## 1 Introduction  
A growing demand for plant proteins possessing high nutritional and functional properties has urged scientists and the food industry to explore non-conventional protein sources. Hempesed, a by-product in the hempesed oil industry, has gained increasing attention in the past decades as a type of superfood, and it has a rich nutritional profile, excellent digestibility, and well-proportioned amino acid profile [1]. Previous studies have mainly focused on hempesed protein isolate (HPI) extraction yield and its physicochemical properties [2; 3; 4; 5]. Whilst possessing a promising nutritional profile, the usefulness and value of hempesed protein isolate in advanced food applications are highly dependent on its functional properties, such as water solubility, emulsifying capacity, and gelling property in food systems. Recent investigations have suggested that hempesed proteins possess inferior structural and functional properties. At a neutral pH, HPI generally exhibits extremely poor solubility. Especially around its isoelectric point (pH 5.0), the solubility of HPI was found to be merely -8% [6; 7]. [PERSON] and [PERSON] [8] investigated the solubility of two protein fractions in hempesed protein by dialysing. The solubility of albumin (80% at pH 7) was found to be dramatically better than edestin (30% at pH 7), which indicated edestin might be responsible for the poor solubility of hempesed. On the other hand, the emulsifying capacity and stability were relatively low [9; 10] and might cause a series of problems during processing, storage, and utilization. Although the reason for the HPI's poor functionality has not been thoroughly investigated, some researchers have proposed a few reasonable assumptions. Globular edestin accounts for the majority (60-80%) of total hempesed protein content [11]. Edestin was identified to have a hexameric structure via crystallographic techniques [12], comprising six identical subunits. Each subunit contains an acidic and a basic subunit linked by a disulphide bond. [PERSON] et al. [13] identified two edestin types (CsEde1 and CsEde2) by isolating cDNA coding; CsEde2 exhibited abundant cysteine (1.07%), which exceeds the content in glycinin [14], indicating a higher probability of undergoing sulphide bond formation in hempesed protein. [PERSON] et al. [15] reported that HPI contained a three-fold-higher free sulfhydryl (-SH) content than soy protein isolate (SPI), which suggested HPI is more prone to aggregation than conventional protein sources. [PERSON] et al. [16] conducted an SDS-PAGE analysis, and smearing was observed at the top of the gel in both HPI and its protein constituents (HPI-7S, HPI-1 IS) but disappeared under a reducing environment. This phenomenon demonstrated disulphide bond (SS) formation in HPI products. Nevertheless, there is still a lack of sufficient evidence to irrefutably link the intermolecular disulphide bond formation and the poor functional properties in the HPI system. Investigations into protein structural modifications have been carried out to address the limited functional properties of HPI. The hempesed protein structure can be modified by heating between 80 to 100 \({}^{\circ}\)C [17]. However, the improved functionality was found to be very limited, with the solubility at a neutral pH only slightly increased from 20.6% to 25.8% when heated at 80 \({}^{\circ}\)C for 60 min [18]. [PERSON] et al. [19]. even observed that the solubility of heat-treated (90 \({}^{\circ}\)C, 10 min) HPI was lower than untreated HPI when pH was above neutral. Succinylation has been used in other plant proteins to improve their functionality via the introduction of a negatively charged succinate group [20; 21]. Although the solubility of HPI was found to increase from 30% to 85% with the addition of succinin anhydride [22], the toxicity of succinin anhydride is problematic. Succin anhydride can react with other substances in food, forming potentially harmful compounds, such as N-substituted succinimides [23].