Ricinodendron heudelotii kernels were defatted and used as substrate to produce protein hydrolysatesusing papain (PHP), trypsin (PHT), proteases from Abrus precatorius (PHAp)and B. enneandra(PHBe). The degree of hydrolysis (DH), antioxidant (DPPH method), and functional properties of hydrolysates were performed. The DH value, whatever hydrolysis time, was highest with PHP. The water holding capacity decreased with the hydrolysis time from 21.50 ± 0.44% to 5.20 ± 0.07%. After 6h of hydrolysis, PHAp exhibited maximum solubility value (70.17 ± 2.15%) while PHBe had lower solubility value (18.43 ± 0.12%). The highest value of emulsifying activity index was found at pH 9 with 0.25% (w/v) hydrolysate concentration. Within the range of pH used (4-9), the best foam capacity and foam stability were exhibited by PHBe. PHP, PHAp, and PHT inhibited DPPH radical at 83.30 ± 0.46, 75.07 ± 0.15, and 56.78 ± 0.40%, respectively, at 6h of hydrolysis.
TopIntroduction
Protein hydrolysates are a mixture of peptides and amino acids produced during enzymatic hydrolysis of proteins. They are recognized to exhibit certain functional properties that allow their use as a readily natural source of proteins for animal feed, human food and microorganism growth medium (Adjonu, Doran, Torley, & Agboola, 2013). Protein hydrolysates can act as functional foods through their antioxidant activity. Functional foods are known as foods that have a potentially positive biological effect on health a part of their basic traditional nutrition. Several authors have reported that protein hydrolysates from soy bean (Shih, Yang, & Kuo, 2002), mackerel fish (Wu, Chen, & Shiau, 2003), tilapia (Foh, Amadou, Foh, Kamara, & Xia, 2010) pink perch (Naqash & Nazeer, 2013), freshwater fish (Elavarasan & Shamasundar, 2015)and bovine plasma (Seo, Seo, & Yang, 2016) that possess antioxidant activity and can be used as natural antioxidant to substitute synthetic ones (Chi, Wang, Wang, Zhang, & Deng, 2015).Production of protein hydrolysates with good properties and useful for human nutrition requires enzymes whose availability is still a challenge due to their higher cost(Taha, Yamamah, Mohamed, Mohamed, & Wagdy, 2014).Therefore, protein hydrolysates production using local sources of proteases and substrates is a great asset for the population in developing countries.
Abrus precatorius and Burnatia enneandra are two edible domestic plants belonging to Fabaceae and Alismataceae family respectively. Proteolytic enzymes were identified and extracted from the leaves of A. precatorius, B. enneandra tubers (Mezajoug-Kenfack, Ngangoum, Tchiégang, & Linder, 2014; Ngangoum,Mezajoug Kenfack, Sanjit, Tchiégang& Vijayalakshmi, 2017). Their characteristics reveled that they can be used like papain, trypsin, alcalase and flavourzyme for protein hydrolysates production (Foh, Amadou, Foh, Kamara, & Xia, 2010; Martins, Costa, & Prentice-Hernández, 2010).
In Cameroon, some local kernels rich in proteins usually used by the population as spices, can serve as substrate to the hydrolysis. This is for example Ricinodendron heudelotii known as an endemic plant belonging to the Euphorbiaceae family. It is widely distributed in the equatorial forest of Madagascar, the Guinean Zone of West and Central Africa. Its kernels are consumed by the inhabitants for soup thickening (Mezajoug-Kenfack & Tchiégang, 2016). Research works carried out on description, physicochemical characterization and solubility of protein from R. heudelotii kernels, revealed that kernels contain more than 50% of lipids. Its defatted flour possess about 55% of crude proteins (Tchiégang, Kapseu, Ndjouenkeu, & Ngassoum, 1997). Proteins from defatted R. heudelotii kernels have good functional properties such as solubility and possess a good number of essential amino acids (Mezajoug-Kenfack, Arab-Tehrany, Tchiégang, & Linder, 2011). Nevertheless, to the best of our knowledge, no scientific work has been done regarding the production of protein hydrolysates from R. heudelotii kernel and their eventual antioxidant activity.