Synergistic effects of pH shift and heat treatment on solubility, physicochemical and structural properties, and lysinoalanine formation in silkworm pupa protein isolates

Haining Xu; Jiayin Pan; Mokhtar Dabbour; Benjamin Kumah Mintah; Wen Chen; Fan Yang; Zhaoli Zhang; Yu Cheng; Chunhua Dai; Ronghai He; Haile Ma

doi:10.1016/j.foodres.2023.112554

Synergistic effects of pH shift and heat treatment on solubility, physicochemical and structural properties, and lysinoalanine formation in silkworm pupa protein isolates

Food Res Int. 2023 Mar:165:112554. doi: 10.1016/j.foodres.2023.112554. Epub 2023 Feb 2.

Authors

Haining Xu¹, Jiayin Pan¹, Mokhtar Dabbour², Benjamin Kumah Mintah³, Wen Chen¹, Fan Yang¹, Zhaoli Zhang⁴, Yu Cheng¹, Chunhua Dai¹, Ronghai He⁵, Haile Ma¹

Affiliations

¹ School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China; Institute of Food Physical Processing, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China.
² Department of Agricultural and Biosystems Engineering, Faculty of Agriculture, Benha University, P.O. Box 13736, Moshtohor, Qaluobia, Egypt.
³ CSIR - Food Research Institute, P.O. Box M20, Accra, Ghana.
⁴ School of Food Science and Engineering, Yangzhou University, 196 Huayang West Road, Yangzhou, Jiangsu 225127, China.
⁵ School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China; Institute of Food Physical Processing, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China. Electronic address: heronghai1971@126.com.

PMID: 36869538
DOI: 10.1016/j.foodres.2023.112554

Abstract

The application of silkworm pupa protein isolates (SPPI) in food industry was limited because SPPI's solubility is poor and it contains a potential harmful component of lysinoalanine (LAL) which formed during protein extraction. In this study, combined treatments of pH shift and heating were performed to improve the solubility of SPPI and to reduce the content of LAL. The experimental results showed that the promoting effect on SPPI's solubility by alkaline pH shift + heat treatment was greater than that by acidic pH shift + heat. And an 8.62 times increase of solubility was observed after pH 12.5 + 80 ℃ treatment compared to the control SPPI sample which was extracted at pH 9.0 without pH shift treatment. Very strong positive correlation was found between alkali dosage and SPPI solubility (Pearson's correlation coefficient r = 0.938). SPPI with pH 12.5 shift treatment showed the highest thermal stability. Alkaline pH shift combined with heat treatment altered the micromorphology of SPPI and destroyed the disulfide bonds between macromolecular subunits (72 and 95 kDa), resulting in reduced particle size and increased zeta potential and free sulfhydryl content of the isolates. The fluorescence spectra analysis showed red shifts phenomena with pH increasing and fluorescence intensity increase with temperature increasing, implying the alterations in the tertiary structure of protein. Compared to the control SPPI sample, the amount of LAL reduced by 47.40 %, 50.36 % and 52.39 % using pH 12.5 + 70 ℃, pH 12.5 + 80 ℃ and pH 12.5 + 90 ℃ treatment, respectively. These findings provide fundamental information for the development and application of SPPI in food industry.

Keywords: Heat treatment; Lysinoalanine formation; Physicochemical properties; Silkworm pupa protein; Solubility; pH shift.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Bombyx*
Hot Temperature
Hydrogen-Ion Concentration
Lysinoalanine
Pupa
Solubility

Substances

Lysinoalanine