activity, the volume of the untreated tumor mice was found to be 1.4-fold bigger than the volume obtained from the potent hydrolysate. The increase in life span (ILS %) for oral treatment and intraperitoneal injection treatment with the potent hydrolysate increased by 13.91 and 19.42 %, respectively, compared to the untreated tumor.

Formation mechanism and functional properties of walnut protein isolate and soy protein isolate nanoparticles using the pH-cycle technology

Walnut protein isolate (WPI) is a nutritious protein with poor solubility, which severely limits its application. In this study, composite nanoparticles were prepared from WPI and soy protein isolate (SPI) using the pH-cycle technology. The WPI solubility increased from 12.64 to 88.53% with a WPI: SPI ratio increased from 1: 0.01 to 1: 1. Morphological and structural analyses illustrated that interaction forces with hydrogen bonding as the main effect jointly drive the binding of WPI to SPI and that protein co-folding occurs during the neutralization process, resulting in a hydrophilic rigid structure. In addition, the interfacial characterization showed that the composite nanoparticle with a large surface charge enhanced the affinity with water molecules, prevented protein aggregation, and protected the new hydrophilic structure from damage. All these parameters helped to maintain the stability of the composite nanoparticles in a neutral environment. Amino acid analysis, emulsification capacity, foaming, and stability analysis showed that the prepared WPI-based nanoparticles exhibited good nutritional and functional properties. Overall, this study could provide a technical reference for the value-added use of WPI and an alternative strategy for delivering natural food ingredients.