## 3 Results and Discussion
### The WHC and OHC of Protein Extracts  
The hydration characteristics of food are very important for effective digestion to occur and can be defined by the swelling capacity, solubility, WHC and other characteristics. The WHC of a food product describes the ability to hold water within the food matrix [29]. Furthermore, the WHC of foods such as meat relates to quality attributes, which influence product yield and have economic implications but is also important in terms of eating quality [30]. The WHC and OHC of the protein extracts generated from _Spirulina_ sp. and _Isochrysis_ sp. were compared to those of a whey protein isolate and flaxseed protein, respectively (Figure 2). The WHC values for the protein extracts generated from _Spirulina_ sp. and _Isochrysis_ sp. were 2.25 g water/g protein extract and 0.47 g water/gprotein extract, respectively, compared with a WHC of 6.39 g water/g defatted flaxseed protein. Previously, [PERSON] and [PERSON] [30] reported that the overall water-holding capacities of whey powders and demineralized whey powders are generally low, and this is what we observed in this study. These WHC values were lower than those reported previously for seaweed-derived protein extracts, including _Himanthulia elongata_ (WHC value of 10.27 \(\pm\) 0.09 g water/g protein) [9]. The WHC obtained for the _Spirulina_ sp. protein extract (2.25 g water/g protein) was similar to that derived from _Kappahycus alvarezii_, which had a reported WHC of 2.22 \(\pm\) 0.04 g water/g protein [31]. High WHC values are required for viscous foods including custards, sausages, doughs and baked products, as they help to provide thickening and viscosity to the foods [32]. The WHC values observed for both algal protein extracts were lower in WHC value than the _H. elongata_ proteins [9]. The solubility values observed for both protein extracts at pH 4 and 2, respectively, might be because the proteins have their isoelectric point at these pH values, and at more acidic or alkaline pH values, the protein will acquire a net positive or negative charge. Figure 1: Foaming capacity (**A**), as well as foaming stability of _Spirulina_ sp. (**B**), _Isochrysis_ sp. (**C**), flaxseed meal (**D**) and whey protein isolate (**E**) (n = 3). The microalgal protein extracts had greater OHCs than the whey protein isolate and flaxseed protein analyzed. A high OHC value is desirable in food manufacturing for the retention of flavor and improved palatability. The OHC of the _Spirulina_ sp. protein extract was 5.80 g oil/g protein extract, and the OHC for the _Isochrysis_ sp. protein extract was 3.16 g oil/g protein extract, compared with 1.23 g oil/g defatted flaxseed protein extract and \(\sim\)1 g oil/g whey protein isolate. These OHC values compare favorably to other protein isolates, including the seaweed _H. elongata_ protein concentrate, which reported an OHC of 8.1 g oil/g protein extract [9]. The macroalgal protein powder _Kapparazii powder_ TM had an OHC value of 0.20 g/g, and rice bran protein concentrates have reported OHC values of between 3.74 and 9.18 g oil/g [29]. Molecular Weight Distribution Profile of Soluble Proteins Only from Spirulina sp. and Isochrysis sp. The molecular weight distribution profiles of the soluble protein extracts generated from _Spirulina_ sp. and _Isochrysis_ sp. are shown in Figure 3A,B. The profiles varied between the two microalgae, with the largest percentage of proteins in the _Spirulina_ sp. extract found in the \(>\)100 kDa fraction (62.28%). However, this fraction, in fact, not only contained \(>\)100 kDa proteins, as seen by the appearance and distribution (Gel A). A lot of the content was found in the lower part of the gel, indicating a MW far less than 100 kDa. It also contained protein \(>\) 100 kDa. Based on the SDS-PAGE of the individual fraction, the protein in the individual fractions did not have the overall characteristics (i.e., sharp size distribution) intended.