Physical Treatment Reduces Trypsin Inhibitor Activity and Modifies Chemical Composition of Marama Bean (Tylosema esculentum)

The utility of the marama bean (MB) as an alternative protein source to soybean (SB) can be limited by the high concentration of trypsin inhibitors (TI). The physical treatment of MB has the potential to ameliorate the antinutritional activities of TI and modify other chemical components. Thus, this study investigated the effects of physical treatments on the chemical components and trypsin inhibitor activity (TIA) of raw MB and SB. The bean substrates were subjected to each of the following treatment methods: (1) room temperature (20-22 degrees C) soaking for 24 h; (2) electric stove cooking at 100 degrees C for 10, 20, and 30 min; (3) steam autoclaving at a temperature of 110 degrees C and pressure of 7 pounds per square inch (psi), as well as a temperature of 121 degrees C and 7 psi for 5, 15, and 30 min; (4) pre-soaked autoclaving at 110 degrees C (7 psi) and 121 degrees C (17 psi) for 5, 15, and 30 min. Treated MB and SB had greater (p < 0.05) crude protein content than untreated samples. All the treatments (except 24 h soaking of MB) reduced (p < 0.05) the TIA and ash content. Marama and SB are similar in protein content, but their amino acids profile and TIA are quite different. Soaking for 24 h was less effective in reducing TIA in MB and SB, compared to the thermal methods, and it was detrimental to the ash and amino acids profile of the two beans. Soaking prior to autoclaving yielded beans with the lowest TI concentrations. In conclusion, thermal methods reduced the TI contents and modified the level of proximate components and amino acids profile of the beans.

Automated summary

The study found that thermal methods can effectively reduce the trypsin inhibitor activity in marama bean and soybean, while increasing the crude protein content. However, soaking for 24 hours may have a less desirable effect and could potentially have negative impacts on ash content and amino acid profiles.