Precipitation of sword bean proteins by heating and addition of magnesium chloride in a crude extract

Abstract

Sword bean (Canavalia gladiata) seeds are a traditional food in Asian countries. In this study, we aimed to determine the optimal methods for the precipitation of sword bean proteins useful for the food development. The soaking time for sword beans was determined by comparing it with that for soybeans. Sword bean proteins were extracted from dried seeds in distilled water using novel methods. We found that most proteins could be precipitated by heating the extract at more than 90 °C. Interestingly, adding magnesium chloride to the extract at lower temperatures induced specific precipitation of a single protein with a molecular weight of approximately 48 kDa. The molecular weight and N-terminal sequence of the precipitated protein was identical to that of canavalin. These data suggested that canavalin was precipitated by the addition of magnesium chloride to the extract. Our results provide important insights into the production of processed foods from sword bean.

Reversible changes of canavalin solubility controlled by divalent cation concentration in crude sword bean extract

“…In our previous study, we described a method for the extraction of proteins from sword bean in distilled water and their precipitation by the addition of 20 mM MgCl 2 in the crude extract. 5) This was the first study that reported the precipitation of canavalin in the presence of MgCl 2 and showed that a detailed investigation of canavalin precipitation might be important for the study of its physiological function and physicochemical properties.…”

“…We have previously reported a method for the extraction of some proteins from sword bean using only distilled water. 5) In addition, the predominant protein in the crude extract was determined to be canavalin. 5) Canavalin is the major storage protein of sword bean and jack bean (Canavalia ensiformis) with a molecular mass of 47.6 kDa, classified as 7S seed globulin or legume vicilin.…”

“…5) In addition, the predominant protein in the crude extract was determined to be canavalin. 5) Canavalin is the major storage protein of sword bean and jack bean (Canavalia ensiformis) with a molecular mass of 47.6 kDa, classified as 7S seed globulin or legume vicilin. 6) It was first isolated from jack bean, 7) and later its primary structure was determined in both bean species using cDNA sequence.…”

Sword bean variants and different pretreatments influence protein extraction and protein properties

“…The agricultural and nutritional characteristics show the potential for utilizing sword beans in processed foods. Previously, we reported the physicochemical characteristics of sword bean proteins [5,6] and gelation of sword bean extract [7], both of which are important for making processed foods. However, more scientific knowledge is essential to begin using sword beans to make processed foods.…”

“…In our previous studies, dried WSBs were used for protein extraction after water absorption by soaking [5,6]. Dried WSBs absorbed sufficient water for extraction purposes after soaking in 10 volumes of distilled water for 18 h at 20°C [5]. However, dried RSBs absorbed a little amount of distilled water, in contrast to dried WSBs.…”