*4.1.2 Water absorption capacity*

Water absorption capacity (WHC) refers to the amount of water that protein can absorb. It is also be referred to water binding capacity. Commercially prepared soy protein isolate can absorb water at 4–5.5 times its weight, and 2.4–3.4 for concentrates [4]. In fava bean, lentils, cow peas, chickpeas, soybean, beans and peas WHC was reported to be in the range 2.39–6.78 g of water per gram of protein concentrate [44]. This generally indicates wide variation in WHC, and suggests that some of the protein isolates are better suited than others for use where WHC is intended to be achieved. Soybean and pea protein isolates have been reported to improve viscosity and prevent syneresis in cultured dairy products [45]. These are partly functions of their WHC. In another study [46], WHC was found to be 4.09–6.13 g/g for pinto bean, lima bean, red bean, kidney bean, black bean, navy bean, red bean, mung bean, lentil and chickpea. WHC of flour produced from 21 legume samples which included green gram, chickpea, lentil, soybean and several bean varieties was found in another study to be 1.32–3.14 g/g [47]. Protein products from legumes are in the form of flour, protein concentrates and isolates. They differ in level of refining, with flour being less refined and isolate being highly refined source of protein. The various forms of protein have different uses. Refining whole flour such as by defatting and removal of other non-protein components as much as possible improve functional properties such as WHC and oil holding capacity [48]. Compared to other legumes, soybean and pea have generally been extensively characterized for functional properties and also used in food applications. WHC of 7 protein isolates from 7 pea cultivars were reported to range be in the range 1.88–2.37 g/g [49].

## *4.1.3 Oil absorption capacity*

Oil absorption capacity (OAC) refers to the weight of oil absorbed per unit weight of protein. Legume proteins have been reported to have OAC in the range 1–4 g/g protein [50, 51]. OAC has been reported to be in the range 3.46–6.37 grams oil per gram of protein concentrate in fava bean, lentils, cow peas, chickpeas, soybean, beans and peas [44]. Like WHC, OAC also varies among legumes, thus they vary in their effectiveness in achieving OAC. Lentil and chickpea and several types of common beans was reported to have OAC in the range 0.93–1.38 g/g [46]. In another study, flour prepared from 21 legume samples comprising green gram, chickpea, lentil, soybean and several bean varieties had OHC of 0.62–2.57 g/g [47]. OHC as well as other functional properties will vary with type of legume as well as form of protein. In a study, OHC of protein isolates from 7 pea cultivars ranged from 1.07 to 1.40 g/g [49].
